Transplant Center Variability in Organ Offer Acceptance and Mortality Among US Patients on the Heart Transplant Waitlist

A Comprehensive, Multi-Faceted Strategy to Increase Pediatric Donor Heart Utilization

BACKGROUND

Many hearts offered for pediatric heart transplantation (HT) are not placed. In 2016, we initiated a quality improvement endeavor to increase heart offer acceptance. This study assessed the effect of these interventions at our center.

METHODS

Evaluation of pre-/post-implementation cohorts (1/1/2008-12/31/2016 vs. 1/1/2017- 7/1/2023) comparing donor heart utilization. Six interventions were iterated over time to increase offer acceptance ("extended criteria"): ABO-incompatible transplant, ex vivo perfusion for distanced donors, 3-dimensional total cardiac volume (TCV) assessment, acceptance of Hepatitis-C or SARS-COV-2 infected donors, and institutional culture change favoring consideration of donors previously considered unacceptable (Public Health Service Risk, long CPR duration, etc.). Outcomes studied included annual HT volume, median waitlist duration, sequence number at acceptance, and post-transplant clinical outcomes.

RESULTS

From 1/2008-7/2023 annual transplant volume increased from 16/year to 25/year pre-/post-implementation. Three hundred-thirteen/389 (80%) listed patients were transplanted. Waitlist duration shortened post-implementation (P=0.01), as did the percentage of accepted heart offers utilizing at least one extended criterion (P<0.001). Institutional culture change and TCV assessment had the largest impact on donor heart utilization (P=0.04 &P<0.001). There was no difference in post-HT intubation or cardiovascular intensive care unit (CVICU) days (P= 0.05-0.9), though post-transplant hospitalization duration (P<0.001) increased. Post-transplant survival was unaffected by use of extended criteria hearts (P=0.3).

CONCLUSIONS

We report increased donor heart offer acceptance resulting from a longitudinal, multi-faceted effort to increase organ offer utilization, with institutional culture change and TCV assessments having the greatest impact. Use of extended criteria hearts was not associated with inferior survival.

Differences in Donor Heart Acceptance by Race and Gender of Patients on the Transplant Waiting List

Importance

Barriers to heart transplant must be overcome prior to listing. It is unclear why Black men and women remain less likely to receive a heart transplant after listing than White men and women.

Objective

To evaluate whether race or gender of a heart transplant candidate (ie, patient on the transplant waiting list) is associated with the probability of a donor heart being accepted by the transplant center team with each offer.

Design, Setting, and Participants

This cohort study used the United Network for Organ Sharing datasets to identify organ acceptance with each offer for US non-Hispanic Black (hereafter, Black) and non-Hispanic White (hereafter, White) adults listed for heart transplant from October 18, 2018, through March 31, 2023.

Exposures

Black or White race and gender (men, women) of a heart transplant candidate.

Main Outcomes and Measures

The main outcome was heart offer acceptance by the transplant center team. The number of offers to acceptance was assessed using discrete time-to-event analyses, nonparametrically (stratified by race and gender) and parametrically. The hazard probability of offer acceptance for each offer was modeled using generalized linear mixed models adjusted for candidate-, donor-, and offer-level variables.

Results

Among 159 177 heart offers with 13 760 donors, there were 14 890 candidates listed for heart transplant; 30.9% were Black, 69.1% were White, 73.6% were men, and 26.4% were women. The cumulative incidence of offer acceptance was highest for White women followed by Black women, White men, and Black men (P < .001). Odds of acceptance were less for Black candidates than for White candidates for the first offer (odds ratio [OR], 0.76; 95% CI, 0.69-0.84) through the 16th offer. Odds of acceptance were higher for women than for men for the first offer (OR, 1.53; 95% CI, 1.39-1.68) through the sixth offer and were lower for the 10th through 31st offers.

Conclusions and Relevance

The cumulative incidence of heart offer acceptance by a transplant center team was consistently lower for Black candidates than for White candidates of the same gender and higher for women than for men. These disparities persisted after adjusting for candidate-, donor-, and offer-level variables, possibly suggesting racial and gender bias in the decision-making process. Further investigation of site-level decision-making may reveal strategies for equitable donor heart acceptance.

Impact of the coronavirus disease 2019 pandemic on drug overdoses in the United States and the effect on cardiac transplant volume and survival

BACKGROUND

Drug overdose (DO) deaths rose to unprecedented levels during the coronavirus disease 2019 (COVID-19) pandemic. This study examines the impact of COVID-19 on the availability of cardiac allografts from DO donors and the implications of DO donor use on recipient survival.

METHODS

Heart transplants reported to the United Network for Organ Sharing from January 2017 to November 2019 ("pre-COVID") and from March 2020 to June 2021 ("COVID pandemic") were analyzed with respect to DO donor status. Outcomes were analyzed using Kaplan-Meier survival and Cox regression to identify predictors of survival. Characteristics of discarded cardiac allografts were also compared by DO donor status.

