Antithrombotic therapy in patients with valvular heart disease and prosthetic heart valves.

Indications and the type of antithrombotic therapy for the prevention of thromboembolism in patients with valvular heart disease, mechanical prosthetic heart valves and bioprosthetic heart valves are discussed. The evidence for these clinical recommendations is described and graded into five levels. The indications for anticoagulation in patients with valvular heart disease are chronic or paroxysmal atrial fibrillation, sinus rhythm with a very large left atrium, severe left ventricular dysfunction or presence of heart failure or a history of previous thromboembolism. Anticoagulant therapy is administered to prolong the prothrombin time to 1.5 to 2.0 times control, using rabbit brain thromboplastin (standardized international normalized ratio = 3.0 to 4.5). Risk factors for thromboembolism in patients with prosthetic heart valves are discussed. Because intracardiac thrombus formation may start during and continues early after operation, restarting heparin therapy 6 hours after operation and continuing it for the duration of the hospitalization is advised. For mechanical prosthetic heart valves, oral anticoagulation as outlined plus dipyridamole is advised indefinitely. Platelet inhibitor therapy alone is insufficient. For bioprosthetic heart valves, heparin is followed by oral anticoagulation as outlined for 3 months after mitral or aortic valve replacement and indefinitely after mitral valve replacement if there is atrial fibrillation or a very large left atrium; aspirin may be recommended indefinitely after aortic valve replacement. Antithrombotic therapy is also considered for four special situations: noncardiac surgery, prosthetic valve endocarditis, anticoagulation after a thromboembolic event, and antithrombotic therapy during pregnancy.