Leukotriene B4: A Potential Mediator and Biomarker for Cardiac Allograft Vasculopathy

BACKGROUND

Cardiac allograft vasculopathy (CAV) remains the leading cause of long-term graft failure and mortality after heart transplantation. Effective preventive and treatment options are not available to-date, largely because underlying mechanisms remain poorly understood. We studied the potential role of leukotriene B4 (LTB4), an inflammatory lipid mediator, in development of CAV.

METHODS

We used an established pre-clinical rat CAV model to study the role of LTB4 in CAV. We performed syngeneic and allogeneic orthotopic aortic transplantation, after which neointimal proliferation was quantified. Animals were then treated with Bestatin, an inhibitor of LTB4 synthesis, or vehicle control for 30 days post-transplant, and evidence of graft CAV was determined by histology. We also measured serial LTB4 levels in a cohort of 28 human heart transplant recipients with CAV, 17 matched transplant controls without CAV, and 20 healthy non-transplant controls.

RESULTS

We showed that infiltration of the arterial wall with macrophages leads to neointimal thickening and a rise in serum LTB4 levels in our rat model of CAV. Inhibition of LTB4 production with the drug Bestatin prevents development of neointimal hyperplasia, suggesting that Bestatin may be effective therapy for CAV prevention. In a parallel study of heart transplant recipients, we found non-significantly elevated plasma LTB4 levels in patients with CAV, compared to patients without CAV and healthy, non-transplant controls.

CONCLUSIONS

This study provides key evidence supporting the role of the inflammatory cytokine LTB4 as an important mediator of CAV development, and provides preliminary data suggesting the clinical benefit of Bestatin for CAV prevention.

Advancing the Scientific Basis for Determining Death in Controlled Organ Donation After Circulatory Determination of Death

In controlled organ donation after circulatory determination of death (cDCDD), accurate and timely death determination is critical, yet knowledge gaps persist. Further research to improve the science of defining and determining death by circulatory criteria is therefore warranted. In a workshop sponsored by the National Heart, Lung, and Blood Institute, experts identified research opportunities pertaining to scientific, conceptual, and ethical understandings of DCDD and associated technologies. This article identifies a research strategy to inform the biomedical definition of death, the criteria for its determination, and circulatory death determination in cDCDD. Highlighting knowledge gaps, we propose that further research is needed to inform the observation period following cessation of circulation in pediatric and neonatal populations, the temporal relationship between the cessation of brain and circulatory function after the withdrawal of life-sustaining measures in all patient populations, and the minimal pulse pressures that sustain brain blood flow, perfusion, activity, and function. Additionally, accurate predictive tools to estimate time to asystole following the withdrawal of treatment and alternative monitoring modalities to establish the cessation of circulatory, brainstem, and brain function are needed. The physiologic and conceptual implications of postmortem interventions that resume circulation in cDCDD donors likewise demand attention to inform organ recovery practices. Finally, because jurisdictionally variable definitions of death and the criteria for its determination may impede collaborative research efforts, further work is required to achieve consensus on the physiologic and conceptual rationale for defining and determining death after circulatory arrest.

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.

Research opportunities and ethical considerations for heart and lung xenotransplantation research: A report from the National Heart, Lung, and Blood Institute workshop

Xenotransplantation offers the potential to meet the critical need for heart and lung transplantation presently constrained by the current human donor organ supply. Much was learned over the past decades regarding gene editing to prevent the immune activation and inflammation that cause early organ injury, and strategies for maintenance of immunosuppression to promote longer-term xenograft survival. However, many scientific questions remain regarding further requirements for genetic modification of donor organs, appropriate contexts for xenotransplantation research (including nonhuman primates, recently deceased humans, and living human recipients), and risk of xenozoonotic disease transmission. Related ethical questions include the appropriate selection of clinical trial participants, challenges with obtaining informed consent, animal rights and welfare considerations, and cost. Research involving recently deceased humans has also emerged as a potentially novel way to understand how xeno-organs will impact the human body. Clinical xenotransplantation and research involving decedents also raise ethical questions and will require consensus regarding regulatory oversight and protocol review. These considerations and the related opportunities for xenotransplantation research were discussed in a workshop sponsored by the National Heart, Lung, and Blood Institute, and are summarized in this meeting report.

Sex-specific patterns of donor-derived cell-free DNA in heart transplant rejection: An analysis from the Genomic Research Alliance for Transplantation (GRAfT)

BACKGROUND

Noninvasive methods for surveillance of acute rejection are increasingly used in heart transplantation (HT), including donor-derived cell-free DNA (dd-cfDNA). As other cardiac biomarkers differ by sex, we hypothesized that there may be sex-specific differences in the performance of dd-cfDNA for the detection of acute rejection. The purpose of the current study was to examine patterns of dd-cfDNA seen in quiescence and acute rejection in male and female transplant recipients.

