Objective: To explore the changes of coagulation activity and the characters of anticoagulation early after mechanical heart valve replacement. Methods: All patients only took warfarin orally for anticoagulation. The predicted international normalized ratio （INR） was 1.5 to 2.0. Several coagulation markers were monitored early after valve replacement. Complications associated with anticoagulation were recorded and analyzed. The patients were divided into three groups based on the number and position of mechanical valve prothesis

including group M （mitral valve replacement）

group A （aortic valve replacement） and group D （mitral and aortic valve replacement）.Comparison was made between the three groups. Results: Three events of mild cerebral embolism and five events of mild bleeding occurred during the early postoperative period. One patient suffered from mild cerebral embolism on the 4th day after operation

accompanied by large volume of pericardial drainage. Two patients with bleeding had lower INRs than predicted range. However

INR in one patient with mild cerebral embolism was in the predicted range. There was no significant difference in thrombo time （TT）

activated partial thromboplastin time （APTT） and INR on the 3rd day after operation compared to those before operation; meanwhile

plasma fibrinogen （FIB） concentration was higher than that before operation （P<0.05）. INR had no significant changes on the 2nd day after the beginning of anticoagulation compared to that before operation; however

INR was significantly elevated on the 4th day （P<0.05）. Warfarin doses and INRs were similar among the three groups

but FIB concentrations in plasma were higher in groups M and D than in group A （P<0.01）. Conclusion: Hypercoagulabale state exists early after mechanical heart valve replacement. When anticoagulation begins is determined by the change of coagulation markers

not by the volume of chest or pericardial drainage. INR can not accurately reflect the coagulation state sometimes

especially during the first 3 days after anticoagulation. The number and position of mechanical valve prothesis could affect coagulation state. Therefore

anticoagulation therapy should be regulated accordingly.