Metabolomic profiling during ex situ normothermic perfusion before heart transplantation defines patterns of substrate utilization and correlates with markers of allograft injury.

BACKGROUND: Cardiac metabolism is altered in heart failure and ischemia-reperfusion injury states. We hypothesized that metabolomic profiling during ex situ normothermic perfusion before heart transplantation (HT) would lend insight into myocardial substrate utilization and report on subclinical and clinical allograft dysfunction risk. METHODS: Metabolomic profiling was performed on serial samples of ex situ normothermic perfusate assaying biomarkers of myocardial injury in lactate and cardiac troponin I (TnI) as well as metabolites (66 acylcarnitines, 15 amino acids, nonesterified fatty acids [NEFA], ketones, and 3-hydroxybutyrate). We tested for change over time in injury biomarkers and metabolites, along with differential changes by recovery strategy (donation after circulatory death [DCD] vs donation after brain death [DBD]). We examined associations between metabolites, injury biomarkers, and primary graft dysfunction (PGD). Analyses were performed using linear mixed models adjusted for recovery strategy, assay batch, donor-predicted heart mass, and time. RESULTS: A total of 176 samples from 92 ex situ perfusion runs were taken from donors with a mean age of 35 (standard deviation 11.3) years and a median total ex situ perfusion time of 234 (interquartile range 84) minutes. Lactate trends over time differed significantly by recovery strategy, while TnI increased during ex situ perfusion regardless of DCD vs DBD status. We found fuel substrates were rapidly depleted during ex situ perfusion, most notably the branched-chain amino acids leucine/isoleucine, as well as ketones, 3-hydroxybutyrate, and NEFA (least squares [LS] mean difference from the first to last time point -1.7 to -4.5, false discovery rate q < 0.001). Several long-chain acylcarnitines (LCAC), including C16, C18, C18:1, C18:2, C18:3, C20:3, and C20:4, increased during the perfusion run (LS mean difference 0.42-0.67, q < 0.001). Many LCACs were strongly associated with lactate and TnI. The change over time of many LCACs was significantly different for DCD vs DBD, suggesting differential trends in fuel substrate utilization by ischemic injury pattern. Changes in leucine/isoleucine, arginine, C12:1-OH/C10:1-DC, and C16-OH/C14-DC were associated with increased odds of moderate-severe PGD. Neither end-of-run nor change in lactate or TnI was associated with PGD. CONCLUSIONS: Metabolomic profiling of ex situ normothermic perfusion solution reveals a pattern of fuel substrate utilization that correlates with subclinical and clinical allograft dysfunction. This study highlights a potential role for interventions focused on fuel substrate modification in allograft conditioning during ex situ perfusion to improve allograft outcomes.

Towards Allograft Longevity: Leveraging Omics Technologies to Improve Heart Transplant Outcomes.

PURPOSE OF REVIEW: Heart transplantation (HT) remains the optimal therapy for patients living with end-stage heart disease. Despite recent improvements in peri-transplant management, the median survival after HT has remained relatively static, and complications of HT, including infection, rejection, and allograft dysfunction, continue to impact quality of life and long-term survival. RECENT FINDINGS: Omics technologies are becoming increasingly accessible and can identify novel biomarkers for, and reveal the underlying biology of, several disease states. While some technologies, such as gene expression profiling (GEP) and donor-derived cell-free DNA (dd-cfDNA), are routinely used in the clinical care of HT recipients, a number of emerging platforms, including pharmacogenomics, proteomics, and metabolomics, hold great potential for identifying biomarkers to aid in the diagnosis and management of post-transplant complications. Omics-based assays can improve patient and allograft longevity by facilitating a personalized and precision approach to post-HT care. The following article is a contemporary review of the current and future opportunities to leverage omics technologies, including genomics, transcriptomics, proteomics, and metabolomics in the field of HT.

Selection and Interpretation of Molecular Diagnostics in Heart Transplantation.

