A Trial of Genotype-based Warfarin Initiation in Patients With Mechanical Prosthetic Heart Valve

Inclusion Criteria: * the first time to receive elective mitral and/or aortic mechanical prosthetic valve replacement * willing to join in the clinical trial and comply with the protocol. Exclusion Criteria: * other ethnic groups than Han * previously receive any other cardiac surgery * emergent surgery * simultaneously carry out other cardiac surgeries,such as CABG * age younger than 18y or older than 65 year * drug abuser and wine abuser * any malignancy * moderate or severe hepatic or kidney insufficiency * any thyroid disease * the history of warfarin or VitK consumption 2 week before the surgery * any hematological disease or history of bleeding * combination with any drugs that significantly influence warfarin other than Cordarone * pregnancy * any contraindication of warfarin * infectious endocarditis * advanced valvular disease * pathological obesity * psychological disease * any patient having joined in other clinical trial in the previous 30d * basic INR \> 1.4