A challenge to equity in transplantation: Increased center-level variation in short-term mechanical circulatory support use in the context of the updated U.S. heart transplant allocation policy

Racial and ethnic disparities on the heart transplant waiting list

BACKGROUND

Racial disparities continue to affect countless individuals across the United States and is an ongoing issue in heart transplantation (HTx). Though inequities for post-transplant survival have been studied, there remains limited and conflicting data for waitlist outcomes. Our investigation aims to address this by analyzing mortality and transplantation outcomes on the heart transplant waiting list for various racial and ethnic groups.

METHODS

We analyzed adult patients listed for HTx between 1/2000-9/2023 using the UNOS database. Inclusion criteria included patients who identified as "White", "Black", "Hispanic", or "Asian". Patients with a prior HTx, those listed concurrently for heart-lung or lung transplants, and recipients who ultimately received a heterotopic HTx or multi-organ transplant, were excluded. Outcomes that were analyzed include waitlist mortality and odds of transplantation.

RESULTS

Over the course of the study period, the proportion of Black and Hispanic patients listed for HTx increased, while Asian groups remained stagnant and White individuals decreased. In the 21st century, we found that Black patients had increased mortality on the waitlist, however, this risk became negligible in the past decade. Odds of transplantation were significantly lower for Black and Hispanic patients, which persisted today even after implementation of the new allocation policy.

CONCLUSION

Disparities continue to exist for minority groups, namely Black and Hispanic patients, in the listing process for a heart transplant. Outcomes for marginalized populations may be improved through continued training in bias awareness, increased diversity in the HTx evaluation team, and strengthened societal efforts to address social determinants of health.

Inconsistent values and algorithmic fairness: a review of organ allocation priority systems in the United States

BACKGROUND

The Organ Procurement and Transplant Network (OPTN) Final Rule guides national organ transplantation policies, mandating equitable organ allocation and organ-specific priority stratification systems. Current allocation scores rely on mortality predictions.

METHODS

We examined the alignment between the ethical priorities across organ prioritization systems and the statistical design of the risk models in question. We searched PubMed for literature on organ allocation history, policy, and ethics in the United States.

RESULTS

We identified 127 relevant articles, covering kidney (19), liver (60), lung (24), and heart transplants (23), and transplant accessibility (1). Current risk scores emphasize model performance and overlook ethical concerns in variable selection. The inclusion of race, sex, and geographical limits as categorical variables lacks biological basis; therefore, blurring the line between evidence-based models and discrimination. Comprehensive ethical and equity evaluation of risk scores is lacking, with only limited discussion of the algorithmic fairness of the Model for End-Stage Liver Disease (MELD) and the Kidney Donor Risk Index (KDRI) in some literature. We uncovered the inconsistent ethical standards underlying organ allocation scores in the United States. Specifically, we highlighted the exception points in MELD, the inclusion of race in KDRI, the geographical limit in the Lung Allocation Score, and the inadequacy of risk stratification in the Heart Tier system, creating obstacles for medically underserved populations.

CONCLUSIONS

We encourage efforts to address statistical and ethical concerns in organ allocation models and urge standardization and transparency in policy development to ensure fairness, equitability, and evidence-based risk predictions.

Risk and Reward: Nationwide Analysis of Cardiac Transplant Center Variation in Organ Travel Distance and the Effects on Outcomes

BACKGROUND

The 2018 UNOS allocation policy change deprioritized geographic boundaries to organ distribution, and the effects of this change have been widespread. The aim of this investigation was to analyze changes in donor transplant center distance for organ travel and corresponding outcomes before and after the allocation policy change.

METHODS

The UNOS database was utilized to identify all adult patients waitlisted for heart transplants from 2016 to 2021. Transplant centers were grouped by average donor heart travel distance based on whether they received more or less than 50% of organs from >250 miles away. Descriptive statistics were provided for waitlisted and transplanted patients. Regression analyses modeled waitlist mortality, incidence of transplant, overall survival, and graft survival.

