Prediction of Donor Heart Acceptance for Transplant and Its Clinical Implications: Results From The Donor Heart Study.

BACKGROUND: Despite a shortage of potential donors for heart transplant in the United States, most potential donor hearts are discarded. We evaluated predictors of donor heart acceptance in the United States and applied machine learning methods to improve prediction. METHODS: We included a nationwide (2005-2020) cohort of potential heart donors in the United States (n=73 948) from the Scientific Registry of Transplant Recipients and a more recent (2015-2020) rigorously phenotyped cohort of potential donors from DHS (Donor Heart Study; n=4130). We identified predictors of acceptance for heart transplant in both cohorts using multivariate logistic regression, incorporating time-interaction terms to characterize their varying effects over time. We fit models predicting acceptance for transplant in a 50% training subset of DHS using logistic regression, least absolute shrinkage and selection operator, and random forest algorithms and compared their performance in the remaining 50% (test) of the subset. RESULTS: Predictors of donor heart acceptance were similar in the nationwide and DHS cohorts. Among these, older age (P value for time interaction, 0.0001) has become increasingly predictive of discard over time while other factors, including those related to drug use, infection, and mild cardiac diagnostic abnormalities, have become less influential (P value for time interaction, <0.05 for all). A random forest model (area under the curve, 0.908; accuracy, 0.831) outperformed other prediction algorithms in the test subset and was used as the basis of a novel web-based prediction tool. CONCLUSIONS: Predictors of donor heart acceptance for transplantation have changed significantly over the last 2 decades, likely reflecting evolving evidence regarding their impact on posttransplant outcomes. Real-time prediction of donor heart acceptance, using our web-based tool, may improve efficiency during donor management and heart allocation.

Just a number? Donor age and (lack of) associated reasons for heart offer refusal.

The use of 50+ year-old donors for heart transplant (HT) is rare in the United States. We assessed reasons for this-and whether it reflects concern about age itself or associated risk factors-using a survey of US HT centers. The Donor Heart Study enrolled US adult potential heart donors from 2015 to 2020. A total of 6,814 surveys across 2,197 donors cited, on average, 2.4 reasons (per donor) for offer refusal. Age was cited often (by ≥50% of centers surveyed) for 715 donors (33%). In this subgroup, accompanying donor-related reasons for refusal were infrequent, with no cardiac abnormality cited in most cases. Donor age showed associations with (1) age as a reason for refusal and (2) discard. Both abruptly increased at age 50: 55% of 50 to 51-year-old donors were refused often due to age (vs 38% of 48-49-year-olds), and 72% were discarded (vs 55% of 48-49-year-olds), despite no evidence of a threshold effect of age on outcomes.

Trends in heart transplant outcomes for patients over the age of 70 years in the United States: An analysis of the scientific registry of transplant recipients database.

BACKGROUND: Patients of advanced age are often considered to be poor candidates for heart transplant (HT). As the U.S. population continues to age, it is important for clinicians to understand how best to select patients for advanced therapies. METHODS: This was a retrospective analysis of the U.S. Scientific Registry of Transplant Recipients data from 2006 to August 2022 in adult recipients. Patients were excluded if they were multiorgan transplant, re-do transplants, or less than 1 year post transplant. RESULTS: Recipients ≥70 had a 1-year survival of 87.5%, compared to 91.1% for <60%, and 88.4% for 60-69 years (p < 0.001). Survival improved numerically, but not significantly, as transplant eras progressed for those ≥70 years. Survival by Kaplan-Meier analysis was greatest at 5 years for <60 years (80.6%), compared to 60-69 years (78.2%) and ≥70 years (77.1%). When comparing 60-69 years to ≥70 years by this same metric, there was significant difference (p = 0.12). One year survival for those ≥70 years has improved from 2000-2009 (80.7%) to 88.5% since October 2018 (p < 0.001). As recipients increased in age, they were more likely to be male, and less likely to be Black or Hispanic/Latino (p < 0.001). CONCLUSION: Overall, HT outcomes are excellent for carefully selected patients ≥70 years, and transplanting patients in this age cohort can be considered.

