EComment. Are mechanical valves better than bioprostheses in patients on dialysis?

Abstract

We read with great interest the article by Pai et al. regarding the best valve substitute in patients on dialysis [1]. They included in the results of their research, seven retrospective studies and one meta-analysis. However, we found 4 other relevant articles investigating the same problem. In order to be exhaustive, we will summarize the relevant results of these studies and highlight the safety of implanting bioprosthesis in patients on chronic dialysis. The standard of valve selection has changed over time. It has long been believed that tissue valves undergo premature degeneration due to the derangements in calcium metabolism in patients with end-stage renal disease. This is based on largely anecdotal case reports using first generation bioprostheses. In 1998, ACC/AHA guidelines recommended the use of mechanical valves in patients on dialysis. Accumulating data supporting the very low incidence of rapid tissue valve degeneration in dialysis patients had been taken into consideration, and the latest ACC/AHA practice guidelines do not specify the best choice for valve replacement in dialysis patients. Only four cases of structural valve deterioration (SVD) requiring reoperation were identified from the meta-analysis [1], ranging from 10 to 96 months after the initial valve replacement surgery. However, conclusions on the long-term performance of tissue valves in this patient population cannot be drawn. Bleeding was the most common valve-related complication, and represented a major drawback of mechanical valves. Lucke et al. [2] reviewed 19 consecutive patients with end-stage renal disease from a single institution who had undergone aortic, mitral or aorto-mitral valve replacement, 9 had a bioprosthetic valve and 10 a mechanical valve. Mechanical valve patients had a significantly higher rate of postoperative cerebrovascular events or bleeding complications. No subsequent reoperations were required for biological valve failure. The overall estimated Kaplan-Meier survival was 42% ± 14% at 60 months. Kaplon et al. [3] from The Cleveland Clinic Foundation, found comparable results for both types of valves when reviewing 42 patients on preoperative dialysis undergoing valve replacements. Seventeen patients received mechanical valves and 25 received bioprosthesis. Four patients with a bioprosthesis required reoperation, one of whom experienced mitral bioprosthesis degeneration. Prosthetic valve-related complications and survival were similar for both mechanical and bioprosthetic valves. Toole et al. [4] reviewed 50 dialysis patients undergoing left-sided valve replacement. The tissue valve group had significantly higher Kaplan-Meier freedom from valve-related morbidity and mortality at three years. Freedom from reoperation was not significantly different. Umezu et al. [5] analyzed data from 63 consecutive dialysis patients who underwent valvular surgery. The mechanical group had a higher rate of bleeding events. There was no case of SVD up to the 5-year follow-up. However, both mechanical and bioprosthetic valve patients had similar survival and event-free rates. It can be concluded that dialysis patients after cardiac valve replacement suffer poor mid- and long-term survival. Therefore, surgeons should not hesitate to implant bioprosthetic valves because SVD will be uncommon in this patient population. Prosthesis selection should be based on the same criteria used for non-dialysis patients. Conflict of Interest: None declared