High-Risk (bridging anticoagulation suggested):
• any mechanical prosthetic mitral valve
• older generation (cage-ball, tilting disc) mechanical aortic valve
• recent (within 3 months) arterial thromboembolism (stroke, systemic embolism, transient ischemic attack [TIA])
• recent (within 3 months) venous thromboembolism (deep vein thrombosis, pulmonary embolism)
• prior arterial or venous thromboembolism during interruption of warfarin
• severe thrombophilia (e.g. deficiency of protein C, protein S or antithrombin, antiphospholipid antibodies)
Intermediate-Risk (bridging anticoagulation optional and based on individual patient characteristics):
• newer generation (bileaflet) mechanical aortic valve
• bioprosthetic aortic valve
• chronic atrial fibrillation (valvular or nonvalvular) and at least 1 major stroke risk factor: prior stroke/TIA, left ventricular dysfunction, hypertension, diabetes, or age >75 years
• prior venous thromboembolism within last 3-12 months
Low-Risk (no bridging anticoagulation suggested):
• chronic atrial fibrillation (valvular or nonvalvular) and no major stroke risk factors
• prior venous thromboembolism over 12 months ago