Donor Electrocardiogram Associations With Cardiac Dysfunction, Heart Transplant Use, and Survival: The Donor Heart Study.

BACKGROUND: Potential organ donors often exhibit abnormalities on electrocardiograms (ECGs) after brain death, but the physiological and prognostic significance of such abnormalities is unknown. OBJECTIVES: This study sought to characterize the prevalence of ECG abnormalities in a nationwide cohort of potential cardiac donors and their associations with cardiac dysfunction, use for heart transplantation (HT), and recipient outcomes. METHODS: The Donor Heart Study enrolled 4,333 potential cardiac organ donors at 8 organ procurement organizations across the United States from 2015 to 2020. A blinded expert reviewer interpreted all ECGs, which were obtained once hemodynamic stability was achieved after brain death and were repeated 24 ± 6 hours later. ECG findings were summarized, and their associations with other cardiac diagnostic findings, use for HT, and graft survival were assessed using univariable and multivariable regression. RESULTS: Initial ECGs were interpretable for 4,136 potential donors. Overall, 64% of ECGs were deemed clinically abnormal, most commonly as a result of a nonspecific St-T-wave abnormality (39%), T-wave inversion (19%), and/or QTc interval >500 ms (17%). Conduction abnormalities, ectopy, pathologic Q waves, and ST-segment elevations were less common (each present in ≤5% of donors) and resolved on repeat ECGs in most cases. Only pathological Q waves were significant predictors of donor heart nonuse (adjusted OR: 0.39; 95% CI: 0.29-0.53), and none were associated with graft survival at 1 year post-HT. CONCLUSIONS: ECG abnormalities are common in potential heart donors but often resolve on serial testing. Pathologic Q waves are associated with a lower likelihood of use for HT, but they do not portend worse graft survival.

Disparities in donor heart acceptance between the USA and Europe: clinical implications.

BACKGROUND AND AIMS: Given limited evidence and lack of consensus on donor acceptance for heart transplant (HT), selection practices vary widely across HT centres in the USA. Similar variation likely exists on a broader scale-across countries and HT systems-but remains largely unexplored. This study characterized differences in heart donor populations and selection practices between the USA and Eurotransplant-a consortium of eight European countries-and their implications for system-wide outcomes. METHODS: Characteristics of adult reported heart donors and their utilization (the percentage of reported donors accepted for HT) were compared between Eurotransplant (n = 8714) and the USA (n = 60 882) from 2010 to 2020. Predictors of donor acceptance were identified using multivariable logistic regression. Additional analyses estimated the impact of achieving Eurotransplant-level utilization in the USA amongst donors of matched quality, using probability of acceptance as a marker of quality. RESULTS: Eurotransplant reported donors were older with more cardiovascular risk factors but with higher utilization than in the USA (70% vs. 44%). Donor age, smoking history, and diabetes mellitus predicted non-acceptance in the USA and, by a lesser magnitude, in Eurotransplant; donor obesity and hypertension predicted non-acceptance in the USA only. Achieving Eurotransplant-level utilization amongst the top 30%-50% of donors (by quality) would produce an additional 506-930 US HTs annually. CONCLUSIONS: Eurotransplant countries exhibit more liberal donor heart acceptance practices than the USA. Adopting similar acceptance practices could help alleviate the scarcity of donor hearts and reduce waitlist morbidity in the USA.

Left Ventricular Dysfunction Associated With Brain Death: Results From the Donor Heart Study.

