Five-year survival benefit following heart transplant varies widely across transplant centers, and patient management practices at individual centers may confer benefits not currently accounted for in the US heart allocation system, according to a study published in JAMA.
There are a limited number of donor hearts available for transplantation each year, and candidates are ranked primarily based on the type of supportive therapy they receive. Transplant center-specific outcomes are not considered in organ allocations. In this observational study, researchers used data from the Scientific Registry of Transplant Recipients to identify adult candidates for heart transplant in the United States between January 1, 2006, and December 31, 2015 (n=29,199).
The primary outcome was the estimated improvement in absolute 5-year survival benefit gained by undergoing heart transplant. Secondary outcomes were the characteristics of patients who underwent heart transplants at high- vs low-survival benefit centers. Researchers fit a mixed-effects Cox proportional hazard model to estimate survival benefit associated with heart transplant.
Of the candidates on the transplant waiting list at 113 centers who underwent heart transplant (n=19,815), 27% died or underwent another transplant operation during the study period (n=5389). Of the candidates who did not undergo heart transplant (n=9384), 2644 died while on the waiting list, and 3025 died after being delisted. Heart transplant was associated with a mean hazard ratio (HR) for death of 0.24 (interquartile range [IQR], 0.14-0.35), compared with candidates on the waiting list without transplant. After adjusting for status, the candidates’ risk for death while on the waiting list without transplant varied by center (HR, 0.71-1.63) relative to the mean center. The reduction in mortality risk after heart transplant also varied significantly (HR, 0.71-1.68). Center effects led to wide variation in adjusted survival benefit associated with heart transplant. The mean improvement in estimated 5-year survival ranged from 30% to 55% by center (IQR, 40%-47%). For every 10% decrease in estimated transplant candidate waiting list survival at a given center, there was an increase of 6.2% in the 5-year survival benefit (95% CI, 5.2%-7.3%).
Limitations of this study include the fact that an increased mortality risk for candidates on the waiting list may reflect suboptimal care management before transplant rather than illness severity within the center’s population. Also, there was the potential for a bias in the results of the individual centers because the models used may not have fully captured the quality of donor hearts as a result of limited accuracy of the donor risk index.
“The novel mixed-effects approach identified a large group of low survival benefit centers that prioritized less medically urgent candidates who had a lower risk [for] death without transplant and less potential survival benefit than the statistical mean recipient,” noted the researchers. “The study results also suggest that the priority reassignments in the new 6-tier allocation system may reduce the variability in survival benefit, potentially through the limited incorporation of objective medical acuity criteria and disease-specific status adjustments.”
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Parker WF, Anderson AS, Gibbons RD, et al. Association of transplant center with survival benefit among adults undergoing heart transplant in the United States. JAMA. 2019;322(18):1789-1798.