Time course of regional function after coronary occlusions of 1- to 120-min duration.

The purpose of this study was to characterize the degree and duration of functional impairment in previously ischemic tissue following coronary artery occlusions of varying duration. Open-chest dogs with left ventricular pressure transducers and ultrasonic segment length crystals were subjected to coronary artery occlusions of 1 (n = 22), 5 (n = 8), 10 (n = 7), 15 (n = 8), 20 (n = 7), 30 (n = 6), 60 (n = 10), or 120 (n = 8) min and segment length motion was measured during 6 h of reperfusion. Active shortening was replaced by passive lengthening during coronary occlusion and regional myocardial blood flow within the ischemic zone was always less than 0.4 ml . min-1 . g-1. Following reperfusion, the improvement of ischemic segment length function was inversely proportional to the duration of coronary occlusion. Function in previously ischemic segment lengths recovered rapidly after 1- and 5-min coronary occlusions, but after occlusions of 10-20 min, there was slow, though incomplete, return of some degree of active shortening yet no evidence of myocardial infarction. With occlusions exceeding 20 min there was persistence of systolic passive lengthening for 6 h despite the absence of infarction in the segment lengths in which function was being evaluated, although infarcted tissue was present ranging from 16.5 +/- 2.6% of the area of ischemia in dogs with 60-min coronary occlusions to 37.2 +/- 4.6% of the area of ischemia in dogs with 120-min occlusions.