Utility of implantable cardioverter defibrillator electrograms to estimate repolarization alternans preceding a tachyarrhythmic event.

Electrical alternans is a pattern of variation in the shape of the ECG waveform that appears on an every-other-beat basis. In humans, alternation in ventricular repolarization, namely, repolarization alternans, has been associated with increased vulnerability to ventricular tachycardia/ventricular fibrillation and sudden cardiac death. This study investigates the utility of implantable cardioverter defibrillator electrograms to estimate repolarization alternans preceding a tachyarrhythmic event. It is demonstrated that microvolt-level repolarization alternans is present prior to an arrhythmic event, and one can record low-amplitude-noise signals that can be used to obtain reliable estimates of repolarization alternans. This study eventually may lead to new methods that would prevent the onset of malignant tachyarrhythmias.