Sustained protection by iloprost of the porcine heart in the acute and chronic phases of myocardial infarction

The effects of iloprost (ZK 36 374) on myocardial ischemia and infarction were studied in three groups of four anesthetized and heparinized pigs. Coronary microembolization was evoked by the injection of microspheres (50 microM) into the left coronary artery. A dose of 12 million beads/kg was followed by ventricular fibrillation and death after 11 +/- 5 min (group A). In group B, ischemia was evident at 15 min after the injection of 6 million beads/kg from an ST segment elevation in the precordial electrocardiogram (2.9 +/- 1.1 mV; p less than 0.05) and from an arterial-coronary venous difference in inosine concentration of -8.5 +/- 0.3 microM (p less than 0.05). However, in the presence of iloprost--an infusion of 0.18 micrograms/kg/min started 30 min before embolization--no ST segment elevation (0.45 +/- 0.23 mV; NS) or inosine release (-1.5 +/- 1.0 microM) was detected after the injection of 12 million beads/kg (group C). After 7 days, the animals from group B had more frequent spontaneous ventricular arrhythmias than those from group C. Programmed electrical stimulation induced intraventricular reentry in some animals of both groups (3 of 4 in B and 2 of 4 in C). Ventricular tachycardia was induced in two animals from group B. Postmortem examination revealed small myocardial infarcts in all group B animals; however, in group C no infarcts were detected. These data corroborate the view that prostacyclin-mimetic compounds are beneficial in the acute and in the chronic phases of myocardial infarction.