METHODS

Patients enrolled in the Genomic Research Alliance for Transplantation who were ≥18 years at the time of HT were included. Rejection was defined by endomyocardial biopsy with acute cellular rejection (ACR) grade ≥2R and/or antibody-mediated rejection ≥ pAMR 1. dd-cfDNA was quantitated using shotgun sequencing. Median dd-cfDNA levels were compared between sexes during quiescence and rejection. The performance of dd-cfDNA by sex was assessed using area under the receiver operator characteristic (AUROC) curve. Allograft injury was defined as dd-cfDNA ≥0.25%.

RESULTS

One hundred fifty-one unique patients (49 female, 32%) were included in the analysis with 1,119 available dd-cfDNA measurements. Baseline characteristics including demographics and comorbidities were not significantly different between sexes. During quiescence, there were no significant sex differences in median dd-cfDNA level (0.04% [IQR 0.00, 0.16] in females vs 0.03% [IQR 0.00, 0.12] in males, p = 0.22). There were no significant sex differences in median dd-cfDNA for ACR (0.33% [0.21, 0.36] in females vs 0.32% [0.21, 1.10] in males, p = 0.57). Overall, median dd-cfDNA levels were higher in antibody-mediated rejection (AMR) than ACR but did not significantly differ by sex (0.50% [IQR 0.18, 0.82] in females vs 0.63% [IQR 0.32, 1.95] in males, p = 0.51). Elevated dd-cfDNA detected ACR/AMR with an AUROC of 0.83 in females and 0.89 in males, p-value for comparison = 0.16.

CONCLUSIONS

There were no significant sex differences in dd-cfDNA levels during quiescence and rejection. Performance characteristics were similar, suggesting similar diagnostic thresholds can be used in men and women for rejection surveillance.

Knowledge gaps in heart and lung donation after the circulatory determination of death: Report of a workshop of the National Heart, Lung, and Blood Institute

In a workshop sponsored by the U.S. National Heart, Lung, and Blood Institute, experts identified current knowledge gaps and research opportunities in the scientific, conceptual, and ethical understanding of organ donation after the circulatory determination of death and its technologies. To minimize organ injury from warm ischemia and produce better recipient outcomes, innovative techniques to perfuse and oxygenate organs postmortem in situ, such as thoracoabdominal normothermic regional perfusion, are being implemented in several medical centers in the US and elsewhere. These technologies have improved organ outcomes but have raised ethical and legal questions. Re-establishing donor circulation postmortem can be viewed as invalidating the condition of permanent cessation of circulation on which the earlier death determination was made and clamping arch vessels to exclude brain circulation can be viewed as inducing brain death. Alternatively, TA-NRP can be viewed as localized in-situ organ perfusion, not whole-body resuscitation, that does not invalidate death determination. Further scientific, conceptual, and ethical studies, such as those identified in this workshop, can inform and help resolve controversies raised by this practice.

HLA sensitization is associated with an increased risk of primary graft dysfunction after heart transplantation

Primary graft dysfunction (PGD) is a leading cause of early morbidity and mortality following heart transplantation (HT). We sought to determine the association between pretransplant human leukocyte antigen (HLA) sensitization, as measured using the calculated panel reactive antibody (cPRA) value, and the risk of PGD.

METHODS

Consecutive adult HT recipients (n = 596) from 1/2015 to 12/2019 at 2 US centers were included. Severity of PGD was based on the 2014 International Society for Heart and Lung Transplantation consensus statement. For each recipient, unacceptable HLA antigens were obtained and locus-specific cPRA (cPRA-LS) and pre-HT donor-specific antibodies (DSA) were assessed.

RESULTS

Univariable logistic modeling showed that peak cPRA-LS for all loci and HLA-A was associated with increased severity of PGD as an ordinal variable (all loci: OR 1.78, 95% CI: 1.01-1.14, p = 0.025, HLA-A: OR 1.14, 95% CI: 1.03-1.26, p = 0.011). Multivariable analysis showed peak cPRA-LS for HLA-A, recipient beta-blocker use, total ischemic time, donor age, prior cardiac surgery, and United Network for Organ Sharing status 1 or 2 were associated with increased severity of PGD. The presence of DSA to HLA-B was associated with trend toward increased risk of mild-to-moderate PGD (OR 2.56, 95% CI: 0.99-6.63, p = 0.053), but DSA to other HLA loci was not associated with PGD.

CONCLUSIONS

Sensitization for all HLA loci, and specifically HLA-A, is associated with an increased severity of PGD. These factors should be included in pre-HT risk stratification to minimize the risk of PGD.

Post-transplant survival after normothermic regional perfusion versus direct procurement and perfusion in donation after circulatory determination of death in heart transplantation

BACKGROUND

Since 2019, the annual transplantation rate of hearts donated following circulatory death (DCD) has increased significantly in the United States. The 2 major heart procurement techniques following circulatory death are direct procurement and perfusion (DPP) and normothermic regional perfusion (NRP). Post-transplant survival for heart recipients has not been compared between these 2 techniques.

