Prevention of occlusive coronary artery thrombosis by prostacyclin infusion in the dog.

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Abstract
The hemodynamic and antithrombotic properties of prostacyclin (PGI2) were evaluated in an in vivo canine model in which left circumflex coronary artery (LCX) thrombus formation was initiated by electrical stimulation (150 .mu.A, DC for 6 h) of the arterial intimal surface via an implanted silver wire electrode. Eleven of the 12 control dogs (92%) developed totally occlusive LCX thrombi after an average of 3.2 .+-. 0.4 h of LCX stimulation; the remaining control dog underwent spontaneous ventricular fibrillation. A PGI2 infusion (150, 300 or 500 ng/kg per min) into the left atrial appendage was begun 10 min before the start of LCX stimulation and continued throughout the 6 h stimulating period. LCX thrombus wet weight and the incidence of occlusive LCX thrombosis decreased in the PGI2-treated dogs in a dose-dependent manner. Hemodynamically, after 6 h of PGI2 infusion at 500 ng/kg per min, mean arterial pressure decreased by 36 .+-. 4%, cardiac output increased by 51 .+-. 14% and the effect on heart rate was inconsistent. Light and scanning electron microscopic examination of the LCX at the site of electrode insertion in PGI2-treated dogs (500 ng/kg per min) revealed a damaged and denuded intimal surface but no thrombi, in contrast to the thrombus formation in similar specimens taken from control dogs. The potent hemodynamic effects of prolonged PGI2 infusion is described and its ability to prevent coronary artery thrombosis in response to intimal injury is demonstrated.