FLOW CAPACITIES OF ARTERIAL GRAFTS FOR CORONARY-ARTERY BYPASS-GRAFTING

The flow capacities of arterial and saphenous vein grafts in 100 patie nts who had coronary artery bypass grafting were compared under exerci se conditions by continuous ventricular function monitoring, which rec ords serial beat-to-beat radionuclide data and calculates left ventric ular ejection fractions every 20 seconds. Ejection fraction profiles d uring graded bicycle exercise were divided into four types. In type A, the ejection fraction continued to increase. In type B, the ejection fraction initially increased, but decreased during the late exercise s tage. In type C, the ejection fraction did not change. In type D, the ejection fraction continued to decrease throughout exercise. A decreas e in ejection fraction, observed in type B or D, is an early indicator of myocardial ischemia. Before operation, 10 patients showed type A, 30 type B, 11 type C, and 49 type D responses. After operation, 68 pat ients showed type A, 21 type B, and 11 type C responses. Patients were divided into three groups according the type of bypass graft. Group 1 included 21 patients with two arterial grafts and vein grafts; group 2, 61 patients with an internal thoracic artery graft and vein grafts; group 3, 18 patients with only vein grafts. All of the grafts were pa tent on angiography. Eight patients (38%) in group 1 and 13 (21%) in g roup 2 showed a postoperative type B response, but none of the patient s in group 3 had a postoperative type B response (p < 0.02). Seven of 8 patients in group 1 with postoperative type B responses had only art erial grafts to the left-side coronary arteries. It was suggested that flow through arterial grafts was adequate for moderate exercise but i nadequate for maximal exercise, as evidenced by the group of patients with type B ejection fraction response on graded bicycle exercise.