Recovery of myocardial function after repetitive episodes of reversible ischemia.

Abstract

The question of whether recovery of regional myocardial function after repetitive, reversible ischemia differs from recovery after a single episode of myocardial ischemia remains controversial. Therefore, eight conscious dogs were instrumented with ultrasonic dimension transducers and left ventricular micromanometers. Each animal underwent (in random sequence, 72 h apart) a single 15-min left anterior descending coronary arterial (LAD) occlusion and two 15-min LAD occlusions separated by 1 h of reperfusion. The preload recruitable work area (PRWA; the area beneath the regional stroke work vs. end-diastolic length relationship) quantified regional myocardial performance. Repetitive ischemia significantly delayed recovery of PRWA over the first 24 h (P < 0.05). Although postischemic myocardial creep resolved rapidly after single occlusion, double occlusion prevented recovery of creep during the first 4 h of reperfusion. The recovery time course of PRWA paralleled the resolution of myocardial creep, suggesting that creep contributed significantly to delayed functional recovery and that myocardial "stunning" after repetitive ischemia may result in part from interaction between postischemic diastolic properties and systolic dysfunction.