Inhibition of blood coagulation activation and oral anticoagulants in patients with mechanical heart valve prostheses

Oral anticoagulants are widely used for preventing thromboembolic events in many pathological conditions, such as mechanical or biological heart valve prosthesis, atrial fibrillation, deep vein thrombosis and post-myocardial infarction (1). Particularly, the intensity of anticoagulation to be induced in patients with mechanical heart prosthesis is not well established. In fact, the Dutch Thrombosis Policy recommends deep anticoagulation (3.6-4.8 INR) irrespective of whether the prosthesis is aortal or mitral (2). In contrast the Consensus Committee for antithrombotic therapy in patients with mechanical prosthetic valves, with North American thromboplastins, suggests a therapeutic range between 2.2 and 3.3 INR for both ball and tilt disk prosthesis (3). Again, the guidelines on oral anticoagulation published on behalf of the British Society for Hematology recommend a target of between 3 and 4.5 for mechanical heart valves (1). But is deeper anticoagulation more effective in the biochemical inhibition of the coagulation cascade ? Is there any difference between aortal and mitral prosthesis considering that a higher thromboembolic risk may be present in the latter due to hypercoagulability secondary to atrial fibrillation and blood stagnation ? For this purpose we chose to measure prothrombin F 1+2 peptide that is cleaved by factor Xa from the prothrombin molecule, since it has recently been shown that F 1+2 is reduced during oral anticoagulants (4).