Effects of prostacyclin on myocardial hemodynamics and metabolism after coronary artery bypass grafting.

OBJECTIVE

To study the effects of incremental infusion rates of prostacyclin on myocardial blood flow and metabolism and central hemodynamics shortly after coronary artery bypass grafting.

DESIGN

A pharmacodynamic dose-response study.

SETTING

A multi-institutional university hospital.

PARTICIPANTS

Twelve patients with two- or three-vessel coronary artery disease and with an ejection fraction greater than 0.5 were studied in the operating room after sternal closure and elective coronary artery bypass grafting.

INTERVENTIONS

Prostacyclin was administered at infusion rates of 2.5, 5, 10, and 20 ng/kg/min. Systemic and pulmonary 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%, respectively), systemic vascular resistance (31% and 42%), and pulmonary vascular 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, prostacyclin caused no changes in regional myocardial oxygen extraction, indicating that prostacyclin did not induce direct coronary vasodilation. There were no electrocardiographic or obvious metabolic signs of myocardial ischemia during prostacyclin infusion.

CONCLUSION

Prostacyclin may be a useful afterload-reducing compound after coronary artery bypass grafting because it has no direct coronary vasodilatory effect, which minimizes the risk of myocardial ischemia.