Severe aortic stenosis (AS), when coexisting with chronic kidney disease (CKD), is associated with a faster progression of valvular disease and consequently a poorer prognosis. Aortic valve replacement (AVR) has shown a reduction in mortality compared to conservative treatment. In Spain, CKD affects approximately 10% of the population, and in its terminal stage, patients require renal replacement therapy, with a prevalence around 149 individuals per million inhabitants in 2021. The survival rate for severe AS patients in advanced CKD stages is significantly lower than for those without nephropathy (35% vs. 70%).

This study aims to compare the long-term outcomes of mechanical vs. biological AVR in dialysis patients. It is a retrospective analysis using data from the Japanese Cardiovascular Surgery Database, including dialysis patients who underwent AVR (isolated or combined with annular enlargement, mitral valve surgery, or coronary revascularization) between 2010 and 2012, excluding transcatheter interventions (TAVI) and aortic surgery. An additional period from 2019 to 2020 was designated to gather data on dialysis duration and clinical outcomes. A comparative analysis of mortality, cerebral infarction, cerebral hemorrhage, gastrointestinal bleeding, and prosthetic valve failure was conducted. The analysis included a total of 1,016 patients, evenly split into two groups (n = 508) after propensity score matching. The maximum follow-up period was 8 years.

No significant differences were found in 5-year survival (49% for bioprosthesis vs. 53% for mechanical prosthesis) per the Cox regression model (p = .318). Secondary event comparisons showed no significant differences between mechanical and biological prostheses in cerebral infarction (p = .747) and prosthetic valve failure (p = .09). However, the incidence of cerebral (p = .002) and gastrointestinal bleeding (p = .0005), necessitating admission, was higher in patients with mechanical aortic prostheses. Study data indicate that the number of dialysis patients undergoing AVR increased by nearly 20% (from 2,369 procedures in 2014 to 2,834 in 2016), with a corresponding reduction in mortality from 11.7% to 10.7% during this period.

The authors conclude that the average survival for dialysis patients undergoing AVR is approximately 50%, regardless of whether a mechanical or biological prosthesis is used. Although survival does not differ, bleeding complications are more common in patients with mechanical prostheses.

COMMENTARY:

The choice of prosthesis type (mechanical or biological) remains a point of contention in the treatment of severe AS in dialysis patients. Traditionally, it has been considered that valve degeneration in biological prostheses is higher in these patients. This may involve the same pathophysiological processes that cause greater degeneration and calcification of the native valve, although the exact mechanisms behind this degeneration are not fully understood. The durability timelines of biological prostheses in this subgroup of patients are also not well-defined, as most studies have short follow-up periods. Although historically, American guidelines recommended mechanical prostheses for such patients (class II indication), this recommendation was later removed from subsequent valvular disease guidelines without issuing specific guidance. However, choosing a mechanical prosthesis entails a higher bleeding risk due to anticoagulation and the coagulopathy that accompanies CKD. The benefits of durability must be weighed considering the reduced survival rate of dialysis patients compared to the general population.

This article provides useful findings; however, limitations exist due to its retrospective nature and reliance on national database data, which may be incomplete and make extrapolation to other populations challenging. Additionally, the lack of stratification based on concomitant surgeries may introduce bias. For example, patients who undergo mechanical mitral valve replacement, requiring a higher anticoagulation range and with a greater likelihood of bleeding complications, could skew study results. Furthermore, data on quality of life and echocardiographic data on bioprosthetic degeneration, which could guide decision-making, are missing.

In treating AS with AVR in dialysis patients, prosthesis choice should be individualized and discussed with the patient, taking into account not only age but also other conditions associated with their renal disease, such as life expectancy or kidney transplant eligibility. It is crucial to assess how these factors will impact patient quality of life, with the patient’s informed opinion being integral to the decision-making process.

REFERENCE:

Matsuura K, Yamamoto H, Miyata H, Matsumiya G, Motomura N. Mechanical vs Bioprosthetic Aortic Valve Replacement in Patients on Dialysis: Long-term Outcomes. Ann Thorac Surg. 2023 Jul;116(1):61-67. doi: 10.1016/j.athoracsur.2022.12.037.