ObjectiveTo investigate the influence of high activity of CYP2C9 (Cytochrome P450 proteins 2C9)and VKORC (Vitamin K epoxide reductase C)on warfarin anticoagulation of patients after heart valve replacement (HVR). MethodsFrom February 2010 to May 2013, 40 patients with high activity of CYP2C9 and VKORC underwent HVR in the Department of Cardiac Surgery, the First Affiliated Hospital of Zhengzhou University. There were 18 male and 22 female patients with their age of 40-51 (45.18±2.93)years. There were18 patients receiving mitral valve replacement (MVR), 14 patients receiving MVR and tricuspid valvuloplasty (TVP), and 8 patients receiving double valve replacement (DVR). Depen-ding on whether they received preoperative genetic polymorphism detection of CYP2C9 and VKORC1, all the patients were divided into 2 groups with 20 patients in each group. Patients in group A didn't receive preoperative genetic polymorphism detection of CYP2C9 and VKORC1, while patients in group B received preoperative genetic polymorphism detection of CYP2C9 and VKORC1. Postoperatively, periodic examination of international normalized ratio (INR)was performed to adjust warfarin dosage. Time to reach expected INR value and morbidity were collected. All the patients were followed up for 3-12 months after discharge. Monthly telephone follow-up was performed to record INR values, morbidity and general recovery. ResultsPostoperatively, in group A, 2 patients had cerebral infarction, 2 patients had popliteal artery throm-bosis, 1 patient had pulmonary embolism, and 1 patient had thrombosis in the annulus. Expected INR was achieved 15-20 days after warfarin treatment among the other 14 patients without thromboembolism. Three months after surgery, CYP2C9 and VKORC1 gene polymorphism was examined to find 17 patients with positive CYP2C9*1/*1 (*2CC/*3AA)and positive VKORC1-1639 GA, and 3 patients with positive CYP2C9*1/*1 (*2CC/*3AA)and positive VKORC1-1639 GG. In Group B, patients received aspirin (100 mg/d)and low molecular heparin (0.4 ml/d)in addition to warfarin since the second posto-perative day. Expected INR was achieved 5-9 days after warfarin treatment, and then aspirin and low molecular heparin were discontinued. During the 6 months follow-up period, no obvious thromboembolism was found, and only 1 patient had epistaxis who was cured with nasal tamponade. ConclusionPreoperative detection of genetic polymorphisms of CYP2C9 and VKORC1 can provide important guidance for warfarin anticoagulation after HVR.