METHODS

This observational study uses data on adult heart transplants from donors after circulatory death from January 1, 2019 to December 31, 2021 in the Scientific Registry of Transplant Recipients. We identified comparable transplant cases across procurement types using propensity-score matching and measured the association between procurement technique and 1-year post-transplant survival using Kaplan-Meier and Cox proportional hazards model stratefied by matching pairs.

RESULTS

Among 318 DCD heart transplants, 216 (68%) were procured via DPP, and 102 (32%) via NRP. Among 22 transplant centers that accepted circulatory-death donors, 3 used NRP exclusively, and 5 used both procurement techniques. After propensity-score matching on recipient and donor factors, there was no significant difference in 1-year post-transplant survival (93.1% for NRP vs 91.1% for DPP, p = 0.79) between procurement techniques.

CONCLUSIONS

NRP and DPP procurements are associated with similar 1-year post-transplant survival. If NRP is ethically permissible and improves outcomes for abdominal organs, it should be the preferred procurement technique for DCD hearts.

Development and Validation of a Risk Score Predicting Death Without Transplant in Adult Heart Transplant Candidates

Importance

The US heart allocation system prioritizes medically urgent candidates with a high risk of dying without transplant. The current therapy-based 6-status system is susceptible to manipulation and has limited rank ordering ability.

Objective

To develop and validate a candidate risk score that incorporates current clinical, laboratory, and hemodynamic data.

Design, Setting, and Participants

A registry-based observational study of adult heart transplant candidates (aged ≥18 years) from the US heart allocation system listed between January 1, 2019, and December 31, 2022, split by center into training (70%) and test (30%) datasets. Adult candidates were listed between January 1, 2019, and December 31, 2022.

Main Outcomes and Measures

A US candidate risk score (US-CRS) model was developed by adding a predefined set of predictors to the current French Candidate Risk Score (French-CRS) model. Sensitivity analyses were performed, which included intra-aortic balloon pumps (IABP) and percutaneous ventricular assist devices (VAD) in the definition of short-term mechanical circulatory support (MCS) for the US-CRS. Performance of the US-CRS model, French-CRS model, and 6-status model in the test dataset was evaluated by time-dependent area under the receiver operating characteristic curve (AUC) for death without transplant within 6 weeks and overall survival concordance (c-index) with integrated AUC.

Results

A total of 16 905 adult heart transplant candidates were listed (mean [SD] age, 53 [13] years; 73% male; 58% White); 796 patients (4.7%) died without a transplant. The final US-CRS contained time-varying short-term MCS (ventricular assist-extracorporeal membrane oxygenation or temporary surgical VAD), the log of bilirubin, estimated glomerular filtration rate, the log of B-type natriuretic peptide, albumin, sodium, and durable left ventricular assist device. In the test dataset, the AUC for death within 6 weeks of listing for the US-CRS model was 0.79 (95% CI, 0.75-0.83), for the French-CRS model was 0.72 (95% CI, 0.67-0.76), and 6-status model was 0.68 (95% CI, 0.62-0.73). Overall c-index for the US-CRS model was 0.76 (95% CI, 0.73-0.80), for the French-CRS model was 0.69 (95% CI, 0.65-0.73), and 6-status model was 0.67 (95% CI, 0.63-0.71). Classifying IABP and percutaneous VAD as short-term MCS reduced the effect size by 54%.

Conclusions and Relevance

In this registry-based study of US heart transplant candidates, a continuous multivariable allocation score outperformed the 6-status system in rank ordering heart transplant candidates by medical urgency and may be useful for the medical urgency component of heart allocation.

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.

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.

The International Consortium on Primary Graft Dysfunction: Redefining Clinical Risk Factors in the Contemporary Era of Heart Transplantation

BACKGROUND

Primary Graft Dysfunction (PGD) is the leading cause of morbidity and mortality early after heart transplant (HT). The International Consortium on PGD is a multicenter collaboration dedicated to identifying the clinical risk factors for PGD in the contemporary era of HT. The objectives of the current report were to 1) assess the incidence of severe PGD in an international cohort, 2) evaluate the performance of the most validated PGD risk tool, the RADIAL score, in a contemporary cohort, and 3) redefine clinical risk factors for severe PGD in the current era of HT.

METHODS

This is a retrospective, observational study of consecutive adult HT recipients between 2010 and 2020 in 10 centers in the United States, Canada, and Europe. Patients with severe PGD were compared to those without severe PGD (comprising those with no, mild and moderate PGD). The RADIAL score was calculated for each transplant recipient. The discriminatory power of the RADIAL score was evaluated using receiver operating characteristic (ROC) analysis and its calibration was assessed by plotting the percentage of PGD predicted versus observed. To identify clinical risk factors associated with severe PGD, we performed multivariable mixed-effects logistic regression modeling to account for among-center variability.