BACKGROUND: Left ventricular dysfunction in potential donors meeting brain death criteria often results in nonuse of donor hearts for transplantation, yet little is known about its incidence or pathophysiology. Resolving these unknowns was a primary aim of the DHS (Donor Heart Study), a multisite prospective cohort study. METHODS: The DHS enrolled potential donors by neurologic determination of death (n=4333) at 8 organ procurement organizations across the United States between February 2015 and May 2020. Data included medications administered, serial diagnostic tests, and transthoracic echocardiograms (TTEs) performed: (1) within 48 hours after brain death was formally diagnosed; and (2) 24±6 hours later if left ventricular (LV) dysfunction was initially present. LV dysfunction was defined as an LV ejection fraction <50% and was considered reversible if LV ejection fraction was >50% on the second TTE. TTEs were also examined for presence of LV regional wall motion abnormalities and their reversibility. We assessed associations between LV dysfunction, donor heart acceptance for transplantation, and recipient 1-year survival. RESULTS: An initial TTE was interpreted for 3794 of the 4333 potential donors by neurologic determination of death. A total of 493 (13%) of these TTEs showed LV dysfunction. Among those donors with an initial TTE, LV dysfunction was associated with younger age, underweight, and higher NT-proBNP (N-terminal pro-B-type natriuretic peptide) and troponin levels. A second TTE was performed within 24±6 hours for a subset of donors (n=224) with initial LV dysfunction; within this subset, 130 (58%) demonstrated reversibility. Sixty percent of donor hearts with normal LV function were accepted for transplant compared with 56% of hearts with reversible LV dysfunction and 24% of hearts with nonreversible LV dysfunction. Donor LV dysfunction, whether reversible or not, was not associated with recipient 1-year survival. CONCLUSIONS: LV dysfunction associated with brain death occurs in many potential heart donors and is sometimes reversible. These findings can inform decisions made during donor evaluation and help guide donor heart acceptance for transplantation.

Utilization of COVID-19 positive donors for Heart transplantation and associated short-term outcomes.

BACKGROUND: The safety and efficacy of using COVID-19 positive donors in heart transplantation (HT) are increasingly relevant, but not well established. The present study evaluated the characteristics and utilization of such donors and associated post-HT outcomes. METHODS: All adult (≥18 years old) potential donors and HT recipients in the United States from April 21, 2020 to March 31, 2022 were included. Donor COVID-19 status was defined by the presence (or absence) of any positive test within 21 days of organ recovery. Donor and recipient characteristics and post-HT outcomes, including a primary composite of death, graft failure, and re-transplantation, were compared by donor COVID-19 status. RESULTS: Of 967 COVID-19(+) potential donors, 19.3% (n = 187) were used for HT compared to 26.7% (n = 6277) of COVID-19(-) donors (p < 0.001). Transplanted COVID-19(+) vs COVID-19(-) donors were younger, but otherwise were similar. Recipients of hearts from COVID-19+ vs COVID-19(-) donors less frequently received pre-HT inotropes (24.1% vs 31.7%, p = 0.023) and ventricular assist device therapy (29.7% vs 36.8%, p = 0.040). There were no significant differences in any post-HT outcome by donor COVID-19 status, including the primary composite outcome at 90 days (5.4% vs 5.6%, p = 0.91). Among COVID-19(+) donors, the presence of a subsequent negative test prior to transplant was not associated with posttransplant outcomes. CONCLUSIONS: Our results suggest that carefully selected COVID-19 positive donors may be used for HT with no difference in short-term post-transplant outcomes. Additional data regarding donor and recipient treatments and impact of vaccination should be collected to better inform our use of organs from COVID(+) donors.

Donor heart selection: Evidence-based guidelines for providers.

The proposed donor heart selection guidelines provide evidence-based and expert-consensus recommendations for the selection of donor hearts following brain death. These recommendations were compiled by an international panel of experts based on an extensive literature review.

Combining donor derived cell free DNA and gene expression profiling for non-invasive surveillance after heart transplantation.

