Among patients with bio- prosthetic valves, those with a mitral prosthesis have higher rates of thromboembolism than do those with an aortic prosthesis (2.4% per patient- year versus 1.9% per patient-year).15 In studies of patients with bioprosthetic aortic valves who were in sinus rhythm and had no other indi- cations for anticoagulation, the incidence of thromboembolic events, bleeding, and death was similar in those who received aspirin or aspirin- like antiplatelet agents only and in those who There are no studies examin- ing the long-term effects of antiplatelet agents in patients with bioprosthetic mitral valve repair or mitral valve repair; the beneficial effects seen with bioprosthetic aortic valves may apply to mitral valves, as well.9,18 7. Many patients who undergo surgical implantation of a bioprosthetic mitral or aortic valve will not require lifelong anticoagulation in the absence of an independent indication, such as AF. However, there is an increased risk of ischemic stroke early after operation, particularly in the first 90 to 180 days after either bioprosthetic AVR or mitral valve Anticoagulation early after valve implantation is intended to decrease the risk of thromboembolism until the prosthetic valve is fully endothelialized. The potential ben- efit of anticoagulation therapy must be weighed against the risk of bleeding. In a nonrandomized Figure 12. Antithrombotic therapy for prosthetic valves. Colors correspond to Table 2. *Thromboembolic risk factors include an older-generation valve, AF, previous thromboembolism, hypercoagulable state, and LV sys- tolic dysfunction. For a mechanical On-X AVR and no thromboembolic risk factors, a goal INR of 1.5 2.0 plus aspirin 75 100 mg daily may be reasonable starting 3 months after surgery. ASA indicates aspirin; AVR, aortic valve replacement; INR, international normalized ratio; MVR, mitral valve replacement; VKA, vitamin K antagonist; Rx, medication; and TAVI, transcatheter aortic valve implantation. 