309 pubblicazioni classificate nel seguente modo:

A biomechanical model for the evaluation by electrogoniometry of spatio-temporal parameters during walking
INTERNATIONAL JOURNAL OF BIOMECHATRONICS AND BIOMEDICAL ROBOTICS
Autore/i: Maranesi, Elvira; DI NARDO, Francesco; Giacomo, G. GHETTI; Burattini, Laura; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: The aim of the study is to propose a new methodology to assess step length, duration and speed, using only two 1-degree-of-freedom electrogoniometers, positioned on hip and knee joints. To this purpose, a novel model was introduced, which represents the lower limb modelled as two rigid segments (thigh and shank). Model validation was performed comparing the results with those automatically achieved from two classic gait analysis systems (a 6-camera stereophotogrammetric system and GAITRite), during walking at three different speeds (natural, fast and slow). The absence of significant differences among parameter values estimated by the three systems indicates a strong reliability of the model. Thus, the study candidates this electrogoniometer-based model as a reliable and not expensive tool for an easy and flexible assessment of spatio-temporal gait parameters in normal subjects, and propose it as a valid alternative to traditional methods using foot switches, ground reaction forces, IMU or stereo-photogrammetric systems.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/228445

Myoelectric activity of antagonist ankle-muscles in 6-to-8-year-old children during walking
2015 12th International Workshop on Intelligent Solutions in Embedded Systems, WISES 2015
Autore/i: DI NARDO, Francesco; Mengarelli, Alessandro; Maranesi, Elvira; Burattini, Laura; Fioretti, Sandro; Agostini, Valentina; Knaflitz, Marco; Nascimbeni, Alberto
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Great co-contraction, i.e. simultaneous contraction of agonist and antagonist muscles crossing a joint, of ankle muscles during the stance phase has been identified as one of the typical features of the immature gait. The goal of the present study was the assessment of the co-contractions of tibialis anterior (TA) and gastrocnemius lateralis (GL) during walking in 20 healthy 6-to-8-year-old children, critical age for the maturation of gait. To this aim, Statistical gait analysis, a recent methodology performing a statistical characterization of gait by averaging spatial-temporal and surface-EMG-based parameters over numerous strides, was performed in each subject. Co-contractions were assessed as the period of overlap between activation intervals of TA and GL. Results showed that GL and TA act as pure antagonists for ankle plantar/dorsiflexion (no co-contractions) in only 18.7% of strides. In the remaining strides, statistically significant (p<0.05) co-contractions were detected in early stance (45.0% of the strides), mid-stance (27.7%), pre-swing (14.6%), and swing (74.1%). The presence of all these different kinds of ankle-muscle co-contractions seems to suggest the need of a stabilizing control in children, supporting the hypothesis that a young neurocontrol system can operate on more degrees of freedom. In conclusion, the present analysis represents the first attempt for providing a quantitative assessment for ankle-muscle co-contraction in healthy 6-to-8-year-old children, in order to give further information on the maturation of gait in children.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/234891

Gender differences in the myoelectric activity of lower limb muscles in young healthy subjects during walking
BIOMEDICAL SIGNAL PROCESSING AND CONTROL
Autore/i: DI NARDO, Francesco; Mengarelli, Alessandro; Maranesi, Elvira; Burattini, Laura; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: The present study was designed to achieve a comprehensive analysis of gender-related differences in themyoelectric activity of lower limb muscles during normal walking at self-selected speed and cadence,in terms of muscle activation patterns and occurrence frequencies. To this aim, statistical gait analysis(SGA) of surface EMG signal from tibialis anterior (TA), gastrocnemius lateralis (GL), rectus femoris (RF),biceps femoris (BF) and vastus lateralis (VL) was performed in 11 female (F-group) and 11 male (M-group)age-matched healthy young adults. SGA is a recent methodology performing a statistical characteriza-tion of gait, by averaging spatio-temporal and sEMG-based parameters over numerous strides. Findingsshowed that males and females walk at the same comfortable speed, despite the significantly lowerheight and higher cadence detected in females. No significant differences in muscle onset/offset weredetected between groups. The analysis of occurrence frequencies of muscle activity showed no signif-icant differences in BF and RF, between groups. Conversely, in F-group, compared with M-group, GL,TA and VL showed a significantly higher occurrence frequency in the modalities with a high number ofactivations, and a significantly lower occurrence frequency in the modalities with a low number of acti-vations. These findings indicate a propensity of females for a more complex recruitment of TA, GL and VLduring walking, compared to males. The observed differences recommend the suitability of developingelectromyographic databases, separated for males and females.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/224133

Cleaning the electrocardiographic signal from muscular noise
2015 12th International Workshop on Intelligent Solutions in Embedded Systems, WISES 2015
Autore/i: Burattini, Laura; Agostinelli, Angela; Maranesi, Elvira; Sbrollini, Agnese; Fioretti, Sandro; DI NARDO, Francesco
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Electrocardiography is a simple clinically useful non-invasive technique to evaluate the activity of the heart. The heart rate is very variable parameter and sometimes reaches very high values. In these cases, the frequency band of the electrocardiographic (ECG) signal overlaps the band of the surface electromyographic (sEMG) signal, which it represents an interfering signal. The aim of the present study is to show how the Segmented Beat Modulation Method (SBMM) can be used to clean the ECG signal from muscular noise. To this aim, a real ECG signal (characterized by a fast heart rate and corrupted by muscular noise) was acquired from a violinist while he was playing. Results indicate that the ECG and the sEMG signal can be separated without losing morphological features and spectral components of both signals. Thus SBMM is a promising tool for cleaning the ECG signal from muscular noise.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236110

Evaluation of gender-related differences in co-contraction activity of shank muscles during gait
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Mengarelli, Alessandro; Maranesi, Elvira; Barone, Vinicio; Burattini, Laura; Fioretti, Sandro; DI NARDO, Francesco
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This study aims to investigate the possible differences between genders in co-contractions of tibialis anterior (TA) and gastrocnemius lateralis (GL), during walking at self-selected speed. To this purpose, the statistical gait analysis (SGA) was performed on seven female (F-group) and seven male (M-group) adults. SGA is a recently developed methodology for the characterization of gait, by averaging spatiotemporal and electromyographic parameters over hundreds of strides per subject. Co-contractions were assessed as the overlapping periods between TA and GL activity. Results showed that four co-contraction intervals are present during gait cycle in both groups. No relevant differences between genders were detected in onset-offset time instants of co-activations or in their temporal length. On the contrary, significant differences were observed in the number of strides where each co-contraction happens (i.e. the occurrence frequency). All the four co-contraction intervals result significantly (p<0.05) more recurrent in females compared to males. This outcome suggests a larger presence of co-contraction activity in females walking, related to a female tendency for a more complex muscular strategy during gait. These findings could be useful to better understand gender differences in walking mechanisms and to develop separated normal walking reference frames for males and females.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/234913

Clinical application of the Segmented-Beat Modulation Method for fetal ECG extraction
2015 12th International Workshop on Intelligent Solutions in Embedded Systems, WISES 2015
Autore/i: Agostinelli, Angela; Fioretti, Sandro; DI NARDO, Francesco; Burattini, Laura
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The assessment of the fetal well-being is accomplished with the monitoring of fetal cardiac activity. In presence of risk labor, direct fetal electrocardiography (fECG) can be obtained by positioning an electrode on the fetal scalp. However, its invasiveness and application limited to labor have led to the introduction of the indirect (noninvasive) fECG, obtained by applying the electrodes on the maternal abdomen. The abdominal recordings are corrupted by the maternal ECG (mECG) that often covers the fECG (the signal of interest). To extract the fECG, the mECG has to be estimated and then subtracted from the abdominal recording. To this aim, template-based techniques are often applied. However, such techniques are typically not able to reproduce physiological heart rate (HR) and morphological variability. To overcome this limit, an innovative template-based filtering technique termed the Segmented-Beat Modulation Method (SBMM) has recently been proposed. To evaluate its ability to extract the fECG, SBMM is applied here to an abdominal recording. Direct fECG was simultaneously recorded for comparison. Each RR interval of the direct fECG was correlated with the corresponding RR interval of the indirect fECG, and a statistically significant strong correlation (ρ=0.86, P<10-26) was found. Thus, the SBMM proved to be a potentially useful tool to provide a reliable fECG signal (extracted from an abdominal recording) that can be used for monitoring the fetus health conditions.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236109

Assessment of the activation patterns of the muscles involved in the FR test in diabetic neuropathic patients
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Maranesi, Elvira; DI NARDO, Francesco; Ghetti, G. G.; Mercante, O.; Rabini, R. A.; Burattini, Laura; Fioretti, Sandro
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This study was designed to assess, in elderly neuropathic diabetic (DN) patients, the activation patterns of the main muscles involved in the Functional Reach (FR) Test, a well-recognized method to identify elderly subjects at risk of recurrent falls. Surface electromyographic (sEMG) analysis of Sternocleidomastoideus (Scm), Rectus Abdominis (RAbd), Erectores Spinae at L4 level (L4), Rectus Femoris (RF), Hamstrings (Ham), Tibialis Anterior (TA) and Soleus (Sol) was performed to this aim. Results in DN patients are compared with a control group (CH) of healthy age-matched subjects. In DN patients, TA is identified as the first muscle to be recruited (ON at -34% of the FR-period) before the movement start, in order to initiate the body forward displacement. RF is the first muscle to be recruited after TA and, togheter with RAbd, showed a progressive earlier onset from CH group. Sol and Ham (ON after the FR-start), followed by L4, act mainly as tonic muscles, opposing the movement and preventing falls. Compared to the CH group, the DN subjects show an anticipatory recruitment (-34%±6%) of TA, showing a statistically significant difference (p<0.05) in comparison to CH group, together with the Scm activation. Results suggest a trend of DN patients in anticipating the activation of the anterior muscles of the body. This is likely due to an attempt to compensate the neuropathy-related proprioception dysfunction and to adjust the movement timing. In conclusion, the present study shows that sEMG is a suitable tool to deepen the interpretation of the FR-test execution and proposes the earlier start of TA as a possible element to identify the presence of neuropathy in diabetic subjects
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/234918

Assessment of the ankle muscle co-contraction during normal gait: A surface electromyography study
JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY
Autore/i: DI NARDO, Francesco; Mengarelli, Alessandro; Maranesi, Elvira; Burattini, Laura; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: The study was designed to assess the co-contractions of tibialis anterior (TA) and gastrocnemius lateralis (GL) in healthy young adults during gait at self-selected speed and cadence, in terms of variability of onset–offset muscular activation and occurrence frequency. Statistical gait analysis (SGA), a recent methodology performing a statistical characterization of gait by averaging spatio-temporal and EMG-based parameters over numerous strides, was performed in twenty-four healthy young adults. Co-contractions were assessed as the period of overlap between activation intervals of TA and GL. Results showed that GL and TA act as pure agonist/antagonists for ankle plantar/dorsiflexion (no co-contractions) in only 21.3 ± 8.2% of strides. In the remaining strides, statistically significant (p < 0.05) co-contractions appear in early stance (29.2 ± 1.7%), mid-stance (32.1 ± 18.3%) and swing (62.2 ± 2.0%). This significantly increased complexity in muscle recruitment strategy beyond the activation as pure ankle plantar/dorsiflexors, suggests that cocontractions are likely functional to further physiological tasks as foot inversion, balance improvement, control of ankle stability and knee flexion. This study represents the first attempt for the development in healthy young adults of a ‘‘normality’’ reference frame for GL/TA co-contractions, able to include the physiological variability of the phenomenon and eliminate the confounding effect of age.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205328

The segmented-beat modulation method for ECG estimation
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Agostinelli, Angela; Giuliani, Corrado; Fioretti, Sandro; DI NARDO, Francesco; Burattini, Laura
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Electrocardiographic (ECG) tracings corrupted by noise with frequency components in the ECG frequency band, may result useless unless appropriately processed. The estimation of the clean ECG from such recordings, however, is quite challenging; being linear filtering inappropriate. In the common situations in which the R peaks are detectable, template-based techniques have been proposed to estimate the ECG by a template-beat concatenation. However, such techniques have the major limit of not being able to reproduce physiological heart-rate and morphological variability. Thus, the aim of the present study was to propose the segmented-beat modulation method (SBMM) as the technique that overcomes such limit. The SBMM is an improved template-based technique that provides good-quality estimations of ECG tracings characterized by some heart-rate and morphological variability. It segments the template ECG beat into QRS and TUP segments and then, before concatenation, it applies a modulation/demodulation process to the TUP-segment so that the estimated-beat duration and morphology adjust to those of the corresponding original-beat. To test its performance, the SBMM was applied to 19 ECG tracings from normal subjects. There were no errors in estimating the R peak location, and the errors in the QRS and TUP segments were low (≤65 μV and ≤30 μV, respectively), with the former ones being significantly higher than the latter ones. Eventually, TUP errors tended to increase with increasing heart-rate variability (correlation coefficient:0.59, P<10-2). In conclusion, the new SBMM proved to be a useful tool for providing good-quality ECG estimations of tracings characterized by heart-rate and morphological variability.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236150

Dependence of gait parameters on height in typically developing children
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Agostini, Valentina; Nascimbeni, Alberto; DI NARDO, Francesco; Fioretti, Sandro; Burattini, Laura; Knaflitz, Marco
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In clinical gait analysis is fundamental to have access to normative data, to be used as a reference in the interpretation of pathological walking. In a paediatric population this may be complicated by the dependence of gait parameters on child growth. The aim of this work is to provide the correlations of spatial-temporal gait parameters with children's height. We obtained the regression lines of cadence, double support, and gait phases, with respect to height, from a sample of 85 normally typically developing children aged 6 to 11. Our analysis of gait phases was not limited to the traditional analysis of stance and swing, but rather focused on the sub-phases of stance - heel contact, flat foot contact, push off - which proved to be an innovative approach to gait analysis. Heel contact decreased, flat foot contact increased and push off remained essentially unchanged with respect to children's height. These results may be useful in the interpretation of gait data in developing children, and the regression lines obtained may be used to normalize their gait parameters.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236153

