Can QT/RR relationship differentiate between low- and high-risk patients with hypertrophic cardiomyopathy?

Background: Abnormal dynamicity of repolarization is considered to be a marker of myocardial vulnerability contributing to increased risk of arrhythmic events and sudden death. However, little is known about QT dynamics in hypertrophic cardiomyopathy (HCM). In this study, we aimed to evaluate ventricular repolarization by QT dynamicity in patients with HCM, focusing on its value to define if it is able to differentiate among low- and high-risk HCM patients.

Enhanced modified moving average analysis of T-wave alternans using a curve matching method: a simulation study.

T-wave alternans (TWA) are beat-to-beat amplitude oscillations in the T-waves of electrocardiograms (ECGs). Numerous clinical studies have demonstrated the link between these oscillations and ventricular arrhythmias. Several methods have been developed in recent years to detect and quantify this important feature.

Unsupervised classification of ventricular extrasystoles using bounded clustering algorithms and morphology matching.

Ventricular extrasystoles (VE) are ectopic heartbeats involving irregularities in the heart rhythm. VEs arise in response to impulses generated in some part of the heart different from the sinoatrial node. These are caused by the premature discharge of a ventricular ectopic focus.

Gender differences in electrical remodeling and susceptibility to ventricular arrhythmias in rabbits with left ventricular hypertrophy.

Background: Left ventricular hypertrophy (LVH) is associated with an increased risk of death, vulnerability to ventricular arrhythmia, and multiple electrophysiological abnormalities.

Objectives: The purpose of the present study was to determine the gender-dependent differences in electrical remodeling and the susceptibility to ventricular arrhythmias in a rabbit model of renovascular hypertension.

Methods: Rabbits of both sexes underwent unilateral renal artery banding and contralateral nephrectomy or were placed in the control group.

Role of dipolar and nondipolar components of the T wave in determining the T wave residuum in an isolated rabbit heart model.

Introduction: Repolarization heterogeneity has been shown to constitute a substrate for malignant ventricular arrhythmias. Noninvasive measurement of abnormal repolarization through assessment of QT interval dispersion from the resting standard 12-lead ECG initially had shown promise in assessing arrhythmia risk but was challenged recently. The relative T wave residuum (TWR) has been proposed recently to reflect regional repolarization dispersion more accurately.

Developmental changes of cardiac repolarization in rabbits: implications for the role of sex hormones.

Objectives: Firstly, to compare gender-dependent differences of cardiac repolarization in both adult and young rabbits. Secondly, to analyze the effect of gonadectomy on these gender differences in cardiac repolarization.

Methods: We evaluated potential gender differences in cardiac repolarization with both microelectrode and ECG recordings.

Beat-to-beat repolarization variability measured by T wave spectral variance index in chronic infarcted animals.

Background: Recent experimental and clinical studies have shown that beat-to-beat variability of repolarization morphology is associated with an increased risk for developing malignant ventricular arrhythmias. However, few data exist on the relationship between beat-to-beat repolarization variability and myocardial infarction itself.

Methods And Results: In the present work we tested the algorithm of T wave spectral variance (TWSV) using the two dimension fast Fourier transform, in an animal model of myocardial infarction to extend the evidences that support the existence of beat-to-beat alteration in repolarization during the chronic stage of myocardial infarction.

Lack of effect of conduction direction on action potential durations in anisotropic ventricular strips of pig heart.

Introduction: The influence of activation sequence on the rate of rise of the depolarization phase of action potentials in atrial or ventricular muscles has been well established. However, whether myocardial fiber orientation is important in modulating the repolarization process is unclear.

Methods And Results: We examined the influence of activation sequence on the repolarization phase of action potentials in epicardial tissues from the right and left ventricles of domestic pigs.