RESULTS

A total of 2,746 patients have been enrolled in the registry to date, including 2,015 (73.4%) from North America, and 731 (26.6%) from Europe. 215 participants (7.8%) met the criteria for severe PGD. There was an increase in the incidence of severe PGD over the study period (p-value for trend by difference sign test = 0.004). The Kaplan Meier estimate for 1-year survival was 75.7% [95%CI 69.4-80.9%] in patients with severe PGD as compared to 94.4% [95% CI 93.5-95.2%] in those without severe PGD (log-rank p-value <0.001). The RADIAL score performed poorly in our contemporary cohort and was not associated with severe PGD with an AUC of 0.53 (95%CI 0.48-0.58). In the multivariable regression model, acute preoperative dialysis (OR 2.41, 95% CI 1.31 - 4.43), durable LVAD support (OR 1.77, 95% CI 1.13 - 2.77), and total ischemic time (OR 1.20 for each additional hour, 95% CI 1.02 - 1.41) were associated with an increased risk of severe PGD.

CONCLUSIONS

Our consortium has identified an increasing incidence of PGD in the modern transplant era. We identified contemporary risk factors for this early post-transplant complication, which confers a high mortality risk. These results may enable the identification of patients at high risk for developing severe PGD in order to inform peri-transplant donor and recipient management practices.

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.

Understanding and Investigating Sex-Based Differences in Heart Transplantation: A Call to Action

Women represent only about 25% of heart transplant recipients annually. Although the number of women living with advanced heart failure remains unknown, epidemiologic research suggests that more women should be receiving advanced heart failure therapies. Sex differences in risk factors, presentation, response to pharmacotherapy, and outcomes in heart failure have been well described. Yet, less is known about sex differences in heart transplant candidate selection, waitlist management, donor selection, perioperative considerations, and post-transplant management and outcomes. The purpose of this review was to summarize the existing published reports related to sex differences in heart transplantation, highlighting areas in which sex-based considerations are well described and supported by available evidence, and emphasizing topics that require further study.

Predicted Heart Mass: A Tale of 2 Ventricles

BACKGROUND

Total predicted heart mass (PHM) is the recommended metric to assess donor-recipient size matching in patients undergoing heart transplantation. Separately measuring right ventricular (RV) and left ventricular (LV) PHM may improve risk prediction of 1-year graft failure.

METHODS

Adult heart transplant recipients from the UNOS database from 2000 to 2018 were included in the study. LV and RV PHM were modeled as restricted cubic splines. The association with 1-year graft failure was determined using adjusted Cox regression. The risk reclassification of using both LV and RV PHM versus total PHM was assessed using the net reclassification index.

RESULTS

A total of 34 976 recipients were included. We observed a U-shaped association between total PHM and 1-year graft failure, such that risk increased for hearts undersized by >15% and those oversized by more than 27%. Graft failure incrementally increased when LV PHM was undersized by more than 5% and when RV was oversized by >20%. There was 1.5-fold greater risk of graft failure for an LV undersized by >26% or an RV oversized by more than 40%. Using LV and RV PHM risk-assessment separately led to a net reclassification index=8.5% ([95% CI, 5.3%-11.7%], nonevent net reclassification index=9.1%, event net reclassification index=-0.6%).

CONCLUSIONS

The association between donor-recipient PHM match and the risk of graft failure after heart transplantation can be further understood as risk attributable to LV undersizing and RV oversizing. Assessing LV and RV PHM separately instead of total PHM could further refine the methods used to match donors and recipients for heart transplantation, minimize the risk of 1-year graft failure, and increase the use of donor organs.

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.

Primary Graft Dysfunction Is Associated With Development of Early Cardiac Allograft Vasculopathy, but Not Other Immune-mediated Complications, After Heart Transplantation

BACKGROUND

We investigated associations between primary graft dysfunction (PGD) and development of acute cellular rejection (ACR), de novo donor-specific antibodies (DSAs), and cardiac allograft vasculopathy (CAV) after heart transplantation (HT).

METHODS

A total of 381 consecutive adult HT patients from January 2015 to July 2020 at a single center were retrospectively analyzed. The primary outcome was incidence of treated ACR (International Society for Heart and Lung Transplantation grade 2R or 3R) and de novo DSA (mean fluorescence intensity >500) within 1 y post-HT. Secondary outcomes included median gene expression profiling score and donor-derived cell-free DNA level within 1 y and incidence of cardiac allograft vasculopathy (CAV) within 3 y post-HT.