Dependency of Exercise-Induced T-Wave Alternans Predictive Power for the Occurrence of Ventricular Arrhythmias from Heart Rate
ANNALS OF NONINVASIVE ELECTROCARDIOLOGY
Autore/i: Burattini, Laura; Sumche, Man; Fioretti, Sandro; DI NARDO, Francesco; Cees A., Swenne
Classificazione: 1 Contributo su Rivista
Abstract: T-wave alternans (TWA) is a noninvasive index of risk for the occurrence of ventricular arrhythmias. It is known that TWA amplitude (TWAA) increases with heart rate (HR) but how the TWA predictive power varies with HR remains unknown. Thus, the aim of this study was to evaluate the dependency of exercise-induced TWA predictive power for the occurrence of ventricular arrhythmias from HR.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205717

Comparison of ankle-muscles activity between school-aged children and young adults during gait: An electromyographic analysis
2015 12th International Workshop on Intelligent Solutions in Embedded Systems, WISES 2015
Autore/i: Mengarelli, Alessandro; Fioretti, Sandro; Maranesi, Elvira; Burattini, Laura; DI NARDO, Francesco; Agostini, V.; Knaflitz, M.; Nascimbeni, A.
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Electrocardiogram (ECG) represents, with the electroencephalogram (EEG), the principal bio-vital signals, providing information on the human physical condition. Although surface electromyogram (sEMG) is not classified as bio-vital, it is frequently used to integrate and increase information obtained from ECG and EEG, making these three signals the main electric-biological signals. The sEMG is widely used for the assessment of muscular activity during gait, providing valuable information in particular for subjects presenting impaired or non-completely developed gait, like children. Thus, this study aimed to quantify and compare lower limb muscle activity during walking in healthy, school-aged children (C-group) and young adults (A-group). The statistical analysis of tibialis anterior (TA) and gastrocnemius lateralis (GL) myoelectric signal revealed the absence of any significant difference between the two groups in the activation modalities adopted by both muscles, in terms of temporal characteristics and occurrence frequency. These outcomes underline similar activation patterns for children and adults during gait, confirming the hypothesis about an achieved mature gait in 6-to-8-year-old children, also in terms of sEMG activity. The findings of this study could help for better understanding the degree of mature gait advancement in children and for discriminating muscular physiological behavior in healthy and pathological children
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/234889

Heart-rate dependency of T-wave alternans during the exercise and recovery
2015 12th International Workshop on Intelligent Solutions in Embedded Systems, WISES 2015
Autore/i: Burattini, Laura; Agostinelli, Angela; Fioretti, Sandro; DI NARDO, Francesco; Man, S.; Swenne, C. A.
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Microvolt T-wave alternans (TWA), a subtle every-other-beat fluctuation of the electrocardiographic (ECG) T-wave amplitude, is a risk index for the occurrence of malignant ventricular arrhythmias. It is well-known that TWA increases with HR so that TWA is often analyzed during exercise. Since TWA during recovery is usually not evaluated, it is not clear if there is a HR-TWA one-to-one correspondence, or if TWA depends on how such HR was reached. Thus, the aim of the present study was to investigate TWA during both HR-increasing exercise and HR-decreasing recovery. To this aim, our HR adaptive match filter (AMF) for automatic TWA identification was applied to ECG recordings of 266 patients with implanted cardio-defibrillator (ICD). HR varied from 70 bpm to 125 bpm during exercise and vice versa during recovery. Our results indicate that TWA increased (from 17 μV to 51 μV) with increasing HR during exercise, and decreased (from 28 μV to 17 μV) with decreasing HR during recovery. However, such TWA changes did not occur symmetrically, but TWA was significantly lower during exercise than during recovery at low HRs (17-18 μV vs. 20-25 μV for HR<100 bpm; P100 bpm; P<10-6). Thus, there is not a HR-TWA one-to-one correspondence but the value of TWA at a specific HR depends on how such HR was reached.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236111

Validation of an optimized algorithm to use Kinect in a non-structured environment for Sit-to-Stand analysis.
2015 Annual International Conference of the IEEE Engineering in Medicine and Biology Society.
Autore/i: Cippitelli, Enea; Gasparrini, Samuele; Spinsante, Susanna; Gambi, Ennio; Verdini, Federica; Burattini, Laura; DI NARDO, Francesco; Fioretti, Sandro
Editore: IEEE
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The aim of this work is to obtain reliable kinematic measures relative to the execution of the Sit-to-Stand functional evaluation test, by low-cost and widely diffused instrumentation, that even non-experienced users can adopt in non-structured environments, like ambulatory or domestic settings. In particular, the paper refers to a low cost RGB-Depth sensor widely used in the gaming scenario like the Microsoft Kinect sensor. An algorithm is proposed that allows a reliable measure of human motion in a sagittal view. The performance of the proposed algorithm is compared to other two classic commercial algorithms. Results obtained by all the three algorithms have been compared to kinematic results obtained by the use of a stereophotogrammetric system that represents the gold-standard for kinematic measurement of human movement. Average errors of about 4 degrees, both for the trunk/leg angle and for the knee flexion/extension angle, have been obtained by the proposed algorithm and open the way to its possible adoption in non-clinical environments and further applications.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/230156

Assessment of the variability of vastii myoelectric activity in young healthy females during walking: A statistical gait analysis
JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY
Autore/i: DI NARDO, Francesco; Maranesi, Elvira; Mengarelli, Alessandro; Ghetti, Giacomo; Burattini, Laura; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: The study was designed to assess the natural variability of the activation modalities of vastus medialis (VM) and vastus lateralis (VL) during walking at a self-selected speed and cadence of 30 young, healthy, females. This was achieved by conducting statistical gait analysis on the surface electromyographic signals from hundreds of strides for each subject. Results revealed variability in the number of activations, occurrence frequency, and onset-offset instants across the thousands of strides analyzed. However, despite the variability, there was one activation occurrence which remained consistent across subjects for both VM and VL. This occurred from terminal swing to the following loading response (observed in 100% of strides). A second, less frequent, activation occurred between mid-stance up to pre-swing (observed in 39.3 ± 22.4% of strides for VM and in 35.1 ± 20.6% for VL). No significant differences (p>. 0.05) were observed in the onset-offset instants or in the occurrence frequency, which suggest a simultaneous recruitment of VM and VL. This "normality" pattern represents the first attempt at developing a reference frame for vastii sEMG activity during walking, that is able to include the physiological variability of the phenomenon and control the confounding effects of age and gender.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/228439

C-peptide-based assessment of insulin secretion in the Zucker fatty rat: A modelistic study
PLOS ONE
Autore/i: DI NARDO, Francesco; Cogo, Carla E.; Faelli, Emanuela; Morettini, Micaela; Burattini, Laura; Ruggeri, Piero
Classificazione: 1 Contributo su Rivista
Abstract: A C-peptide-based assessment of β-cell function was performed here in the Zucker fatty rat, a suitable animal model of human metabolic syndrome. To this aim, a 90-min intravenous glucose tolerance test (IVGTT) was performed in seven Zucker fatty rats (ZFR), 7-to-9week-old, and seven age-matched Zucker lean rats (ZLR). The minimal model of C-peptide (CPMM), originally introduced for humans, was adapted to Zucker rats and then applied to interpret IVGTT data. For a comprehensive evaluation of glucose tolerance in ZFR, CPMM was applied in combination with the minimal model of glucose kinetics (GKMM). Our results showed that the present CPMM-based interpretation of data is able to: 1) provide a suitable fit of C-Peptide data; 2) achieve a satisfactory estimation of parameters of interest 3) quantify both insulin secretion by estimating the time course of pre-hepatic secretion rate, SR(t), and total insulin secretion, TIS, and pancreatic sensitivity by means of three specific indexes of β-cell responsiveness to glucose stimulus (first-phase, φ1, second-phase, φ2, and steady-state, φsss, never assessed in Zucker rats before; 4) detect the significant enhancement of insulin secretion in the ZFR, in face of a severe insulin-resistant state, previously observed only using a purely experimental approach. Thus, the methodology presented here represents a reliable tool to assess β-cell function in the Zucker rat, and opens new possibilities for the quantification of further processes involved in glucose homeostasis such as the hepatic insulin degradation.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/228443

The occurrence frequency: A suitable parameter for the evaluation of the myoelectric activity during walking
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: DI NARDO, Francesco; Agostini, Valentina; Knaflitz, Marco; Mengarelli, Alessandro; Maranesi, Elvira; Burattini, Laura; Fioretti, Sandro
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Many studies have recently addressed the quantification of the natural variability of myoelectric activity during walking, considering hundreds of strides. The availability of so many strides allows assessing a parameter seldom considered in classic surface EMG (sEMG) studies: the occurrence frequency, defined as the frequency each muscle activation occurs with, quantified by the number of strides in which a muscle is recruited with that specific activation modality. Aim of this study is to point out the occurrence frequency as a suitable parameter for the evaluation of the variability of the myoelectric activity during walking. This goal was pursued by means of the statistical gait analysis of sEMG signal acquired from Gastrocnemius Lateralis (GL) in six healthy subjects, with different characteristics. Results show that among these six subjects relevant differences were not detected in the temporal parameters, i.e., activation onset/offset instant and activation duration. In the same subjects, the values of the occurrence frequency ranged from 3% to 74% in the different activation modalities, indicating a large variability of this parameter. These findings show that occurrence frequency is able to provide further and different information with respect to classical temporal parameters. Thus, the occurrence frequency is proposed as a suitable parameter to support the classic temporal parameters in the evaluation of variability of myoelectric activity during walking.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/234917

Noninvasive fetal electrocardiography: an overview of the signal electrophysiological meaning, recording procedures and processing techniques
ANNALS OF NONINVASIVE ELECTROCARDIOLOGY
Autore/i: Agostinelli, A; Grillo, M; Biagini, A; Giuliani, C; Burattini, L; Fioretti, S; DI NARDO, Francesco; Giannubilo, Sr; Ciavattini, A
Classificazione: 1 Contributo su Rivista
Abstract: Background Noninvasive fetal electrocardiography (fECG), obtained positioning electrodes on the maternal abdomen, is important in safeguarding the life and the health of the unborn child. This study aims to provide a review of the state of the art of fECG, and includes a description of the parameters useful for fetus clinical evaluation; of the fECG recording procedures; and of the techniques to extract the fECG signal from the abdominal recordings. Methods The fetus clinical status is inferred by analyzing growth parameters, supraventricular arrhythmias, ST-segment variability, and fetal-movement parameters from the fECG signal. This can be extracted from an abdominal recording obtained using one of the following two electrode-types configurations: pure-abdominal and mixed. Differently from the former, the latter also provides pure maternal ECG tracings. From a mathematical point of view, the abdominal recording is a summation of three signal components: the fECG signal (i.e., the signal of interest to be extracted), the abdominal maternal ECG (amECG), and the noise. Automatic extraction of fECG includes noise removal by abdominal signal prefiltration (0.5-45 Hz bandpass filter) and amECG cancellation. Conclusions Differences among methods rely on different techniques used to extract fECG. If pure abdominal electrode configurations are used, fECG is extracted directly from the abdominal recording using independent component analysis or template subtraction. Eventually, if mixed electrode configurations are used, the fECG can be extracted using the adaptive filtering fed with the maternal ECG recorded by the electrodes located in the woman thorax or shoulder.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205720

A stereophotogrammetric-based method to assess spatio-temporal gait parameters on healthy and Parkinsonian subjects
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Maranesi, E; Capitanelli, L.; Capecci, Marianna; Ghetti, G. G.; Mercante, O.; DI NARDO, Francesco; Burattini, Laura; Ceravolo, MARIA GABRIELLA; Fioretti, Sandro
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Generally, the study of gait requires the detection of successive heel contacts and toe-off instants. Traditional gait analysis methods obtain these gait events using dynamometric platforms together with stereophotogrammetric data. Usually, are kept valid only those walking trials where the subjects step on each platform by only one foot. For subjects suffering from walking impairments it is very difficult or sometimes impossible to walk naturally and step properly on the dynamometric platforms. The aim of the present study is to propose a new method to identify, in an automatic manner, the initial contact (IC) and the toe-off (TO) time instants using only stereophotogrammetric data and a classic gait analysis protocol. The assessment of spatio-temporal gait variables during natural walking is also performed. The study consisted in analyzing healthy and Parkinsonian elderly subjects. The reliability of the proposed stereophotogrammetric-based method was tested by direct comparison with the IC and TO instants determined by the dynamometric platform data. The absence of any statistically significant differences between the values estimated by the two different modalities, highlights the reliability of the proposed method in the assessment of these two gait events. Results underline, as expected, the reduction of walking velocity in pathological patients during free ambulation. The present study proposes this method as a valid alternative to the traditional technique that use dynamometric platforms to identify main gait events, for subjects unable to walk naturally and to step properly on the platforms.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/234691

Extraction of the fetal ECG in noninvasive recordings using a new method based on segmented-beat modulation
MBIDA - Proceedings of the International Workshop Mobile Networks for Biometric Data Analysis
Autore/i: Agostinelli, Angela; Giuliani, Corrado; DI NARDO, Francesco; Fioretti, Sandro; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205744

METODO PER IL FILTRAGGIO DI SEGNALI ELETTROCARDIOGRAFICI O SIMILI, IMPIEGABILE IN PARTICOLARE PER IL MONITORAGGIO DELLA FUNZIONALITA’ CARDIACA FETALE
Autore/i: Burattini, Laura; Agostinelli, Angela
Classificazione: 6 Brevetti
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/248994

