Results of mechanical versus tissue AVR: caution in young patients with tissue AVR.

The first aortic valve prosthesis, implanted more than 50 years ago, was a mechanical prosthesis (ball-and-cage design). Over the ensuing decades, tissue prostheses and new mechanical designs were introduced to mitigate the need for anticoagulation with its associated side effects. Tissue and mechanical heart valve prostheses were compared in two head-to-head randomised control trials. Both of these confirmed that mechanical prostheses were durable but patients suffered anticoagulant-related bleeds. Patients who received a tissue prosthesis were more likely to suffer prosthetic dysfunction and require reoperation. This trend was stronger in younger patients. Since the publication of those two trials, several large retrospective studies using data from meta-analyses of published papers or registries have failed to show a survival advantage of either prostheses when implanted in the aortic position in younger patients. This equipoise has been reflected in the heart valve disease guidelines published by European and US societies. In recent years, the primacy of patient choice, the rapid increase in life expectancy of populations, the increased incidence of atrial fibrillation with requirement for anticoagulation, the advent of transcatheter techniques to treat degenerating tissue valves as well as advances in anticoagulant therapy and in new tissue and to a lesser extent mechanical prosthetic design continue to influence choice of aortic valve prosthesis in younger patients undergoing aortic valve replacement.