Coagulant activity during one year after bioprosthetic aortic valve replacement.

Anticoagulant therapy with warfarin is recommended in the early postoperative period after bioprosthetic aortic valve replacement (bAVR). However, some studies have addressed questions about its necessity. We evaluated postoperative coagulant activity data including prothrombin time-international normalized ratio (PT-INR) and thrombin-antithrombin III complex (TAT), measured every month in 21 bAVR patients during the 1st postoperative year. The results were divided into four time intervals after the operation: 1-3 months (P-1), 4-6 (P-2), 7-9 (P-3), and 10-12 (P-4). Warfarin, which was administrated in the first six months, in combination with aspirin, 100 mg, was started targeting PT-INR of 1.75-2.25. The values of TAT in P-1, P-2, P-3 and P-4 were 1.35+/-1.07 (ng/ml), 0.82+/-0.55, 0.81+/-0.78, and 0.72+/-0.62, respectively, showing significantly high values in P-1. Furthermore, the TAT values of P-1 and P-2 within the range of PT-INR from 1.75 to 2.25 were 1.15+/-0.71 (ng/ml) and 0.79+/-0.52; demonstrating statistical difference between them. The coagulant activity assessments suggest that warfarin administration during the first three months is necessary for bAVR patients to keep the TAT within the normal range.