RESULTS

Centers with a longer average travel distance had a higher mean annual transplant volume with a reduction in total days on a waitlist (86.6 vs. 149.2 days), an increased cold ischemic time (3.6 vs. 3.2 h), with no significant difference in post-transplant overall survival or graft survival.

CONCLUSIONS

The benefits of reducing waitlist time while preserving post-transplant outcomes extend broadly. The trends observed in this investigation will be useful as we revise organ transplant policy in the era of new organ procurement and preservation techniques.

Characterizing Adaptive Changes and Patient Survival After 2018 Donor Allocation Restructuring: A UNOS Database Analysis

PURPOSE

We sought to characterize adaptive changes to the revised United Network for Organ Sharing donor heart allocation policy and estimate long-term survival trends for heart transplant (HTx) recipients.

METHODS

Patients listed for HTx between October 17, 2013 and September 30, 2021 were identified from the United Network for Organ Sharing database, and stratified into pre- and postpolicy revision groups. Subanalyses were performed to examine trends in device utilization for extracorporeal membranous oxygenation (ECMO), durable left ventricular assist device (LVAD), intra-aortic balloon pump (IABP), microaxial support (Impella), and no mechanical circulatory support (non-MCS). Survival data post-HTx were fitted to parametric distributions and extrapolated to 5 years.

RESULTS

We identified 27,523 HTx waitlist candidates during the study period, most of whom (n = 16,376) were waitlisted in the prepolicy change period. Overall, 19,554 patients underwent HTx during the study period (pre: 12,037 and post: 7517). Listings increased after the policy change for ECMO ( P < 0.01), Impella ( P < 0.01), and IABP ( P < 0.01) patients. Listings for LVAD ( P < 0.01) and non-MCS ( P < 0.01) patients decreased. HTx increased for ECMO ( P < 0.01), Impella ( P < 0.01), and IABP ( P < 0.01) patients after the policy change and decreased for LVAD ( P < 0.01) and non-MCS ( P < 0.01) patients. Waitlist survival increased for the overall ( P < 0.01), ECMO ( P < 0.01), IABP ( P < 0.01), and non-MCS ( P < 0.01) groups. Waitlist survival did not differ for the LVAD ( P = 0.8) and Impella ( P = 0.1) groups. Post-transplant survival decreased for the overall ( P < 0.01), LVAD ( P < 0.01), and non-MCS ( P < 0.01) populations.

CONCLUSIONS

Allocation policy revisions have contributed to greater utilization of ECMO, Impella, and IABP, decreased utilization of LVADs and non-MCS, increased waitlist survival, and decreased post-HTx survival.

OPTN/SRTR 2022 Annual Data Report: Heart

The number of heart transplants in the United States has continued to increase. Since 2011, pediatric heart transplants have increased 31.7% to 494 and adult heart transplants have increased 85.8% to 3,668 in 2022. The numbers of new candidates for pediatric and adult heart transplants have also increased, with 703 new pediatric candidates and 4,446 new adult candidates in 2022. Adult heart transplant rates continue to rise, peaking at 122.5 transplants per 100 patient-years in 2022; however, the pediatric heart transplant rate decreased to its lowest rate in the past decade, 104.2 transplants per 100 patient-years, a decrease of 13.9% from 121 transplants per 100 patient-years in 2011. Despite this, pretransplant mortality among pediatric candidates has decreased by 52.2%, from 20.8 deaths per 100 patient-years in 2011 to 10.0 deaths per 100 patient-years in 2022, but remains excessive for candidates younger than 1 year at 25.7 deaths per 100 patient-years. Among adult candidates, pretransplant mortality declined from 15 deaths per 100 patient-years in 2011 to 8.7 deaths per 100 patient-years in 2022. Since 2011, posttransplant mortality has been stable to slightly better; among recipients who underwent transplant in 2015-2017, the 1-, 3-, and 5-year pediatric survival rates were 93.7%, 89.2%, and 85.0%, respectively, and the adult survival rates were 91.3%, 85.7%, and 80.4%. Donor trends have been favorable, with an increase in the numbers of hearts recovered and growing numbers of hearts procured after circulatory death.

