Effects of ischaemia and coronary reperfusion on regional myocardial blood flow and on the epicardial electrogram.

Abstract

Effects of reperfusion on the epicardial electrogram and on regional myocardial blood flow were investigated in 3 groups of dogs undergoing acute anterior wall ischaemia for 1 (Group I), 2 (Group II), or 6 (Group III) hours. Regional blood flow was assessed utilising the microsphere technique. Rapid development of abnormal Q waves, associated with accelerated decrease or loss of R wave electromotive forces, was observed after reperfusion in the central ischaemic zone in 25% of dogs in Group I, 75% of dogs in Group II, and in 92% of animals in Group III. These rapidly evolving changes occurred concomitant with significant reductions in mean S-T segment elevation. In contrast to the epicardial electrogram changes in the central ischaemic zone, coronary reperfusion was not associated with development of abnormal Q waves or accelerated loss of R wave amplitude in the peripheral ischaemic zone or in the border zone in Group I animals. However, in Group II, Q waves appeared in the peripheral ischaemic zone in all but one of the dogs developing Q waves in the central ischaemic zone. Border zone Q waves appeared in only 17% of these animals. In Group III, Q waves appeared in the peripheral ischaemic zone in 92% and in the border zone in 75% of animals. Impaired reflow of blood to ischaemic zones was seen following coronary reperfusion. In Group I mean flow was 88±10% of nonischaemic flow in endocardial layers of the central ischaemic zone after reperfusion. In contrast, mean flow to this region in Group II and Group III animals was only restored to 59 ±17% and 53 ± 11% of nonischaemic flow, respectively. Pathological findings of subendocardial haemorrhage and transmural oedema were uniformly present in areas showing reduced reflow and abnormal 0 waves after reperfusion.