Regional myocardial volume alterations induced by brief repeated coronary occlusion in conscious dogs.

The purpose of this study was to evaluate whether brief repeated coronary occlusions induce changes in regional myocardial geometry at rest. Five conscious dogs were instrumented for the measurement of subendocardial segment length and transmural wall thickness in the ischemic area, subendocardial segment length in the normally perfused area, coronary flow and left ventricular pressure. After recovery from surgery, 180 (mean) 2 min coronary occlusions were given over a period of 20 days. The heart rate at rest, left ventricular peak systolic and end-diastolic pressures and peak positive first derivative of left ventricular pressure (dP/dt) remained unchanged throughout the experiment. In the normal area, the end-diastolic segment length at rest did not change significantly. By contrast, in the ischemic area, at 14 days after the initiation of repeated coronary occlusion, the end-diastolic regional cross-sectional area (product of segment length and wall thickness) at rest had increased by 9.7% (p less than 0.05); thereafter it decreased to 6.5% (p less than 0.05) above the value at rest before repeated occlusion despite an additional 6 days of coronary occlusions. At 10 days after the interruption of repeated occlusion, this value had regressed to 4.3% (p = NS) above control. These findings suggest the occurrence of regional myocardial hypertrophy confined to the ischemic area in response to the periodic ischemic stimulus.