RESULTS

During the COVID-19 pandemic, 27.2% of cardiac allografts were from DO donors vs 20.5% pre-COVID, a 32.7% increase (p < 0.001). During the pandemic, DO donors were younger (84.7% vs 76.3% <40 years, p < 0.001), had higher cigarette use (16.1% vs 10.8%, p < 0.001), higher cocaine use (47.4% vs 19.7%, p < 0.001), and higher incidence of hepatitis C antibodies (26.8% vs 6.1%, p < 0.001) and RNA positivity (16.2% vs 4.2%, p < 0.001). While DO donors were less likely to require inotropic support (30.8% vs 35.4%, p = 0.008), they were more likely to have received cardiopulmonary resuscitation (95.3% vs 43.2%, p < 0.001). Recipient survival was equivalent using Kaplan-Meier analysis (log-rank, p = 0.33) and survival probability at 36 months was 85.6% (n at risk = 398) for DO donors vs 83.5% (n at risk = 1,633) for all other donors. Cox regression demonstrated that DO donor status did not predict mortality (hazard ratio 1.05; 95% confidence interval 0.90-1.23, p = 0.53).

CONCLUSIONS

During the COVID-19 pandemic, there was a 32.7% increase in heart transplants utilizing DO donor hearts, and DO became the most common mechanism of death for donors. The use of DO donor hearts did not have an impact on short-term recipient survival.

Non-inferior outcomes in lower urgency patients transplanted with extended criteria donor hearts

BACKGROUND

Recent work has suggested that outcomes among heart transplant patients listed at the lower-urgency (United Network for Organ Sharing Status 4 or 6) status may not be significantly impacted by donor comorbidities. The purpose of this study was to investigate outcomes of extended criteria donors (ECD) in lower versus higher urgency patients undergoing heart transplantation.

METHODS

The United Network for Organ Sharing (UNOS) database was queried for all adult patients undergoing heart transplantation from October 18, 2018 through December 31, 2021. Patients were stratified by degree of urgency (higher urgency: UNOS 1 or 2 vs lower urgency: UNOS 4 or 6) and receipt of ECD hearts, as defined by donor hearts failing to meet established acceptable use criteria. Outcomes were compared using propensity score matched cohorts.

RESULTS

Among 9,160 patients included, 2,320 (25.4%) were low urgency. ECD hearts were used in 35.5% of higher urgency (HU) patients and 39.2% of lower urgency (LU) patients. While ECD hearts had an impact on survival among high-urgency patients (p < 0.01), there was no difference in 1- and 2-year survival (p > 0.05) found among low urgency patients receiving ECD versus standard hearts. Neither ECDs nor individual ECD criteria were independently associated with mortality in low urgency patients (p > 0.05).

CONCLUSIONS

Post-transplant outcomes among low urgency patients are not adversely affected by receipt of ECD vs. standard hearts. Expanding the available donor pool by optimizing use of ECDs in this population may increase transplant frequency, decrease waitlist morbidity, and improve postoperative outcomes for the transplant community at large.

Does Failure to Rescue Drive Race/Ethnicity-based Disparities in Survival After Heart Transplantation?

OBJECTIVE

The objective was to assess whether race/ethnicity is an independent predictor of failure to rescue (FTR) after orthotopic heart transplantation (OHT).

SUMMARY BACKGROUND DATA

Outcomes following OHT vary by patient level factors; for example, non-White patients have worse outcomes than White patients after OHT. Failure to rescue is an important factor associated with cardiac surgery outcomes, but its relationship to demographic factors is unknown.

METHODS

Using the United Network for Organ Sharing database, we included all adult patients who underwent primary isolated OHT between 1/1/2006 snd 6/30/2021. FTR was defined as the inability to prevent mortality after at least one of the UNOS-designated postoperative complications. Donor, recipient, and transplant characteristics, including complications and FTR, were compared across race/ethnicity. Logistic regression models were created to identify factors associated with complications and FTR. Kaplan Meier and adjusted Cox proportional hazards models evaluated the association between race/ethnicity and posttransplant survival.

RESULTS

There were 33,244 adult, isolated heart transplant recipients included: the distribution of race/ethnicity was 66% (n=21,937) White, 21.2% (7,062) Black, 8.3% (2,768) Hispanic, and 3.3% (1,096) Asian. The frequency of complications and FTR differed significantly by race/ethnicity. After adjustment, Hispanic recipients were more likely to experience FTR than White recipients (OR 1.327, 95% CI[1.075-1.639], P =0.02). Black recipients had lower 5-year survival compared with other races/ethnicities (HR 1.276, 95% CI[1.207-1.348], P <0.0001).

CONCLUSIONS

In the US, Black recipients have an increased risk of mortality after OHT compared with White recipients, without associated differences in FTR. In contrast, Hispanic recipients have an increased likelihood of FTR, but no significant mortality difference compared with White recipients. These findings highlight the need for tailored approaches to addressing race/ethnicity-based health inequities in the practice of heart transplantation.

