Abstract and Introduction
Increasing rates of simultaneous heart-kidney (SHK) transplant in the United States exacerbate the overall shortage of deceased donor kidneys (DDK). Current allocation policy does not impose constraints on SHK eligibility, and how best to do so remains unknown. We apply a decision-analytic model to evaluate options for heart transplant (HT) candidates with comorbid kidney dysfunction. We compare SHK with a “Safety Net” strategy, in which DDK transplant is performed 6 months after HT, only if native kidneys do not recover. We identify patient subsets for whom SHK using a DDK is efficient, considering the quality-adjusted life year (QALY) gains from DDKs instead allocated for kidney transplant-only. For an average-aged candidate with a 50% probability of kidney recovery after HT-only, SHK produces 0.64 more QALYs than Safety Net at a cost of 0.58 more kidneys used. SHK is inefficient in this scenario, producing fewer QALYs per DDK used (1.1) than a DDK allocated for KT-only (2.2). SHK is preferred to Safety Net only for candidates with a lower probability of native kidney recovery (24%–38%, varying by recipient age). This finding favors the implementation of a Safety Net provision and should inform the establishment of objective criteria for SHK transplant eligibility.
Kidney dysfunction is a common sequela of end-stage heart failure and afflicts many patients awaiting heart transplant (HT). Kidney function may recover after heart transplant alone (HT-only), particularly when acute and mild or moderate in severity. More chronic and severe kidney dysfunction may not be reversible after HT-only and often prompts consideration of simultaneous heart-kidney (SHK) transplant, the rates of which have doubled over the last decade.
This rise in SHK transplants has been facilitated by the current allocation system, in which all SHK candidates are prioritized above all candidates waiting for a kidney transplant alone (KT-only), with no standard criteria for SHK eligibility. In contrast, those with persistent kidney dysfunction after HT-only receive no such priority and, in the absence of a living donor, face the same expected wait time for a deceased donor kidney (DDK) as KT-only candidates. Such a policy produces an obvious incentive to favor SHK over HT-only whenever the reversibility of an HT candidate’s kidney dysfunction is in question.
A similar situation existed in liver transplantation until a new allocation policy for simultaneous liver-kidney (SLK) transplant was introduced in August 2017. The SLK policy established a set of objective eligibility requirements for SLK and a “Safety Net” system, in which patients exhibiting irreversible kidney failure within the first year of liver transplant gain priority access to DDKs. Consistent with the results of a prior modeling study, this policy reduced kidney utilization for SLK, particularly among those with mild or moderate kidney dysfunction, with no adverse impact on kidney graft outcomes or liver transplant recipient survival.
From the standpoint of an individual SHK candidate, the incentive favoring SHK is harmless and potentially beneficial.[9–14] But on a system-wide level, the liberal utilization of SHK transplant comes at a substantial cost. Each kidney used in the over 200 SHK transplants performed annually is one fewer available to the over 100,000 patients waiting for KT-only, for most of whom a kidney transplant will improve life expectancy and quality of life.[15,16] Those KT-only candidates who “lose out” on a DDK due to its allocation instead for SHK suffer measurably worse outcomes.
The Final Rule of transplantation states that each organ should be allocated on the basis of medical judgment and not systemic biases. The allocation of a DDK to an HT recipient with reversible kidney dysfunction, and thus unclear benefit, ahead of a KT-only candidate with higher expected benefit reflects a systemic bias that violates this principle. To stem such “overuse” of kidneys for SHK, many have advocated for standardized SHK eligibility requirements[3,14,17,20–24] and an accompanying Safety Net provision.[20–22]
No studies have provided quantitative support for this policy. As a randomized controlled trial would be infeasible, we apply a decision-analytic model to quantify the trade-off between costs and benefits of SHK and to identify subgroups for which SHK is optimal from a societal standpoint.