Objective: To evaluate the plasma concentration of thrombus precursor protein （TPP） in patients after mechanical heart valve replacement

and to explore whether it can be used as a marker for monitoring anticoagulation. Methods: Totally 60 patients who took warfarin after mitral valve replacement and 20 control patients with non-valvular heart diseases were subjected in this study. Their plasma TPP concentration and international normalized ratio （INR） were determined

and compared not only between the anticoagulant patients and the control patients

but also between the patients with atrial fibrillaiton （AF

n=37） and the patients with sinus rhythm （SR

n=23） after mechanical valve replacement. The relationship between plasma TPP concentration and INR in the 60 anticoagulant patients was analyzed with linear regression. Results: It was found that the anticoagulant therapy effectively decreased plasma TPP concentration and elevated INR. In the anticoagulant group

the patients with AF had higher plasma TPP concentration than the others with sinus rhythm （P<0.05）

although there was no significant difference in INR level between these 2 groups of patients （P>0.05）. No significant correlation was found between plasma TPP concentration and INR in the anticoagulant patients （P>0.05）. INR did not accord with plasma TPP concentration in several patients. Conclusion: INR can’t reflect the coagulation status and guide the anticoagulation correctly sometimes; TPP may be a valuable assistant marker for monitoring anticoagulation in patients with mechanical heart valve prothesis; Patients with AF may require higher density of anticoagulation and TPP is strongly suggested to be monitored in these patients.