The number of heart transplants performed annually in the United States and worldwide continues to increase, but there has been little change in graft longevity and patient survival over the past 2 decades. The reference standard for diagnosis of acute cellular and antibody-mediated rejection includes histologic and immunofluorescence evaluation of endomyocardial biopsy samples, despite invasiveness and high interrater variability for grading histologic rejection. Circulating biomarkers and molecular diagnostics have shown substantial predictive value in rejection monitoring, and emerging data support their use in diagnosing other posttransplant complications. The use of genomic (cell-free DNA), transcriptomic (mRNA and microRNA profiling), and proteomic (protein expression quantitation) methodologies in diagnosis of these posttransplant outcomes has been evaluated with varying levels of evidence. In parallel, growing knowledge about the genetically mediated immune response leading to rejection (immunogenetics) has enhanced understanding of antibody-mediated rejection, associated graft dysfunction, and death. Antibodies to donor human leukocyte antigens and the technology available to evaluate these antibodies continues to evolve. This review aims to provide an overview of biomarker and immunologic tests used to diagnose posttransplant complications. This includes a discussion of pediatric heart transplantation and the disparate rates of rejection and death experienced by Black patients receiving a heart transplant. This review describes diagnostic modalities that are available and used after transplant and the landscape of future investigations needed to enhance patient outcomes after heart transplantation.

Mitochondrial metabolites predict adverse cardiovascular events in individuals with diabetes.

Metabolic mechanisms underlying the heterogeneity of major adverse cardiovascular (CV) event (MACE) risk in individuals with type 2 diabetes mellitus (T2D) remain unclear. We hypothesized that circulating metabolites reflecting mitochondrial dysfunction predict incident MACE in T2D. Targeted mass-spectrometry profiling of 60 metabolites was performed on baseline plasma samples from the Trial Evaluating Cardiovascular Outcomes with Sitagliptin (TECOS; discovery cohort) and Exenatide Study of Cardiovascular Event Lowering (EXSCEL; validation cohort) biomarker substudy cohorts. A principal components analysis metabolite factor comprising medium-chain acylcarnitines (MCACs) was associated with MACE in TECOS and validated in EXSCEL, with higher levels associated with higher MACE risk. Meta-analysis showed that long-chain acylcarnitines (LCACs) and dicarboxylacylcarnitines were also associated with MACE. Metabolites remained associated with MACE in multivariate models and favorably changed with exenatide therapy. A third cohort (Cardiac Catheterization Genetics [CATHGEN]) with T2D was assessed to determine whether these metabolites improved discriminative capability of multivariate models for MACE. Nine metabolites (MCACs and LCACs and 1 dicarboxylacylcarnitine) were associated with time to MACE in the CATHGEN cohort. Addition of these metabolites to clinical models minimally improved the discriminative capability for MACE but did significantly down reclassify risk. Thus, metabolites reporting on dysregulated mitochondrial fatty acid oxidation are present in higher levels in individuals with T2D who experience subsequent MACE. These biomarkers may improve CV risk prediction models, be therapy responsive, and highlight emerging risk mechanisms.

Beyond Stage C: Considerations in the Management of Patients With Heart Failure Progression and Gaps in Evidence.

Despite treatment with contemporary medical therapies for chronic heart failure (HF), there has been an increase in the prevalence of patients progressing to more advanced disease. Patients progressing to and living at the interface of severe stage C and stage D HF are underrepresented in clinical trials, and there is a lack of high-quality evidence to guide clinical decision making. For patients with severe HF phenotypes, the medical therapies used for patients with less advanced stages of illness are often no longer tolerated or provide inadequate clinical stability. The limited data on these patients highlights the need to increase formal research characterizing this high-risk population. This review summarizes existing clinical trial data and incorporates our considerations for approaches to the medical management of patients advanced "beyond stage C" HF.

Donation after circulatory determination of death in heart transplant: impact on current and future allocation policy.

PURPOSE OF REVIEW: Historically, the selection criteria for heart transplant candidates has prioritized posttransplant survival while contemporary allocation policy is focused on improving waitlist survival. Donor scarcity has continued to be the major influence on transplant allocation policy. This review will address the opportunity of donation after circulatory determination of death (DCDD) and potential impact on future policy revisions. RECENT FINDINGS: In 2018, changes to U.S. heart allocation policy led to several intended and unintended consequences. Beneficial changes include reduced waitlist mortality and broader geographic sharing. Additional impacts include scarcer pathways to transplant for patients with a durable left ventricular assist device, increased reliance on status exceptions, and expanded use of temporary mechanical support. DCDD is anticipated to increase national heart transplant volumes by ∼30% and will impact waitlist management. Centers that offer DCDD procurement will have reduced waitlist times, reduced waitlist mortality, and higher transplant volumes. SUMMARY: While DCDD will provide more transplant opportunities, donor organ scarcity will persist and influence allocation policies. Differential patient selection, waitlist strategy, and outcome expectations may indicate that allocation is adjusted based on the procurement options at individual centers. Future policy, which will consider posttransplant outcomes, may reflect that different procurement strategies may yield different outcomes.