RESULTS

When adjusted for death as a competing risk, the estimated cumulative incidence of ACR (PGD 0.13 versus no PGD 0.21; P  = 0.28), median gene expression profiling score (30 [interquartile range, 25-32] versus 30 [interquartile range, 25-33]; P  = 0.34), and median donor-derived cell-free DNA levels was similar in patients with and without PGD. After adjusting for death as a competing risk, estimated cumulative incidence of de novo DSA within 1 y post-HT in patients with PGD was similar to those without PGD (0.29 versus 0.26; P  = 0.10) with a similar DSA profile based on HLA loci. There was increased incidence of CAV in patients with PGD compared with patients without PGD (52.6% versus 24.8%; P  = 0.01) within the first 3 y post-HT.

CONCLUSIONS

During the first year after HT, patients with PGD had a similar incidence of ACR and development of de novo DSA, but a higher incidence of CAV when compared with patients without PGD.

Rethinking Donor and Recipient Risk Matching in Europe and North America: Using Heart Transplant Predictors of Donor and Recipient Risk

BACKGROUND

In Europe, there is greater acceptance of hearts from higher-risk donors for transplantation, whereas in North America, the donor heart discard rate is significantly higher. A Donor Utilization Score (DUS) was used to compare European and North American donor characteristics for recipients included in the International Society for Heart and Lung Transplantation registry from 2000 to 2018. DUS was further evaluated as an independent predictor for 1-year freedom from graft failure, after adjusting for recipient risk. Lastly, we assessed donor-recipient risk matching with the outcome of 1-year graft failure.

METHODS

DUS was applied to the International Society for Heart and Lung Transplantation cohort using meta-modeling. Posttransplant freedom from graft failure was summarized by Kaplan-Meier survival. Multivariable Cox proportional hazard regression was applied to quantify the effects of DUS and Index for Mortality Prediction After Cardiac Transplantation score on the 1-year risk of graft failure. We present 4 donor/recipient risk groups using the Kaplan-Meier method.

RESULTS

European centers accept significantly higher-risk donor hearts compared to North America. DUS 0.45 versus 0.54, P<0.005). DUS was an independent predictor for graft failure with an inverse linear relationship when adjusted for covariates (P<0.001). The Index for Mortality Prediction After Cardiac Transplantation score, a validated tool to assess recipient risk, was also independently associated with 1-year graft failure (P<0.001). In North America, 1-year graft failure was significantly associated with donor-recipient risk matching (log-rank P<0.001). One-year graft failure was highest with pairing of high-risk recipients and donors (13.1% [95% CI, 10.7%-13.9%]) and lowest among low-risk recipients and donors (7.4% [95% CI, 6.8%-8.0%]). Matching of low-risk recipients with high-risk donors was associated with significantly less graft failure (9.0% [95% CI, 8.3%-9.7%]) than high-risk recipients with low-risk donors (11.4% [95% CI, 10.7%-12.2%]) Conclusions: European heart transplantation centers are more likely to accept higher-risk donor hearts than North American centers. Acceptance of borderline-quality donor hearts for lower-risk recipients could improve donor heart utilization without compromising recipient survival.

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.

Preemptive treatment of de novo donor-specific antibodies in lung transplant patients reduces subsequent risk of chronic lung allograft dysfunction or death

The development of donor-specific antibodies after lung transplantation is associated with downstream acute cellular rejection, antibody-mediated rejection (AMR), chronic lung allograft dysfunction (CLAD), or death. It is unknown whether preemptive (early) treatment of de novo donor-specific antibodies (dnDSAs), in the absence of clinical signs and symptoms of allograft dysfunction, reduces the risk of subsequent CLAD or death. We performed a multicenter, retrospective cohort study to determine if early treatment of dnDSAs in lung transplant patients reduces the risk of the composite endpoint of CLAD or death. In the cohort of 445 patients, 145 patients developed dnDSAs posttransplant. Thirty patients received early targeted treatment for dnDSAs in the absence of clinical signs and symptoms of AMR. Early treatment of dnDSAs was associated with a decreased risk of CLAD or death (hazard ratio, 0.36; 95% confidence interval, 0.17-0.76; P < .01). Deferring treatment until the development of clinical AMR was associated with an increased risk of CLAD or death (hazard ratio, 3.00; 95% confidence interval, 1.46-6.18; P < .01). This study suggests that early, preemptive treatment of donor-specific antibodies in lung transplant patients may reduce the subsequent risk of CLAD or death.

Impact of myocardial bridging on coronary artery plaque formation and long-term mortality after heart transplantation

OBJECTIVES

This study aimed to explore the impact of myocardial bridging (MB) on early development of cardiac allograft vasculopathy and long-term graft survival after heart transplantation.

BACKGROUND

MB has been reported to be associated with acceleration of proximal plaque development and endothelial dysfunction in native coronary atherosclerosis. However, its clinical significance in heart transplantation remains unclear.

