Management of patients with prosthetic heart valves: potential impact of valve site, clinical characteristics, and comorbidity.

Nearly four decades have passed since the first mechanical prosthetic aortic valve was placed. Since then several design changes and modifications have been made to improve longevity and hemodynamics and reduce thrombogenicity. Despite these advances thromboembolism remains the major problem for mechanical prosthetic valves. The type and the position of the prosthetic valve and several clinical characteristics such as age greater than 70, atrial fibrillation, depressed left ventricular systolic function, left atrial enlargement, left atrial thrombus and a prior history of systemic embolization influence the risk of thromboembolism and the level of anticoagulation needed to prevent this complication. Through clinical experience guidelines have been developed by the American College of Chest Physicians to determine the optimal level of anticoagulation needed to lower the thromboembolic rate with an acceptable hemorrhagic event rate.