Heart Transplantation

Heart transplantation (HTx) remains the last therapeutic resort for patients with advanced heart failure. The present work is a clinically focused review discussing current issues in heart transplantation. Several factors have been associated with the outcome of HTx, such as ABO and HLA compatibility, graft size, ischemic time, age, infections, and the cause of death, as well as imaging and laboratory tests. In 2018, UNOS changed the organ allocation policy for HTx. The aim of this change was to prioritize patients with a more severe clinical condition resulting in a reduction in mortality of people on the waiting list. Advanced heart failure and resistant angina are among the main indications of HTx, whereas active infection, peripheral vascular disease, malignancies, and increased body mass index (BMI) are important contraindications. The main complications of HTx include graft rejection, graft angiopathy, primary graft failure, infection, neoplasms, and retransplantation. Recent advances in the field of HTx include the first two porcine-to-human xenotransplantations, the inclusion of hepatitis C donors, donation after circulatory death, novel monitoring for acute cellular rejection and antibody-mediated rejection, and advances in donor heart preservation and transportation. Lastly, novel immunosuppression therapies such as daratumumab, belatacept, IL 6 directed therapy, and IgG endopeptidase have shown promising results.

The impact of obesity and LVAD-bridging on heart transplant candidate outcomes: a linked STS INTERMACS - OPTN/UNOS data analysis

BACKGROUND

Limited data integrating waitlist and postheart transplant (HT) mortality have evaluated outcomes of left ventricular assist device (LVAD)-bridged strategy vs no LVAD according to patient characteristics. We evaluated waitlist and post-HT mortality in LVAD-bridged vs nonbridged patients based on body mass index (BMI).

METHODS

We included linked adults listed for HT in Organ Procurement and Transplant Network/United Network for Organ Sharing and patients receiving durable LVAD as bridge to HT or candidacy in Society of Thoracic Surgeons/Interagency Mechanical Circulatory Support databases (2010-2019). Using BMI at listing or LVAD implant, we categorized patients as underweight (<18.5 kg/m2), normal weight (18.5-24.99 kg/m2), overweight (25-29.99 kg/m2), and obese (≥30 kg/m2). Kaplan-Meier analysis and multivariable Cox proportional hazards models informed the effect of LVAD-bridged and nonbridged strategy by BMI on waitlist, post-HT, and overall mortality (including waitlist and post-HT mortality).

RESULTS

Among 11,216 LVAD-bridged and 17,122 nonbridged candidates, bridged candidates were more frequently obese (37.3% vs 28.6%) (p < 0.001). Multivariable analysis indicated increased waitlist mortality in LVAD-bridged vs nonbridged with overweight (Hazard ratio (HR) 1.18, 95% confidence interval (CI) 1.02-1.36) or obesity (HR 1.35, 95%CI 1.17-1.56) in comparison to normal weight candidates (HR 1.02, 95%CI 0.88-1.19) (p-interaction < 0.001). Post-transplant mortality was not statistically different in LVAD-bridged vs nonbridged patients across BMI categories (p-interaction = 0.26). There was a nonsignificant graded increase in overall mortality in LVAD-bridged with overweight (HR 1.53, 95%CI 1.39-1.68) or obesity (HR 1.61, 95%CI 1.46-1.78) compared to nonbridged patients (p-interaction = 0.13).

CONCLUSIONS

LVAD-bridged candidates with obesity had higher waitlist mortality compared to nonbridged candidates with obesity. Post-transplant mortality was similar in LVAD-bridged and nonbridged patients, but obesity remained associated with increased mortality in both groups. This study may aid clinicians and advanced heart failure patients with obesity in decision-making.