METHODS

In 103 heart-transplant recipients, serial (baseline and 1-year post-transplant) volumetric intravascular ultrasound (IVUS) analyses were performed in the first 50 mm of the left anterior descending (LAD) artery. Standard IVUS indices were evaluated in 3 equally divided LAD segments (proximal, middle, and distal segments). MB was defined by IVUS as an echolucent muscular band lying on top of the artery. The primary endpoint was death or re-transplantation, assessed for up to 12.2 years (median follow-up: 4.7 years).

RESULTS

IVUS identified MB in 62% of the study population. At baseline, MB patients had smaller intimal volume in the distal LAD than non-MB patients (p = 0.002). During the first year, vessel volume decreased diffusely irrespective of the presence of MB. Intimal growth diffusely distributed in non-MB patients, whereas MB patients demonstrated significantly augmented intimal formation in the proximal LAD. Kaplan-Meier analysis revealed significantly lower event-free survival in patients with versus without MB (log-rank p = 0.02). In multivariate analysis, the presence of MB was independently associated with late adverse events [hazard ratio 5.1 (1.6-22.2)].

CONCLUSION

MB appears to relate to accelerated proximal intimal growth and reduced long-term survival in heart-transplant recipients.

The evolving use of biomarkers in heart transplantation: consensus of an expert panel

In heart transplantation, the use of biomarkers to detect the risk of rejection has been evolving. In this setting, it is becoming less clear as to what is the most reliable test or combination of tests to detect rejection and assess the state of the alloimmune response. Therefore, a virtual expert panel was organized in heart and kidney transplantation to evaluate emerging diagnostics and how they may be best utilized to monitor and manage transplant patients. This manuscript covers the heart content of the conference and is a work product of the American Society of Transplantation's Thoracic and Critical Care Community of Practice. This paper reviews currently available and emerging diagnostic assays and defines the unmet needs for biomarkers in heart transplantation. Highlights of the in-depth discussions among conference participants that led to development of consensus statements are included. This conference should serve as a platform to further build consensus within the heart transplant community regarding the optimal framework to implement biomarkers into management protocols and to improve biomarker development, validation and clinical utility. Ultimately, these biomarkers and novel diagnostics should improve outcomes and optimize quality of life for our transplant patients.

The End of Endomyocardial Biopsy?: A Practical Guide for Noninvasive Heart Transplant Rejection Surveillance

Noninvasive heart transplant rejection surveillance using gene expression profiling (GEP) to monitor immune activation is widely used among heart transplant programs. With the new development of donor-derived cell-free DNA (dd-cfDNA) assays, more programs are transitioning to a predominantly noninvasive rejection surveillance protocol with a reduced frequency of endomyocardial biopsies. As a result, many practical questions arise that potentially delay implementation of these valuable new tools. The purpose of this review is to provide practical guidance for clinicians transitioning toward a less invasive acute rejection monitoring protocol after heart transplantation, and to answer 10 common questions about the GEP and dd-cfDNA assays. Evidence supporting GEP and dd-cfDNA testing is reviewed, as well as guidance on test interpretation and future directions.

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.

Contemporary Management of Cardiogenic Shock During Pregnancy

Cardiogenic shock is the most extreme cardiovascular disease state during pregnancy. Peripartum cardiomyopathy is the most common cause of cardiogenic shock toward the end of pregnancy and in the early postpartum period. Therapy for cardiogenic shock relies on appropriate phenotyping of shock etiology, severity and ventricular predominance, which are critical in the appropriate selection of medical and mechanical therapy. Mechanical circulatory support may be used as a bridge to recovery or as definitive therapy. Intra-aortic balloon pumps, percutaneous left ventricular assist devices and venoarterial extracorporeal circulatory devices have been successfully used in pregnancy and the postpartum period. The most commonly used mechanical therapy in the pregnant patient is extracorporeal membranous oxygenation circulatory support. The use of mechanical circulatory devices in peripartum cardiomyopathy has contributed to improved survival rates in recent years. Further efforts to identify the optimal mechanical circulatory support strategy for peripartum cardiomyopathy and cardiogenic shock in the peripartum period are needed.

Clinical features and allograft failure rates of pulmonary antibody-mediated rejection categories

BACKGROUND

Pulmonary antibody-mediated rejection (AMR) consensus criteria categorize AMR by diagnostic certainty. This study aims to define the clinical features and associated outcomes of these recently defined AMR categories.

METHODS

Adjudication committees reviewed clinical data of 335 lung transplant recipients to define clinical or subclinical AMR based on the presence of allograft dysfunction, and the primary endpoints, time from transplant to allograft failure, a composite endpoint of chronic lung allograft dysfunction and/or death. Clinical AMR was subcategorized based on diagnostic certainty as definite, probable or possible AMR if 4, 3, or 2 characteristic features were present, respectively. Allograft injury was assessed via plasma donor-derived cell-free DNA (ddcfDNA). Risk of allograft failure and allograft injury was compared for AMR categories using regression models.

