Until very recently, warfarin is still the best drug of choice for long-term anticoagulation for patients with mechanical prosthetic heart valve. However, the complication of warfarin account for 75 percent of the whole complication after the mechanical prosthetic heart valve replacement.

Interindividual variation in warfarin dose is mediated by multiple factors.Advanced models using combinations of clinical attributes and genetic factors(CYP2C9, VKORC1, and CYP4F2) explain 50-75% of variability in warfarin dose requirements.These warfarin dosing models have the potential to improve patient safety by reducing or eliminating serious adverse events. The investigators conducted a prospective, randomized, blinded, two arm trial to test this hypothesis.

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