INHIBITION OF BLOOD-COAGULATION ACTIVATION AND ORAL ANTICOAGULANTS INPATIENTS WITH MECHANICAL HEART-VALVE PROSTHESES

Oral anticoagulants are widely used for preventing thromboembolic even ts in many pathological conditions, such as mechanical or biological h eart valve prosthesis, atrial fibrillation, deep vein thrombosis and p ost-myocardial infarction (I). Particularly, the intensity of anticoag ulation 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 prosthe sis is aortal or mitral (2). In contrast the Consensus Committee for a ntithrombotic therapy in patients with mechanical prosthetic valves, w ith North American thromboplastins, suggests a therapeutic range betwe en 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 Brit ish Society for Hematology recommend a target of between 3 and 4.5 for mechanical heart valves (1). But is deeper anticoagulation more effec tive in the biochemical inhibition of the coagulation cascade? Is ther e any difference between aortal and mitral prosthesis considering that a higher thromboembolic risk may be present in the latter due to hype rcoagulability 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 rece ntly been shown that F 1+2 is reduced during oral anticoagulants (4).