Risk-benefit analysis of warfarin therapy in Hancock mitral valve replacement

The purpose of this investigation was to analyze the thromboembolic and/or major bleeding complications of 124 consecutive but nonrandomized patients who had only mitral valve replacement with the Hancock porcine xenograft between September, 1974 and June, 1979. These patients were treated either with or without anticoagulants. Four basic study groups were created: Group 1, warfarin; Group 2, aspirin; Group 3, no anticoagulants; and Group 4, warfarin and aspirin. Group 5 combined Groups 1 and 4 (warfarin and warfarin plus aspirin) and Group 6 combined Groups 2 and 3 (aspirin and no anticoagulants). The cardiac rhythm, history of embolism, and intraoperative findings of a thrombus in the left atrium were examined as risk factors for later thromboembolism . Follow-up time was 3.03 years (range 2.0 to 4.2 years). The embolic rate was not significantly different in any group (n = NS). In Groups 5 and 6 the embolic rate was 2.97 and 3.25 embolisms per 100 patient-years, respectively. Warfarin therapy resulted in significant major bleeding episodes, including two deaths (p less than 0.05). The number of patients with a history of a previous embolism, the finding of an intraoperative left atrial thrombus, or abnormal cardiac rhythm was insufficient to test embolic risk in the four treatment groups. We conclude that long-term warfarin therapy increases the risk of bleeding complications but may not significantly influence the incidence of thromboembolism arising from the Hancock porcine xenograft mitral valve. Other and larger studies are needed to confirm this last point.