The optimal therapeutic range for oral anticoagulant treatment as suggested by fibrinopeptide A (FpA) levels in patients with heart valve prostheses

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Abstract
Fibrinopeptide A is a good marker of in vivo thrombin formation. The aim of oral anticoagulants (OA) is to lower in vivo thrombin formation. We therefore assessed FpA levels on several occasions in 38 patients receiving OA for artificial heart valve prostheses and in 20 patients receiving OA for biological heart valve prostheses. The mean FpA level, 1 82 ng ml‐1 (SEM 0.14, n= 176), in patients with artificial valves was significantly higher than the mean, 1.02 ng ml‐1 (SEM 0.4), obtained in 41 healthy subjects (P=0.01). FpA mean value for biological valves was 1.41 ng ml‐1 (SEM 0.14, n=76), which was not significantly higher than controls (P=0.08). A decrease in FpA levels, for both artificial and biological heart valve prostheses, was associated with a parallel increase in the intensity of anticoagulation. When considering FpA values obtained in the optimal therapeutic range for oral anticoagulant treatment, (International Normalized Ratio [INR] between 3 and 4.5), the mean level for artificial valves, 1.87 ng ml‐1 (SEM 0.18, n=102), was significantly higher than the mean value, 1.25 ng ml‐1 (SEM 0.16, n=55), obtained for biological valves. From a biological point of view, this indicates that artificial valves should be kept at a higher intensity of anticoagulation.