Improved graft patency with anticoagulant therapy after aortocoronary bypass surgery: a prospective, randomized study.

We conducted a prospective, randomized study to evaluate the influence of oral anticoagulation on graft patency early after aortocoronary bypass surgery. Eighty-nine patients who received 251 distal venous anastomoses were treated with phenoprocoumon, a vitamin K antagonist, starting on the seventh postoperative day; 84 patients with 238 distal venous anastomoses received no anticoagulation. Both groups were comparable with respect to age, exercise hemodynamics, extent of coronary disease and left ventricular dysfunction. In each group, 2.8 distal anastomoses were constructed per patient. Graft patency after surgery was 90.4% in the treatment group and 84.6% in the control group (p less than 0.015). All anastomoses were patent in 81% and 67% of patients, respectively (p less than 0.02). Flow measurements in 279 grafts suggest that grafts with a flow of less than 90 ml/min benefit from oral anticoagulation. No graft with a flow of more than 90 ml/min was occluded.