Experimental Myocardial Infarction in the Dog

Control measurements of myocardial blood flow were made in intact dogs by a method of133 Xe clearance, using a catheter positioned radiographically in the circumflex artery. Acute myocardial infarction was then caused by tying the anterior descending artery. A small catheter was inserted distally beyond the obstructed artery into the infarct, and another proximally toward the anterior ventricular artery supplying adjacent left ventricular muscle. Their ends were brought out as the chest was closed.133 Xe in solution was injected serially over 4 hours to determine myocardial blood flow within the infarct, in adjacent muscle, and in more distant muscle supplied by the circumflex artery. Myocardial blood flow in the circumflex artery usually fell as a result of infarction. A constant finding was that adjacent flow exceeded the more distant flow by 6% up to 43% (mean 20%) regardless of either spontaneous or induced changes in blood pressure. The difference was not related to the collateral flow rate and was abolished by dipyridamole. Perfusion of muscle adjacent to the infarct was less homogenous than that of more distant muscle.In the normal dog rates of myocardial blood flow in the distribution of the circumflex and anterior descending branches of the left coronary artery were the same, contrasting with lower rates for the right.