Distribution of coronary arterial flow in acute myocardial ischemia.

Thioflavin S (TS), a fluorescent dye, was used to visualize the distribution of coronary flow within the area of ischemia produced by circumflex artery occlusions. In the ischemic region, TS failed to penetrate the subendocardium and was seen in the subepicardium. Even though collateral flow was noted in the subepicardium, studies with methylene blue showed that it was inadequate to prevent the development of ischemia. The proportion of the posterior papillary muscle and subjacent myocardium showing TS nonfluorescence was similar after 15 and 60 minutes of ischemia and correlated with maximum lead II ST segment elevation and the percent of grossly injured myocardium found at 60 minutes postocclusion. The results suggest that flow to ischemic myocardium is reduced to the greatest extent in the subendocardium, ie, the site where irreversible injury first appears.