“…Such risk factors include atrial fibrillation, previous thromboembolism, hypercoagulable condition, older-generation mechanical valves, LV dysfunction (ejection fraction less than 0.30), or more than 1 mechanical valve. [971][972][973] When UFH is used, it should be started when INR falls below 2.0 (i.e., 48 h before surgery) and stopped 4 to 6 h before the procedure. UFH should be restarted as early after surgery as bleeding stability allows, and the aPTT should be maintained at 55 to 70 s until warfarin is therapeutic.…”