RESULTS

Over the 38.5 months follow-up, 28.7% of subjects developed clinical AMR (n = 96), 18.5% developed subclinical AMR (n = 62) or 58.3% were no AMR (n = 177). Clinical AMR showed higher risk of allograft failure and ddcfDNA levels compared to subclinical or no AMR. Clinical AMR included definite/probable (n = 21) or possible AMR (n = 75). These subcategories showed similar clinical characteristics, ddcfDNA levels, and risk of allograft failure. However, definite/probable AMR showed greater measures of AMR severity, including degree of allograft dysfunction and risk of death compared to possible AMR.

CONCLUSIONS

Clinical AMR showed greater risk of allograft failure than subclinical AMR or no AMR. Subcategorization of clinical AMR based on diagnostic certainty correlated with AMR severity and risk of death, but not with the risk of allograft failure.

Donor hyperoxia is a novel risk factor for severe cardiac primary graft dysfunction

BACKGROUND

Primary graft dysfunction (PGD) is a major cause of early mortality following heart transplant (HT). Donor risk factors for the development of PGD are incompletely characterized. Donor management goals (DMG) are predefined critical care endpoints used to optimize donors. We evaluated the relationship between DMGs as well as non-DMG parameters, and the development of PGD after HT.

METHODS

A cohort of HT recipients from 2 transplant centers between 1/1/12 and 12/31/19 was linked to their respective donors in the United Network for Organ Sharing (UNOS) DMG Registry (n = 1,079). PGD was defined according to modified ISHLT criteria. Variables were subject to univariate and multivariable multinomial modeling with development of mild/moderate or severe PGD as the outcome variable. A second multicenter cohort of 4,010 donors from the DMG Registry was used for validation.

RESULTS

Mild/moderate and severe PGD occurred in 15% and 6% of the cohort. Multivariable modeling revealed 6 variables independently associated with mild/moderate and 6 associated with severe PGD, respectively. Recipient use of amiodarone plus beta-blocker, recipient mechanical circulatory support, donor age, donor fraction of inspired oxygen (FiO₂), and donor creatinine increased risk whereas predicted heart mass ratio decreased risk of severe PGD. We found that donor age and FiO₂ ≥ 40% were associated with an increased risk of death within 90 days post-transplant in a multicenter cohort.

CONCLUSIONS

Donor hyperoxia at heart recovery is a novel risk factor for severe primary graft dysfunction and early recipient death. These results suggest that excessive oxygen supplementation should be minimized during donor management.

Early trends in cardiac allograft vasculopathy after implementation of the 2018 donor heart allocation policy in the United States

STUDY OBJECTIVE

To evaluate the impact of the new donor heart allocation system implemented in the United States in October 2018 on development of early cardiac allograft vasculopathy (CAV).

DESIGN

Retrospective cohort study.

PARTICIPANTS

Adult (≥ 18 years) heart transplant recipients registered in the United Network for Organ Sharing database between October 18, 2015 and October 17, 2018 (old system) and October 18, 2018 and May 31, 2020 (new system).

MAIN OUTCOME MEASURE

Incidence of angiographic CAV at 1 year (accelerated CAV) in the overall transplant population and among the highest acuity subgroup-Status 1A (old) and Status 1 or 2 (new). We included recipient and donor demographic, cardiovascular, and transplant factors in multivariable logistic regression models to identify predictors of accelerated CAV.

RESULTS

Of 10,375 transplant recipients, 6,660 (64%) and 3,715 (36%) were listed in the old and new allocation cohorts, respectively. The incidence of accelerated CAV was 521 (8%) in the old period compared with 272 (7%) in the new period (P = .36). Similar incidence rates were observed in the highest acuity subgroup-363 (8%) compared with 143 (7%), respectively (P = .13). In adjusted analyses of the high-acuity cohort, the new allocation system was not associated with a higher likelihood of accelerated CAV (odds ratio = 0.87, 95% confidence interval: 0.70-1.08, P = .20).

CONCLUSIONS

The new donor heart allocation system is not associated with development of accelerated angiographic CAV at 1 year, including among recipients requiring the most urgent transplants.

Comparison of donor-derived cell-free DNA between single versus double lung transplant recipients

Plasma donor-derived cell-free DNA (dd-cfDNA) is a sensitive biomarker for the diagnosis of acute rejection in lung transplant recipients; however, differences in dd-cfDNA levels between single and double lung transplant remains unknown. We performed an observational analysis that included 221 patients from two prospective cohort studies who had serial measurements of plasma dd-cfDNA at the time of bronchoscopy and pulmonary function testing, and compared dd-cfDNA between single and double lung transplant recipients across a range of disease states. Levels of dd-cfDNA were lower for single vs. double lung transplant in stable controls (median [IQR]: 0.15% [0.07, 0.44] vs. 0.46% [0.23, 0.74], p < .01) and acute rejection (1.06% [0.75, 2.32] vs. 1.78% [1.18, 5.73], p = .05). Doubling dd-cfDNA for single lung transplant to account for differences in lung mass eliminated this difference. The area under the receiver operating curve (AUC) for the detection of acute rejection was 0.89 and 0.86 for single and double lung transplant, respectively. The optimal dd-cfDNA threshold for the detection of acute rejection was 0.54% in single lung and 1.1% in double lung transplant. In conclusion, accounting for differences in dd-cfDNA in single versus double lung transplant is key for the interpretation of dd-cfDNA testing in research and clinical settings.

