Pedro Gomis

Analysis of abnormal intra-QRS potentials : Improved predictive value for arrhythmic events with the signal-averaged electrocardiogram

BACKGROUND Using the signal-averaged ECG (SAECG), this study developed a new electrical index for predicting arrhythmic events: abnormal intra-QRS potentials (AIQP). METHODS AND RESULTS We studied 173 patients followed after myocardial infarction for a mean duration of 14 +/- 7 months. Sixteen arrhythmic events occurred, defined as sudden cardiac death, documented sustained ventricular tachycardia, or non-fatal cardiac arrest. Noninvasive indices of arrhythmia risk were measured, including AIQP, conventional SAECG, Holter, and left ventricular ejection fraction (LVEF). Abnormal intra-QRS potentials were defined as abnormal signals occurring anywhere within the QRS period. They were estimated with a lead-specific, parametric modeling method that removed the smooth, predictable part of the QRS. AIQPs are characterized by the remaining transient, unpredictable component of the QRS and manifest as low-amplitude notches and slurs. A combined XYZ-lead AIQP index exhibited higher specificity (95%) and predictive value (PV) (+PV, 47%; -PV, 94%) than the conventional SAECG in combination with Holter and LVEF (specificity, 89%; +PV, 25%; -PV, 93%). CONCLUSIONS AIQP improved specificity and predictive value, compared with conventional tests, for prediction of arrhythmic events. AIQP emerged as the best noninvasive univariate predictor of arrhythmic events after myocardial infarction in this study. A review of several other reports shows that AIQP in the present study outperformed the conventional predictive indices reported in those other data sets.

Multifractal and nonlinear assessment of autonomous nervous system response during transient myocardial ischaemia

We assess autonomic nervous system response during prolonged percutaneous transluminal coronary angioplasty (PTCA) using heart rate variability analysis with multifractal indices. These indices are used to evaluate the effects of the PTCA procedures at different arteries and locations. A total of 55 patients from the Staff3 database, with no prior history of myocardial infarction, were included in the study. The indices increased significantly during the transient ischaemia and reperfusion periods, indicating an increase in nonlinear multifractal characteristics and a change in temporal correlations in heartbeat fluctuations. This indicates that significant multifractal and nonlinear complex reactions in the autonomic control of the heart rate occurred during coronary artery occlusions and suggests that the multifractal indices may be a promising nonlinear technique for evaluating autonomic nervous system response in the presence of transient myocardial ischaemia.

Analysis of high-resolution ECG changes during percutaneous transluminal coronary angioplasty

The authors have hypothesized that low-level, electrocardiographic changes may accompany transient ischemia induced by percutaneous transluminal coronary angioplasty. Altered repolarization may manifest as subclinical changes in ST-T morphology. Changes in depolarization may manifest as low-amplitude notches and slurs, a phenomenon the authors term abnormal intra-QRS potentials. The initial aim of this study was to characterize changes in high-resolution electrocardiograph signals that might be linked to ischemic involvement of the ventricular myocardium.

Electrophysiological Effects of Selective Atrial Coronary Artery Occlusion in Humans

Background— The arrhythmogenesis of ventricular myocardial ischemia has been extensively studied, but models of atrial ischemia in humans are lacking. This study aimed at describing the electrophysiological alterations induced by acute atrial ischemia secondary to atrial coronary branch occlusion during elective coronary angioplasty. Methods and Results— Clinical data, 12-lead ECG, 12-hour Holter recordings, coronary angiography, and serial plasma levels of high-sensitivity troponin T and midregional proatrial natriuretic peptide were prospectively analyzed in 109 patients undergoing elective angioplasty of right or circumflex coronary arteries. Atrial coronary branches were identified and after the procedure patients were allocated into two groups: atrial branch occlusion (ABO, n=17) and atrial branch patency (non-ABO, n=92). In comparison with the non-ABO, patients with ABO showed: (1) higher incidence of periprocedural myocardial infarction (20% versus 53%, P=0.01); (2) more frequent intra-atrial conduction delay (19% versus 46%, P=0.03); (3) more marked PR segment deviation in the Holter recordings; and (4) higher incidence of atrial tachycardia (15% versus 41%, P=0.02) and atrial fibrillation (0% versus 12%, P=0.03). After adjustment by a propensity score, ABO was an independent predictor of periprocedural infarction (odds ratio, 3.4; 95% confidence interval, 1.01–11.6, P<0.05) and atrial arrhythmias (odds ratio, 5.1; 95% confidence interval, 1.2–20.5, P=0.02). Conclusions— Selective atrial coronary artery occlusion during elective percutaneous transluminal coronary angioplasty is associated with myocardial ischemic damage, atrial arrhythmias, and intra-atrial conduction delay. Our data suggest that atrial ischemic episodes might be considered as a potential cause of atrial fibrillation in patients with chronic coronary artery disease.

Bayesian hierarchical model with wavelet transform coefficients of the ECG in obstructive sleep apnea screening

The Wavelet Transform allows one to analyze the properties of a variety of signals: one being able to emphasize changes in either the time or the frequency domain once the appropriate scale is chosen. Since a signal can be expressed in terms of coefficients from wavelet functions, the behavior of this signal could be sparsely represented in these functions, expressing possible properties behind nonstationary signals. Recently, methods based on hierarchical Bayes analysis have been found to be a feasible tool in the approach of physical science and engineering applications. In order to participate in the apnea screening event at the Computers in Cardiology Challenge 2000 and estimate a model that could bring one to an adequate classification between groups the authors developed the present methodology.