Increasing waiting times for status 2 patients in new United Network for Organ Sharing allocation system: Impact on waitlist and posttransplant outcomes

OBJECTIVE

Since the heart transplant allocation policy change in 2018, there has been an increase in temporary mechanical circulatory support for Status 2 patients. We sought to examine the temporal pattern of waitlist and posttransplant outcomes for Status 2 patients.

METHODS

Adult patients in the United Network for Organ Sharing registry who were listed as Status 2 from January 2019 to June 2022 were included. Temporal trends in waitlist time, waitlist events, and posttransplant outcomes were assessed. Probability of transplant or death after being listed was compared over time. Multivariable regression was performed to identify risk factors for mortality after transplant.

RESULTS

A total of 6310 patients were included. From 2019 to 2022, the number of Status 2 patients listed increased from 4.2 to 5.9 per day. Microaxial ventricular assist devices at Status 2 listing increased over time (P < .001). During the study period, median waitlist time (18 days vs 23 days, P < .001) as well as Status 2 days (8 days vs 12 days, P < .001) increased. Waitlist mortality remained stable (5.5%); however, probability of transplant within 90 days of Status 2 listing progressively declined (P < .001). Finally, longer waitlist duration was independently associated with 30-day posttransplant mortality (odds ratio, 1.01; 95% confidence interval, 1.00-1.01, P = .02).

CONCLUSIONS

Since the allocation policy change there has been a steady rise in the number of patients listed for Status 2. This has led to increasing waitlist times and lower probability of transplantation for Status 2 patients, which may have negative consequences for posttransplant outcomes.

Heart Transplant Waitlist Outcomes and Wait Time by Center Volume in the Pre-2018 Allocation Change Era

Although the transplant outcomes of centers are heavily monitored and compared, with a particular link between posttransplant outcomes and center volume demonstrated, little data exist comparing waitlist outcomes. Here, we explored waitlist outcomes by transplant center volume. We performed a retrospective analysis of adults listed for primary heart transplantation (HTx) from 2008 to 2018 using the United Network for Organ Sharing database. Transplant centers were split into low (<10 HTx/year), medium (10-30 HTx/year), and high (>30 HTx/year) volume, and waitlist outcomes were compared. Of the 35,190 patients included in our study, 23,726 (67.4%) underwent HTx, 4,915 (14.0%) died or deteriorated before receiving HTx, 1,356 (3.9%) were delisted due to recovery, and 1,336 (3.8%) underwent left ventricular assist device (LVAD) implantation. High-volume centers had higher rates of survival to transplant (71.3% vs. 60.6% for low-volume centers and 64.9% for medium-volume centers), and low rates of death or deterioration (12.6% vs. 14.6% for low-volume centers and 15.1% for medium-volume centers). Listing at a low-volume center was independently associated with death or delisting before HTx (HR 1.18, p = 0.007), whereas listing at a high-volume center (HR 0.86; p < 0.001) and prelisting LVAD (HR 0.67, p < 0.001) were protective. Death or delisting before HTx was lowest for patients listed in higher volume centers.

Specialized Thoracic Adapted Recovery Model for Thoracic Organ Recovery: a 15-Year Review

BACKGROUND

To review outcomes from a regionalized heart and lung transplant service over a 15-year period.

METHODS

Data on organ procurements made by the Specialized Thoracic Adapted Recovery (STAR) team. The STAR team staff recorded data from November 2, 2004 to June 30, 2020, were reviewed.

RESULTS

The STAR teams recovered thoracic organs from 1118 donors between November 2004 and June 2020. The teams recovered 978 hearts, 823 bilateral lungs, 89 right lungs and 92 left lungs, and 8 heart and lung sets. A total of 79% of hearts and 76.1% of lungs were transplanted, whereas 2.5% of hearts and 5.1% of lungs were declined; the remainder were used for research, valves, or abandoned. A total of 47 transplantation centers received at least 1 heart, and 37 centers received at least 1 lung during this period. The 24-hour graft survival among organs recovered by STAR teams was 100% for lungs and 99% for hearts.

CONCLUSIONS

A specialized regional thoracic organ procurement team may improve transplantation rates.

Heart transplant offers are less likely to be accepted on weekends, holidays, and conferences

BACKGROUND

The existence of a "weekend effect" in heart transplantation (HTx) is understudied. The present study sought to determine whether the odds of (HTx) offer acceptance differed for adult and pediatric candidates depending upon the day on which the offer occurred.

METHODS

United Network for Organ Sharing data were used to identify all HTx offers to adult (listing age ≥18) and pediatric candidates from 2000-2019. Odds of offer acceptance were studied, comparing weekends, holidays, and conferences (Society of Thoracic Surgeons [STS], American Association for Thoracic Surgery [AATS], International Society for Heart and Lung Transplantation [ISHLT]) to "baseline" (all other days). Multivariable binary logistic regression analyses were performed to determine independent predictors of offer nonacceptance, controlling for the impacts of program transplant volume, region, and candidate characteristics.

