Effect of PGE1, PGE2 and PGI2 on ventricular arrhythmias during myocardial infarction in conscious dogs: Relation to infarct size

The relation between the effect of vasodilator prostaglandins on ventricular arrhythmias during myocardial infarction and infarct size was studied in conscious dogs. Two infarct-limiting drugs, nitroglycerin and ibuprofen, were also studied for comparison. Infusions were given between 20 and 380 minutes after occlusion of the left circumflex coronary artery: intravenously for saline (N = 27), ibuprofen (N = 14), and nitroglycerin (N = 14); left atrially for PGE₁ (N = 11), PGE₂ (N = 12) and PGI₂ (N = 18). Doses of prostaglandins and nitroglycerin were adjusted to decrease mean arterial pressure by 5%. Pathologic infarct size was measured 2 days post-occlusion. During the infusion period, ventricular fibrillation (VF) deaths were nil with PGI₂ (p < 0.05) and nitroglycerin (p < 0.1), ventricular premature beats (VPB's) were less (p < 0.01) with PGI₂, PGE₂ and nitroglycerin, and collateral blood flow (microspheres) increased with PGE₁, PGI₂ and nitroglycerin but did not change with saline, PGE and ibuprofen. Infarct size, as percent of left ventricle or occluded bed, was less (p < 0.05) with PGE₁, PGI₂, nitroglycerin and ibuprofen but similar with PGE₂ and saline. Thus, PGE₂ diminished VPB's despite no effect on flow or infarct size. In contrast, both PGE₁ and PGI₂ diminished VPB's, increased flow and decreased infarct size, but PGI₂ also reduced VF mortality.