Characterization of the nonlinear content of the heart rate dynamics during myocardial ischemia

We develop a method to quantify the changes in heart rate dynamics during local myocardial ischemia induced by a percutaneous transluminal coronary angioplasty procedure (PTCA). The method introduces an index measuring the nonlinear content of the beat-to-beat (RR) time series by using nonlinear time series techniques such as surrogate data analysis and average mutual information. The index is applied to RR data from 67 subjects obtained before, during, and after the ischemic period and shows an increase in the nonlinearity of the cardiac control dynamics during ischemic and reperfusion stages. The nonlinear index is also used to characterize the effects of performing the coronary occlusion at different arteries and distances. We observe that the effect of ischemia becomes larger as the occlusion distance is reduced, and that most of the changes in the nonlinear content of the dynamics occur at long time scales typically related to sympathetic modulation of the cardiac rhythm (6-25 s).

Non-linear dynamic analysis of the cardiac rhythm during transient myocardial ischemia.

Abstract Coronary artery occlusions related to myocardial ischemia drive cardiac control system reactions that may lead to heart failure. The purpose of this study was to assess the autonomic nervous system (ANS) response during prolonged percutaneous transluminal coronary angioplasty (PTCA). Continuous ECG data were acquired from 50 patients before and during PTCA, with occlusions in the left anterior descending, left circumflex or right coronary artery. Heart rate variability (HRV) was analyzed for 3-min segments of the R-R interval signal obtained from ECG data. The ANS behavior was evaluated by HRV analysis using fractal-like indices. The fractal scalar exponent α1 and power-law slope β decreased considerably during PTCA. This indicates that significant reactions of autonomic control of the heart rate occurred during coronary artery occlusions, with a reduction in complexity of the ANS.

Abnormal intra-QRS signals and late potentials in the high resolution ECG associated with chagasic myocarditis

One major public health problem in Latin America is Chagas disease. This is caused by infection with Trypanosoma Cruzi. In the chronic phase, infected patients develop chagasic myocarditis, ultimately resulting in arrhythmic death. The purpose of this paper is to identify, distinct stages in the evolution of chagasic myocarditis through the quantification of abnormal intra-QRS and late potentials in the high resolution electrocardiogram. Preliminary results suggest that intra-QRS potentials may have value to distinguish between chagasic subjects with initial cardiac involvement and late-stage chagasic patients prone to ventricular arrhythmia.

Evaluation of very low amplitude intra-QRS potentials during the initial minutes of acute transmural myocardial ischemia

INTRODUCTION Low-level electrocardiographic changes from depolarization wavefront may accompany acute myocardial ischemia. The purpose of this study was to assess the changes of microvolt amplitude intra-QRS potentials induced by elective percutaneous coronary interventions (PCI). METHODS Fifty-seven patients with balloon inflation periods ranging from 3.1 to 7.3 minutes (4.9±0.7 min) were studied. Nine leads continuous high-resolution ECG before and during PCI were recorded and signal-averaged. Abnormal intra-QRS at microvolt level (μAIQP) were obtained using a signal modeling approach. μAIQP, R-wave amplitude and QRS duration were measured in the processed ECG during baseline and PCI episodes. RESULTS The mean μAIQP amplitude significantly decreased for each of the standard 12 leads at the PCI event respect to baseline. Left anterior descending artery (LAD) occlusion resulted in a decrease μAIQP in both the precordial leads and the limb leads, while right coronary (RCA) and left circumflex (LCx) arteries occlusions mainly affected limb leads. R-wave amplitude increased during PCI in RCA and LCx groups in lead III but decreased in the precordial leads, while the amplitude decreased in the LAD group in lead III. The average duration of the QRS augmented in groups RCA and LCx but not in the LAD group. CONCLUSIONS Abnormal intra-QRS potentials at the level of μV provide an excellent tool to characterize the very-low amplitude fragmentation of the QRS complex and its changes due to ischemic injuries. μAIQP shows promise as a new ECG index to measure electrophysiologic changes associated with acute myocardial ischemia.

Heart rate recovery in the diagnosis of diabetic Cardiovascular Autonomic Neuropathy

Cardiovascular Autonomic Neuropath (CAN) is a poorly understood chronic complication of Diabetes Mellitus (DM). A single instrument to evaluate CAN is not available yet, because of the complex balance between both sympathetic and parasympathetic drives. Heart Rate Recovery (HRR) is a promising parameter for clinicians to use, which is the difference between the maximal heart rate achieved at the end of the exercise phase and the heart rate at different stages of the recovery. The objective of this study was to characterize parameters obtained from RR trends during the recovery phase of the Exercise ECG. Our preliminary analysis is performed with 23 patients enrolled in the DM group and 6 patients in the control group. It showed that both HRR1 after the first minute of recovery and HRR2 after the second minute of recovery are able to discriminate between groups. These results are encouraging and more trends analysis within a different window period is still needed.