RESULTS

A total of 323,953 offers occurred - 298,405 to adults and 25,548 to pediatric candidates. Clinically significant differences did not exist in donor or candidate characteristics between baseline or other events. The number of offers per day was stable throughout the year for both adults (p = 0.191) and pediatrics (p = 0.976). In adults, independently lower odds of acceptance existed on weekends (OR 0.88 [95% CI 0.84-0.92]), conferences in aggregate (0.86 [0.77-0.95]), and holidays in aggregate (0.81 [0.72-0.91]). In children, independently lower odds of acceptance were seen on weekends (0.88 [0.79-0.98]), during STS (0.46 [0.25-0.83], and during Christmas (0.32 [0.14-0.76]).

CONCLUSIONS

The day on which a HTx offer occurs significantly impacts its likelihood of acceptance. Further work can determine the impacts of human behavior or resource distribution, but knowledge of this phenomenon can inform efforts to ensure ideal organ allocation throughout the year.

Overly Selective Offer Acceptance is Associated With High Waitlist Mortality for the Most Ill Lung Transplant Candidates

The demand for organs for lung transplantation (LTx) continues to outweigh supply. However, nearly 75% of donor lungs are never transplanted. LTx offer acceptance practices and the effects on waitlist/post-transplant outcomes by candidate clinical acuity are understudied. UNOS was used to identify all LTx candidates, donors, and offers from 2005 to 2019. Candidates were grouped by Lung Allocation Score (LAS; applicable post-2005, ages ≥12 years): LAS<40, 40-60, 61-80, and >80. Offer acceptance patterns, waitlist death/decompensation, and post-transplant survival (PTS) were compared. "Acceptable organ offers" were those from donors whose organs were accepted for transplantation. Approximately 3 million offers to 34,531 candidates were reviewed. Median waitlist durations were: 9 days-(LAS>80), 17 days-(LAS 61-80), 42 days-(LAS 40-60), 125 days-(LAS<40) (P < 0.001 between all). Per waitlist-day, offer rates were: total offers - 0.8/day-(LAS>80), 0.7/day-(LAS 61-80), 0.6/day-(LAS 40-60), 0.4/day-(LAS<40); acceptable offers - 0.34/day-(LAS>80), 0.32/day-(LAS 61-80), 0.24/day-(LAS 40-60), 0.15/day-(LAS<40) (both P < 0.001 between all LAS). Among patients who experienced waitlist mortality/decompensation, ≥1 acceptable offer was declined in 92% (3939/4270) of patients - 78% for LAS >80, 88% for LAS 61-80, 93% for LAS 40-60, and 96% for LAS <40. Thirty-day waitlist mortality/decompensation rates were: 46%-(LAS>80), 24%-(LAS 61-80), 5%-(LAS 40-60), <1%-(LAS<40) (P < 0.001 between all). PTS was equivalent between patients for whom the first/second offer vs later offers were accepted (all LAS P > 0.4). The first offers that LTx candidates receive (including acceptable organs) are declined for nearly all candidates. Healthier candidates can afford offer selectivity but more ill patients (LAS>60) cannot, experiencing exceedingly high 30-day waitlist mortality.

Pediatric heart transplantation: The past, the present, and the future

Heart transplantation (HTx) has a storied past, with origins dating back to the early twentieth century and the first pediatric orthotopic heart transplant performed in 1967 on a neonate with Ebstein abnormality. Today, approximately 500 pediatric HTx are performed annually, with survival times now measured in decades rather than days or weeks. In large part, advances in immunosuppression, critical care, dedicated transplant teams and mechanical circulatory support have paved the way for improvements in waitlist mortality and post-transplant survival, with future directions including the development of intracorporeal ventricular assist devices (VADs) for small children, expanding/standardizing donor criteria, and xenotransplantation.

Center variations in patient selection for simultaneous heart-kidney transplantation

There are no established regulations governing patient selection for simultaneous heart-kidney (SHK) transplantation, creating the potential for significant center-level variations in clinical practice.

METHODS

Using the United Network for Organ Sharing (UNOS) Standard Transplant Analysis and Research (STAR) file, we examined practice trends and variations in patient selection for SHK at the center level between January 1, 2004 and March 31, 2019.

RESULTS

Overall, SHK is becoming more common with most centers performing heart transplants also performing SHK. Among patients who underwent heart transplant who were receiving dialysis, the rate of SHK varied from 22% to 86% at the center level. Among patients not on dialysis, the median estimated glomerular filtration rate (eGFR) of patients receiving SHK varied between 19 and 59 mL/min/1.73 m² . When adjusting for other factors, the odds of SHK varied 57-fold between the highest and lowest SHK performing centers.

CONCLUSION

Variation in SHK at the center level suggests the need for national guidelines around the selection of patients for SHK.

