Antithrombotic therapy in patients with mechanical and biological prosthetic heart valves

Mechanical Prosthetic Heart Valves 1. Long-term (permanent) warfarin therapy offers the most consistent protection. 2. Doses of warfarin that increase the PT ratio to an INR greater than 4.5 are associated with excessive bleeding. 3. Levels of warfarin that prolong the PT ratio to an INR of 1.8 or less appear to lead to a high risk of thromboembolic events (level II). 4. Levels of warfarin that prolong the PT ratio to an INR of 2.5 to 3.5 are as satisfactory for tilting disk valves as higher levels (level II and V studies). 5. Experience in patients with ball valves with a PT ratio below an INR of 4.5 is sparse (level II). Levels of warfarin that prolong the PT ratio to an INR of 2.2 to 3.3 are probably adequate for ball valves as well as tilting disk valves (level II). 6. Dipyridamole (375 to 400 mg/d) in addition to warfarin may have an additive benefit (level I, II), although beneficial effects sometimes were not shown (level II). Bleeding was not increased with dipyridamole. 7. Aspirin (100 mg/d) in addition to warfarin PT ratio (INR) 3.0 to 4.5 may have an additive effect without greatly increasing the risk of bleeding (level I). However, no benefit, as well as increased bleeding, was shown with aspirin 500 mg/d plus warfarin PT ratio (INR) 2.5 to 7.8 (level II). 8. Antiplatelet agents alone may offer satisfactory protection in patients in sinus rhythm with St. Jude valves in the aortic position (level III, V), but good results were inconsistent. Antiplatelet agents alone with the standard Bjork-Shiley valve showed unsatisfactory results (level IV). 9. Among patients with bioprosthetic valves in the mitral position less intense warfarin therapy (PT ratio with an INR of 2.0 to 2.25) was as effective as a more intense regimen (INR 2.5 to 4.5) but was associated with fewer bleeding complications (level I).