The Association of the UNOS Heart Allocation Policy Change With Transplant and Left Ventricular Assist Device Access and Outcomes

In October 2018, the allocation policy for adult orthotopic heart transplant (OHTx) in the United States was changed, with the goal of reducing waitlist mortality and providing broader sharing of donor organs within the United States. This study aimed to assess the association of this policy change with changes in access to OHTx versus left ventricular assist devices (LVADs), overall and in key sociodemographic subgroups, in the United States from 2016 to 2019. We identified all patients receiving OHTx or LVAD between 2016 and 2019 using the National Inpatient Sample. Controlling for medical co-morbidities, prepolicy trends, and within-hospital-year effects, we fit a dynamic logistic regression model to evaluate patient and hospital factors associated with receiving OHTx versus LVAD before versus after policy change. We also examined the frequency of temporary mechanical circulatory support in the same fashion. We identified 2,264 patients who received OHTx and 3,157 who received LVADs during the study period. In its first year of implementation, the United Network for Organ Sharing policy change of 2018 was associated with no overall change utilization of OHTx versus LVAD. In OHTx recipients, the frequency of use of temporary mechanical circulatory support changed from 15.6% in the before period to 42.6% in the after period (p <0.001). Although the policy change was associated with differences in the odds of receiving an OHTx versus LVAD between different regions of the country, there were no significant changes based on age, gender, race/ethnicity, insurance status, or rurality. In conclusion, the United Network for Organ Sharing policy change on access to OHTx was associated with no overall change in OHTx versus LVAD use in its first year of implementation although we observed small changes in relative odds of transplant based on rurality. Shifts in regional allocation were not significant overall, although certain regions appeared to have a relative increase in their use of OHTx.

Challenges with the current United Network for Organ Sharing heart allocation system

PURPOSE OF REVIEW

The revised United States heart organ allocation system was launched in October 2018. In this review, we summarize this United Network for Organ Sharing (UNOS) policy and describe intended and unintended consequences.

RECENT FINDINGS

Although early studies published after the change suggested postheart transplant survival declined at 6 months and 1 year, recent publications with longer follow-up time have confirmed comparable posttransplant survival in adjusted models and several patient cohorts. Moreover, the new allocation decreased overall waitlist time from 112 to 39 days ( P  < 0.001). Mean ischemic time increased because of greater distances traveled to acquire donor hearts under broader sharing. Despite the intention to decrease exception requests by expanding the number of priority tiers to provide more granular risk stratification, ∼30% of patients remain waitlisted under exception status. Left-ventricular assist device (LVAD) implants are declining and the number of LVAD patients on the transplant list has decreased dramatically after the allocation system change.

SUMMARY

As the next allocation system is developed, it is imperative to curtail the use of temporary mechanical support as a strategy solely for listing purposes, identify attributes that more clearly stratify the severity of illness, provide greater oversight of exception requests, and address concerns regarding patients with durable LVADs.

Ethics of allocation of donor organs

PURPOSE OF REVIEW

There is no widely accepted single ethical principle for the fair allocation of scarce donor organs for transplantation. Although most allocation systems use combinations of allocation principles, there is a particular tension between 'prioritizing the worst-off' and 'maximizing total benefits'. It is often suggested that empirical research on public preferences should help solve the dilemma between equity and efficiency in allocation policy-making.

RECENT FINDINGS

This review shows that the evidence on public preferences for allocation principles is limited, and that the normative role of public preferences in donor organ allocation policy making is unclear. The review seeks to clarify the ethical dilemma to the transplant community, and draws attention to recent attempts at balancing and rank-ordering of allocation principles.

SUMMARY

This review suggests that policy makers should make explicit the relative weights attributed to equity and efficiency considerations in allocation policies, and monitor the effects of policy changes on important ethics outcomes, including equitable access among patient groups. Also, it draws attention to wider justice issues associated not with the distribution of donor organs among patients on waiting lists, but with barriers in referral for transplant evaluation and disparities among patient groups in access to waiting lists.

Practical application of the French two-score heart allocation scheme: Insights from a high-volume heart transplantation centre

BACKGROUND

In 2018, a cardiac allocation scheme based on an individual score considering the risk of death both on the waitlist and after heart transplantation was implemented in France.

AIMS

To analyse the practical application of the pre- and post-transplant risk score in a French high-volume heart transplantation centre.