Risk Aversion, Organ Utilization and Changing Behavior

Improving organ acceptance and utilization rates is critical to ensure we maximize usage of donated organs as a scarce resource. Many factors underlie unnecessary discard of viable organs. Declined transplantation opportunities for candidates is associated with increased wait-list mortality. Technological advancements in organ preservation may help bridge the gap between donation and utilization, but an overlooked obstacle is the practice of risk aversion by transplant professionals when decision-making under risk. Lessons from behavioral economics, where experimental work has outlined the impact of loss or risk aversion on decision-making, have not been translated to transplantation. Many external factors can influence decision-making when accepting or utilizing organs, which are potentially amendable if external conditions are improved. However, attitudes and perceptions to risk for transplant professionals can pervade decision-making and influence behaviour. If we wish to change this behavior, then the underlying nature of decision-making under risk when accepting or utilizing organs must be studied to facilitate the design of targeted behavior change interventions to convert risk aversion to risk tolerance. To ensure optimal use of donated organs, we need more research into decision-making under risk.

Trends and Outcomes of Cardiac Transplantation in the Lowest Urgency Candidates

Background Due to discrepancies between donor supply and recipient demand, the cardiac transplantation process aims to prioritize the most medically urgent patients. It remains unknown how recipients with the lowest medical urgency compare to others in the allocation process. We aimed to examine differences in clinical characteristics, organ allocation patterns, and outcomes between cardiac transplantation candidates with the lowest and highest medical urgency. Methods and Results We performed a retrospective analysis of the United Network for Organ Sharing database. Patients listed for cardiac transplantation between January 2011 and May 2020 were stratified according to status at time of transplantation. Baseline recipient and donor characteristics, waitlist survival, and post-transplantation outcomes were compared in the years before and after the 2018 allocation system change. Lower urgency patients in the old system were older (58.5 vs. 56 years) and more likely female (54.4% vs. 23.8%) compared to the highest urgency patients, and these trends persisted in the new system (p<0.001, all). Donors for the lowest urgency patients were more likely older, female, or have a history of CMV, hepatitis C, or diabetes (p<0.01, all). The lowest urgency patients had longer waitlist times, and under the new allocation system received organs from shorter distances with decreased ischemic times (178 vs. 269 miles, 3.1 vs 3.5 hours, p<0,001, all). There was no difference in post-transplantation survival (p<0.01, all). Conclusions Patients transplanted as lower urgency receive hearts from donors with additional comorbidities compared to higher urgency patients, but outcomes are similar at one year.

Impact of transplant center volume on donor heart offer utilization rates in the United States

BACKGROUND

We tested the hypothesis that transplant centers (TCs) with higher volumes have higher donor heart (DH) offer utilization rates.

METHODS

Using the Annual Data reports of the US Organ Procurement and Transplantation Network and the Scientific Registry of Transplant Recipients (SRTR) we reviewed all adult heart transplant offers between July 1, 2016 and June 29, 2019. Unadjusted donor offer utilization rates and observed to expected (O/E) DH utilization ratios adjusted using the SRTR model were calculated for each TC for all DH offers and for the following sub-categories: DH with left ventricular ejection fraction <60%, DH >40 years, DH >500 miles from TC, "hard-to-place hearts" (defined as those offered to >50 TCs) and DH designated as increased infectious risk. Univariable linear regression was used to identify a relationship between average yearly center volume and DH utilization.

RESULTS

During the study 118,841 total offers were made to 107 TCs and 8300 transplants were performed. The unadjusted utilization rate was not associated with TC volume for all donor offers (p = .517). However, among all subcategories other than DH >40 years, the unadjusted DH utilization rate was associated with TC volume (p < .05). In addition, using the adjusted SRTR O/E ratio, there was a significant impact of TC volume on utilization rate for all donor offers (for an increase TC volume of 10 transplants/year coefficient = 0.095, 95% confidence interval: 0.037-0.151, p = .001). This relationship persisted with an identifiable change for each of the subcategories (p ≤ .001).

CONCLUSIONS

TC volume is significantly correlated to DH offer utilization rate.

Impact of center donor acceptance patterns on utilization of extended-criteria donors and outcomes

BACKGROUND

This study investigated the impact of transplanting center donor acceptance patterns on usage of extended-criteria donors (ECDs) and posttransplant outcomes following orthotopic heart transplantation (OHT).

METHODS

The Scientific Registry of Transplant Recipients was queried to identify heart donor offers and adult, isolated OHT recipients in the United States from January 1, 2013 to October 17, 2018. Centers were stratified into three equal-size terciles based on donor heart acceptance rates (<13.7%, 13.7%-20.2%, >20.2%). Overall survival was compared between recipients of ECDs (≥40 years, left ventricular ejection fraction [LVEF] <60%, distance ≥500 miles, hepatitis B virus [HBV], hepatitis C virus [HCV], or human immunodeficiency virus [HIV], or ≥50 refusals) and recipients of traditional-criteria donors, and among transplanting terciles.