An innovative approach to compute the Functional Ambulation Profile (FAP) Score
MBIDA - Proceedings of the International Workshop Mobile Networks for Biometric Data Analysis
Autore/i: Maranesi, Elvira; M., Petrini; G. G., Ghetti; O., Mercante; Burattini, Laura; DI NARDO, Francesco; Fioretti, Sandro
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The Functional Ambulation Profile (FAP) Score, a global parameter of gait, is a performance index which integrates selected time and distance parameters, obtained during a standard gait test. The FAP score ranges from 95 to 100 points in the healthy adult population. The first FAP score obtained in an automatic way is that provided by GAITRite Walkway System. The GAITRite system consists of a portable electronic mat embedded with pressure-activated sensors. The aim of this work was to develop the FAP score from data acquired by a classic stereophotogrammetric system, and to compare it with the one provided by GAITRite. Results underline as, during normal, slow, fast, small steps and foot-drop walking tests satisfactory results were ob-tained. Less satisfactory results were obtained in compromised walking, such as in fes-tinating or in spastic walking.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205335

A non-invasive assessment of variability in sEMG signals from lower limb muscles during gait
MBIDA - Proceedings of the International Workshop Mobile Networks for Biometric Data Analysis
Autore/i: Mengarelli, Alessandro; Maranesi, Elvira; Burattini, Laura; Fioretti, Sandro; DI NARDO, Francesco
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Surface electromyography (sEMG) is commonly used in gait analysis for detecting muscle activity in a non-invasive way, preserving the normal mobility of the subject. Aim of this study was to assess the variability of sEMG signals acquired from lower limb muscles during gait at self-selected speed and cadence, in terms of onset-offset muscular activation and frequency of occurrence. To this aim, a statistical analysis of sEMG signals from Tibialis Anterior, Gastrocnemius Lateralis, Rectus Femoris, Biceps Femoris and Vastus Lateralis was performed in twenty-two healthy young volunteers. Findings illustrated that a single muscle can show a different number of activation intervals in different strides of the same walk. Moreover, muscles showed activity also in phases of the gait cycle usually not reported in healthy adults that could be related to tasks different from the typical sagittal plane movement, as foot inversion, balance improvement during single support and control of joint dynamic stability. The concomitance of these results indicates a large variability in onset-offset muscular activation and occurrence frequency, which should be considered in discriminating pathological from physiological behaviour and for designing more focused gait studies.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205333

Functional Reach Test evaluated by wireless surface electromyography: a non-invasive assessment of fall risk in diabetic patients
MBIDA - Proceedings of the International Workshop Mobile Networks for Biometric Data Analysis
Autore/i: Maranesi, Elvira; Fioretti, Sandro; Burattini, Laura; DI NARDO, Francesco
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This study analyzed the Functional Reach Test used in the clinical practice to identify elderly subjects at risk of recurrent falls. This study was designed to assess the fall risk in diabetic neuropathic subjects by means a non-invasive analysis of muscle activation patterns involved in the FR test using a wireless surface electro-myography. A population of diabetic non-neuropathic subjects was also considered, as control group for neuropathy. Surface electromyographic analysis of Sternocleido-mastoideus (Scm), Rectus Abdominis (RAbd), Erectores Spinae at L4 level (L4), Rec-tus Femoris (RF), Hamstrings (Ham), Tibialis Anterior (TA) and Soleus (Sol) was per-formed to this aim. In CTRL subjects, TA was identified as the first motor, since it activates before the start of FR period; its action can be attributed to the anticipatory muscular activity necessary to initiate the body forward displacement. Then, a caudo-cranial activation sequence of the anterior muscles was observed. Sol and Ham, fol-lowed by L4, act mainly as tonic muscles, opposing the movement and preventing falls. Compared to the CTRL group, the DN subjects show an anticipatory recruitment of TA. Results suggest that the anticipatory postural adjustment patterns exerted dur-ing the FR task and the earlier activation of TA in the diabetic neuropathic subjects could be the predictor of a greater propensity of this groups to the fall compared to di-abetic without neuropathy.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205334

Preventing sudden cardiac death in sports: a novel monitoring service of the heart-rate variability trough wearable sensors
MBIDA - Proceedings of the International Workshop Mobile Networks for Biometric Data Analysis
Autore/i: Maranesi, Elvira; Morettini, Micaela; F., Palmieri; DI NARDO, Francesco; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205745

Adaptive Match-Filtering: A Biomedical Application to Identify T-Wave Alternans
NATURAL SCIENCE
Autore/i: Burattini, Laura; Giovanni, Ottaviano; DI NARDO, Francesco; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: T-wave alternans (TWA), consisting in an alternation of the electrocardiographic (ECG) repolari- zation segment (T-wave), is a promising index of the risk of sudden cardiac death. By definition, it is characterized by a frequency component, termed fTWA, that matches half heart rate. The heart- rate adaptive match filter (AMF) based method is a technique for automatic TWA identification from the digital ECG. Aim of the present study was to provide a complete technical description of the filter able to explain its methodological principles. The AMF is usually realized as a 6th order Butterworth filter with a narrow (0.12 Hz) passing band centered in fTWA. It is applied in a bidirec- tional fashion, so that final filtering order is 12. While extracting the TWA component, the AMF simultaneously filters out every ECG component including noise and artefacts, and thus results are very robust. Goodness of the technique was tested using 8 synthetic ECG tracings corrupted by typical noisy factors, such as white random noise, baseline wanderings, heart-rate variability, and others. Six ECG tracings were affected by 100 µV TWA, whereas two were not. Results indicate that the AMF-based method is able to prevent false-positive and false-negative detections and, thus, represents a useful tool for a reliable TWA identification.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205713

Ventricular Arrhythmias Assessment: a New Repolarization Index of Risk
Computing in Cardiology
Autore/i: Giuliani, Corrado; Ca, Swenne; S., Man; Agostinelli, Angela; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Defects in the cardiac repolarization are associated to cardiac electrical instability but no repolarization index has proven sufficient sensitivity and specificity to justify preventive interventions yet. Aim of the present study was to propose a new repolarization frequency-based index. termed 199, and to test its predictive power on exercise 15-lead (X, Y, Z, V1 to V6, I to III, aVr, a Vl, aVf) ECG recordings from 266 JCD patients, of which 76 developed ventricular tachycardia or fibrillation during the 4-year follow-up (ICD-Cases), and 190 did not (ICD-Controls). After performing the frequency-content evaluation of the repolarization signal (RPS) at the maximum heart-rate reached during exercise, f99 was computed as the frequency at which the RPS energy first reaches or overcomes 99%. Eventually, f99 single-lead values were maximized over lead-systems (MaxXYZ, MaxV1-V6 and Max12L), and predictive power of these parameters was evaluated as the area-under the receiver operating curve (AUC). Compared to the ICD-Controls, the ICD-Cases showed significantly higher values of MaxXYZ (38 vs. 27 Hz; AUC=0.61), MaxV1-V6 (42 vs. 33 Hz; AUC=0.60) and Max12L (46 vs. 37 Hz; AUC=0.65). Thus, the new f99 represents a promising tool to identify the risk of ventricular tachycardia or fibrillation, with Max12L showing the best predictive power.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205734

T-wave offset localization from 8 vs. 15 lead dominant T wave.
Proceeding of the 8th ESGCO conference
Autore/i: Giuliani, Corrado; Agostinelli, Angela; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205733

A goniometer-based method for the assessment of gait parameters
2014 IEEE/ASME 10th International Conference on Mechatronic and Embedded Systems and Applications (MESA)
Autore/i: Maranesi, Elvira; DI NARDO, Francesco; G., Ghetti; Burattini, Laura; Fioretti, Sandro
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Basic prerequisites for gait analysis are the assessment of spatiooral gait parameters and the analysis of movements within subsequent stride cycles. The aim of the present study is to propose a new method to assess spatiooral gait parameters using only 1-degree-of-freedom electrogoniometers positioned on hip and knee joints. The model validation is performed comparing the model results with those automatically obtained from another gait analysis system: GAITRite. The results underline the model reliability and show that the model could be a valid alternative to the traditional methods that use foot switches, ground reaction forces or accelerometers. These results show that essential spatiooral gait parameters can be determined during overground walking using only two 1-dof electrogoniometers. The method is easy-to-use and does not interfere with regular walking patterns.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205331

Use of the dominant T wave to enhance reliability of T-wave offset identification
JOURNAL OF ELECTROCARDIOLOGY
Autore/i: Agostinelli, Angela; Giuliani, Corrado; Burattini, Laura
Classificazione: 1 Contributo su Rivista
Abstract: T-wave offset (Toff) identification may be jeopardized by the presence of a significant inter-method (IMV) and inter-lead (ILV) Toff variability. Thus, aim of the present study was to investigate if the dominant T wave (DTW) may be used to enhance Toff-identification reliability. DTWs and 15-lead ECG T waves of 46 control healthy subjects (CHS) and 103 acute myocardial infarction patients (AMIP) were analyzed for Toff identification using the Zhang et al.’s (M1) and the Daskalov and Christov’s (M2) methods. Results indicate that IMV is significantly reduced when identifying Toff from the DTW rather than from single ECG leads in both populations (CHS: 5 ms vs. 5-15 ms; AMIP: 10 ms vs. 10-20 ms). Moreover, when analyzing ILV, Toff was found to be equivalent (correlation=0.71-0.98; P<10-14) to the median Toff among leads, but required only one identification instead of 15. Thus, the DTW can be used to enhance Toff-identification reliability.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/112863

Influence of gender on the myoelectric signal of shank muscles
2014 IEEE/ASME 10th International Conference on Mechatronic and Embedded Systems and Applications (MESA)
Autore/i: DI NARDO, Francesco; Mengarelli, Alessandro; Maranesi, Elvira; Burattini, Laura; Fioretti, Sandro
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The surface electromyographic (sEMG) signal is commonly utilized as principal input information to the controller of robotic systems, such as exoskeleton robots. It has been shown that sEMG signals could vary from subject to subject, and that gender is one of the factors influencing this variation. Thus, the goal of this study is to detect possible gender-related differences in the EMG activity of the two main ankle-flexor muscles (tibialis anterior, TA and gastrocnemius lateralis, GL) during gait at comfortable speed and cadence. The statistical analysis of surface EMG signals, performed in seven male (M-group) and seven female (F-group) age-matched adults, showed clear gender-related differences in the behavior of TA and GL. The estimation of the different activation modalities, indeed, permitted to detect that F-group choose a walking modality with a more elevated number of activations during gait cycle, compared to M-group. This suggests a propensity of females for a more complex recruitment of the muscles during gait. The novel information on gender-related differences provided here suggest considering a separate approach for males and females, in providing electromyographic signals as input information to the controller of exoskeleton robot.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205330

Extracting a clean ECG from a noisy recording: a new method based on segmented-beat modulation
Computing in Cardiology
Autore/i: Agostinelli, Angela; Giuliani, Corrado; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Electrocardiogram (ECG) testing is a common non-invasive diagnostic tool to identify heart diseases. Generally, an ECG recording is corrupted by different types of noise which may jeopardize clinical evaluation. Thus, aim of the present study is to introduce the new segmented-beat modulation method (SBMM) for extracting a clean ECG from a noisy recording. Each cardiac cycle (CC) is segmented into the QRS segment and the TUP segment, respectively independent and proportional to preceding RR interval. TUP-segment modulation is initially used to force all CC to have the same duration, in order to allow a template-beat computation as the median beat. Then, a clean ECG is obtained by concatenating the template-beat after TUP-segment demodulation in order to obtain reconstructed beats whose duration matches that of the corresponding beats in the original noisy recording. Optimization procedures are performed to compensate for small inter-beat morphological ECG variations independent from actual heart rate. SBMM was tested in two applications respectively involving an ECG corrupted by motion artifacts and an abdominal recording from a woman in labor. Results clearly demonstrate the SBMM ability to provide a clean, and thus clinically useful, ECG tracing from a noisy recording.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205743

Abnormal Repolarization in the Acute Myocardial Infarction Patients: A Frequency-Based Characterization
THE OPEN BIOMEDICAL ENGINEERING JOURNAL
Autore/i: Giuliani, Corrado; Agostinelli, Angela; Fioretti, Sandro; DI NARDO, Francesco; Burattini, Laura
Classificazione: 1 Contributo su Rivista
Abstract: Despite ST elevation having poor sensitivity for acute myocardial infarction (AMI), it remains the main electrocardiographic (ECG) repolarization index for AMI diagnosis. Aim of the present study was to propose a new f99 index, defined as the frequency at which the repolarization normalized cumulative energy reaches 99%, for ECG AMI discrimination from health with good sensitivity and good specificity. Evaluation of such f99 index was performed on 12-standard-lead (I, II, III, aV1, aVr, aVf, V1 to V6) ECG recordings of 47 healthy controls and 108 acute myocardial infarction (AMI) patients. Repolarization dispersion caused f99 distributions to be significantly lead dependent. In most leads (leads I, II, aVl, aVr, V2-V6), f99 median value was lower in the healthy controls (10-17 Hz) than in the AMI patients (12-38 Hz) indicating higher frequency components (i.e. a more fragmented repolarization) in the latter population. AMI patients from healthy controls discrimination by f99, evaluated in terms of sensitivity (Se) and specificity (Sp), was also lead dependent. Single-lead analysis indicated leads I (Se=80%, Sp=77%) and aVl (Se=84%, Sp=74%) as optimal. Instead, lead-system analysis, performed to overcome dispersion issues, provided the best results when averaging over the 6 precordial leads (Se= 81% and Sp=74%). In conclusion, our new f99 index appears as a promising tool for noninvasively and reliably discriminate AMI patients from healthy subjects.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205715

