Is low-intensity anticoagulant therapy possible with an open pivot valve?: analysis of its development

In 1976, the authors became the codevelopers of the first successful bileaflet heart valve which has become the standard in valvular surgery. However, there still remains a significant rate of thromboembolism and thrombosis which can be attributed to the inherent design of cavities in the pivot area. These cavities contribute to stagnant areas that lead to thrombus formation. The literature indicates that this rate is approximately 2% to 2.5% per patient year. To maintain these thromboembolism rates, certain levels of warfarin have had to be used leading to a significant rate of bleeding complications. We present the theory and development of the new generation of heart valves without cavities and with an open semisphere pivot area. Results of 912 years of clinical studies of almost 50,000 valves, as well as additional features that have been incorporated to improve hemodynamics and quality of life for the patient, are discussed. The clinical results of the European Community Certification and U.S. Food and Drug Administration premarket application (PMA) studies also are given. The differences in the pivot area suggest that a reduction in thromboembolism is possible at anticoagulant levels as low as 1.5 international normalization ratio (INR) resulting in virtually no bleeding complications. Midterm clinical results are encouraging, and studies are being conducted presently to eliminate totally anticoagulants in certain patients.