Ventricular repolarization significantly influences contractility, refractoriness, and ion channel state. Factors affecting repolarization will thus affect these secondary phenomena. To understand the influence of age on ventricular repolarization, we studied neonatal, young, and adult dogs using electrocardiogram, action potential, and whole-cell voltage-clamp recordings from single epicardial...

OBJECTIVES This study tested the correlation of QT and JT dispersion and other potentially useful electrocardiographic (ECG) indexes with dispersion of repolarization and recovery time. BACKGROUND Dispersion of ventricular repolarization is currently being assessed noninvasively from the surface ECG by means of QT and JT dispersion, although their correlation with dispersion of repolarization...

The effect of two consecutive ventricular premature stimuli (S1S2) during atrial pacing on dispersion of repolarization and inducibility of ventricular arrhythmias was studied in 16 dogs under control conditions and in four dogs in the presence of an increased dispersion of repolarization during atrial pacing induced by general hypothermia and regional warm blood perfusion via selective cannula...

The molecular heterogeneity of repolarizing currents produces significant spatial heterogeneity and/or dispersion of repolarization in many mammalian cardiac tissues. Transgenic mice are prominent experimental models for the study of the molecular basis of repolarization and arrhythmias. However, it is debated whether the small mouse heart can sustain physiologically relevant heterogeneity of r...

Although inactivation of the rapidly activating delayed rectifier current (I(Kr)) limits outward current on depolarization, the role of I(Kr) (and recovery from inactivation) during repolarization is uncertain. To characterize I(Kr) during ventricular repolarization (and compare with the inward rectifier current, I(K1)), voltage-clamp waveforms simulating the action potential were applied to ca...

Although transmural heterogeneity of action potential duration (APD) is established in single cells isolated from different tissue layers, the extent to which it produces transmural gradients of repolarization in electrotonically coupled ventricular myocardium remains controversial. The purpose of this study was to examine the relative contribution of intrinsic cellular gradients of APD and ele...

We previously showed that a premature stimulus can significantly alter vulnerability to arrhythmias by modulating spatial gradients of ventricular repolarization (ie, modulated dispersion). However, it is not clear if such changes in arrhythmia vulnerability can be attributed to the formation of an electrophysiological substrate for unidirectional block and what the potential role is of tissue ...

Having found the regional differences in right atrial action potentials shown in an accompanying article, we tested two seemingly paradoxical hypotheses: 1) The spatial pattern of repolarization provides a protective mechanism against reentry, and 2) repolarization inhomogeneities interact with anisotropic discontinuous propagation to produce reentry. Measurement of multidimensional refractory ...