Improved Outcomes in Severe Primary Graft Dysfunction After Heart Transplantation Following Donation After Circulatory Death Compared With Donation After Brain Death.

BACKGROUND: Primary graft dysfunction (PGD), the leading cause of early mortality after heart transplantation, is more common following donation after circulatory death (DCD) than donation after brain death (DBD). We conducted a single-center, retrospective cohort study to compare the incidence, severity and outcomes of patients experiencing PGD after DCD compared to DBD heart transplantation. METHODS AND RESULTS: Medical records were reviewed for all adult heart transplant recipients at our institution between March 2016 and December 2021. PGD was diagnosed within 24 hours after transplant according to modified International Society for Heart and Lung Transplant criteria. A total of 459 patients underwent isolated heart transplantation during the study period, 65 (14%) following DCD and 394 (86%) following DBD. The incidence of moderate or severe PGD in DCD and DBD recipients was 34% and 23%, respectively (P = 0.070). DCD recipients were more likely to experience severe biventricular PGD than DBD recipients (19% vs 7.4%; P = 0.004). Among patients with severe PGD, DCD recipients experienced shorter median (Q1, Q3) duration of post-transplant mechanical circulatory support (6 [4, 7] vs 9 [5, 14] days; P = 0.039), shorter median post-transplant hospital length of stay (17 [15, 29] vs 52 [26, 83] days; P = 0.004), and similar 60-day survival rates (100% [95% CI: 76.8%-100%] vs 80.0% [63.1%-91.6%]; P = 0.17) and overall survival (log-rank; P = 0.078) compared with DBD recipients. CONCLUSIONS: DCD heart transplant recipients were more likely to experience severe, biventricular PGD than DBD recipients. Despite this, DCD recipients with severe PGD spent fewer days on mechanical circulatory support and in the hospital than similar DBD patients. These findings suggest that patterns of graft dysfunction and recovery may differ between donor types, and they support the expansion of the heart-donor pool with DCD.

Protein biomarkers of cardiac remodeling and inflammation associated with HFpEF and incident events.

There is increasing evidence that HFpEF is a heterogeneous clinical entity and distinct molecular pathways may contribute to pathophysiology. Leveraging unbiased proteomics to identify novel biomarkers, this study seeks to understand the underlying molecular mechanisms of HFpEF. The discovery cohort consisted of HFpEF cases and non-HF controls from the CATHGEN study (N = 176); the validation cohort consisted of participants from the TECOS trial of patients with diabetes (N = 109). Proteins associated with HFpEF were included in a LASSO model to create a discriminative multi-protein model and assessed in the validation cohort. Survival models and meta-analysis were used to test the association of proteins with incident clinical outcomes, including HF hospitalization, mortality and HFpEF hospitalization in CATHGEN, TECOS and the Jackson Heart Study. In the derivation set, 190 proteins were associated with HFpEF in univariate analysis, of which 65 remained significant in the multivariate model. Twenty (30.8%) of these proteins validated in TECOS, including LCN2, U-PAR, IL-1ra, KIM1, CSTB and Gal-9 (OR 1.93-2.77, p < 0.01). LASSO regression yielded a 13-protein model which, when added to a clinical model inclusive of NT-proBNP, improved the AUC from 0.82 to 0.92 (p = 1.5 × 10-4). Five proteins were associated with incident HF hospitalization, four with HFpEF hospitalization and eleven with mortality (p < 0.05). We identified and validated multiple circulating biomarkers associated with HFpEF as well as HF outcomes. These biomarkers added incremental discriminative capabilities beyond clinical factors and NT-proBNP.

Donation After Circulatory Death in Heart Transplantation: History, Outcomes, Clinical Challenges, and Opportunities to Expand the Donor Pool.

