The transient nature of myocardial ischemia during partial occlusion of the coronary artery in waking immobilized rabbits

: The radioactive microsphere technique was used to study mechanisms of disappearance of myocardial ischemia during partial occlusion of the left descending anterior coronary artery with implanted device in conscious immobilized rabbits. Microspheres (15 microns, NEN, USA) were injected before occlusion, immediately after ST-segment elevation and after disappearance of ST-segment shift. In ischemic region blood flow dropped by 45% (p less than 0.05) and mean blood pressure decreased by 12% (P less than 0.05) on the 1st minute of coronary occlusion. 8-15 min later ST-segment elevation disappeared and the blood flow in ischemic region became higher than control level (on the average by 35%). It is suggested that ischemia is abolished mainly by dilatation of distal coronary vessels, than by activation of collateral blood flow.