Aortic bioprosthesis without early anticoagulation--risk of thromboembolism.

Anticoagulation after implantation of a bioprosthetic heart valve has been suggested during a high-risk period of 3 months following surgery. There is little information available concerning the risk of thromboembolism during this period if anticoagulation is not carried out. However, this is of interest since 60-80% of all bleeding complications due to anticoagulation occur during the first year of treatment. Between 1983 and 1993, 57 of our patients did not receive oral anticoagulation after implantation of a bioprothesis in the aortic position (49 Hancock, 7 Mitroflow and one Edwards stentless). All patients were investigated retrospectively. A risk for thromboembolic complications of 1.75% is calculated for the first six months following surgery, being 3.5 per 100 patients/year. There seems to be no advantage in standard anticoagulation (INR 2.5-4) with its risk of serious bleeding complications of about 4% during this period of treatment. Low-dose anticoagulation (INR 2.0-2.3), however, preferably in combination with prothrombin estimation by the patients, seems to offer a relatively safe treatment for these patients.