Signal-averaged electrocardiography and the significance of late potentials in patients with "idiopathic" ventricular tachycardia: a review.

High-frequency, low-amplitude electrical activity during and in continuation with the ventricular electrogram in sinus rhythm is now accepted as an indirect marker for reentrant pathways in ventricular muscle. Because the amplitude of these signals is low, much effort has recently been directed toward finding methods of recording these noninvasively. This essentially involves averaging the electrocardiogram, amplifying it, and filtering out the low frequency and nonrepetitive signals. This review discusses the methods presently available for signal-averaged electrocardiography and their background. The clinical application of signal-averaged electrocardiograms in patients with or suspected to have ventricular tachycardia is summarized. Data regarding the incidence of abnormal signal-averaged electrocardiography in patients with "idiopathic" ventricular tachycardia compared with normal subjects and patients with ventricular tachycardia related to ischemic heart disease are presented.