Heart transplantation remains the gold-standard therapy for end-stage heart failure; the expected median survival range is 12-13 years. More than 30,000 heart transplants have been performed globally in the past decade alone. With advances in medical and surgical therapies for heart failure, including durable left ventricular assist devices, an increasing number of patients are living with end-stage disease. Last year alone, more than 2500 patients were added to the heart-transplant waitlist in the United States. Despite recent efforts to expand the donor pool, including an increase in transplantation of hepatitis C-positive and extended-criteria donors, supply continues to fall short of demand. Donation after circulatory death (DCD), defined by irreversible cardiopulmonary arrest rather than donor brain death, is widely used in other solid-organ transplants, including kidney and liver, but has not been widely adopted in heart transplantation. However, resurging interest in DCD donation and the introduction of ex vivo perfusion technology has catalyzed recent clinical trials and the development of DCD heart-transplantation programs. Herein, we review the history of DCD heart transplantation, describe the currently used procurement protocols for it and examine clinical challenges and outcomes of such a procedure.

Increased Opportunities for Transplantation for Women in the New Heart Allocation System.

BACKGROUND: Historically, women have had less access to advanced heart failure therapies, including temporary and permanent mechanical circulatory support and heart transplantation (HT), with worse waitlist and post-transplant survival compared with men. This study evaluated for improvement in sex differences across all phases of HT in the 2018 allocation system. METHODS AND RESULTS: The United Network for Organ Sharing registry was queried to identify adult patients (≥18 years) listed for HT from October 18, 2016, to October 17, 2018 (old allocation), and from October 18, 2018, to October 18, 2020 (new allocation). The outcomes of interest included waitlist survival, pretransplant use of temporary and durable mechanical circulatory support, rates of HT, and post-transplant survival. There were 15,629 patients who were listed for HT and included in this analysis; 7745 (2039 women, 26.3%) in the new and 7875 patients (2074 women, 26.3%) in the old allocation system. When compared with men in the new allocation system, women were more likely to have lower priority United Network for Organ Sharing status at time of transplant, and less likely to be supported by an intra-aortic balloon pump (27.1% vs 32.2%, P < .001), with no difference in the use of venoarterial extracorporeal membrane oxygenation (5.5% vs 6.3%, P = .28). Despite these findings, when transplantation was viewed in the context of risk for death or delisting, the cumulative incidence of transplant within 6 months of listing was higher in women than men in the new allocation system (62.4% vs 54.9%, P < .001) with no differences in post-transplant survival. When comparing women in the old with the new allocation system, the distance traveled for organ procurement was 187.5 ± 207.0 miles vs 272.8 ± 233.7 miles (P < .001). CONCLUSIONS: Although the use of temporary mechanical circulatory support in women remains lower than in men in the new allocation system, more women are being transplanted with comparable waitlist and post-transplant outcomes as men. Broader sharing may be making its greatest impact on improving transplant opportunities for women.

Residual mitral regurgitation in patients with left ventricular assist device support - An INTERMACS analysis.

BACKGROUND: Left ventricular assist device (LVAD) placement frequently leads to a reduction in the severity of functional mitral regurgitation (MR). However, a significant number of LVAD supported patients have residual MR. We sought to assess the impact of residual MR in LVAD patient outcomes. METHODS: Patients in the INTERMACS registry who received a continuous flow LVAD between 2006 and 2017 without a prior mitral valve repair were included for analysis. Residual MR was defined as moderate or severe MR within the first 3 months device support. Baseline characteristics, echocardiographic and hemodynamic variables, and clinical outcomes were comparatively analyzed between those with or without residual MR. RESULTS: A total of 8,364 patients were included in the study, of which 18.8% demonstrated residual MR. Younger age, female gender, and non-ischemic heart failure were predictors of residual MR, as were increased LVEDD, RV dysfunction, severe baseline MR or TR, and elevated right heart pressures. Concomitant mitral valve repair reduced the risk of residual MR. Those with residual MR demonstrated worse LV remodeling, more right ventricular dysfunction, and higher right heart pressures at almost all time points analyzed. Residual MR was associated with increased risk of right heart failure and renal failure, and a trend toward increased mortality on LVAD support. CONCLUSIONS: Residual MR is associated with worse clinical outcomes on LVAD support. Strategies to minimize MR including medical and device optimization as well as valve repair should be considered in LVAD patients with residual MR.

Critically appraising the 2018 United Network for Organ Sharing donor allocation policy: adding life boats or rearranging the deck chairs?

