Effects of prostaglandin‐E1 on ST segment elevation and regional myocardial blood flow during experimental myocardial ischaemia in dogs

Abstract

Abstract. The effects of prostaglandin E1 (PGE1) on myocardial ischaemia (as measured by epicardial ST segment changes), myocardial flow and substrate exchange has been studied in dogs. Myocardial ischaemia was induced by intermittent external clipping of a branch of the left anterior descending coronary artery.During occlusion with a continuous intravenous infusion of isoprenaline, elevated epicardial ST segments (∑ST), were raised to 46 ± 6 mV (mean ± SEM). Pretreatment with PGE1 reduced ∑ST to 34 ± 6 mV (P<0.001), but had no effect on mean aortic blood pressure (AP¯) or on regional myocardial blood flow. Isoprenaline infusion increased plasma free fatty acids (FFA) to 1925 ± 150 μmol/l and this was reduced to 1320 ± 220 μmol/l by PGE1 (P<0.005).During occlusion without isoprenaline, PGE1 did not effect ∑ST or plasma FFA when infused intravenously or into the left atrium. Mean aortic blood pressure decreased from 131 ± 7 to 108 ± 10 (PGE1 i.v.) or 109 ± 8 mmHg (PGE1 i.a.) (P<0.001). This was associated with a decrease in regional myocardial blood flow, both in the ischaemic and non‐ischaemic myocardium. However, when blood pressure was maintained constant, intravenous PGE1 tended to decrease occlusion‐induced ST segment elevation.These results suggest that PGE1 can reduce isoprenaline‐stimulated myocardial ischaemia through its antilipolytic action but in the absence of catecholamine stimulation the main effect is to reduce blood pressure thereby counterbalancing any potentially beneficial effects on the ischaemic myocardium.