METHODS

All consecutive adult patients listed for a first non-combined heart transplantation between 02 January 2018 and 30 June 2022 at our centre were included. Baseline characteristics of candidates and recipients were retrieved from the national CRISTAL registry. Both scores were calculated at listing and at transplant.

RESULTS

Overall, 364 patients were included. During follow-up, 257 patients (70.6%) were transplanted, and 57 (15.6%) died or were removed from the waitlist. Post-transplant 3-month survival was 84.8%. Total bilirubin and natriuretic peptides had the most important weight in the pretransplant risk score. This score had a major impact on waitlist outcomes: quartile 1 was characterized by low access to heart transplantation (58.2%) and risk of death on the waitlist (9.9%) compared with quartile 4 (heart transplantation rate 74.1%, mortality on the waiting list>20%). According to the post-transplant risk score, a minimal number of candidates were considered ineligible for heart transplantation (<1%), but 12.4% were contraindicated to at least one donor category. The number of contraindicated donor categories had a significant impact on waitlist outcomes. Although adequately calibrated, the post-transplant score had a limited discrimination (area under the curve 0.65, 95% confidence interval 0.59-0.71).

CONCLUSION

Our results highlight the major impact of pre- and post-transplantation risk scores on waitlist outcomes following the allocation scheme update.

Impact of the 2018 UNOS Heart Transplant Policy Changes on Patient Outcomes

In 2018, the United Network for Organ Sharing implemented a 6-tier allocation policy to replace the prior 3-tier system. Given increasing listings of critically ill candidates for heart transplantation and lengthening waitlist times, the new policy aimed to better stratify candidates by waitlist mortality, shorten waiting times for high priority candidates, add objective criteria for common cardiac conditions, and further broaden sharing of donor hearts. There have been significant shifts in cardiac transplantation practices and patient outcomes following the implementation of the new policy, including changes in listing practices, waitlist time and mortality, transplant donor characteristics, post-transplantation outcomes, and mechanical circulatory support use. This review aims to highlight emerging trends in United States heart transplantation practice and outcomes following the implementation of the 2018 United Network for Organ Sharing heart allocation policy and to address areas for future modification.

Impact of the 2018 French two-score allocation scheme on the profile of heart transplantation candidates and recipients: Insights from a high-volume centre

BACKGROUND

In 2018, a new cardiac allograft allocation scheme, based on an individual scoring system, considering the risk of death both on the waiting list and after heart transplantation, was implemented in France.

AIM

To assess the impact of this new scheme on the profile of transplantation candidates and recipients.

METHODS

In this single-centre retrospective study, we included consecutive patients listed and/or transplanted between 01 January 2012 and 30 September 2021 at La Pitié-Salpêtrière Hospital. Baseline characteristics of patients were retrieved from the national CRISTAL registry and were compared according to the type of allocation scheme (before or after 2018).

RESULTS

A total of 1098 newly listed transplantation candidates and 855 transplant recipients were included. One-year mortality rates after listing and after transplantation were 12.4% and 20%, respectively. At listing, the proportion of candidates on inotropes significantly declined following the scheme update (26.3 versus 20.9%; P=0.038), reflecting a change in medical practice. At transplantation, recipients had worse kidney function (estimated glomerular filtration rate<60mL/min/1.73 m²: old scheme, 29.7%; new scheme, 46.4%; P<0.001) and were more likely to be on extracorporeal membrane oxygenation support (33.5% versus 28.1%; P=0.080) under the new scheme, reflecting the prioritization of more severe patients. Outcomes after transplantation were not significantly influenced by the allocation system.

CONCLUSIONS

The implementation of the 2018 French allocation scheme had a limited impact on the profile of transplantation candidates, but selected more severe patients for transplantation without significant impact on outcomes after transplantation.

Comparison of Evaluations for Heart Transplant Before Durable Left Ventricular Assist Device and Subsequent Receipt of Transplant at Transplant vs Nontransplant Centers

Importance

In 2020, the Centers for Medicare & Medicaid Services revised its national coverage determination, removing the requirement to obtain review from a Medicare-approved heart transplant center to implant a durable left ventricular assist device (LVAD) for bridge-to-transplant (BTT) intent at an LVAD-only center. The association between center-level transplant availability and access to heart transplant, the gold-standard therapy for advanced heart failure (HF), is unknown.

