Prostacyclin prevents ventricular fibrillation in a canine model of sudden cardiac death

Abstract

The antifibrillatory, antithrombotic and hemodynamic properties of intraventricular prostacyclin (PGI₂) application were studied in a conscious canine model of sudden cardiac death. In anesthetized dogs, a wire electrode was implanted into the left circumflex coronary artery (LCX) and acute myocardial ischemia was produced by 90 min occlusion of the left anterior descending coronary artery (LAD) followed by reperfusion. An intracardiac pressure transducer measured ventricular pressure, heart rate, filling pressure and dP/dt. The ECG was obtained from subcutaneous chest needles. Six days later while in ambulatory state, a 180 μA DC current was applied for 4 h to the LCX intimal lining in Tris-HCl (n=10) and PGI₂-treated dogs (50 and 100 ng/kg/min, 11 and 12 dogs, respectively). Myocardial injury and coronary thrombosis induced by electrical stimulation produced ventricular fibrillation in all vehicle-treated dogs at 145±33 min (mean±S.D.). In PGI₂-treated hearts only 2 animals fibrillated at 150±29 min and 180±52 min following 50 and 100 ng/kg/min of the prostanoid, respectively. Thus, 18/23 PGI₂-treated dogs survived 4h electrical stimulation of the artery. Within the LAD perfusion zone infarction was observed of equal volumes in vehicle and PGI₂-treated animals. No ischemia occurred distal to the LCX coronary thrombosis. Ventricular pressure fell in all groups. Heart rate increased in the controls and those animals treated with 50 ng/kg/min PGI₂ while 100 ng/kg/min PGI₂ increased heart rate by 22±5% (p2-treated hearts. The results indicate that PGI₂ can prevent ventricular fibrillation resulting from acute ischemia at a site distant to previous myocardial ischemia with superimposed intimal injury and coronary thrombosis. The PGI₂ properties are due to prevention of coronary thrombosis and the occlusion of the artery. Antifibrillatory effects of the prostanoids are suggested.