Modern cardiac valve devices--bioprostheses and mechanical prostheses: state of the art

The choice of bioprostheses and mechanical prostheses as valvular substitutes for cardiac valve replacement surgery has existed for over 20 years. The extensive developments over the past three decades have been introduced to reduce or eliminate valve related complications, namely thromboembolism, anticoagulant related hemorrhage, and structural failure, as well as to optimize hemodynamic performance. The biological valvular prostheses, namely porcine aortic or bovine pericardium, have been developed with tissue preservation, together with stent designs, that contribute to preservation of anatomical characteristics and biomechanical properties of the leaflets. The mechanical prostheses have been developed to eliminate structural failure, to facilitate prevention of blood status and thrombus formation, to facilitate radiopacity for evaluation of prosthesis function, and to facilitate intraoperative leaflet positioning. The implantation of the various present generation bioprostheses and mechanical prostheses requires special considerations to avoid technical complications and support ventricular performance. The studies of biological and mechanical prostheses, both randomized and nonrandomized, as well as specific prosthesis assessments, have contributed to the establishment of indications for types of prostheses. Bioprostheses have a high risk of structural failure and reoperation, while mechanical prostheses have a high risk of thromboembolism and anticoagulant hemorrhage. Within the bioprostheses population, the risk factors for structural valve deterioration are younger age and mitral prosthesis. Older patients (> 65 years of age) have a greater risk of valve related complications with mechanical prostheses, while younger patients (< 40 years of age) are at greater risk with bioprostheses. Comparison of large bioprostheses and mechanical prostheses populations by age groups revealed that regardless of the differences in the freedom from structural valve deterioration, the freedom from treatment failure (valve related mortality and permanent impairment from thromboembolism, anticoagulant hemorrhage, and septal emboli from prosthetic valve endocarditis) is essentially the same for mechanical prostheses and bioprostheses at 10 years. The quality of life is superior with bioprostheses, while patient survival and total valve related morbidity/mortality are similar with both types of prostheses.