Objective

To investigate the association of center transplant availability with LVAD implant strategies and subsequent heart transplant following LVAD implant before the Centers for Medicare & Medicaid Services policy change.

Design, Setting, and Participants

A retrospective cohort study of the Society of Thoracic Surgeons Intermacs multicenter US registry database was conducted from April 1, 2012, to June 30, 2020. The population included patients with HF receiving a primary durable LVAD.

Exposures

LVAD center transplant availability (LVAD/transplant vs LVAD only).

Main Outcomes and Measures

The primary outcomes were implant strategy as BTT and subsequent transplant by 2 years. Covariates that might affect listing strategy and outcomes were included (eg, patient demographic characteristics, comorbidities) in multivariable models. Parameters for BTT listing were estimated using logistic regression with center-level random effects and for receipt of a transplant using a Cox proportional hazards regression model with death as a competing event.

Results

The sample included 22 221 LVAD recipients with a median age of 59.0 (IQR, 50.0-67.0) years, of whom 17 420 (78.4%) were male and 3156 (14.2%) received implants at LVAD-only centers. Receiving an LVAD at an LVAD/transplant center was associated with a 79% increased adjusted odds of BTT LVAD designation (odds ratio, 1.79; 95% CI, 1.35-2.38; P < .001). The 2-year transplant rate following LVAD implant was 25.6% at LVAD/transplant centers and 11.9% at LVAD-only centers. There was an associated 33% increased rate of transplant at LVAD/transplant centers compared with LVAD-only centers (adjusted hazard ratio, 1.33; 95% CI, 1.17-1.51) with a similar hazard for death at 2 years (adjusted hazard ratio, 0.99; 95% CI, 0.90-1.08).

Conclusions and Relevance

Receiving an LVAD at an LVAD-transplant center was associated with increased odds of BTT intent at implant and subsequent transplant receipt for patients at 2 years. The findings of this study suggest that Centers for Medicare & Medicaid Services policy change may have the unintended consequence of further increasing inequities in access to transplant among patients at LVAD-only centers.

Association of center-level temporary mechanical circulatory support use and waitlist outcomes after the 2018 adult heart allocation policy

BACKGROUND

The present study characterizes the association of center-level temporary mechanical circulatory support use with waitlist outcomes after the 2018 adult heart allocation policy change.

METHODS

The United Network for Organ Sharing database was queried for all single-organ, adult heart transplant candidates from November 2015 to October 2021. The study population was divided into 2 cohorts, prepolicy and postpolicy, centered around the rule change on October 18, 2018. The primary study outcome was center-level rate of poor waitlist outcome, defined as death or deterioration on the waitlist. Competing-risks regression was used to generate risk-adjusted rates of poor waitlist outcome at each center, while Pearson's correlation coefficient (r) was used to assess the significance of center-level temporary mechanical circulatory support use (defined as the proportion listed with temporary mechanical circulatory support) and poor waitlist outcome.

RESULTS

Of 22,077 transplant candidates included in analysis, 50.5% were listed during postpolicy. Compared to prepolicy, postpolicy candidates were more often listed with temporary mechanical circulatory support and less commonly listed with a durable left-ventricular assist device. The proportion of hospitals not using any temporary mechanical circulatory support decreased significantly from prepolicy to postpolicy (15% to 1%, P < .001). During prepolicy, center-level temporary mechanical circulatory support use showed no correlation with adjusted poor waitlist outcome. However, center-level temporary mechanical circulatory support use showed a negative correlation with poor waitlist outcome during postpolicy (r = -0.42, P < .001).

CONCLUSION

The 2018 adult heart allocation policy appears to benefit patients listed at high temporary mechanical circulatory support using centers, with significant interhospital variation in temporary mechanical circulatory support use in the new era. Given the growing role of temporary mechanical circulatory support on the heart transplant waitlist, greater standardization of its application is warranted.