RESULTS

A total of 85,505 donor heart offers were made to 133 centers with 15,264 (17.9%) accepted for OHT. High-acceptance programs (>20.2%) more frequently accepted donors with LVEF <60%, HIV, HCV, and/or HBV, ≥50 offers, or distance >500 miles from the transplanting center (each p < .001). Posttransplant survival was comparable across all three terciles (p = .11). One- and five-year survival were also similar across terciles when examining recipients of all five ECD factors. Acceptance tier and increasing acceptance rate were not found to have any impact on mortality in multivariable modeling. Of ECD factors, only age ≥40 years was found to have increased hazards for mortality (hazard ratio, 1.33; 95% confidence interval [CI], 1.22-1.46; p < .001).

CONCLUSIONS

Of recipients of ECD hearts, outcomes are similar across center-acceptance terciles. Educating less aggressive programs to increase donor acceptance and ECD utilization may yield higher national rates of OHT without major impact on outcomes.

A machine learning approach for the prediction of overall deceased donor organ yield

BACKGROUND

Optimizing organ yield (number of organs transplanted per donor) is a potentially modifiable way to increase the number of organs available for transplant. Models to predict the expected deceased donor organ yield have been developed based on ordinary least squares regression and logistic regression. However, alternative modeling methodologies incorporating machine learning may have superior performance compared with conventional approaches.

METHODS

We evaluated the predictive accuracy of 14 machine learning models for predicting overall organ yield in a cross-validation procedure. The models were parameterized using data from the Organ Procurement and Transplantation Network database from 2000 to 2018. The inclusion criteria for the study were adult deceased donors between 18 and 84 years of age that had at least 1 organ procured for transplantation.

RESULTS

A total of 89,520 donors met the inclusion criteria. Their mean (standard deviation) age was 44 (15) years, and approximately 58% were male. Our cross-validation analysis showed that a tree-based gradient boosting model outperformed the remaining 13 models. Compared with the currently used prediction models, the gradient boosting model improves prediction accuracy by reducing the mean absolute error between 3 and 11 organs per 100 donors.

CONCLUSION

Our analysis demonstrated that the gradient boosting methodology had the best performance in predicting overall deceased donor organ yield and can potentially serve as an aid to assess organ procurement organization performance.

The 2018 adult heart allocation policy change benefits low-volume transplant centers

INTRODUCTION

The effect of the 2018 adult heart allocation policy change at an institution-level remains unclear. The present study assessed the impact of the policy change by transplant center volume.

METHODS

The United Network for Organ Sharing database was queried for all adults undergoing isolated heart transplantation from November 2016 to September 2020. Era 1 was defined as the period before the policy change and Era 2 afterwards. Hospitals were divided into low-(LVC) medium-(MVC) and high-volume (HVC) tertiles based on annual transplant center volume. Competing-risks regressions were used to determine changes in waitlist death/deterioration, while post-transplant mortality was assessed using multivariable Cox proportional-hazards models.

RESULTS

A total of 3531 (47.0%) patients underwent heart transplantation in Era 1 and 3988 (53.0%) in Era 2. At LVC, Era 2 patients were less likely to experience death/deterioration on the waitlist (subhazard ratio .74, 95% CI .63-.88), while MVC and HVC patients experienced similar waitlist death/deterioration across eras. After adjustment, transplantation in Era 2 was associated with worse 1-year mortality at MVC (hazard ratio, HR, 1.42 95% CI 1.02-1.96) and HVC (HR 1.42, 95% CI 1.02-1.98) but not at LVC.

CONCLUSION

Early analysis shows that LVC may be benefitting under the new allocation scheme.

Assessing predicted heart mass size matching in obese heart transplant recipients

BACKGROUND

Predicted heart mass (PHM) is currently the most reliable metric for donor-recipient size matching in heart transplantation. Undersizing PHM donor-recipient match more than 20% independently predicts reduced survival. However, it is unclear if this is the case in obese recipients, in whom size matching can be challenging. We examined the use of PHM undersized hearts in obese recipients and assessed its impact on survival.

METHODS

The United Network for Organ Sharing database was queried for adult patients undergoing heart transplantation from 1995 to 2020. Obese recipients (BMI ≥ 30) were categorized based on donor-recipient PHM match ≤-20% (undersized) or >-20% (size-matched). Nearest-neighbor propensity score matching was performed to adjust for baseline differences between cohorts. Temporal outcomes were compared by Kaplan-Meier survival analysis.

RESULTS

A total of 13,668 obese recipients met inclusion criteria, with 9.6% receiving undersized and 90.4% receiving size-matched hearts. The proportion of undersized donor hearts in obese recipients significantly decreased over the study period (16.2% [1995] to 7.4% [2019], NP-trend < 0.001). Propensity-score matching resulted in 984 well-matched pairs of undersized and size-matched obese recipients. Recipients of undersized hearts saw similar 30-day mortality (5.5% vs 6.0%, p= 0.11) and re-transplantation rates (1.2% vs 1.2%, p = 1.00) as size-matched recipients. Survival at 1 year (88.4% vs 87.9%, p = 0.14), and 15 years (35.1% vs 31.0%, p = 0.12) was similar across cohorts.

CONCLUSIONS

A decreasing proportion of PHM undersized hearts are being utilized in obese recipients. However, utilizing PHM undersized hearts in obese recipients was not associated with a detriment in survival.

