The effect of coronary flow restriction on the viability of porcine myocardium.

The effect of a prolonged (3 hours) defined coronary flow restriction on early (30 minutes) and late (24 hours) reperfusability and survival of the myocardium was studied in a closed-chest pig model. Coronary blood flow (CBF) was restricted to 51 +/- 4% (moderate flow restriction) and 36 +/- 6% (severe flow restriction) of preexisting resting flow values. Regional determination of the restricted CBF after severe flow restriction showed the anticipated extension of the ischemic area from endocardial to epicardial layers and to the lateral border zone. Upon early reperfusion a hyperemic effect was observed, which reflected the preceding degree of underperfusion. The maximal hyperemic effect was found in samples with CBF restriction to 38% of the control flow values. Twenty-four hours after blood flow restitution the hyperemic effect had disappeared. At this time control flow values had not returned, where previous CBF restriction had exceeded 50%. The amount of infarcted tissue in the area supplied by the left circumflex artery was 5.7% after moderate, and 31.6% after severe flow restriction. Morphologically the infarcted myocardium consisted of disseminated necrosis after moderate, and of confluent necrosis after severe flow restriction. At flow restriction exceeding 50%, the chances of reestablishing perfusion and thus salvaging the myocardium appear minimal.