PURPOSE OF REVIEW: Due to the growing mismatch between donor supply and demand as well as unacceptably high transplant waitlist mortality, the heart organ allocation system was revised in October 2018. This review gives an overview of the changes in the new heart organ allocation system and its impact on heart transplant practice and outcomes in the United States. RECENT FINDINGS: The 2018 heart allocation system offers a 6-tiered policy and therefore prioritizes the sickest patients on the transplant waitlist. Patients supported with temporary mechanical circulatory support devices are prioritized as Status 1 or Status 2, resulting in increased utilization of this strategy. Patients supported with durable left ventricular assist devices have been prioritized as Status 3 or 4, which has resulted in decreased utilization of this strategy. Broader geographic sharing in the new heart allocation system has resulted in prolonged donor ischemic times. Overall, the new heart allocation system has resulted in significantly lower candidate waitlist mortality, shorter waitlist times, and higher incidence of transplantation. SUMMARY: The new United Network for Organ Sharing allocation policy confers significant advantages over the prior algorithm, allowing for decreased waitlist times and improved waitlist mortality without major impact on posttransplant survival.

Cardiovascular risk stratification in the noncardiac solid organ transplant candidate.

PURPOSE OF REVIEW: Solid organ transplantation (SOT) has become a widely accepted therapy for end-stage disease across the spectrum of thoracic and abdominal organs. With contemporary advances in medical and surgical therapies in transplantation, candidates for SOT are increasingly older with a larger burden of comorbidities, including cardiovascular disease (CVD). CVD, in particular, is a leading cause of morbidity and mortality in SOT candidates with end-stage disease of noncardiac organs [1]. RECENT FINDINGS: Identification of coronary artery disease (CAD), heart failure, and valvular disease are important in noncardiac SOT to ensure both appropriate peri-transplant management and equitable organ allocation. Although the American College of Cardiology (ACC) and the American Heart Association (AHA) have published guidelines and recommendations for the perioperative cardiovascular evaluation of patients undergoing noncardiac surgery, the implications of both symptomatic and asymptomatic CVD differ in patients with end-stage organ failure being considered for SOT when compared to the general population. SUMMARY: Herein, we review the epidemiology, diagnosis, and evidence for the management of CVD in kidney and liver transplantation, combining current guidelines from the 2012 ACC/AHA scientific statement on cardiac disease evaluation in SOT with more contemporary evidenced-based algorithms.

Proteomic profiling identifies CLEC4C expression as a novel biomarker of primary graft dysfunction after heart transplantation.

PURPOSE: Clinical models to identify patients at high risk of primary graft dysfunction (PGD) after heart transplantation (HT) are limited, and the underlying pathophysiology of this common post-transplant complication remains poorly understood. We sought to identify whether pre-transplant levels of circulating proteins reporting on immune activation and inflammation are associated with incident PGD. METHODS: The study population consisted of 219 adult heart transplant recipients identified between 2016 and 2020 at Duke University Medical Center, randomly divided into derivation (n = 131) and validation (n = 88) sets. PGD was defined using modified ISHLT criteria. Proteomic profiling was performed using Olink panels (n = 354 proteins) with serum samples collected immediately prior to transplantation. Association between normalized relative protein expression and PGD was tested using univariate and multivariable (recipient age, creatinine, mechanical circulatory support, and sex; donor age; ischemic time) models. Significant proteins identified in the derivation set (p < 0.05 in univariate models), were then tested in the validation set. Pathway enrichment analysis was used to test candidate biological processes. The predictive performance of proteins was compared to that of the RADIAL score. RESULTS: Nine proteins were associated with PGD in univariate models in the derivation set. Of these, only CLEC4C remained associated with PGD in the validation set after Bonferroni correction (OR [95% CI] = 3.04 [1.74,5.82], p = 2.8 × 10-4). Patterns of association were consistent for CLEC4C in analyses stratified by biventricular/left ventricular and isolated right ventricular PGD. Pathway analysis identified interferon-alpha response and C-type lectin signaling as significantly enriched biologic processes. The RADIAL score was a poor predictor of PGD (AUC = 0.55). CLEC4C alone (AUC = 0.66, p = 0.048) and in combination with the clinical covariates from the multivariable model (AUC = 0.69, p = 0.018) improved discrimination for the primary outcome. CONCLUSIONS: Pre-transplantation circulating levels of CLEC4C, a protein marker of plasmacytoid dendritic cells (pDCs), may identify HT recipients at risk for PGD. Further studies are needed to better understand the potential role pDCs and the innate immune response in PGD.