BACKGROUND: Donor-derived cell free DNA (dd-cfDNA) and gene expression profiling (GEP) offer noninvasive alternatives to rejection surveillance after heart transplantation; however, there is little evidence on the paired use of GEP and dd-cfDNA for rejection surveillance. METHODS: A single center, retrospective analysis of adult heart transplant recipients. A GEP cohort, transplanted from January 1, 2015 through December 31, 2017 and eligible for rejection surveillance with GEP was compared to a paired testing cohort, transplanted July 1, 2018 through June 30, 2020, with surveillance from both dd-cfDNA and GEP. The primary outcomes were survival and rejection-free survival at 1 year post-transplant. RESULTS: In total 159 patients were included, 95 in the GEP and 64 in the paired testing group. There were no differences in baseline characteristics, except for less use of induction in the paired testing group (65.6%) compared to the GEP group (98.9%), P < .01. At 1-year, there were no differences between the paired testing and GEP groups in survival (98.4% vs. 94.7%, P = .23) or rejection-free survival (81.3% vs. 73.7% P = .28). CONCLUSIONS: Compared to post-transplant rejection surveillance with GEP alone, pairing dd-cfDNA and GEP testing was associated with similar survival and rejection-free survival at 1 year while requiring significantly fewer biopsies.

Challenges encountered in conducting donor-based research: Lessons learned from the Donor Heart Study.

Solid organ transplantation continues to be constrained by a lack of suitable donor organs. Advances in donor management and evaluation are needed to address this shortage, but the performance of research studies in deceased donors is fraught with challenges. Here we discuss several of the major obstacles we faced in the conduct of the Donor Heart Study-a prospective, multi-site, observational study of donor management, evaluation, and acceptance for heart transplantation. These included recruitment and engagement of participating organ procurement organizations, ambiguities related to study oversight, obtaining authorization for donor research, logistical challenges encountered during donor management, sustaining study momentum, and challenges related to study data management. By highlighting these obstacles encountered, as well as the solutions implemented, we hope to stimulate further discussion and actions that will facilitate the design and execution of future donor research studies.

Cost-effectiveness and system-wide impact of using Hepatitis C-viremic donors for heart transplant.

BACKGROUND: The advent of direct-acting antiviral therapy for Hepatitis C (HCV) has made using HCV-viremic donors a viable strategy to address the donor shortage in heart transplantation. We employed a large-scale simulation to evaluate the impact and cost-effectiveness of using HCV-viremic donors for heart transplant. METHODS: We simulated detailed histories from time of listing until death for the real-world cohort of all adults listed for heart transplant in the United States from July 2014 to June 2019 (n = 19,346). This population was imputed using historical data and captures "real-world" heterogeneity in geographic and clinical characteristics. We estimated the impact of an intervention in which all candidates accept HCV+ potential donors (n = 472) on transplant volume, waitlist outcomes, and lifetime costs and quality-adjusted life years (QALYs). RESULTS: The intervention produced 232 more transplants, 132 fewer delistings due to deterioration, and 50 fewer waitlist deaths within this 5-year cohort and reduced wait times by 3% to 11% (varying by priority status). The intervention was cost-effective, adding an average of 0.08 QALYs per patient at a cost of $124 million ($81,892 per QALY). DAA therapy and HCV care combined account for 11% this cost, with the remainder due to higher costs of transplant procedures and routine post-transplant care. The impact on transplant volume varied by blood type and region and was correlated with donor-to-candidate ratio (ρ = 0.71). CONCLUSIONS: Transplanting HCV+ donor hearts is likely to be cost-effective and improve waitlist outcomes, particularly in regions and subgroups experiencing high donor scarcity.

Optimal patient selection for simultaneous heart-kidney transplant: A modified cost-effectiveness analysis.

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.

Impact of diabetes mellitus on clinical outcomes after heart transplantation.

