Pedro David Arini

Novel set of vectorcardiographic parameters for the identification of ischemic patients

New signal processing techniques have enabled the use of the vectorcardiogram (VCG) for the detection of cardiac ischemia. Thus, we studied this signal during ventricular depolarization in 80 ischemic patients, before undergoing angioplasty, and 52 healthy subjects with the objective of evaluating the vectorcardiographic difference between both groups so leading to their subsequent classification. For that matter, seven QRS-loop parameters were analyzed, i.e.: (a) Maximum Vector Magnitude; (b) Volume; (c) Planar Area; (d) Maximum Distance between Centroid and Loop; (e) Angle between XY and Optimum Plane; (f) Perimeter and, (g) Area-Perimeter Ratio. For comparison, the conventional ST-Vector Magnitude (ST(VM)) was also calculated. Results indicate that several vectorcardiographic parameters show significant differences between healthy and ischemic subjects. The identification of ischemic patients via discriminant analysis using ST(VM) produced 73.2% Sensitivity (Sens) and 73.9% Specificity (Spec). In our study, the QRS-loop parameter with the best global performance was Volume, which achieved Sens=64.5% and Spec=74.6%. However, when all QRS-loop parameters and ST(VM) were combined, we obtained Sens=88.5% and Spec=92.1%. In conclusion, QRS loop parameters can be accepted as a complement to conventional ST(VM) analysis in the identification of ischemic patients.

Novel technique for ST-T interval characterization in patients with acute myocardial ischemia

BACKGROUND The novel signal processing techniques have allowed and improved the use of vectorcardiography (VCG) to diagnose and characterize myocardial ischemia. Herein, we studied vectorcardiographic dynamic changes of ventricular repolarization in 80 patients before (control) and during Percutaneous Transluminal Coronary Angioplasty (PTCA). METHODS We propose four vectorcardiographic ST-T parameters, i.e., (a) ST Vector Magnitude Area (aSTVM); (b) T-wave Vector Magnitude Area (aTVM); (c) ST-T Vector Magnitude Difference (ST-TVD), and (d) T-wave Vector Magnitude Difference (TVD). For comparison, the conventional ST-Change Vector Magnitude (STCVM) and Spatial Ventricular Gradient (SVG) were also calculated. RESULTS Our results indicate that several vectorcardiographic parameters show significant differences (p-value<0.05) before starting and during PTCA. Statistical minute-by-minute PTCA comparison against the control situation showed that ischemic monitoring reached a sensitivity=90.5% and a specificity=92.6% at the 5th minute of the PTCA, when aSTVM and ST-TVD were used as classifiers. CONCLUSIONS We conclude that the sensitivity and specificity for acute ischemia monitoring could be increased with the use of only two vectorcardiographic parameters. Hence, the proposed technique based on vectorcardiography could be used in addition to the conventional ST-T analysis for better monitoring of ischemic patients.

Analysis of QRS loop changes in the beat-to-beat Vectocardiogram of ischemic patients undergoing PTCA

In the present work, we have studied dynamic changes of QRS loop in the Vectocardiogram (VCG) of 80 patients that underwent Percutaneous Transluminal Coronary Angioplasty (PTCA). The VCG was obtained for each patient using the XYZ orthogonal leads of their electrocardiographic (ECG) records acquired before, during and after PTCA procedure. In order to analyze the variations of VCG, it has been proposed in this study the following parameters a) Maximum module of the cardiac depolarization vector, b) Volume, c) and Area of vectocardiographic loop corresponding to the QRS complex of each beat, d) Maximum distance between Centroid and the Loop, e) Angle between the XY plane and the Optimum Plane, f) Relation between the Area and Perimeter. The results obtained indicate that the parameters proposed show significant statistics differences (p-value<0.05) before, during (with some exceptions at the first minute of balloon inflation) and after PTCA. We conclude that the variations observed in the proposed parameters correctly represent not only the morphological changes in the depolarization VCG but also they reflect the modifications in the levels of cardiac ischemia induced by PTCA.

