[A comparative study of cardiac function during hypoxia and ischemia in dogs]

Mongrel dogs were instrumented with 4 pairs of Sonomicrometers to measure ventricular wall thickness (WT) and a Konigsberg (PT) high fidelity micromonometer to measure left ventricular pressure (LVP). Two weeks after surgical operation, studies were conducted. The dWT/dT-WT loop, dP/dt-LVP loop and dP/dt-dP/dt loop, etc. were used to observe the changes in cardiac dynamics. In 6 dogs, the circumflex artery was occluded with hydraulic occluder for three minutes under conscious condition. Three dogs were ventilated with hypoxic gas to reduce the arterial blood oxygen saturation to near 45%. The heart rate increased markedly under both hypoxia and ischemia. During coronary arterial occlusion contraction and relaxation tended to decrease and the ischemic myocardium was in a dysfunctional condition. During hypoxia, contraction and relaxation increased and myocardial movement was enhanced. Only under severe hypoxia, a decrease in heart rate occurred and contraction and relaxation began to be inhibited. These indicated that cardiac function under hypoxia is different from that under ischemia.