T-wave alternans rate of change with exercise for cardiac risk assessment
Computing in Cardiology
Autore/i: Burattini, Laura; S., Man; G., Ottaviano; Fioretti, Sandro; DI NARDO, Francesco; Ca, Swenne
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: T-wave alternans (TWA) amplitude is an index of risk for arrhythmic events. It increases with heart rate (HR) so that its evaluation is often performed under exercise. This study aims to investigate if TWA rate of change with HR can be also used for risk assessment. Our HR adaptive match filter for automatic TWA identification was applied to exercise ECG recordings of 266 ICD patients, 76 of which developed ventricular arrhythmias during the 4-year follow-up (ICD-Cases), and 190 did not (ICD-Controls). TWA amplitude was measured at 80 bpm (TWA80) and at 115 bpm (TWA115). Instead, TWA rate of change was evaluated as the ratio (TWAratio) and difference (TWAdiff) between TWA115 and TWA80. TWA predictive power was quantified as the area under the receiver operating curve (AUC) when discriminating the two ICD groups. Compared to ICD-Controls, ICD-Cases showed significantly higher TW A80 (22 μV vs. 16 μV) but not TWA115 (24 μV vs. 30 μV vs). The latter group also showed significantly lower TWAratio (1.05 vs. 1.63) and TWAdiff (1 μV vs. 11 μV). TWAratio showed the highest AUC (0.6914) followed by TWAdiff (0.6816), TWA80 (0.6414) and TWA115 (0.4547). Thus, TWA rate of change with HR provided better risk assessment for the occurrence of ventricular arrhythmias than TWA amplitude at both fast (115 bpm) and slow (80 bpm) HRs.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205741

Influence of gender on the myoelectric signal of thigh muscles
2014 IEEE/ASME 10th International Conference on Mechatronic and Embedded Systems and Applications (MESA)
Autore/i: DI NARDO, Francesco; Mengarelli, Alessandro; Maranesi, Elvira; Burattini, Laura; Fioretti, Sandro
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The surface electromyographic (EMG) signal is commonly used as main input information to the controller of robotic systems, such as exoskeleton robots. It has been shown that EMG signals could vary from person to person, and that gender is one of the factors influencing this variation. Thus, the aim of the present study is to detect possible gender-related differences in the EMG activity of the main thigh muscles (rectus femoris (RF), biceps femoris (BF) and vastus lateralis (VL), during gait at self-selected speed and cadence. The statistical analysis of surface EMG signals, performed in seven male (M-group) and seven female (F-group) age-matched adults, showed clear gender-related differences, in terms of frequency of occurrence, in the behavior of VL, and no relevant differences in the behavior of RF and BF. This suggests a propensity of females for a more complex recruitment of the muscles during gait, performed mainly by muscles involved in the motion of the lower leg joints. The novel informations on gender-related differences provided here suggest considering a separate approach for males and females, in providing electromyographic signals as input information to the controller of exoskeleton robot.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205329

T-wave alternans dependency on T-wave amplitude in exercise electrocardiographic recordings
INTERNATIONAL JOURNAL OF BIOELECTROMAGNETISM
Autore/i: Burattini, Laura; S., Man; Ca, Swenne
Classificazione: 1 Contributo su Rivista
Abstract: T-wave alternans (TWA), an electrophysiologic phenomenon which manifests as an every-other-beat alternation of the electrocardiographic (ECG) T-wave amplitude or shape, is generally associated to malignant ventricular arrhythmias and sudden cardiac death. TWA is usually identified with no adjustment for T-wave amplitude. However, a possible dependency of TWA on T-wave amplitude has been recently hypothesized. Evaluation of such dependency in exercise ECG tracings was the aim of the present work. Exercise ECG recordings from 58 patients with an implanted cardiac defibrillator were analyzed. TWA was identified using our heart-rate adaptive match filter based method, whereas T-wave amplitude was quantified as the absolute value of the ECG amplitude along the repolarization segment. Inter-patients and intra-patient (inter-leads) TWA dependency on T-wave amplitude was evaluated by computing the correlation coefficient (ρ) between the two quantities. Results indicate a weak (0.28≤ρ≤0.51, P<0.05) inter-patients association between TWA and T-wave amplitude, which were instead linked by a strong (r=0.86, P<0.05) intra-patient (inter-leads) association.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/84850

Abnormal repolarization discrimination by an innovative T-wave frequency index
EUROPACE
Autore/i: Giuliani, Corrado; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205757

Effect of exercise on T-wave alternans predictive power for the occurrence of ventricular arrhythmias
EUROPACE
Autore/i: Burattini, Laura; S., Man; Ca, Sweene
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205756

The power of exercise-induced T-wave alternans to predict ventricular arrhythmias in patients with implanted cardiac defibrillator
JOURNAL OF HEALTHCARE ENGINEERING
Autore/i: Burattini, Laura; S., Man; Ca, Swenne
Classificazione: 1 Contributo su Rivista
Abstract: Exercise-induced T-wave alternans (TWA) predictive power for the occurrence of ventricular arrhythmias was evaluated in 67 patients with an implanted cardiac defibrillator (ICD). During the 4-year follow-up, electrocardiographic (ECG) tracings were recorded while performing a bicycle ergometer test with increasing workload ranging from zero (NoWL) to the patient’s maximal capacity (MaxWL). After the follow-up, patients were classified as either ICD_Cases (n=29), if developed ventricular tachycardia/fibrillation, or ICD_Controls (n=38). TWA was quantified using our heart-rate adaptive match filter. Compared to NoWL, MaxWL was characterized by faster heart rates and higher TWA in both ICD_Cases (12-18 µV vs. 20-39 µV; P<0.05) and ICD_Controls (9-15 µV vs. 20-32 µV; P<0.05 ). Still, TWA was able to discriminate the two ICD groups during NoWL (sensitivity=59-83%, specificity=53-84%) but not MaxWL (sensitivity =55-69%, specificity=39-74%). Thus, this retrospective observational case-control study suggests that TWA predictive power for the occurrence of ventricular arrhythmias could increase at low heart rates.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/90661

Dependency of T-Wave Alternans Predictive Power for the Occurrence of Ventricular Arrhythmias on Heart Rate
Computing in Cardiology
Autore/i: Burattini, Laura; S., Man; Ca, Sweene
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: T-wave alternans (TWA), a promising index of cardiac electrical instability, is known to increase its amplitude (TWAA) with heart rate. Still, the effect of heart rate on the TWA predictive power for the occurrence of ventricular arrhythmias remains unclear. Thus, aim of the present study was to evaluate if fast heart rates, besides inducing higher amplitude TWA, also enhances TWA ability to discriminate patients at increased risk of major cardiac events. To this aim, our heart-rate adaptive match filter was used to measure TWA at 80 bpm and at 120 bpm in exercise ECGs of 266 lCD patients, 76 of which developed ventricular tachycardia or fibrillation during the 4-year follow-up (lCD_Cases), and 190 did not (lCD_Controls). TWA ability to discriminate lCD_Cases from lCD_Controls was evaluated using the area under the receiver operating characteristic (AUC). At 80 bpm TW AA was significantly higher in the lCD_Cases than the lCD_Controls (median: 23 mu V vs. 16 mu V, P= 0.0018; AUC= 0.672), whereas at 120 bpm TWAA was comparable in the two groups (median: 36 mu V for both the lCD_Cases and lCD_Controls; AUC= 0.487). Thus, in our lCD populations, TWA predictive power for the occurrence of ventricular arrhythmias was higher at 80 bpm, when TW AA was smaller, than at 120 bpm, when TW AA was higher.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/112865

T-Wave Alternans Identification in Routine Exercise ECG Tracings: Comparison of Methods
Computing in Cardiology
Autore/i: Bini, Silvia; Ca, Swenne; S., Man; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: T-wave alternans (TWA) is often measured in special exercise ECGs specifically made for TWA testing in order to minimize the noise level. Still, TWA utility in clinical evaluation would be magnified by the possibility of measuring it in routine standard exercise ECGs, usually affected by a high level of noise. Thus, aim of the present study was to evaluate the performances of 3 automatic TWA identification methods, namely the spectral (SM), the modified-moving-average (MMAM) and the adaptive-match-filter (AMFM) methods, on routine exercise ECGs with increasing heart rate (HR) of 46 implanted-cardiac-defibrillator patients (ICDP). TWA amplitude (TWAA) was measured in 1-min windows during the minimum (MinHR=83 +/- 12 bpm) and maximum (MaxHR=123 +/- 19 bpm) HR. At MinHR and MaxHR, the SM identified TWA in 12 and 23 ICDP, respectively (median TWAA: 4 mu V and 29 mu V, respectively; P<10(-3)), whereas the MMAM and AMFM identified TWA in all ICDP but the former method provided much higher median TWAA estimates (MinHR: 1507 mu V, MaxHR: 1602 mu V; P=0.5258) than the latter (MinHR: 22 mu V, MaxHR: 38 mu V; P<10(-4)). Eventually, only the SM and AMFM detected the expected significant TWAA increment at MaxHR. Thus, the AMFM appeared the most reliable method for TWA identification in routine exercise ECG recordings.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/112867

Use of Dominant T-wave to Reduce T-Wave Offset Location Uncertainty
Computing in Cardiology
Autore/i: Giuliani, Corrado; Agostinelli, Angela; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Abnormalities in the electrocardiographic (ECG) T wave are associated to sudden cardiac death. Despite the QT-interval prolongation being the standard marker of cardiac risk, its reliability is limited by the T-wave offset (Toff) uncertainty provided by different automatic methods. Thus, the aim of the present study was to evaluate if the dominant T wave (DTW) can be used to reduce Toff uncertainty. Our clinical data consisted of a sinus 15-lead ECG beat randomly extracted from ECG recordings of 36 control healthy subjects (CHS) and 62 acute myocardial infarction patients (AMIP). Toff, localized measuring its distance from the preceding R peak, was independently identified in the DTW and in each single-lead T wave by means of the Zhang et al. 's method (M1) and the Daskalov et al.'s method (M2). In both populations the distributions of the temporal distances between Toff values provided by the two techniques for the DTW showed a significantly lower median value than those measured over the 15 leads (CHS: 5 ms vs. 5-18 ms, respectively; AMIP: 10 ms vs. 10-20 ms, respectively), or a comparable median value but a significantly lower variability (CHS: 5 ms vs. 3-10 ms, respectively; AMIP: 5 ms vs. 5-13 ms, respectively). Thus, the use of the DTW allowed a significant reduction of Toff uncertainty.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/112866

T-wave frequency content evaluation in healthy subjects and patients affected by myocardial infarction
Signal Processing: New Research
Autore/i: Burattini, Laura; Giuliani, Corrado
Editore: Nova Science Publishers Inc.
Classificazione: 2 Contributo in Volume
Abstract: Abnormalities in the cardiac repolarization and, thus, in the electrocardiographic (ECG) T wave, are known to be associated to several cardiovascular diseases. For this reason, cardiac repolarization has recently became matter of major interest and several T-wave indexes have been proposed in the literature in the attempt to noninvasively discriminate pathological from healthy conditions. In the present chapter we designed two new indexes based on the T-wave frequency content at low and high frequencies, respectively. Abilities of such indexes in automatically detecting abnormal cases of repolarization were tested and compared using ECG recordings of 39 control healthy (CH) subjects and 39 acute myocardial infarction (AMI) patients. T-wave frequency evaluation was performed on the ECG vector magnitude signal (VMS) by computing the normalized power spectrum and the normalized energy according to the Fourier transformation. In both populations most of the T-wave frequency content was comprised within 10 Hz, frequency at which the normalized energy relative to the CH subjects and AMI patients reached 97.5±2.7% and 96.3±2.6%, respectively (P<0.01). Nevertheless, the normalized energy distribution relative to the two populations was significantly different. Indeed, the T-wave energy curve of the AMI patients was significantly (P<0.01) higher in correspondence of any frequency between 2 Hz and 5 Hz, due to a reduced repolarization variability observed over this frequency range. Consequently, the area under the normalized energy curve in the 2-5 Hz band (AUNE2-5) was found to be significantly greater for the AMI patients (AUNE2-5=248±15Hz) than the CH subjects (AUNE2-5=230±15 Hz; P<10-5), and allowed a discrimination between the two populations with a sensitivity and specificity of 79.5% and 74.4%, respectively. Instead, for frequencies comprised between 10 Hz and 35 Hz, the normalized T-wave energy curve of the AMI patients was significantly (P<0.01) lower than that of the CH subjects, due to an increased high-frequency variability observed in the AMI spectra. Thus, the area under the normalized energy curve in the 10-35 Hz band (AUNE10-35) was found to be significantly lower for the AMI patients (AUNE10-35=2467±32 Hz) than the CH subjects (AUNE10-35=2491±28 Hz; P<10-8), and allowed a discrimination between the two populations with a sensitivity and specificity of 94.9% and 74.4%, respectively. In conclusion, the differences in the T-wave frequency content of CH subjects and AMI patients can be described using our new AUNE2-5 and AUNE10-35 indexes. The latter, however, showed a greater ability to discriminate abnormal repolarization associated to the acute myocardial infarction.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/80536

Response to Dr. Madias’ comments on “T-wave alternans by a 16-lead Electrocardiogram System”
ANNALS OF NONINVASIVE ELECTROCARDIOLOGY
Autore/i: Burattini, Laura; Maan, S; Swenne, Ca
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/82195

