Regional myocardial hypertrophy induced by repeated brief coronary occlusion in conscious dogs

The purpose of the present study was to evaluate whether repeated brief coronary occlusion induces myocardial hypertrophy in the region subjected to reversible ischemic insult. In five conscious dogs, a subendocardial segment length in the area perfused by the left circumflex coronary artery (LCCA) was measured along with left ventricular pressure. After complete recovery from surgery, 167 (mean) 2-minute LCCA occlusions were repeated for 22 days. Before and after repeated coronary occlusion, the resting heart rate, left ventricular systolic and end-diastolic pressures, and dP/dt were unchanged. The resting end-diastolic segment length in the LCCA area was increased by 6.6% (p less than 0.05). On histologic examination, there was a disproportionate increase in myocardial cell size in the LCCA area compared with the area perfused by the left anterior descending coronary artery (LAD) (18.2 mu vs 15.4 mu, p less than 0.05). In an additional similarly instrumented five dogs, myocardial cell size in the LCCA and LAD areas was comparable (14.2 mu vs 14.0 mu, p = NS). We conclude that the repeated brief ischemic episodes induce regional myocardial hypertrophy confined to the ischemic area.