[Inhibition of thrombocyte aggregation after heart valve replacement]

After implantation of a mechanical cardiac valve, lifelong, full anticoagulation has been the tradition. After implantation of a biological valve, anticoagulation during 3 months subsequent to the operation is customary. This review evaluates the role of platelet inhibition after cardiac valve replacement. Platelet aggregation is inhibited effectively by aspirin in a daily dose of 100-160 mg. At this dose, episodes of severe bleeding are not significantly more frequent than during placebo, whereas patients on full anticoagulation bleed at a rate of 2% per year. After implantation of a mechanical cardiac valve, sole platelet inhibition is inferior to full anticoagulation. With a lower rate of bleeding, aspirin appears to prevent thromboembolic episodes caused by mechanical bileaflet prostheses (e.g., St. Jude) in the aortic position, and is almost as efficient as full anticoagulation. In Germany, patients with a porcine bioprosthesis, as currently in use, in the aortic position, frequently receive 100 mg aspiring per day. For patients with porcine bioprostheses in the mitral plus eventually in the aortic position in stable sinus rhythm, 100 mg aspirin per day is preferred to anticoagulation. For children with mechanical aortic valves, aspirin (2 mg/kg/day) needs to be considered an effective and convenient alternative to anticoagulation. Combining anticoagulation with 100 mg aspirin per day after implantation of a left-sided mechanical cardiac valve is pathophysiologically sound, but used to be considered as rendering the patients too bleeding-prone. Recently, total mortality and morbidity definitely have been demonstrated to be reduced by combined anticoagulation and platelet inhibition as compared to sole anticoagulation. Combining platelet inhibition with moderate anticoagulation (INR 2.0-3.0) was superior to combining it with full anticoagulation in terms of safety (INR > 3.0). Thus, current evidence favors combining moderate anticoagulation with 100 mg aspirin per day after left-sided mechanical cardiac valve replacement.