[Anticoagulation of valvular prostheses]

Abstract

Prosthetic valve replacement has transformed the outcome of patients with severe or poorly tolerated valvular heart disease. Between the two main families of prostheses, only mechanical prostheses require indefinite anticoagulant therapy to lower the thromboembolic risk. National and international guidelines have been published within the past decade. They have outlined how anticoagulation, essentially oral anticoagulant therapy and transient heparin, should be used. The intensity of anticoagulation depends on the type of prosthesis, its position, the presence of atrial fibrillation and the individual's risk of thromboembolism. Monitoring is based on the INR. Temporary recourse to heparin therapy is necessary for all situations in which the risk of major hemorrhage requires more flexible treatment (postoperative period, extracardiac surgery, stroke, severe hemorrhage) or when warfarin is contraindicated because of its risk of inducing malformation (pregnancy). Low molecular weight heparins are not yet authorized for use in prosthesis bearers. Nonetheless, they are being prescribed by more-and-more teams, seduced by the facility of their use, their more stable action and, usually, no need for biological monitoring. And their use is supported by the most recent guidelines, several favorable publications, and the excellent results obtained with them in treating other thromboembolic pathologies. Indispensable to lower the rate of thromboembolic events, anticoagulant therapy bears a hemorrhagic risk that is higher for prolonged and marked anticoagulation. On the other hand, despite effective anticoagulation, the occurrence of thromboemboli can lead to considering the adjunction, in certain cases, of anti-platelet aggregating agents, particularly favored in North America, and recommended in Europe for patients with a predilection for atheromas.