Dual Procurement of Lung and Heart Allografts Does Not Negatively Affect Lung Transplant Outcomes

BACKGROUND

The data that exists regarding multiorgan procurement outcomes is conflicted. Given the increasing demand for pulmonary allografts, it is critical to assess the impact of dual procurement on lung transplant recipient outcomes.

METHODS

The United Network for Organ Sharing transplant registry was queried for all first-time adult (age ≥18) lung transplant recipients between 2006 and 2018 and stratified by concurrent heart donor status. Multiorgan transplant recipients and recipients with missing survival time were excluded. Donors were excluded if they were donating after circulatory death, did not consent or were not approached for heart donation, the heart was recovered for nontransplant purposes, or the heart was recovered for transplant but not transplanted. Post-transplant survival was analyzed using the Kaplan-Meier method and multivariable Cox proportional hazards regression.

RESULTS

A total of 18,641 recipients met inclusion criteria, including 6230 (33.4%) in the nonheart donor group (NHD) and 12,409 (66.6%) in the heart donor group (HD). HD recipients demonstrated longer survival at 10 years posttransplant, with a median survival of 6.5 years as compared with 5.9 years in NHD recipients. On adjusted analysis, HD and NHD recipients demonstrated comparable survival (AHR 0.95, 95% CI 0.90-1.01).

CONCLUSIONS

Concomitant heart and lung procurement was not associated with worse survival. This finding encourages maximizing the number of organs procured from each donor, particularly in the setting of urgency-driven thoracic transplantation.

State-Level Variation in Waitlist Mortality and Transplant Outcomes Among Patients Listed for Heart Transplantation in the US From 2011 to 2016

IMPORTANCE

Little is known about geographic variation in the outcomes of adult patients listed for heart transplantation in the US. Identifying the patterns and extent of variation is important to minimize disparity in outcomes.

OBJECTIVE

To evaluate the geographic patterns, extent, and factors associated with state-level variation in outcomes of adult patients listed for heart transplantation in the US.

DESIGN, SETTING, AND PARTICIPANTS

This nationwide retrospective cohort study used data from the United Network for Organ Sharing database to identify adult patients listed for heart transplantation at status 1A between January 1, 2011, and December 31, 2016. Patients were followed up until March 31, 2018. Data were analyzed from November 1, 2019, to September 19, 2020.

MAIN OUTCOMES AND MEASURES

The study evaluated state-level variation in the 3 main organ transplant measures: waitlist mortality, transplant rate, and risk-adjusted 1-year graft survival. The rate of death while on the waitlist and the rate of transplant were calculated for each state per 1000 waitlist person-days listed at status 1A over the study period. Risk-adjusted 1-year graft survival was calculated based on the Scientific Registry of Transplant Recipients risk-adjustment model. State-level variation in each outcome measure was evaluated via multivariable-adjusted models.

RESULTS

Across 50 states and the District of Columbia, a total of 15 036 patients (mean [SD] age, 52 [13] years; 3531 women [24%]; 9626 White [64%]) were listed at status 1A for adult heart transplantation between 2011 and 2016. Of those, 2146 patients (14.3%) died while on the waitlist, and 10 982 patients (73.0%) received transplants. Among those who received transplants, the median time on the waitlist was 31 days (interquartile range, 13-61 days). State-level outcomes ranged from 1.0 to 7.8 deaths per 1000 waitlist person-days for waitlist mortality, 5.6 to 34.5 transplants per 1000 waitlist person-days for transplant rate, and 87% to 92% for risk-adjusted 1-year graft survival. In a comparison of the highest and lowest quartiles, significant state-level variation was found in waitlist mortality (hazard ratio [HR], 1.53; 95% CI, 1.27-1.86), transplant rate (HR, 1.57; 95% CI, 1.31-1.87), and 1-year graft survival (odds ratio, 2.07; 95% CI, 1.64-2.62).

CONCLUSIONS AND RELEVANCE

The study's findings indicate that significant state-level variation exists in the outcomes of patients listed for heart transplantation in the US. Identifying and addressing the factors associated with these geographic variations in outcomes is important to ensure a fair allocation system.

A coordinated approach to improving pediatric heart transplant waitlist outcomes: A summary of the ACTION November 2019 waitlist outcomes committee meeting

The number of children needing heart transplantation continues to rise. Although improvements in heart failure therapy, particularly durable mechanical support, have reduced waitlist mortality, the number of children who die while waiting for a suitable donor organ remains unacceptably high. Roughly, 13% of children and 25% of infants on the heart transplant waitlist will not survive to transplantation. With this in mind, the Advanced Cardiac Therapies Improving Outcomes Collaborative Learning Network (ACTION), through its Waitlist Outcomes Committee, convened a 2-day symposium in Ann Arbor, Michigan, from 2-3 November 2019, to better understand the factors that contribute to pediatric heart transplant waitlist mortality and to focus future efforts on improving the organ allocation rates for children needing heart transplantation. Using improvement science methodology, the heart failure-transplant trajectory was broken down into six key steps, after which modes of failure and opportunities for improvement at each step were discussed. As a result, several projects aimed at reducing waitlist mortality were initiated.

