Newer anticoagulant agents have not been shown to be safe or effective in patients with mechanical heart valves. 3. Patients <50 years of age at the time of AVR incur a higher and earlier risk of bioprosthetic valve Overall, the predicted 15-year risk of needing reoperation because of structural deterioration is 22% for patients 50 years of age, 30% for patients 40 years of age, and 50% for patients 20 years of age, although it is recognized that all bioprostheses are not alike in terms of durability.14 Anticoagulation with a VKA can be accomplished with acceptable risk in most patients <50 years of age, particularly in compliant patients with appropriate monitoring of INR levels. Thus, the balance between valve durability and risk of bleeding and thromboem- bolic events favors the choice of a mechanical valve in patients <50 years of age, unless antico- agulation is not desired, cannot be monitored, or is contraindicated. 4. Uncertainty and debate continue about which type of AVR is appropriate for patients 50 to 65 years of age. Newer surgical bioprosthetic valves may show greater freedom from struc- tural deterioration, specifically in the older indi- vidual, although a high late mortality rate in these studies may preclude recognition of valve The risks of bleeding and throm- boembolism with mechanical prostheses are low, especially in compliant patients with appropriate INR monitoring. Several studies have shown a survival advantage with a mechanical prosthesis in this age group. 