PURPOSE: Diabetes mellitus (DM) is common among recipients of heart transplantation (HTx) but its impact on clinical outcomes is unclear. We evaluated the associations between pretransplant DM and posttransplant DM (PTDM) and outcomes among adults receiving HTx at a single center. METHODS: We performed a retrospective study (range 01/2008 - 07/2018), n = 244. The primary outcome was survival; secondary outcomes included acute rejection, cardiac allograft vasculopathy, infection requiring hospitalization, macrovascular events, and dialysis initiation post-transplant. Comparisons were performed using Kaplan-Meier and multivariable Cox regression analyses. RESULTS: Pretransplant DM was present in 75 (30.7%) patients and was associated with a higher risk for infection requiring hospitalization (p < 0.05), but not with survival or other outcomes. Among the 144 patients without pretransplant DM surviving to 1 year, 29 (20.1%) were diagnosed with PTDM at the 1-year follow-up. After multivariable adjustment, PTDM diagnosis at 1-year remained associated with worse subsequent survival (hazard ratio 2.72, 95% confidence interval 1.03-7.16). Predictors of PTDM at 1-year included cytomegalovirus seropositivity and higher prednisone dose (> 5 mg/day) at 1-year follow-up. CONCLUSIONS: Compared to HTx recipients without baseline DM, those with baseline DM have a higher risk for infections requiring hospitalization, and those who develop DM after HTx have worse survival.

Effect of Socioeconomic Status on Patients Supported with Contemporary Left Ventricular Assist Devices.

Continuous-flow left ventricular assist devices (CF-LVADs) are increasingly used in advanced heart failure patients. Recent studies suggest that low socioeconomic status (SES) predicts worst survival after heart transplantation. Both individual-level and neighborhood-level SES (nSES) have been linked to cardiovascular health; however, the impact of SES in CF-LVAD patients remains unknown. We hypothesized that SES is a major determinant of CF-LVAD candidacy and postimplantation outcomes. A retrospective chart review was conducted on 362 patients between February 2009 and May 2016. Neighborhood-level SES was measured using the American Community Survey data and the Agency for Healthcare Research and Quality SES index score. Individual-level SES was self reported. Kaplan-Meier survival analysis and multivariable Cox proportional hazards regression determined survival statistics. Patients in the highest SES tertile were older (58 ± 13 vs. 53 ± 14; p < 0.001), less likely to be black or Hispanic (26% vs. 70%; p < 0.001), more likely to be married (87% vs. 65%; p < 0.001), more likely to have private insurance (50% vs. 39%; p < 0.001), and more likely to have employment (29% vs. 15%; p < 0.001) compared with patients in the lowest tertile. Low nSES was associated with a decreased risk of death (hazard ratio [HR], 0.580; 95% confidence interval [CI], 0.347-0.970; p = 0.038) in comparison to the high nSES. However, after adjusting for baseline clinical morbidities, the relationship was no longer present. When selecting patients for a LVAD, SES should not be thought of as an immutable risk factor. Carefully selected low-SES patients could be safely implanted with CF-LVAD with outcomes comparable to high-SES patients.

Aortic Insufficiency During Contemporary Left Ventricular Assist Device Support: Analysis of the INTERMACS Registry.

OBJECTIVES: This study sought to evaluate the impact of moderate to severe aortic insufficiency (AI) on outcomes in patients with continuous flow left ventricular assist devices (CF-LVADs). BACKGROUND: Development of worsening AI is a common complication of prolonged CF-LVAD support and portends poor prognosis in single-center studies. Predictors of worsening AI and its impact on clinical outcomes have not been examined in a large cohort. METHODS: We conducted a retrospective analysis of patients with CF-LVAD in the INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) study. Development of significant AI was defined as the first instance of at least moderate AI. Primary outcomes of interest were survival after development of significant AI and time to adverse events, including device complications and rehospitalizations. RESULTS: Among 10,603 eligible patients, 1,399 patients on CF-LVAD support developed moderate to severe AI. Prevalence of significant AI progressively increased over time. Predictors of worsening AI included older age, female sex, smaller body mass index, mild pre-implantation AI, and destination therapy strategy. Moderate to severe AI was associated with significantly higher left ventricular end-diastolic diameter, reduced cardiac output, and higher levels of brain natriuretic peptide. Significant AI was associated with higher rates of rehospitalization (32.1% vs. 26.6%, respectively, at 2 years; p = 0.015) and mortality (77.2% vs. 71.4%, respectively, at 2 years; p = 0.005), conditional upon survival to 1 year. CONCLUSIONS: Development of moderate to severe AI has a negative impact on hemodynamics, hospitalizations, and survival on CF-LVAD support. Pre- and post-implantation management strategies should be developed to prevent and treat this complication.