Influence of Filtering Techniques on the Time-Domain Analysis of Signal-Averaged P Wave Electrocardiogram

Differences in P Wave Filtering Techniques. introduction: The advent of signal‐averaged ECG (SAECG) systems for P wave analysis has made it important to determine if the use of different filtering techniques in these systems is diagnostically equivalent.

Acute myocardial ischemia monitoring before and during angioplasty by a novel vectorcardiographic parameter set

BACKGROUND This work evaluates the vectorcardiographic dynamic changes in ischemic patients before and during Percutaneous Transluminal Coronary Angioplasty (PTCA). METHODS Four QRS-loop parameters were computed in 51 ischemic and 52 healthy subjects with the objective of assessing the vectorcardiographic differences between both groups: maximum vector magnitude (QRS(mVM)), planar area (QRS(PA)), maximum distance between centroid and loop (QRS(mDCL)) and perimeter (QRS(P)).The conventional ST-change vector magnitude (STC(VM)), QRS-vector difference (QRS(VD)) and spatial ventricular gradient (SVG) were also calculated. RESULTS Statistical minute-by-minute PTCA comparison against a healthy population showed that ischemic patients monitoring is greatly enhanced when all the QRS-loop parameters, in combination with the standard STC(VM), QRS(VD) and SVG indexes, are used in the classification. Sensitivity and Specificity, in turn, reached rather high values, 95.4% and 95.2%, respectively. CONCLUSIONS These new vectorcardiographic set of complementary QRS-loop parameters, when combined with the classics STC(VM), QRS(VD) and SVG indexes, increase sensitivity and specificity for acute ischemia monitoring.

Probability of ventricular fibrillation: allometric model based on the ST deviation

BackgroundAllometry, in general biology, measures the relative growth of a part in relation to the whole living organism. Using reported clinical data, we apply this concept for evaluating the probability of ventricular fibrillation based on the electrocardiographic ST-segment deviation values.MethodsData collected by previous reports were used to fit an allometric model in order to estimate ventricular fibrillation probability. Patients presenting either with death, myocardial infarction or unstable angina were included to calculate such probability as, VFp= δ + β (ST), for three different ST deviations. The coefficients δ and β were obtained as the best fit to the clinical data extended over observational periods of 1, 6, 12 and 48 months from occurrence of the first reported chest pain accompanied by ST deviation.ResultsBy application of the above equation in log-log representation, the fitting procedure produced the following overall coefficients: Average β = 0.46, with a maximum = 0.62 and a minimum = 0.42; Average δ = 1.28, with a maximum = 1.79 and a minimum = 0.92. For a 2 mm ST-deviation, the full range of predicted ventricular fibrillation probability extended from about 13% at 1 month up to 86% at 4 years after the original cardiac event.ConclusionsThese results, at least preliminarily, appear acceptable and still call for full clinical test. The model seems promising, especially if other parameters were taken into account, such as blood cardiac enzyme concentrations, ischemic or infarcted epicardial areas or ejection fraction. It is concluded, considering these results and a few references found in the literature, that the allometric model shows good predictive practical value to aid medical decisions.

Measurement of QT interval and duration of the QRS complex at different ECG sampling rates

The precise measurement of QT interval and QRS complex duration is important to characterize the electrical cardiac activity of the surface ECG. Variations of these intervals were evaluated when ECG sampling rate changes. The ECG recordings used in this study (n=78) were obtained from a combination of pharmacological blockage and postural changes. The ECG recordings were originally sampled at 500 Hz, and then were down-sampled by intervals of 25 Hz until the minimum sampling rate of 75 Hz. In all cases the down-sampling was implemented using cubic spline interpolation. The QRS complex duration, RR and QT intervals for each subject, condition and sampling rate were measured. The QT interval was corrected using two different techniques: Bazzett and individualized QT corrections. The effect of the sampling rate was modeled with an exponential decay function, which was used later to measure where the exponential reaches an asymptotic value (at 5tau). The 5tau value for uncorrected QT was at 290 Hz, corrected QT with Bazzett was at 303 Hz, and corrected QT with Individual method was at 253 Hz, finally QRS complex duration was at 297 Hz. An overestimation of the QT interval and QRS complex duration was observed when decreasing the sampling rate below 300 Hz