Circulating long chain acylcarnitines and outcomes in diabetic heart failure: an HF-ACTION clinical trial substudy.

BACKGROUND: Whether differences in circulating long chain acylcarnitines (LCAC) are seen in heart failure (HF) patients with and without diabetes mellitus (DM), and whether these biomarkers report on exercise capacity and clinical outcomes, remains unknown. The objective of the current study was to use metabolomic profiling to identify biomarkers that report on exercise capacity, clinical outcomes, and differential response to exercise in HF patients with and without DM. METHODS: Targeted mass spectrometry was used to quantify metabolites in plasma from participants in the heart failure: a controlled trial investigating outcomes of exercise training (HF-ACTION) trial. Principal components analysis was used to identify 12 uncorrelated factors. The association between metabolite factors, diabetes status, exercise capacity, and time to the primary clinical outcome of all-cause mortality or all-cause hospitalization was assessed. RESULTS: A total of 664 participants were included: 359 (54%) with DM. LCAC factor levels were associated with baseline exercise capacity as measured by peak oxygen consumption (beta 0.86, p = 2 × 10-7, and were differentially associated in participants with and without DM (beta 1.58, p = 8 × 10-8 vs. 0.67, p = 9 × 10-4, respectively; p value for interaction = 0.012). LCAC levels changed to a lesser extent in participants with DM after exercise (mean ∆ 0.09, p = 0.24) than in those without DM (mean ∆ 0.16, p = 0.08). In univariate and multivariate modeling, LCAC factor levels were associated with time to the primary outcome (multivariate HR 0.80, p = 2.74 × 10-8), and were more strongly linked to outcomes in diabetic participants (HR 0.64, p = 3.21 × 10-9 v. HR 0.90, p = 0.104, p value for interaction = 0.001). When analysis was performed at the level of individual metabolites, C16, C16:1, C18, and C18:1 had the greatest associations with both exercise capacity and outcomes, with higher levels associated with worse outcomes. Similar associations with time to the primary clinical outcome were not found in a control group of patients without HF from the CATHeterization GENetics (CATHGEN) study. CONCLUSIONS: LCAC biomarkers are associated with exercise status and clinical outcomes differentially in HF patients with and without DM. Impaired fatty acid substrate utilization and mitochondrial dysfunction both at the level of the skeletal muscle and the myocardium may explain the decreased exercise capacity, attenuated response to exercise training, and poor clinical outcomes seen in patients with HF and DM. Trial Registration clinicaltrials.gov Identifier: NCT00047437.

Incidence and impact of primary graft dysfunction in adult heart transplant recipients: A systematic review and meta-analysis.

PURPOSE: Primary graft dysfunction (PGD) is a leading cause of early mortality after heart transplant (HTx). To identify PGD incidence and impact on mortality, and to elucidate risk factors for PGD, we systematically reviewed studies using the ISHLT 2014 Consensus Report definition and reporting the incidence of PGD in adult HTx recipients. METHODS: We conducted a systematic search in January 2020 including studies reporting the incidence of PGD in adult HTx recipients. We used a random effects model to pool the incidence of PGD among HTx recipients and, for each PGD severity, the mortality rate among those who developed PGD. For prognostic factors evaluated in ≥2 studies, we used random effects meta-analyses to pool the adjusted odds ratios for development of PGD. The GRADE framework informed our certainty in the evidence. RESULTS: Of 148 publications identified, 36 observational studies proved eligible. With moderate certainty, we observed pooled incidences of 3.5%, 6.6%, 7.7%, and 1.6% and 1-year mortality rates of 15%, 21%, 41%, and 35% for mild, moderate, severe and isolated right ventricular-PGD, respectively. Donor factors (female sex, and undersized), recipient factors (creatinine, and pre-HTx use of amiodarone, and temporary or durable mechanical support), and prolonged ischemic time proved associated with PGD post-HTx. CONCLUSION: Our review suggests that the incidence of PGD may be low but its risk of mortality high, increasing with PGD severity. Prognostic factors, including undersized donor, recipient use of amiodarone pre-HTx and recipient creatinine may guide future studies in exploring donor and/or recipient selection and risk mitigation strategies.