Thromboembolic complications of current cardiac valvular prostheses.

Thromboembolic complications associated with twelve different models of currently available aortic and mitral valve prostheses are reviewed. There is a need to standardize definitions of thrombotic phenomena and to report these events for valve model and anatomic location actuarially and in terms of incidence per 100 patient-years of follow-up. The incidence of thromboemboli is less than 2 per 100 patient-years for aortic biological valves without coumarin anticoagulation and for the best mechanical valves with coumarin. For mitral biological prostheses with and without coumarin, and for the best mechanical mitral valves with coumarin, the incidence approximates 4 per 100 patient years. The incidence of mortality and morbidity due to coumarin anticoagulation in patients with prosthetic valves is 0.17 and 2.2 per 100 patient-years, respectively. Omission, poor control or withdrawal of coumarin anticoagulation substantially increases the incidence of thromboemboli in patients with mechanical valves. Some reports suggest that the combination of dipyridamole and coumarin may further reduce thromboembolic complications without increasing bleeding problems. Atrial fibrillation clearly increases thromboembolic complications, but the importance of other factors such as atrial clot, large left atrial size, history of emboli, and first postoperative year is less definite.