Therefore, no spe- cific management recommendations can be made for these conditions. 4. In patients undergoing bioprosthetic mitral or aor- tic valve replacement surgery, oral anticoagulation with warfarin to achieve a target INR of 2.5 (range, 2.0 3.0) is reasonable for at least 3 months and for as long as 6 months after surgery in patients at low risk of bleeding.33 This recommendation is based on the results of observational studies that have reported an increased risk of ischemic stroke early after surgery.488 490 After 3 to 6 months after surgery, long-term therapy with only aspirin 75 to 100 mg daily is recommended.473,491 493 Patients with a history of ischemic stroke or TIA (before the bioprosthetic valve surgery) who are already receiving antiplatelet therapy and have no indica- tion for anticoagulation therapy should continue to be managed with antiplatelet therapy alone after the bioprosthetic valve insertion. 5. In patients with mechanical prosthetic heart valves, effective antithrombotic therapy requires continu- ous effective warfarin anticoagulation with an INR in the target range.33 ACC/AHA guidance on the selection of the most appropriate antithrombotic regimen in patients with mechanical heart valves has been published in separate guidelines.33 Anticoagulation with warfarin to achieve an INR of 2.5 is typically recommended for patients with a mechanical bileaflet or current-generation single- tilting-disk aortic valve replacement and no risk factors for thromboembolism.458,469,472,473 However, patients with an aortic mechanical prosthesis who have a history of ischemic stroke or TIA are at higher risk of thromboembolic complications, and it is recommended to maintain the INR at a higher target of 3.0 (range, 2.5 3.5) or to add aspirin 75 6. 