Antithrombotic therapy for patients with cardiac disease

The use and type of antithrombotic therapy for patients with cardiac disease are described based on an understanding of the pathophysiologic mechanisms involved, the risk of thromboembolism, and the evidence from prospective and, if necessary, retrospective clinical trials. The indications and intensity of anticoagulant therapy in patients with valvular heart disease and prosthetic valves are first discussed. We recommend that the prothrombin time be reported as a ratio and standardized using the International Normalized Ratio. The pivotal role of platelets and the clotting system in the initiation and progression of atherosclerosis and the acute coronary syndromes is described. There is no evidence to date that antiplatelet therapy is of value in primary prevention or in patients with stable angina, but the value of aspirin in patients with unstable angina was clearly shown in two well-designed studies. Adequate prophylactic therapy to prevent the thrombotic complications of acute myocardial infarction (i.e., venous thrombosis and intracardiac thrombosis) is described, and the available data on the prevention of coronary reocclusion after thrombolysis reviewed. There is now convincing evidence from studies in animals and in patients that vascular injury during aortocoronary vein bypass graft surgery requires antitihrombotic therapy starting before the procedure to minimize acute platelet thrombus deposition and prevent occlusion. Restenosis after arterial angioplasty appears to be related to acute platelet thrombus deposition on the site of deep arterial injury. Therapeutic interventions should probably involve both anticoagulants and platelet inhibitor therapy. Implications derived from recent animal studies are discussed.