Quantitative Characterization of Repolarization Alternans in Terms of Amplitude and Location: What Information from Different Methods?
BIOMEDICAL SIGNAL PROCESSING AND CONTROL
Autore/i: Bini, Silvia; Burattini, Laura
Classificazione: 1 Contributo su Rivista
Abstract: The qualitative definition of repolarization alternans (RA) as an every-other-beat alternation of the repolarization amplitude allows several possible quantitative characterizations of RA. In the absence of a standardization, any correct comparison among quantitative outputs by different automatic methods requires knowledge of the differences in the RA parameterization at the basis of their algorithms. Thus, aim of the present study was to investigate the kind of information provided by five methods, namely the fast Fourier spectral method (FFTSM), the complex demodulation method (CDM), the modified moving average method (MMAM), the Laplacian likelihood ratio method (LLRM) and the heart-rate adaptive match filter method (AMFM) when characterizing RA in terms of its amplitude and location. Eight synthetic ECG recordings affected by stationary RA with uniform and triangular profiles localized along the ST segment, over the T wave, at the end of the T wave and all along the JT segment, respectively, were considered. Results indicate that quantitative RA characterization is method dependent. More specifically, the FFTSM and the LLRM provide a measure that matches the root mean square of the RA profile over the JT segment. Instead, the CDM and the AMFM compute RA amplitude as the mean value of the RA profile over the JT segment. Eventually, the MMAM provides the maximum amplitude difference between consecutive beats along repolarization. RA location is homogeneously among methods, since they all provide the time instant in correspondence of which the center of mass of the alternation occurs.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/112862

T-wave alternans dependency on T-wave amplitude in exercise electrocardiographic recordings
Proceedings of the 7th International Workshop on Biosignal Interpretation
Autore/i: Burattini, Laura; Man, S; Swenne, Ca
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Abstract 00300040.pdf
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/80576

T-wave frequency content evaluation in healthy subjects and patients affected by myocardial infarction
Proceedings of the 7th International Workshop on Biosignal Interpretation
Autore/i: Giuliani, Corrado; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/80577

Automatic analysis of ECG repolarization alternans heterogeneity
GNB2012
Autore/i: Bini, Silvia; Burattini, Laura
Editore: Pàtron Editore
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/80574

Single-lead vs. 12 standard lead-system indexes for ECG T-wave alternans identification
GNB2012
Autore/i: Burattini, Laura; Man, S; Swenne, Ca
Editore: Pàtron Editore
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/80572

T-wave frequency content of healthy subjects and myocardial infarction patients
GNB2012
Autore/i: Giuliani, Corrado; Burattini, Laura
Editore: Pàtron Editore
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/80571

Characterization of repolarization alternans in coronary artery disease
Coronary Artery Diseases
Autore/i: Burattini, Laura; Burattini, Roberto
Editore: InTech, Open Access Publisher
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/61500

Is T-wave alternans T-wave amplitude dependent?
BIOMEDICAL SIGNAL PROCESSING AND CONTROL
Autore/i: Burattini, Laura; Zareba, W; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Abstract: The possible dependence of T-wave alternans (TWA) on T-wave amplitude was investigated in 3 orthogonal leads (X, Y, Z) 20-min resting ECG recordings and in the derived vector magnitude (VM) from 176 healthy (H) subjects and 200 coronary-artery-disease (CAD) patients. After application of our adaptive-match-filter based method for parameterization of TWA in terms of its amplitude (TWA_A) and product-magnitude (TWA_PM, defined as the product of TWA A times TWA duration), and once a TW_A parameter was defined for T-wave amplitude quantification, the existence of intra- and intersubjects relationships of TWA_A and TWA_PM vs. TW_A was tested. Compared to the H-population, the CAD-population showed a significant (P < 0.05) increase of TWA_A (62±38 V vs. 54±25 microV) and TWA_PM (4029±2974 beat microV vs. 3107±1976 beat microV) and a significant decrease of TW_A (298±194 microV vs. 467±246 microV). These repolarization changes, however, occurred with no significant intra- or intersubjects relationships of TWA_A and TWA_PM vs. TW_A. Thus, in our CAD and H populations there was no evidence of TWA dependence on T-wave amplitude.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/58263

Comparison of standard versus orthogonal ECG leads for T-wave alternans identification
ANNALS OF NONINVASIVE ELECTROCARDIOLOGY
Autore/i: Burattini, Laura; Man, S.; Burattini, Roberto; Swenne, C. A.
Classificazione: 1 Contributo su Rivista
Abstract: T-wave alternans (TWA), an electrophysiologic phenomenon associated with ventricular arrhythmias, is usually detected from selected ECG leads. TWA amplitude measured in the 12-standard and the 3-orthogonal (vectorcardiographic) leads were compared here to identify which lead system yields a more adequate detection of TWA as a noninvasive marker for cardiac ulnerability to ventricular arrhythmias. Our adaptive match filter (AMF) was applied to exercise ECG tracings from 58 patients with an implanted cardiac defibrillator, 29 of which had ventricular tachycardia or fibrillation during follow-up (cases), while the remaining 29 were used as controls. Two kinds of TWA indexes were considered, the single-lead indexes, defined as the mean TWA amplitude over each lead (MTWAA), and lead-system indexes, defined as the mean and the maximum MTWAA values over the standard leads and over the orthogonal leads. Significantly (P < 0.05) higher TWA in the cases versus controls was identified only occasionally by the single-lead indexes (odds ratio: 1.0–9.9, sensitivity: 24–76%, specificity: 76–86%), and consistently by the lead-system indexes (odds ratio: 4.5–8.3, sensitivity: 57–72%, specificity: 76%). The latter indexes also showed a significant correlation (0.65–0.83) between standard and orthogonal leads. Hence, when using the AMF, TWA should be detected in all leads of a system to compute the lead-system indexes, which provide a more reliable TWA identification than single-lead indexes, and a better discrimination of patients at increased risk of cardiac instability. The standard and the orthogonal leads can be considered equivalent for TWA identification, so that TWA analysis can be limited to one-lead system.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/66691

Repolarization alternans heterogeneity in healthy subjects and acute myocardial infarction patients.
MEDICAL ENGINEERING & PHYSICS
Autore/i: Burattini, Laura; Bini, Silvia; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Abstract: An association between heterogeneity of repolarization alternans (RA) and cardiac electrical instability has been reported. Characterization of RA in health and identification of physiological RA heterogeneity may help discrimination of abnormal RA cases more likely associated to arrhythmic events. Thus, aim of the present study was the identification of a physiological RA region in terms of mean temporal location (MRAD) with respect to the T apex, and mean amplitude (MRAA), by application of our heart-rate adaptive match filter method to clinical ECG recordings from 51 control healthy (CH) subjects and 43 acute myocardial infarction (AMI) patients. Results indicate that RA occurring within the first half of the T wave is dominant in both CH and AMI populations (74.5% and 53.5% of cases, respectively; P< 0.05). Definition of physiological RA region in the MRAD vs. MRAA plane (-83 ms ≤ MRAD ≤ 23 ms, 0 ≤ MRAA ≤ 30 μV) provided 0% and 32.6% abnormal RA cases among the CH subjects and AMI patients, respectively. We conclude that myocardial infarction may associate with an RA occurring early (MRAD < -83. ms) or late (MRAD > 23. ms) along the JT segment, in addition or in alternative to an abnormally high RA amplitude (MRAA > 30 μV).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/59921

Exercise‐induced Repolarization Alternans Heterogeneity in Patients with an Implanted Cardiac Defibrillator
Computing in Cardiology 2012
Autore/i: Burattini, Laura; Man, S.; Swenne, C. A.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Repolarization alternans (RA), generally recognized as a promising noninvasive index for risk stratification, is often measured under exercise conditions, since RA increases its amplitude with heart rate. Instead, the effect of exercise on the RA location along the JT interval is still unknown. Aim of the present study was to evaluate exercise-induced RA heterogeneity in terms of both amplitude and location. To this aim, we analyzed the ECG precordial leads of 36 patients with an implanted cardiac defibrillator (ICD) who underwent a bicycle ergometer test during which the working load was increased from zero (NoWL) to the patient's maximum capacity (MaxWL). RA was analyzed using our heart-rate adaptive match filter method, which provides an RA parameterization in terms of its amplitude (RAA, mu V) and location, the latter measured as time-delay (RAD, ms) with respect to the T-wave apex, so that positive values of RAD indicate RA occurring in the T-wave right side and vice versa. According to our results, during MaxWL, RAA was higher than during NoWL (34 +/- 21 mu V vs. 16 +/- 10 mu V; P< 10(-5)), whereas RAD was shorter (26 +/- 29 ms vs. 69 +/- 45 ms; P< 10(-4)). Thus, in ICD patients, exercise not only induced a significant increment of RA amplitude, but also caused RA location to move from very late in the repolarization segment toward the T-wave apex.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/80581

Response to the Letter to the Editor entitled “Temporal locations of repolarization alternans within the electrocardiogram JT-interval in patients with acute myocardial infarction and healthy subjects
MEDICAL ENGINEERING & PHYSICS
Autore/i: Burattini, Laura; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63315

A New T‐wave Frequency Based Index for Discrimination of Abnormal Repolarization
Computing in Cardiology 2012
Autore/i: Giuliani, Corrado; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Aim of the present study was to propose an innovative TCE10 index (defined as the T-wave cumulative normalized energy at 10 Hz, in %) as a useful tool to characterize the T wave in terms of its frequency content, and to test the TCE10 ability to discriminate abnormal cases of repolarization. To this aim, ECG recordings (X, Y, Z leads and vector-magnitude signal, VMS) of 23 control healthy (CH) subjects and 23 antero-septal acute myocardial infarction (ASAMI) patients were analysed. Abnormal repolarization was identified when TCE10 was below a threshold value, defined as the 25th percentile of the TCE10 distribution over the CH population. Results indicate that the ASAMI population was characterized by lower TCE10 values than the CH population (X: 93.9 +/- 5.9% vs. 98.2 +/- 1.2%; Y: 95.2 +/- 4.5% vs. 97.8 +/- 1.4%; Z: 97.4 +/- 1.6% vs. 99.1 +/- 1.5%; VMS: 95.7 +/- 2.8% vs. 97.9 +/- 1.3%; P<0.01). Moreover, the ASAMI patients were discriminated from the CH subjects with a lead-independent specificity of 74% and a lead-dependent sensitivity of 78%, 61%, 87% and 57% for lead X, Y, Z and VMS, respectively. In conclusion, compared to the CH subjects, the ASAMI patients show increased high-frequency spectral energy and were discriminated from the former with satisfactory values of sensibility and specificity.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/80580

Automatic microvolt T-wave alternans identification in relation to ECG interferences surviving preprocessing
MEDICAL ENGINEERING & PHYSICS
Autore/i: Burattini, Laura; Bini, S.; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Abstract: The aim was to investigate the effect of interferences surviving preprocessing (residual noise, baseline wanderings, respiration modulation, replaced beats, missed beats and T-waves misalignment) on automatic identification of T-wave alternans (TWA), an ECG index of risk for sudden cardiac death. The procedures denominated fast-Fourier-transform spectral method (FFTSM), complex-demodulation method (CDM), modified-moving-average method (MMAM), Laplacian-likelihood-ratio method (LLRM), and adaptive-match-filter method (AMFM) were applied to interferences-corrupted synthetic ECG tracings and Holter ECG recordings from control-healthy subjects (CH-group; n = 25) and acute-myocardial-infarction patients (AMI group; n = 25). The presence of interferences in simulated data caused detection of false-positive TWA by all techniques but the FFTSM and AMFM. Clinical applications evidenced a discrepancy in that the FFTSM and LLRM detected no more than one TWA case in each population, whereas the CDM, MMAM, and AMFM detected TWA in all CH-subjects and AMI-patients, with significantly lower TWA amplitude in the former group. Because the AMFM is not prone to false-positive TWA detections, the latter finding suggests TWA as a phenomenon having continuously changing amplitude from physiological to pathological conditions. Only occasional detection of TWA by the FFTSM and LLRM in clinics can be ascribed to their limited ability in identifying TWA in the presence of interferences surviving preprocessing.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/56745

Predictive Power of T-wave Alternans and of Ventricular Gradient 2 Hysteresis for the Occurrence of Ventricular Arrhythmias in Primary Prevention ICD Patients
JOURNAL OF ELECTROCARDIOLOGY
Autore/i: S., Man; P. V., De Winter; A. C., Maan; J., Thijssen; C. J., Borleffs; W. P., van Meerwijk; M., Bootsma; van Erven, L.; E. E., van der Wall; M. J., Schalij; Burattini, Laura; Burattini, Roberto; C. A., Swenne
Classificazione: 1 Contributo su Rivista
Abstract: Background and purpose: Left ventricular ejection fraction lacks specificity to predict sudden cardiac death in heart failure. T-wave alternans (TWA; beat-to-beat T-wave instability, often measured during exercise) is deemed a promising noninvasive predictor of major cardiac arrhythmic event. Recently, it was demonstrated that TWA during recovery from exercise has additional predictive value. Another mechanism that potentially contributes to arrhythmogeneity is exercise-recovery hysteresis in action potential morphology distribution, which becomes apparent in the spatial ventricular gradient (SVG). In the current study, we investigated the performance of TWA amplitude (TWAA) during a complete exercise test and of exercise-recovery SVG hysteresis (SVGH) as predictors for lethal arrhythmias in a population of heart failure patients with cardioverter-defibrillators (ICDs) implanted for primary prevention. Methods: We performed a case-control study with 34 primary prevention ICD patients, wherein 17 patients (cases) and 17 patients (controls) had no ventricular arrhythmia during follow-up. We computed, in electrocardiograms recorded during exercise tests, TWAA (maximum over the complete test) and the exercise-recovery hysteresis in the SVG. Statistical analyses were done by using the Student t test, Spearman rank correlation analysis, receiver operating characteristics analysis, and Kaplan-Meier analysis. Significant level was set at 5%. Results: Both SVGH and TWAA differed significantly (P < .05) between cases (mean ± SD, SVGH: -18% ± 26%, TWAA: 80 ± 46 μV) and controls (SVGH: 5% ± 26%, TWAA: 49 ± 20 μV). Values of TWAA and SVGH showed no significant correlation in cases (r = -0.16, P = .56) and in controls (r = -0.28, P = .27). Receiver operating characteristics of SVGH (area under the curve = 0.734, P = .020) revealed that SVGH less than 14.8% discriminated cases and controls with 94.1% sensitivity and 41.2% specificity; hazard ratio was 3.34 (1.17-9.55). Receiver operating characteristics of TWA (area under the curve = 0.699, P = .048) revealed that TWAA greater than 32.5 μV discriminated cases and controls with 93.8% sensitivity and 23.5% specificity; hazard ratio was 2.07 (0.54-7.91). Discussion and conclusion: Spatial ventricular gradient hysteresis bears predictive potential for arrhythmias in heart failure patients with an ICD for primary prevention, whereas TWA analysis seems to have lesser predictive value in our pilot group. Spatial ventricular gradient hysteresis is relatively robust for noise, and, as it rests on different electrophysiologic properties than TWA, it may convey additional information. Hence, joint analysis of TWA and SVGH may, possibly, improve the noninvasive identification of high-risk patients. Further research, in a large group of patients, is required and currently carried out by our group.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/55457