Cocaine use in organ donors and long-term outcome after heart transplantation: An International Society for Heart and Lung Transplantation registry analysis

BACKGROUND

Cardiac allografts from donors with a history of cocaine use (DHCU) are often discarded owing to concerns regarding organ quality. We investigated long-term outcomes of de novo adult heart transplantation (HTx) using DHCU.

METHODS

Using the International Society for Heart and Lung Transplantation Thoracic Organ Transplant Registry, we identified 24,430 adult recipients of primary, deceased donor, heart-alone transplants between January 1, 2000, and June 30, 2013. Transplants were categorized on the basis of DHCU. Survival rates were compared using Kaplan-Meier curves and log-rank tests.

RESULTS

A total of 3,246 (13.3%) HTx were performed using DHCU during the study period. Of these, 1,477 (45.5%) were classified as current users. Organs from DHCU were transplanted at a later sequence number (data from a sub-group of patients transplanted in the United States) than those from the non-cocaine use group (mean sequence number 16.1 ± 55.6 vs 11.5 ± 38.2; p < 0.001), suggesting higher decline rates by centers. Kaplan-Meier estimates of survival were not different between groups (p = 0.16), with post-transplant survival rates at 1, 5, and 10 years of 88.1%, 75.8%, and 58.5%, respectively, in the non-cocaine use group and 90.0%, 76.7%, and 59.7%, respectively, in the DHCU group. On multivariate analysis, DHCU were not associated with mortality (hazard ratio [HR]: 0.94; 95% CI: 0.88-1.00; p = 0.050), cardiac allograft vasculopathy (HR: 1.02; 95% CI: 0.94-1.11; p = 0.56), or allograft rejection (HR: 0.98; 95% CI: 0.92-1.05; p = 0.61).

CONCLUSIONS

Our findings demonstrate that adult HTx performed using DHCU is not associated with an adverse impact on long-term clinical outcomes. These findings should spur efforts to reduce discard rates of organs from DHCU.

Evaluation of Case Volumes of a Heart Transplant Program and Short-term Outcomes After Changes in the United Network for Organ Sharing Donor Heart Allocation System

IMPORTANCE

Institution-level strategic changes may be associated with heart transplant volume and outcomes.

OBJECTIVE

To describe changes in practice that markedly increased heart transplant volume at a single center, as well as associated patient characteristics and outcomes.

DESIGN, SETTING, AND PARTICIPANTS

A pre-post cohort study was conducted of 107 patients who underwent heart transplant between September 1, 2014, and August 31, 2019, at Yale New Haven Hospital before (September 1, 2014, to August 31, 2018; prechange era) and after (September 1, 2018, to August 31, 2019; postchange era) a strategic change in patient selection by the heart transplant program.

EXPOSURE

Strategic change in donor and recipient selection at Yale New Haven Hospital that occurred in August 2018.

MAIN OUTCOMES AND MEASURES

Outcome measures were transplant case volume, donor and recipient characteristics, and 180-day survival.

RESULTS

A total of 49 patients (12.3 per year; 20 women [40.8%]; median age, 57 years [interquartile range {IQR}, 50-63 years]) received heart transplants in the 4 years of the prechange era and 58 patients (58 per year; 19 women [32.8%]; median age, 57 years [IQR, 52-64 years]) received heart transplants in the 1 year of the postchange era. Organ offers were more readily accepted in the postchange era, with an offer acceptance rate of 20.5% (58 of 283) compared with 6.4% (49 of 768) in the prechange era (P < .001). In the postchange era, donor hearts were accepted with a higher median number of prior refusals by other centers than in the prechange era (16.5 [IQR, 6-38] vs 3 [IQR, 1-6]; P < .001). Hearts accepted in the postchange era were from older donors than in the prechange era (median age, 40 years [IQR, 29-48 years] vs 30 years [IQR, 24-42 years]; P < .001). Recipients had a significantly shorter time on the waiting list in the postchange era compared with prechange era (median, 41 days [IQR, 12-289 days] vs 242 days [IQR, 135-428 days]; P < .001). More patients were supported on temporary circulatory assist devices preoperatively in the postchange era than the prechange era (14 [24.1%] vs 0; P < .001). Survival rates at 180 days were not significantly different (43 [87.8%] in the prechange era vs 52 [89.7%] in the postchange era). Mortality while on the waiting list was similar (2.8 deaths per year in the prechange era vs 3 deaths per year in the postchange era). During the comparable time period, 4 other regional centers had volume change ranging from -10% to 68%, while this center's volume increased by 374%.

CONCLUSIONS AND RELEVANCE

This study suggests that strategic changes in donor heart and recipient selection may significantly increase the number of heart transplants while maintaining short-term outcomes comparable with more conservative patient selection. Such an approach may augment the allocation of currently unused donor hearts.