Socioeconomic Disparities in Adherence and Outcomes After Heart Transplant: A UNOS (United Network for Organ Sharing) Registry Analysis.

BACKGROUND: There is mixed evidence of racial and socioeconomic disparities in heart transplant outcomes. Their underlying cause-and whether individual- or community-level traits are most influential-remains unclear. The current study aimed to characterize socioeconomic disparities in outcomes and identify time trends and mediators of these disparities. METHODS AND RESULTS: We used United Network for Organ Sharing registry data and included 33 893 adult heart transplant recipients between 1994 and 2014. Socioeconomic status (SES) indicators included insurance, education, and neighborhood SES measured using a composite index. Black race and multiple indicators of low SES were associated with the primary outcome of death or retransplant, independent of baseline clinical characteristics. Blacks had lower HLA and race matching, but further adjustment for these and other graft characteristics only slightly attenuated the association with black race (HR, 1.25 after adjustment). This and the associations with neighborhood SES (HR, 1.19 for lowest versus highest decile), Medicare (HR, 1.17), Medicaid (HR, 1.29), and college education (HR, 0.90) remained significant after full adjustment. When comparing early (1994-2000) and late (2001-2014) cohorts, the disparities associated with the middle (second and third) quartiles significantly decreased over time, but those associated with lowest SES quartile and black race persisted. Low neighborhood SES was also associated with higher risks of noncompliance (HR, 1.76), rejection (HR, 1.28), hospitalization (HR, 1.13), and infection (HR, 1.10). CONCLUSIONS: Racial and socioeconomic disparities exist in heart transplant outcomes, but the latter may be narrowing over time. These disparities are not explained by differences in clinical or graft characteristics.

Mechanical Circulatory Support Device Utilization and Heart Transplant Waitlist Outcomes in Patients With Restrictive and Hypertrophic Cardiomyopathy.

BACKGROUND: Patients with restrictive cardiomyopathy (RCM) and hypertrophic cardiomyopathy (HCM) generally are considered poor candidates for mechanical circulatory support devices (MCSDs) and often not able to be bridged mechanically to heart transplantation. This study characterized MCSD utilization and transplant waitlist outcomes in patients with RCM/HCM under the current allocation system and discusses changes in the era of the new donor allocation system. METHODS AND RESULTS: Patients waitlisted from 2006 to 2016 in the United Network for Organ Sharing registry were stratified by RCM/HCM versus other diagnoses. MCSD utilization and waitlist duration were analyzed by propensity score models. Waitlist outcomes were assessed by cumulative incidence functions with competing events. Predictors of waitlist mortality or delisting for worsening status in patients with RCM/HCM were identified by proportional hazards model. Of 30 608 patients on the waitlist, 5.1% had RCM/HCM. Patients with RCM/HCM had 31 fewer waitlist days (P<0.01) and were ≈26% less likely to receive MCSD (P<0.01). Cumulative incidence of waitlist mortality was similar between cohorts; however, patients with RCM/HCM had higher incidence of heart transplantation. Predictors of waitlist mortality or delisting for worsening status in patients with RCM/HCM without MCSD support included estimated glomerular filtration rate <60 mL/min per 1.73 m2, pulmonary capillary wedge pressure >20 mm Hg, inotrope use, and subjective frailty. CONCLUSIONS: Patients with RCM/HCM are less likely to receive MCSD but have similar waitlist mortality and slightly higher incidence of transplantation compared with other patients. The United Network for Organ Sharing RCM/HCM risk model can help identify patients who are at high risk for clinical deterioration and in need of expedited heart transplantation.