Evolution and resolution of long-term cardiac memory

Abstract

Background - Cardiac memory (CM) refers to T-wave changes induced by ventricular pacing or arrhythmia that accumulate in magnitude and duration with repeated episodes of abnormal activation. We report herein the kinetics of long-term CM and its association with the ventricular action potential. Methods and Results - Dogs were paced from the ventricles at rates of 110 to 120 bpm for ≃3 weeks. CM characterized by gradual sinus rhythm T vector rotation toward he paced QRS vector evolved in all dogs regardless of pacing site (left ventricular [LV] anterior apex or base, posterior LV, or right ventricular free wall). Cardiac hemodynamics and myocardial flow (microsphere studies) were unaltered by the pacing. Recovery time for the memory T wave to return to control increased with duration of the previous pacing. The protein synthesis inhibitor cycloheximide markedly (P