Prediction of Arrhythmias in Primary Prevention ICD Patients: Resting versus Exercise ECG
Computing in Cardiology 2011
Autore/i: S., Man; Burattini, Laura; J., Thijssen; Burattini, Roberto; P. V., de Winter; M., Bootsma; L., van Erven; E. E., van der Wall; M. J., Schalij; A. C., Maan; C. A., Swenne
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Ejection fraction and microvolt T-wave alternans (mTWA) lack specificity to predict sudden cardiac death in heart failure (HF). We compared resting ECG variables (QRS duration, lead-dependent T-amplitudes) and exercise-ECG-derived TWA variables (amplitude in the 12 leads, in the orthogonal X, Y, Z leads and in the vector magnitude) of 56 HF patients with an implanted cardioverter-defibrillator: cases and matched controls with/without antiarrhythmic therapy for VT/VF during follow up. Linear discriminant models, using resting and exercise ECG variables, were built in half of the study group, and were tested on the other half. QRS duration and TWA in lead Z discriminated best in the resting and exercise ECG, respectively, and had comparable diagnostic accuracy for VT/VF prediction.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/57494

Identification of repolarization-alternans time occurrence improves discrimination of abnormal cases
Computing in Cardiology 2011
Autore/i: Burattini, Laura; Burattini, Roberto
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Repolarization alternans (RA) is characterized by its amplitude and instant of occurrence along the JT segment, but only the amplitude is generally used to discriminate abnormal cases. The role of RA timing was focused in the present study. ECGs from 201 coronary-artery-disease (CAD) patients and 167 control-healthy (CH) subjects were analyzed by our heart-rate adaptive match filter (AMF) method to parameterize RA in terms of amplitude (RAA; mu V) and time distance (RAD; ms) from the T-wave apex, and to identify an RA normality region out of which abnormal cases (RA+) are expected to fall. Compared to our CH subjects, the CAD patients showed significant higher mean RAA (19 +/- 9 mu V vs. 17 +/- 15 mu V) and RAD variability (-33 +/- 37 ms vs. -27 +/- 23 ms). Especially, RA+ cases occurring abnormally early (RAD<-82 ms) or late (RAD>28 ms) were, overall, 29, more than twice of those (11) characterized by an abnormally high RAA (RAA>35 mu V).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/57493

Assessment of physiological T-wave alternans.
Congresso nazionale di Bioingegneria 2010 Atti
Autore/i: Burattini, Laura; Bini, S; Burattini, Roberto
Editore: patron
Luogo di pubblicazione: BOLOGNA
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/53672

T-wave alternans in healthy subjects: physiological oscillation or noise?
Proceeding of the 6th ESCGO 2010
Autore/i: Burattini, Laura; Bini, S.; Burattini, Roberto
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Proceeding of the 6th Conference of the European Study Group on Cardiovascular Oscillations Paper_ID:25
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50276

Automatic T-wave alternans identification in the presence of physiological noise
Congresso nazionale di bioingegneria 2010 atti
Autore/i: Bini, S; Burattini, Laura; Burattini, Roberto
Editore: Patron
Luogo di pubblicazione: BOLOGNA
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50881

T-Wave Alternans Quantification: Which Information from Different Methods?
Computing in Cardiology 2010
Autore/i: Burattini, Laura; Bini, S; Burattini, Roberto
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: T-wave alternans, qualitatively defined as every-otherbeat alternations of the T-wave morphology, has no standardized quantitative definition yet. Differences in quantitative information provided by the fast-Fouriertransform spectral method (FFTSM), the modifiedmoving- average method (MMAM), and our heart-rate adaptive match filter method (AMFM) were analyzed here making use of two synthetic ECG tracings with stationary TWA: triangular the first (TRI_TWA), with Twaves maximum-amplitude difference (AMAX) of 100 mu V and mean-amplitude difference (AMEAN) of 50 mu V; and uniform the second (UNI_TWA), with A(MAX)= A(MEAN)= 100 mu V. Application of FFTSM, MMAM, and AMFM to TRI_TWA yielded 57 mu V, 100 mu V, and 50 mu V TWA amplitude estimation, respectively. Instead, 100 mu V TWA amplitude was provided by each method after their application to UNI_TWA. Thus, FFTSM and AMFM provide estimates of AMEAN, while MMAM of AMAX.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/48569

Heart-rate adaptive match filter based procedure for automatic detection of T-wave alternans from 24-hour ECG recordings: Issues related to filter implementation
BIOSIGNAL 2010 Proceedings of Third International Joint Conference on Bio-inspired Systems and Signal Processing
Autore/i: Burattini, Laura; S., Bini; Burattini, Roberto
Editore: Ana Fred, Joaquim Filipe and Hugo Gamboa
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Twenty-four hour T-wave alternans (TWA) analysis is a promising approach for risk stratification, which still remains unpractical because TWA identification algorithms are complex and require long computation time (CT). The aim of the present study was to test the applicability to 24-hour ECG recordings of our heart-rate adaptive match filter (AMF) which allows TWA detection by submitting ECG data to a band-pass filter centered at the TWA fundamental frequency fTWA, equal to a half heart rate. Two implementations are possible: 1) the passing-band is adapted to a varying f TWA value (FA-AMF), and 2) the filter band is fixed while conditioning the ECG data (SA-AMF). Simulated ECG tracings, characterized by no TWA or by different kinds of TWA, and 24-hour ECG recordings from healthy subjects and coronary artery disease patients were used to identify the fastest of these two implementations. Our results yielded the conclusions that the CT of our AMF-based procedure is independent of the amount of TWA present in the tracing, but depends on ECG sample length and filter implementation. If filter-design tools are available while performing ECG analysis, the FA-AMF implementation is to be preferred because its CT is about one third of SA-AMF CT.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/55670

Identification of gender-related normality regions for T-wave alternans.
ANNALS OF NONINVASIVE ELECTROCARDIOLOGY
Autore/i: Burattini, Laura; Zareba, W; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Abstract: Background: T-wave alternans (TWA), a harbinger of sudden cardiac death, associates to a broad variety of pathologies. In a previous study, we observed the presence of unstable and low-amplitude TWA also in healthy subjects, and considered it as "physiological TWA." The possible existence of different TWA characteristics between males and female is investigated in the present work. Methods: Resting ECG recordings from 142 control healthy subjects, 77 males and 65 females, were submitted to our adaptive match filter (AMF) based method for TWA detection and characterization in terms of duration, amplitude, and their product. The 99.5th percentile of these parameters distributions over the entire control population and over the male and female subgroups, were used to define thresholds which delimit a gender-independent and male-and female-related TWA normality regions, respectively, out of which abnormal TWA cases (TWA+) are expected to fall. Clinical usefulness of these regions was tested using a population of 151 coronary artery disease (CAD) patients, divided into 128 males and 23 females. Results: In our control-female population, TWA duration was significantly longer than in control-male population (65 ± 13 beat vs 52 ± 14 beat; P < 10 -6). Our gender-related normality regions allowed identification of 36 (23.8%) TWA+ cases among the CAD patients, 17 more than those obtained from a gender-independent region. All these 17 patients were CAD males with over-threshold TWA duration. Conclusions: TWA is a gender-related phenomenon. Definition of gender-related TWA normality regions improves identification of patients at increased TWA stability (i.e., prolonged TWA duration) and, thus, at increased risk of arrhythmic events.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51980

Correlation method versus enhanced modified moving average method for automatic detection of T-wave alternans
COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE
Autore/i: Burattini, Laura; Bini, S; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Abstract: Enhanced modified moving average method (EMMAM) and correlation method (CM) for microvolt TWA identification are compared by aid of simulated ECG tracings (cases of absence of TWA and presence of stationary or time-varying TWA) and ECG recordings from healthy subjects (H-group) and patients who survived an acute myocardial infarction (AMI-group). The two competing methods were found to be equivalent when analyzing clean ECGs affected by stationary TWA. Non-stationary TWA is correctly tracked by the CM, whereas it is identified as stationary by the EMMAM. Moreover, the EMMAM suffers for its tendency to identify as TWA noise and other kinds of repolarization variability. Such limitation is most likely the cause of its false-positive TWA production. Finally, only the CM incorporates a local threshold criterion in the TWA detection algorithm which allows better discrimination between H and AMI groups, who are well known to be at increased risk to develop TWA.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51079

Response to Dr. Selvaraj’s comments on the “assessment of physiological amplitude, duration and magnitude of ECG T-wave alternans”
ANNALS OF NONINVASIVE ELECTROCARDIOLOGY
Autore/i: Burattini, Laura; Bini, S.; Zareba, W.; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/56747

Sensitivity of T-Wave Alternans Identification Algorithms to Residual Physiological Noise Affecting the ECG after Preprocessing.
Computing in Cardiology 2010
Autore/i: Bini, S; Burattini, Laura; Burattini, Roberto
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: To address the issue as to how and at what extent physiological noise that survives preprocessing affects TWA detection and quantification, a test was performed here on the fast-Fourier-transform spectral method (FFTSM), modified-moving-average method (MMAM), and adaptive-match-filter method (AMFM). These methods were applied to four synthetic ECG tracings respectively affected by no TWA, stationary TWA, and time-varying TWA. Absence and presence of physiological noise (from the MIT-BIH noise stress test database from the PhysioNet web site) were considered. Our results indicate that the FFTSM is robust to noise but has an intrinsic limitation in the precision of timevarying TWA quantification. Noise significantly affects TWA detection and quantification by the MMAM, while the AMFM offers a good compromise between robustness to noise and ability to identify both stationary and time varying TWA.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/48567

Comparative analysis of methods for automatic detection and quantification of microvolt T-wave alternans
MEDICAL ENGINEERING & PHYSICS
Autore/i: Burattini, Laura; Bini, S; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Abstract: Microvolt T-wave alternans (TWA), consisting of every-other-beat changes in ECG T-wave morphology, is an index of susceptibility to malignant ventricular arrhythmias, requiring automatic techniques to be identified. Five of these, namely, fast-Fourier-trans form spectral method (FFTSM), complex-demodulation method (CDM), modified-moving-average method (MMAM), Laplacian-likelihood-ratio method (LLRM) and adaptive-match-filter method (AMFM), were applied here to simulated and sample clinical data. The aim was to compare individual methods ability to properly identify stationary and time-varying TWA, avoiding false-positive detections. The MMAM provided false-positive TWA when applied to simulated ECGs affected by amplitude variability, but TWA. Stationary TWA was properly quantified by the MMAM and, occasionally, underestimated by all other methods. The AMFM properly identified time-varying TWA. By contrast, the FFTSM detected not-stationary TWA as stationary, the MMAM introduced a time-delay in the estimated TWA-amplitude signal, while the CDM and LLRM were reliable only in the presence of slow-varying TWA. Altogether, the AMFM accomplished the best compromise between the needs to avoid false-positive TWA and to detect and characterize true-positive TWA. Results of our simulation approach were useful to explain different TWA levels measured by each competing methods applied to sample Hotter ECGs from healthy subjects and coronary artery disease patients.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51066

Assessment of physiological amplitude, duration and magnitude of ECG T-wave alternans
ANNALS OF NONINVASIVE ELECTROCARDIOLOGY
Autore/i: Burattini, Laura; Zareba, W; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Abstract: Background: An association between T-wave alternans (TWA) and malignant ventricular arrhythmias is generally recognized. Because relatively low levels of TWA have also been observed in healthy (H) subjects, the question arises as to whether these are ascribable to noise and artifacts, or can be given the relevance of a physiological phenomenon characterizing a preclinical condition. Methods: To answer this question, in the present study 20-minute not noisy, sinus ECG recordings, from 138 H-subjects and 148 coronary artery diseased (CAD) patients, were submitted to our adaptive match filter (AMF) procedure to identify and parameterize TWA in terms of duration (TWAD), amplitude (TWAA), and magnitude (TWAM, defined as the product of TWAD times TWAA). The 99.5th percentiles of mean values of TWAA, TWAD, and TWAM over 20-minute ECGs were used to define three threshold levels (THRD, THRA, and THRM), which allow discrimination of abnormal TWA levels. Results: Nonstationary TWA was found in all our H-subjects and CAD-patients. TWAD, TWAA, and TWAM levels were classified as being physiological in 99% of H-subjects and 87% of CAD-patients. A linear correlation (r = -0.52, P < 0.001) was found between TWAA and RR interval in the H-population. Conclusions: Our results support the hypothesis of the existence of physiological TWA levels, which are to be considered in the effort to improve reliability of nonphysiological TWA levels discrimination.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51921

Adaptive match filter based method to discriminate risky from noise-ascribable T-Wave alternans
Congresso nazionale di bioingegneria 2008 Atti
Autore/i: Burattini, Laura; Zareba, W; Burattini, Roberto
Editore: Patron
Luogo di pubblicazione: BOLOGNA
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51591

Role of spatial dispersion in electrocardiographic T-wave alternans identification
JOURNAL OF ELECTROCARDIOLOGY
Autore/i: Burattini, Laura; Zareba, W; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Abstract: (ABST)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/53306

