THE DIFFERENTIAL IMPACT AND LONG-TERM EFFECTS OF MECHANICAL OR BIOLOGICAL VALVE REPLACEMENTS IN MEDICARE PATIENTS ON HEMODIALYSIS

Abstract

Hemodialysis patients have increased risk for valve replacement and have decreased long-term survival. Debate is ongoing regarding biologic versus mechanical valve replacements in hemodialysis patients. This study sought to investigate the differential impact of biological and mechanical valves on aortic valve replacement (AVR) and mitral valve replacement (MVR) Medicare patients on hemodialysis. Medicare Provider Analysis and Review (MEDPAR) Files were used to identify all hemodialysis patients undergoing aortic valve replacement (AVR) and mitral valve replacement (MVR) between January 2008 and December 2013. Patients were separated based on the use of either bioprosthetic or mechanical valves. Comorbidities present on implantation were assigned using ICD-9 codes and a modified Elixhauser comorbidity index. Propensity matching was used to analyze bioprosthetic and mechanical valves in AVR and MVR patients. Univariate and multivariate models were used to examine survival; all other analyses were conducted using pearson’s chi-square or independent-sample t tests. A total of 11,850 patients were initially included in the study (8775 AVR and 4298 MVR). In propensity matched samples, Kaplan Meier survival analysis indicates that survival was significantly higher in mechanical AVR patients compared to prosthetic AVR patients, although similar between mechanical and prosthetic MVR patients (Figure 1). Overall AVR mortality was significantly lower than MVR mortality (58% vs. 66%, p < 0.01). Bioprosthetic AVR patients were more likely to require redo operations compared to mechanical AVR (2% vs. 1%, p < 0.01). Multivariate logistic regression models indicate that mechanical valves do not provide a protective effect for 30 day mortality in either AVR or MVR patients. Cox proportional models indicate that mechanical valves may provide some protective effect in long-term mortality for AVR patients (HR 0.94 CI 0.88 - 1.02, p=0.05). These results indicate that there is no significant difference in survival or redo operation between bioprosthetic and mechanical valves in MVR patients. However, bioprosthetic AVR patients are significantly more at risk for death or redo operations. It is possible that mechanical AVR offers a long-term survival benefit to older patients on hemodialysis undergoing valve replacement surgery.