Evaluation of ventricular repolarization dispersion during acute myocardial ischemia: spatial and temporal ECG indices

In this work, we studied the evolution of different electrocardiogram (ECG) indices of ventricular repolarization dispersion (VRD) during acute transmural myocardial ischemia in 95 patients undergoing percutaneous coronary intervention (PCI). We studied both temporal indices of VRD (T-VRD), based on the time intervals of the ECG wave, and spatial indices of VRD (S-VRD), based on the eigenvalues of the spatial correlation matrix of the ECG. The T-wave peak-to-end interval ITPE index showed statistically significant differences during left anterior descending artery and right coronary artery (RCA) occlusion for almost the complete time course of the PCI procedure with respect to the control recording. Regarding S-VRD indices, we observed statistically significant increases in the ratio of second to the first eigenvalue IT21, the ratio of the third to the first eigenvalue IT31 and the T-wave residuum ITWR during RCA occlusions. We also found a statistically significant increase in the IT31 during left circumflex artery occlusions. To evaluate the evolution of VRD indices during acute ischemia, we calculated the relative change parameter RI for each index I. Maximal relative changes (RI) during acute ischemia were found for the S-VRD indices IT21, the first eigenvalue Iλ1 and the second eigenvalue Iλ2, with changes 64, 57 and 52 times their baseline range of variation during the control recording, respectively. Also, we found that relative changes with respect to the baseline were higher in patients with T-wave alternans (TWA) than in those without TWA. In conclusion, results suggest that ITPE as well as IT21, IT31 and ITWR are very responsive to dispersion changes induced by ischemia, but with a behavior which very much depends on the occluded artery.

Analysis of QRS loop in the Vectorcardiogram of patients with Chagas' disease

In the present work, we have studied the QRS loop in the Vectorcardiogram (VCG) of 95 chronic chagasic patients classified in different groups (I, II and III) according to their degree of myocardial damage. For comparison, the VCGs of 11 healthy subjects used as control group (Group O) were also examined. The QRS loop was obtained for each patient from the XYZ orthogonal leads of their High-Resolution Electrocardiogram (HRECG) records. In order to analyze the variations of QRS loop in each detected beat, it has been proposed in this study the following vectorcardiographic parameters a) Maximum magnitude of the cardiac depolarization vector, b) Volume, c) Area of QRS loop, d) Ratio between the Area and Perimeter, e) Ratio between the major and minor axes of the QRS loop and f) QRS loop Energy. It has been found that one or more indexes exhibited statistical differences (p<0.05) between groups 0-II, O-III, I–II, I–III and II–III. We concluded that the proposed method could be use as complementary diagnosis technique to evaluate the degree of myocardial damage in chronic chagasic patients.

Geometrical and temporal ECG features for quantification of increased ventricular repolarization dispersion in an experimental heart rabbit model

Abnormal increase of ventricular repolarization dispersion (VRD) is an important risk factor for severe arrhythmia development. An increased VRD implies a modification of the spatio/temporal T wave morphology. Our objective is to study the ECG derived VRD feature markers that better represent the electrical modifications generated by increased VRD in an in vitro rabbit heart experiment which has global VRD induced, at all myocardium areas, by supplying d-Sotalol (dS) and by premature ventricular stimulation (PVS). Temporal (T-wave duration, T W) and geometrical (mean repolarization axis, ThetaXT , measured respect to a fix reference X axis) features were shown as the better markers of increased VRD, with the higher discrinant power in the T wave duration. Results are: TW:(95plusmn7 ms) vs (118plusmn15 ms) for Control vs PVS; TW:(78plusmn10 ms) vs (133plusmn29 ms) for Control vs dS; ThetaXT-(35plusmn51deg) vs (117plusmn49deg) for Control vs dS