The effects of changing the time course of action potential repolarization on the amplitude and coupling interval of delayed afterdepolarizations were studied in small preparations of coronary sinus atrial fibers exposed to catecholamines. Repolarization was accelerated or retarded by current pulses passed through an intracellular microelectrode in the depolarizing or repolarizing direction. Ac...

BACKGROUND Diabetes is associated with prolongation of the QT interval of the electrocardiogram and enhanced dispersion of ventricular repolarization, factors that, together with atherosclerosis and myocardial ischemia, may promote the occurrence of electrical disorders. Thus, we tested the possibility that alterations in transmembrane ionic currents reduce the repolarization reserve of myocyte...

BACKGROUND Noncontact mapping (NCM) has not been validated as a clinical technique to measure ventricular repolarization. We used NCM to determine repolarization characteristics by analysis of reconstructed unipolar electrograms (UEs) at the same sites as monophasic action potential (MAP) recordings in the human ventricle. METHODS AND RESULTS MAPs were recorded from a total of 355 beats at 46...

The role of I(KCa) in cardiac repolarization remains controversial and varies across species. The relevance of the current as a therapeutic target is therefore undefined. We examined the cellular electrophysiologic effects of I(KCa) blockade in controls, chronic heart failure (HF) and HF with sustained atrial fibrillation. We used perforated patch action potential recordings to maintain intrins...

UNLABELLED Kinetics of Atrial Repolarization Alternans. INTRODUCTION Repolarization alternans (Re-ALT), a beat-to-beat alternation in action potential repolarization, promotes dispersion of repolarization, wavebreaks, and reentry. Recently, Re-ALT has been shown to play an important role in the transition from rapid pacing to atrial fibrillation (AF) in humans. The detailed kinetics of atrial...

BACKGROUND The ability to determine spatial and dynamic changes in ventricular repolarization may help to understand arrhythmogenic mechanisms in humans. We hypothesized that noncontact mapping could be used to investigate global activation-repolarization coupling in the human ventricle during steady state and premature extrastimulation. METHODS AND RESULTS Activation-recovery intervals (ARIs...

At the end of the 19th century Einthoven described the configuration of the human ECG [1] and in later papers he elaborated on the magnitude and direction of its components [2]. From an intellectual point of view it is in fact unacceptable that we still do not know exactly how the T wave emerges. More precisely, we may understand how (dispersion in) repolarization within the ventricles transfor...

BACKGROUND In adults, impaired myocardial repolarization and increased risk of arrhythmia are known consequences of open heart surgery. Little is known, however, about post-operative consequences of cardiopulmonary bypass surgery in children. The aim of this study was to assess ventricular repolarization and coronary perfusion after bypass surgery for atrial septal defect (ASD) repair in childr...

BACKGROUND Congenital and acquired long QT syndrome (LQTS) are caused by abnormalities of ionic currents underlying ventricular repolarization. For a better understanding of the mechanisms by which functional electrical instability at the level of the whole heart leads to torsade de pointes (TdP), a novel model of LQT3 was developed and the role of transmural dispersion of repolarization for th...

Increased repolarization heterogeneity can provide the substrate for reentrant ventricular arrhythmias in animal models of cardiomyopathy. We hypothesized that ventricular repolarization heterogeneity is also greater in patients with cardiomyopathy and ventricular arrhythmia vulnerability (inducible ventricular tachycardia or positive microvolt T wave alternans, VT/TWA) compared with a similar ...