EFFECTS OF PROSTACYCLIN ON MYOCARDIAL HEMODYNAMICS AND METABOLISM AFTER CORONARY-ARTERY BYPASS-GRAFTING

Objective: To study the effects of incremental infusion rates of prost acyclin on myocardial blood flow and metabolism and central hemodynami cs shortly after coronary artery bypass grafting. Design: A pharmacody namic dose-response study. Setting: A multi-institutional university h ospital. Participants: Twelve patients with two- or three-vessel coron ary artery disease and with an ejection fraction greater than 0.5 were studied in the operating room after sternal closure and elective coro nary artery bypass grafting. Interventions: Prostacyclin was administe red at infusion rates of 2.5, 5, 10, and 20 ng/kg/min. Systemic and pu lmonary hemodynamics and global (coronary sinus) as well as regional ( great cardiac vein) myocardial blood flow and metabolic variables were measured. Measurements and Main Results: Infusion rates of 10 and 20 ng/kg/min decreased mean arterial blood pressure (13% and 21%, respect ively), systemic vascular resistance (31% and 42%), and pulmonary vasc ular resistance (11% and 33%), increased cardiac output (28% and 37%), heart rate (9% and 13%), and stroke volume (15% and 20%), but had no effect on central filling pressures. Prostacyclin caused no changes in great cardiac vein flow or coronary sinus flow. Furthermore, prostacy clin caused no changes in regional myocardial oxygen extraction, indic ating that prostacyclin did not induce direct coronary vasodilation. T here were no electrocardiographic or obvious metabolic signs of myocar dial ischemia during prostacyclin infusion. Conclusion: Prostacyclin m ay be a useful afterload-reducing compound after coronary artery bypas s grafting because it has no direct coronary vasodilatory effect, whic h minimizes the risk of myocardial ischemia. Copyright (C) 1996 by WB. Saunders Company