Comparison of adaptive match filter vs. correlation method to detect and characterize ECG T-wave alternans in clinics
5th Conference of teh European Study Group on Cardiovascular Oscillation
Autore/i: Burattini, Laura; Zareba, W; Burattini, Roberto
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Proceeding of the 5th Conference of European Study Group on Cardiovascular Oscillation
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/53570

Identification of time-varying T-wave alternans from 20-minute ECG recordings - Issues related to TWA magnitude threshold and length of ECG time series
Proceedings of BIOSIGNALS 2008
Autore/i: Burattini, Laura; W., Zareba; Burattini, Roberto
Editore: Pedro Encarnacao and Antonio Veloso
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Aim of this study was the assessment of a T-wave alternans (TWA) identification procedure based on application of an adaptive match filter (AMF) method, recently developed by ourselves, to a 20-minute digital ECG recording (ECG20). Three-lead ECG20 tracings from 35 patients who survived an acute myocardial infarction (AMI-group) and 35 healthy subjects (H-group) were analysed. The AMI-group showed, on average, increased levels of TWA (P<0.01). Considering that noise may cause false positive TWA detection, a threshold (THR(TWA)) was defined for TWA magnitude (TWAM) as the mean TWAM +2SD over the H-group. TWAM exceeding this threshold identified a TWA-positive (TWA+) subject as one at increased risk of sudden cardiac death. Fifteen (43%) AMI-patients vs. zero H-subjects were detected as TWA+. This result meets clinical expectation. TWA manifested as a non stationary phenomenon that could even be missed in all TWA+ subjects if our AMF (as well as any other technique) was applied to a single short-term 128-beat ECG series, as usually done in previous reports. In conclusion, our AMF-based TWA identification technique, applied to 20-minute ECG recordings, yields a good compromise between reliability of time-varying TWA identification and computational efforts.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/55666

Adaptive match filter based method for time vs. amplitude characterization of microvolt ECG T-wave alternans
ANNALS OF BIOMEDICAL ENGINEERING
Autore/i: Burattini, Laura; Zareba, W; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Abstract: To develop a new method for non-invasive identification of patients prone to ventricular tachyarrhythmia and sudden cardiac death, an adaptive match-filter (AMF) was applied to detect and characterize T-wave alternans (TWA) in 200 coronary artery diseased (CAD) patients compared with 176 healthy (H) subjects. TWA was characterized in terms of duration (TWAD), amplitude (TWAA), and magnitude (TWAM, defined as the product of TWAD times TWAA). A criterion derived from these parameters, estimated over the H-population, allowed discrimination between a risk (TWA+) and a normality (NO TWA) zone in the TWAD-TWAA plane. To gain further ability to discriminate among different risk levels, the TWA+ zone was divided into four sub-zones respectively characterized by low duration and low amplitude (LDLA), low duration and high amplitude (LDHA), high duration and low amplitude (HDLA), and high duration and high amplitude (HDHA). With our methodology, 21 CAD-patients (10.5%) were identified as TWA+, 9 falling in the LDLA zone, 4 in the HDLA, 7 in the LDHA, and 1 in the HDHA. These results are in agreement with clinical expectations and pave the way to further clinical follow-up studies finalized to analyze pathophysiological implications and risk factors associated to each TWA+ zone.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51714

Threshold criteria to identify clinically remarkable levels of ECG T-wave alternans
Proceedings of the Sixth IASTED International Conference on Biomedical Engineering
Autore/i: Burattini, Laura; W., Zareba; Burattini, Roberto
Editore: A. Hierlemann
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Automatic detection of T-wave alternans (TWA) from Holter ECG recordings is a non-invasive, clinically useful tool to identify patients at risk of malignant arrhythmias. A previously proposed time-domain approach, based on correlation method (CM), provides TWA characterization in terms of local measurements of single T-wave oscillation amplitudes, and global measurements of TWA-episode duration, amplitude, and magnitude (duration times amplitude). A local threshold criterion (LTC) implemented in CM algorithm is supposed to avoid false positive TWA (TWA+) due to noise. The present study was designed to set up a new global threshold criterion (GTC), based on TWA magnitude, to be contrasted to LTC. To this aim, the CM was applied to a population of 150 coronary artery diseased patients (CAD-group), who are known to show increased levels of TWA, compared with a control population of 150 healthy subjects (H-group). Our new GTC identified 28 TWA+ cases among CAD-patients and 1 among H-subjects, whereas, much higher numbers (119 CAD-patients and 61 H-subjects) were detected by LTC. High number of TWA+ among H-subjects is clinically unacceptable. Thus, involvement of GTC in the CM algorithm is decidedly more reliable for identification of TWA+ cases than LTC, which appears prone to false TWA+ prediction.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/55667

Heart-rate adaptive match filter based procedure to detect and quantify T-wave alternans
Computers in Cardiology
Autore/i: Burattini, Laura; Burattini, Roberto
Editore: IEEE Computer Society. INTERNET: http://www.computer.org
Luogo di pubblicazione: Los Alamitos, CA 90720
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Aim of the present study was to test our heart-rate adaptive match filter procedure for TWA analysis, which includes a) a heart-rate adaptive match filter, that filters out every ECG component but the TWA and quantifies TWA in terms of the duration (TWAD), amplitude (TWAA), and magnitude (TWAM, defined as TWAD × TWAA); and b) a statistical threshold criterion (STC) to identify, among all TWA detected cases, the ones (TWA+) most likely associated to an increased risk of sudden cardiac death. Our test, performed on the database assembled for the PhysioNet/Computers in Cardiology Challenge 2008, yielded the following results. On average, the data set was characterized by TWAD= 63±31 beats, TWAA= 48±77 μV, and TWAM= 3249±5107 beats μV. Based on our STC, TWA+ cases were 21, yielding a ranking score of 0.684. Use of STC, in the perspective of discriminating risky cases, among all detected TWA cases, might have limited our score.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/28439

Automatic detection of T-wave alternans in myocardial infarcted patients: role of magnitude threshold and ECG length
XIV Congresso Nazionale della Società Italiana di Ricerche Cardiovascolari. Programma e Atti
Autore/i: Burattini, Laura; Zareba, W; Burattini, Roberto
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: ABSTR
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52277

Heart-rate adapting match filter detection of T-wave alternans in experimental Holter ecg recordings
Proceedings of the Fifth IASTED International Conference, BIOMEDICAL ENGINEERING
Autore/i: Burattini, Laura; Zareba, W; Burattini, Roberto
Editore: ACTA Press
Luogo di pubblicazione: ZURICH
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: T-wave alternans (TWA) is an electrophysiological phenomenon associated with cardiac electrical instability. Recently we proposed a new heart-rate adapting match filter (AMF) to detect TWA in ECG tracings affected by baseline wanders. AMF performance was tested against the third-order spline (TOS) interpolation baselineremoval technique, the only other baseline-removal method proposed in literature for TWA-detection purposes. Using simulated data, we proved that our AMFmethod increased correct TWA identification by significantly reducing the number of TWA false-negative detections. The aim of the present study was to test AMF performance in Holter ECG recordings from 15 patients with acute myocardial infarction (AMI) and 15 healthy (H) subjects. Comparison with TOS was also made. Four AMI patients and two H subjects were identified as TWA-positive after application of AMF. By contrast, eight AMI patients (p<0.05) and nine H subjects (p<0.05) were identified as TWA-positive after application of TOS-method. According to clinical observations TWA is infrequent, especially in H-subjects. Thus, our results suggest that TOS-based technique may introduce falsepositive TWA detections. In conclusion, compared to TOS-method, our AMF-based method reduces both falsepositive (experimental study) and false-negative (simulation study) TWA detections, thus yielding an improvement over the TOS in the effectiveness of automatic TWA detection.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52171

Automatic detection of microvolt T-wave alternans in Holter recordings: Effect of baseline wandering
BIOMEDICAL SIGNAL PROCESSING AND CONTROL
Autore/i: Burattini, Laura; Zareba, W.; Burattini, Roberto
Classificazione: 1 Contributo su Rivista
Abstract: ECG deviations from the isoelectric line (baseline wandering) may affect a reliable detection of T-wave alternans (TWA), a phenomenon associated with increased risk of death. The present study was designed to demonstrate, making use of simulated ECG time series, that baseline wandering might cause erroneous TWA detection from TWA-free ECG tracings, or prevent correct TWA detection whenever TWA was present. Our simulated time series were obtained from a real ECG complex (0.75 s recording, sampled at 200 Hz) repeated 170 times. TWA was simulated by varying T-wave amplitude (10, 50, 100 and 500 μV) in a time window of 160 ms centered around the T-wave apex. TWA fundamental frequency was 0.67 Hz. Baseline fluctuations were simulated by sinusoidal waves of 0.1 mV amplitude and frequency of 0.30, 0.67 and 1.50 Hz, respectively. The presence of baseline oscillations at lower (0.30 Hz) and higher (1.50 Hz) frequency than TWA own frequency prevented TWA detection when TWA amplitude was lower or equal to that of baseline oscillations. TWA detection improved after removal of baseline oscillations by application of a third-order spline interpolation, only for frequencies lower than TWA frequency. For baseline oscillations at greater frequency than heart rate, however, spline interpolation became harmful. An improvement over the spline interpolation was obtained by a new heart-rate adapting match filter with a narrow bandwidth around TWA frequency, which allowed detection of TWA almost independently of baseline frequency components when these were different from TWA own frequency.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50091

The effect of baseline wandering in automatic T-wave alternans detection from Holter recordings
Computers in Cardiology 2006
Autore/i: Burattini, Laura; Zareba, W.; Burattini, Roberto
Editore: IEEE Computer Society. INTERNET: http://www.computer.org
Luogo di pubblicazione: Los Alamitos, CA 90720-1264
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: T-wave alternans (TWA) is an electrophysiologic phenomenon associated with an increased risk of death. ECG baseline wandering may prevent correct detection of TWA. The present study was designed to test the effectiveness of our newly developed heart-rate adaptive match filter (AMF) to remove baseline wanders and improve TWA detection. To this aim, both simulated and experimental (10 Holter ECGs of patients with acute myocardial infarction, AMI) data were used. Performance of our AMF was compared with that of a third-order spline (TOS) interpolation. In simulated data, AMF allowed correct detection of TWA almost independently of baseline frequency components, when these were different from TWA own frequency, whereas the TOS interpolation allowed TWA detection only for baseline frequencies lower than TWA frequency. Application of AMF to AMI patients allowed detection of TWA in 2 out of 10, whereas 10 out of 10 were detected as TWA-positive after application of the TOS (p<0.05). The two patients that resulted TWA-positive after AMF application were characterized by a larger number (p<0.05) of beats involved in the TWA episodes than the number detected by the TOS. Detection of TWA in 100% of AMI patients provided by the TOS-technique (suggesting the presence of false-positive), and presence of false-negative, as deduced from the simulation results, question the reliability of this method. Our AMF allows more reliable identification of TWA almost independently of baseline frequency components.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/59902

Power spectrum analysis of heart-rate variability in the young Zucker rat
Computers in Cardiology 2006
Autore/i: Burattini, Laura; Burattini, Roberto; Cogo, C. E.; Faelli, E.; Ruggeri, P.
Editore: IEEE Computer Society. INTERNET: http://www.computer.org
Luogo di pubblicazione: Los Alamitos, CA 90720-1264
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Cardiac autonomic control was studied in a group of five young hyperinsulinaemic, insulin resistant, Zucker fatty rats (ZFR) compared with a control group of five young Zucker lean rats (ZLR). Power spectrum analysis (PSA) of heart rate variability (HRV) was performed with autoregressive (AR) models. All rats were anaesthetised with sodium pentobarbital. Mean insulinaemia and glycaemia levels were 185±27 μU/ml and 159±38 mg/dl, respectively, in the ZFR, and reduced to 13±13 μU/ml (p<0.05) and 101±15 mg/dl (p<0.05), respectively, in the ZLR. No significant difference in basal blood pressure was found between the two groups. Analysis of power spectrum density, normalized by the total area, showed a marked reduction (p<0.05) in the peak amplitude of the high frequency (HF) component in the ZFR group. No significant difference was observed in the peak amplitude of low frequency (LF) component between the two strains. LF/HF ratio was higher (p<0.05) in the ZFR group. These results indicate that in the young ZFR, hyperinulinemia associates with altered sympathovagal balance in the autonomic cardiovascular control, before the onset of significant changes in both sympathetic nervous activity and blood pressure.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/59901

T Wave Alternans and T Wave Variability: Noninvasive indices of Vulnerability to Ventricular Tachyarrhytmias
Noninvasive Electrocardiology in Clinical Practice
Autore/i: Zareba, W; Couderc, Jp; Burattini, Laura
Editore: Futura Publishing Company
Luogo di pubblicazione: ARMONK, NY
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/41633

Stroke Unit: a Cardio-Cerebral Approach
CLINICAL AND EXPERIMENTAL HYPERTENSION
Autore/i: Bellagamba, G; Assouad, C; Balestrini, F; Burattini, Laura; Fratalocchi, N; Moretti, V; Pennacchietti, L; Postacchini, D.
Editore: Marcel Dekker Incorporated:270 Madison Avenue:New York, NY 10016:(800)228-1160, (212)696-9000, EMAIL: bookorders@dekker.com, INTERNET: http://www.dekker.com, Fax: (212)685-4540
Classificazione: 1 Contributo su Rivista
Abstract: Stroke units are special units where stroke patients receive, simultaneously, medical and physical treatment. Compared to general neurological and medical wards, stroke units show a significant reduction of short- and longtime mortality, and an improvement of long-term quality of life. Nevertheless, mortality in these units is still high (1-year mortality ∼32%; 5-year mortality ∼60%), and consequently, new approaches are needed to control stroke parameters during the acute phase, with the goal to reduce mortality rates. The philosophy of our stroke unit in Fermo (Italy), is to establish a strong association between heart and brain care by approaching each stroke patient as a cardiocerebral patient. In particular, we perform 12-lead Holter ECG monitoring, to prevent the vicious cycle affecting correct cerebral and cardiac functions, and to react to cardiac complications, mostly arrhythmias, that can worsen cerebral damage. Holter ECG monitoring allows a fast physiotherapeutic approach, a better evaluation of metabolic parameters, and collectively, a better global evaluation of the patient during the acute phase of disease. In two years of activity, 80 patients that were admitted to our stroke unit during 1998, and treated as cardio-cerebral patients, were followed-up. This combined treatment decreased the 1-year mortality rate by about 30%, in comparison with the 22% mortality rate reported in the literature. These results confirm the validity of stroke units, as well as of our approach based on cardio-cerebral control of each stroke patient.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/39927

