HIGH-RISK OF THROMBOEMBOLI EARLY AFTER BIOPROSTHETIC CARDIAC-VALVE REPLACEMENT

Objectives. We studied the rate of thromboembolism in patients undergo ing bioprosthetic replacement of the aortic or mitral valve, or bath, at serial intervals after operation and the effects of anticoagulant o r antiplatelet treatment and risk factors. Background. Thromboembolism appears to occur early after operation, but the incidence, timing and risk factors for thromboembolism and the role, timing, adequacy, effe ctiveness, duration and risk of anticoagulation and antiplatelet agent s are uncertain. Methods. The rate of thromboembolism was studied at t hree time intervals after operation (1 to 10, 11 to 90 and >90 days) i n 816 patients who underwent bioprosthetic replacement of the aortic o r mitral valve, or both, at the Mayo Clinic from January 1975 to Decem ber 1982. The effect of antithrombotic therapy (warfarin, aspirin or d ipyridamole, alone or in combination) was evaluated. Results. Median f ollow-up of surviving patients was 8.6 years. The rate of thromboembol ism (%/year) decreased significantly (p < 0.01) at each time interval after operation (1 to 10, 11 to 90 and >90 days) for mitral valve repl acement (55%, 10% and 2.4%/year, respectively) and over the first time interval for aortic valve replacement (41%, 3.6% and 1.9%/year, respe ctively). During the first 10 days, 52% to 70% of prothrombin time rat ios were low (<1.5 x control). Patients with mitral valve replacement who received anticoagulation had a lower rate of thromboembolism for t he entire follow-up period (2.5%/year with vs. 3.9%/year without antic oagulation, p = 0.05). Of 112 patients with a first thrombo embolic ep isode, permanent disability occurred in 38% and death in 4%. Risk fact ors for emboli were lack of anticoagulation, mitral valve location, hi story of thromboembolism and increasing age. Only 10% of aortic, 44% o f mitral and 17% of double valve recipients had anticoagulation at the time of an event. Patients with bleeding episodes (2.3%/year) were ol der and usually underwent anticoagulation. Blood transfusions were req uired in 60 of 111 patients (1.2%/year), and 13 patients (0.3%/year) d ied. Conclusions. Thromboembolic risk was especially high for aortic a nd mitral valve replacement for 90 days after operation, and overall w as increased with lack of anticoagulation, mitral valve location, prev ious thromboembolism and increasing age. Anticoagulation reduced throm boemboli and appears to be indicated in all patients as early as possi ble for 3 months and thereafter in those with risk factors, but needs prospective testing.