Changes in stenosis resistance and myocardial blood flow after a brief coronary occlusion in the dog.
Stress-induced changes in the resistance due to coronary arterial stenosis of a fixed diameter and in the myocardial blood flow distal to the stenosis were investigated in the open-chest dog. Myocardial blood flow in the inner and outer third of the left ventricular wall was continuously measured with heated cross-thermocouples. The circumflex coronary artery was constricted with a thick string so that myocardial reactive hyperemia was nearly eliminated. Without constriction, a 15-second occlusion of the artery produced no significant changes in the resistance of large coronary arteries. On the contrary, in the presence of coronary constriction, a brief coronary occlusion caused a sustained decrease in distal coronary pressure and subendocardial myocardial flow during reactive hyperemia, while coronary flow returned quickly to the pre-occlusion level with significant reactive hyperemia of subepicardial flow. This change resulted in a long-lasting increase in the stenosis resistance. These results suggest that stenosis resistance changes dynamically, resulting in additional myocardial ischemia especially in the subendocardial myocardial layers.
D000818:Animals; D001794:Blood Pressure; D003250:Constriction; D003326:Coronary Circulation; D003327:Coronary Disease / Q000503:physiopathology*; D003331:Coronary Vessels; D004285:Dogs; D005260:Female; D006940:Hyperemia; D008297:Male; D013997:Time Factors; D014655:Vascular Resistance