ECG variability during an transitory cerebral ischemia: a case report
STROKE
Autore/i: Burattini, Laura; G., Bellagamba; F., Balestrini; N., Fratalocchi; L., Pennacchietti
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/82206

Repolarization Variability in 24-h Holter ECG Recordings
Computers in Cardiology 2000
Autore/i: Burattini, Laura; Bellagamba, G; Balestrini, F; Fratalocchi, N; Pennacchietti, L; DE BIE, J.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Repolarization variability (RV) is associated with an increased risk of arrhythmic events. RV is usually measured in short ECG recordings, which do not allow the detection of its potential circadian characteristics and the identification of the time when an arrhythmic event is likely to occur. The aim of our work was to develop and test a computer algorithm to measure RV in 24-hour Holter ECG recordings, and to look for associations between heart rate and RV in 12 patients showing isolated ectopic beats. From each 24-hour ECG, we selected and analyzed 48 128-beat ECG segments, one every 30 minutes. RV was measured analyzing the changes in the T-wave morphology. A RV index, that represents the mean value of the deviations of each consecutive T wave from a template, was computed for each ECG segment. The 48 RV indexes relative to an ECG finally provided information about the circadian trends of the RV signal.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/49277

Stroke unit: A cardio-cerebral approach
STROKE
Autore/i: G., Bellagamba; C., Assuad; F., Balestrini; Burattini, Laura; N., Fratalocchi; V., Moretti; L., Pennacchietti; D., Postacchini
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/82207

Beat-to-Beat Repolarization Variability in LQTS Patients with the SCN5A Sodium Channel Gene Mutation
PACING AND CLINICAL ELECTROPHYSIOLOGY
Autore/i: Couderc, Jp; Burattini, Laura; Zareba, W; Moss, Aj
Editore: Blackwell Publishing Limited:9600 Garsington Road, Oxford OX4 2DQ United Kingdom:011 44 1865 776868 , (781)388-8200, EMAIL: agentservices@oxon.blackwellpublishing.com, e-help@blackwellpublishers.co.uk, INTERNET: http://www.blackwellpublishing.com, Fax: 011 44 1865 714591
Classificazione: 1 Contributo su Rivista
Abstract: Current techniques evaluating beat-to-beat variability of repolarization rely on accurate determination of T wave endpoints. This study proposes a T wave endpoint-independent method to quantify repolarization variability in a standard 12-lead ECG using a wavelet transformation. Our method was used to identify repolarization variability in long QT syndrome patients (LQTS) with the SCN5A sodium channel gene mutation. Using wavelet transformations based on the second Gaussian derivative, we evaluated repolarization variability in 11 LOTS patients with the mutation, 13 noncarrier family members, and 28 unrelated healthy subjects. Time-domain repolarization variability parameters (SDRTo, SDRTm) and wavelet parameters describing temporal (beat-to-beat) variability of repolarization in time (TVT) and in amplitude (TVA) were analyzed. Reproducibility of wavelet parameters and relationship of wavelet-based variability with heart rate and preceding RR interval were investigated. The wavelet-based method quantified beat-to-beat variability of the entire repolarization segment (regardless of QT interval identification) providing insight into variability in repolarization morphology. Our method showed that SCN5A carriers have significantly increased repolarization variability in amplitude (23% +/- 24% vs 8 +/- 4%, P < 0.001) and in time (14 +/- 17 ms vs 3 +/- 2 ms, P < 0.004) compared to noncarriers. Variability of repolarization amplitude was found to be heart rate dependent with variability decreasing with increasing heart rate. Relative error describing reproducibility of TVA and TVT was less than or equal to 5% and less than or equal to 10%, respectively. Our method quantifies repolarization variability in amplitude and in time without the need to identify T or U wave endpoints, wavelet-detected repolarization variability contributes to phenotypic identification of SCN5A carriers, with more pronounced beat-to-beat variability in repolarization amplitude than in time.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/39929

Correlation Method for Detection of Transient T-Wave Alternans in Digital ECG Recordings
ANNALS OF NONINVASIVE ELECTROCARDIOLOGY
Autore/i: Burattini, Laura; Zareba, W; Moss, Aj
Editore: -MALDEN:WILEY-BLACKWELL PUBLISHING, INC. -Armonk, N.Y. : Futura Pub. Co., c1996-
Classificazione: 1 Contributo su Rivista
Abstract: Background: Spectral and complex demodulation methods for detection of microvolt T-wave alternans (TWA) have limited ability to identify transient (nonstationary) TWA episodes. We aimed to develop and test new time-domain technique allowing TWA detection and quantification in as few as 7 consecutive beats from sinus rhythm ECGs. Methods and Results: Quantification of TWA during sinus rhythm required preprocessing consisting of: low-pass filtering, RR stability testing, baseline and respiratory modulation removal, and T-wave windowing and synchronization. Our time-domain correlation method (CM) detects TWA by computing, for each consecutive T wave, an alternans correlation index based on a cross-correlation technique. CM allows quantitative analysis of the amplitude, duration, and overall magnitude of the TWA episode. The technical performance of CM was confirmed in testing with simulated TWA of varying amplitude, duration, and noisy conditions. The clinical performance of CM was demonstrated by analyzing digital Holter recordings of 39 long QT syndrome patients compared to 36 healthy subjects. CM identified TWA in 17 (44%) patients with nonstationary TWA detected in 8. Conclusion: Our computer algorithms consisting of ECG preprocessing and TWA quantification by the correlation method provides the opportunity to detect nonstationary and stationary TWA in sinus rhythm of digital Holter ECG recordings.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/39928

What is the Minimum ECG Length to Quantify Beat-to-Beat Variability of Repolarization Morphology?
Computers in Cardiology 1999
Autore/i: Burattini, Laura; Zareba, W; Bellagamba, G.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Beat-to-beat changes in ventricular repolarization are associated with increased vulnerability to ventricular arrhythmias. Beat-to-beat repolarization variability (RV) is usually measured by, computing consecutive QT or RT intervals, which strongly depend on the definition of the T-wave endpoints. In this study MT describe our new method or measuring RV based on the morphological analysis of the repolarization segment and determine the minimal ECC length needed to quantify RV RV was analyzed in 42 ischemic cardiomyopathy patients. For each one, we analyzed ECGs of 8,16,32,64,96 and 128 consecutive beats from Holter ECG recordings. We found that our method provides a new approach to quantify RT without the need to identify T- wave endpoints. In addition, both long-term and short-term ECGs can be used to defect RI: but only long-term ECGs provide information about time changes of the RV signal.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/49220

Time-Domain Analysis of Beat-to-Beat Variability of Repolarization Morphology in Patients with Ischemic Cardiomyopathy
JOURNAL OF ELECTROCARDIOLOGY
Autore/i: Burattini, Laura; Zareba, W.
Editore: W B Saunders Company:Fulfillment Department, The Curtis Center, Independence Square West:Philadelphia, PA 19106:(800)654-2452, (215)238-7800, EMAIL: wbspcs@harcourt.com, INTERNET: http://elsevierhealth.com, Fax: (215)238-6445
Classificazione: 1 Contributo su Rivista
Abstract: There is growing evidence that beat-to-beat changes in ventricular repolarization contribute to increased vulnerability to ventricular arrhythmias. Beat-to-beat repolarization variability is usually measured in the electrocardiogram (ECG) by tracking consecutive QT or RT intervals. However, these measurements strongly depend on the accurate identification of T-wave endpoints, and they do not reflect changes in repolarization morphology. In this article, we propose a new computerized time-domain method to measure beat-to-beat variability of repolarization morphology without the need to identify T-wave endpoints. The repolarization correlation index (RCI) is computed for each beat to determine the difference between the morphology of repolarization within a heart-rate dependent repolarization window compared to a template (median) repolarization morphology. The repolarization variability index (RVI) describes the mean value of repolarization correlation in a studied ECG recording. To validate our method, we analyzed repolarization variability in 128-beat segments from Holter ECG recordings of 42 ischemic cardiomyopathy (ICM) patients compared to 36 healthy subjects. The ICM patients had significantly higher values of RVI than healthy subjects (in lead X: 0.045 ± 0.035 vs. 0.024 ± 0.010, respectively; P < .001); 18 (43%) ICM patients had RVI values above the 97.5th percentile of healthy subjects (>0.044). No significant correlation was found between the RVI values and the magnitude of heart rate, heart rate variability, QTc interval duration, or ejection fraction in studied ICM patients. In conclusion, our time-domain method, based on computation of repolarization correlation indices for consecutive beats, provides a new approach to quantify beat-to- beat variability of repolarization morphology without the need to identify T- wave endpoints.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/39930

Detection of Non-Stationary T-Wave Alternans: New Correlation Method Compared to Spectral Method
JOURNAL OF ELECTROCARDIOLOGY
Autore/i: Burattini, Laura; Zareba, W; Couderc, Jp; Moss, Aj
Classificazione: 1 Contributo su Rivista
Abstract: (ABSTR)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/39204

Identification of T-Wave Alternans: Review of Methods and Clinical Perspectives
Rhythm control from cardiac evaluation
Autore/i: LOCATI HEIBRON, E; Burattini, Laura; Zareba, W.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Proceeding of the VI Southern Symposium on Cardiac Pacing
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/41417

Microvolt T Wave Alternans in LQTS Patients with the SCN5A Sodium Channel Gene Mutation
CIRCULATION
Autore/i: Burattini, Laura; Zareba, W; Konecki, Ja; Moss, Aj
Classificazione: 1 Contributo su Rivista
Abstract: (ABSTR)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/39205

ECG Features of Microvolt T-Wave Alternans in Coronary Artery Disease and Long QT Syndrome Patients
JOURNAL OF ELECTROCARDIOLOGY
Autore/i: Burattini, Laura; Zareba, W; Rashba, Ej; Couderc, Jp; Konecki, Ja; Moss, Aj
Editore: W B Saunders Company:Fulfillment Department, The Curtis Center, Independence Square West:Philadelphia, PA 19106:(800)654-2452, (215)238-7800, EMAIL: wbspcs@harcourt.com, INTERNET: http://elsevierhealth.com, Fax: (215)238-6445
Classificazione: 1 Contributo su Rivista
Abstract: T-wave alternans (TWA) is a marker of myocardial electrical instability. We compared ECG features of microvolt TWA in coronary artery disease (CAD) and long QT syndrome (LQTS) patients. Method. The study populations consisted of 43 CAD and 39 LQTS patients. TWA was detected in resting Holter recordings using the new correlation method (CM). After preprocessing to adjust for RR variability and respiratory modulation, CM was used to quantify TWA amplitude (A(CM)), duration (N-CM), and magnitude (MAG(CM); defined as the product of A(CM) and N-CM). Results. TWA was detected in 19 (44%) CAD and 17 (44%) LQTS patients. TWA was associated with longer RR intervals (P = 0.006) and had larger magnitudes (P = 0.067) in LQTS than CAD patients. The TWA was identified as transient (nonstationary) in 15 of 19 (79%) TWA-positive CAD patients, and in 8 of 17 (47%) TWA-positive LQTS patients (P = 0.047). Conclusions. The frequency of TWA detected with CM is similar in LQTS and CAD patients. TWA is larger in LQTS than in CAD patients, whereas TWA is more frequently transient (nonstationary) in LAD than LQTS patients. In LQTS patients, but not in CAD patients, a longer RR is associated with TWA, indicating different electrophysiologic mechanisms in the two pathologies.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/39931

Beat-to-Beat Repolarization Variability in Amplitude and Duration in LQTS Patients with the SCN5A Sodium Channel Gene Mutation
JOURNAL OF ELECTROCARDIOLOGY
Autore/i: Couderc, Jp; Zareba, W; Burattini, Laura; Konecki, Ja; Moss, Aj
Classificazione: 1 Contributo su Rivista
Abstract: (ABSTR)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/39206

Non-Stationarity of Microvolt T Wave Alternans in Long QT Syndrome Patients
JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY
Autore/i: Burattini, Laura; Zareba, W; Couderc, Jp; Konecki, Ja; Moss, Aj
Classificazione: 1 Contributo su Rivista
Abstract: (ABSTR)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/39203

Optimizing ECG Signal Sampling Frequency for T-Wave Alternans Detection
Computers in Cardiology 1998
Autore/i: Burattini, Laura; Zareba, W; Couderc, Jp; Konecki, Ja; Moss, Aj
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Computer detection of microvolt T-wave alternans (TWA) is an non-invasive method to identify patients at high risk for ventricular arrhythmias. Since TWA is a transient phenomenon, there is the need for continuous long-term TWA analysis in Holter ECG recordings. TWA detection, usually detected in ECGs sampled at 1000 samples per second (sps), in computationally demanding. We determined the ability of our correlation method (CM) to identify TWA in ECGs sampled at lower frequencies. TWA was identified in 39 long QT syndrome patients, whose ECGs were originally acquired at 1000 sps, and then resampled at 100, 250, 500, and 750 sps. Results obtained at different sampling conditions were compared. We found that TWA can be effectively detected with the CM using sampling frequencies as low as 250 sps. Such sampling frequency seems to be optimal since it provides high accuracy of TWA measurements and substantial saving of computational time.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/49219