Omission of aspirin in patients following coronary artery bypass graft surgery

Graft patency is a major factor contributing to the long-term results of coronary artery bypass graft (CABG) surgery. The systematic overview of the Antiplatelet Trialists' Collaboration provides unequivocal evidence that antiplatelet therapy reduces by nearly one-half the odds of coronary graft occlusion following CABG. We retrospectively reviewed patients undergoing CABG during 1993 at the Cardiothoracic Unit, Northern General Hospital, to determine the incidence of, and indications for, aspirin omission following CABG: 462 patients with isolated CABG, 75 patients with a combined CABG and a heart valve procedure and 21 patients with a combined CABG and other non-valve procedure. Thirty-six patients (7.5%) with isolated CABG and CABG combined with a non-valve procedure were not prescribed aspirin. The reasons for aspirin omission were categorized into three groups depending on whether omission was fully justified (group 1), possibly justified (group 2) or unjustified (group 3). Twenty-one patients were in groups 2 and 3, nine of whom were started on aspirin 2-6 weeks after discharge without any ill effect. Forty-two patients were discharged from hospital on a three month course of warfarin. Four months later four patients had died, 24 had changed to aspirin, 10 were still on warfarin and four were on neither drug. Aspirin was sometimes omitted without clear indications. Better provisions for supervision should be made by either the General Practitioner or Hospital Practitioner during the change-over period from oral anticoagulation to antiplatelet therapy in patients on a short course of warfarin.