Coronary Collateral Circulation in Acute and Chronic Myocardial Ischemia

Abstract

We have recently demonstrated in different animal species that myocardial infarct (MI) size depends mainly on the amount of acute coronary collateral blood flow and time of occlusion (TOC) [1]. In these experiments, myocardial infarction was produced by occlusion of a branch of the left anterior descending artery (LAD). Coronary blood flow was measured by the tracer microsphere technique. The amount of infarcted tissue was determined histochemically by negative pNBT staining and related to the size of the myocardium which was supplied by the occluded coronary vessel. Animals with very low acute residual blood flow develop myocardial infarction rapidly and to a larger extent (rats, rabbits, and pigs) than animals with a noticeable acute collateral blood flow (cats and dogs). No myocardial infarction could be detected in guniea pigs even after an occlusion of 24 h. These results are summarized in Table 1 and Fig. 1. In Table 1, the imbalance between blood flow in the occluded myocardial tissue and tissue perfused by normal coronary arteries is expressed as the supply/ demand ratio (SDR).