ATTENUATION OF CORONARY FLOW RESERVE AND MYOCARDIAL-FUNCTION AFTER TEMPORARY SUBTOTAL CORONARY-ARTERY OCCLUSION AND INCREASED MYOCARDIAL OXYGEN-DEMAND IN DOGS

Objectives. We examined whether subtotal coronary artery occlusion and reperfusion alter coronary flow reserve and regional myocardial funct ion. Background. Total coronary artery occlusion followed by reperfusi on results in decreased coronary flow reserve and regional myocardial dysfunction. Methods. Thirteen anesthetized dogs were subjected to sub total occlusion of the left anterior descending coronary artery for 1 h, followed by reperfusion for 1 h. During subtotal left anterior desc ending occlusion, heart rate was increased by atrial pacing. After rep erfusion, coronary flow reserve, indicated by reactive hyperemia, as w ell as coronary flow responses to acetylcholine and nitroglycerin, reg ional myocardial function and myocardial leukocyte accumulation were m easured. Results. After reperfusion, coronary flow reserve was decreas ed in the ischemic left anterior descending but not the nonischemic ci rcumflex coronary artery region. Myocardial function was also depresse d in the left anterior descending coronary region and did not improve on reperfusion. Histologic study showed no leukocyte infiltration in t he ischemic left anterior descending coronary region. Myeloperoxidase, an index of myocardial leukocyte accumulation, was similar in the lef t anterior descending and circumflex coronary regions. Sensitivity of epicardial left anterior descending coronary artery rings to the throm boxane A(2) analog U46,619 was enhanced, and relaxation of these rings in response to endothelium dependent relaxants was decreased. Conclus ions. Coronary flow reserve is reduced and regional myocardial functio n depressed after subtotal coronary artery occlusion and increased hea rt rate. A decreased synthesis or increased breakdown of endothelium-d erived relaxing factor may be related to a decrease in coronary flea r eserve. However, the reduction in coronary how reserve appears to be u nrelated to leukocyte accumulation in the reperfused region.