Circulating microRNAs in cellular and antibody-mediated heart transplant rejection

BACKGROUND

Noninvasive monitoring of heart allograft health is important to improve clinical outcomes. MicroRNAs (miRs) are promising biomarkers of cardiovascular disease and limited studies suggest they can be used to noninvasively diagnose acute heart transplant rejection.

METHODS

The Genomic Research Alliance for Transplantation (GRAfT) is a multicenter prospective cohort study that phenotyped heart transplant patients from 5 mid-Atlantic centers. Patients who had no history of rejection after transplant were compared to patients with acute cellular rejection (ACR) or antibody-mediated rejection (AMR). Small RNA sequencing was performed on plasma samples collected at the time of an endomyocardial biopsy. Differential miR expression was performed with adjustment for clinical covariates. Regression was used to develop miR panels with high diagnostic accuracy for ACR and AMR. These panels were then validated in independent samples from GRAfT and Stanford University. Receiver operating characteristic curves were generated and area under the curve (AUC) statistics calculated. Distinct ACR and AMR clinical scores were developed to translate miR expression data for clinical use.

RESULTS

The GRAfT cohort had a median age of 52 years, with 35% females and 45% Black patients. Between GRAfT and Stanford, we included 157 heart transplant patients: 108 controls and 49 with rejection (50 ACR and 38 AMR episodes). After differential miR expression and regression analysis, we identified 12 miRs that accurately discriminate ACR and 17 miRs in AMR. Independent validation of the miR panels within GRAfT led to an ACR AUC 0.92 (95% confidence interval [CI]: 0.86-0.98) and AMR AUC 0.82 (95% CI: 0.74-0.90). The externally validated ACR AUC was 0.72 (95% CI: 0.59-0.82). We developed distinct ACR and AMR miR clinical scores (range 0-100), a score ≥ 65, identified ACR with 86% sensitivity, 76% specificity, and 98% negative predictive value, for AMR score performance was 82%, 84% and 97%, respectively.

CONCLUSIONS

We identified novel miRs that had excellent performance to noninvasively diagnose acute rejection after heart transplantation. Once rigorously validated, the unique clinical ACR and AMR scores usher in an era whereby genomic biomarkers can be used to screen and diagnose the subtype of rejection. These novel biomarkers may potentially alleviate the need for an endomyocardial biopsy while facilitating the initiation of targeted therapy based on the noninvasive diagnosis of ACR or AMR.

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.

Indications, Complications, and Outcomes of Cardiac Surgery After Heart Transplantation: Results From the Cash Study

Background

Allograft pathologies, such as valvular, coronary artery, or aortic disease, may occur early and late after cardiac transplantation. Cardiac surgery after heart transplantation (CASH) may be an option to improve quality of life and allograft function and prolong survival. Experience with CASH, however, has been limited to single-center reports.

Methods

We performed a retrospective, multicenter study of heart transplant recipients with CASH between January 1984 and December 2020. In this study, 60 high-volume cardiac transplant centers were invited to participate.

Results

Data were available from 19 centers in North America (n = 7), South America (n = 1), and Europe (n = 11), with a total of 110 patients. A median of 3 (IQR 2–8.5) operations was reported by each center; five centers included ≥ 10 patients. Indications for CASH were valvular disease (n = 62), coronary artery disease (CAD) (n = 16), constrictive pericarditis (n = 17), aortic pathology (n = 13), and myxoma (n = 2). The median age at CASH was 57.7 (47.8–63.1) years, with a median time from transplant to CASH of 4.4 (1–9.6) years. Reoperation within the first year after transplantation was performed in 24.5%. In-hospital mortality was 9.1% (n = 10). 1-year survival was 86.2% and median follow-up was 8.2 (3.8–14.6) years. The most frequent perioperative complications were acute kidney injury and bleeding revision in 18 and 9.1%, respectively.

Conclusion

Cardiac surgery after heart transplantation has low in-hospital mortality and postoperative complications in carefully selected patients. The incidence and type of CASH vary between international centers. Risk factors for the worse outcome are higher European System for Cardiac Operative Risk Evaluation (EuroSCORE II) and postoperative renal failure.

Risk of Renal Dysfunction Following Heart Transplantation in Patients Bridged with a Left Ventricular Assist Device

Acute renal failure (ARF) and chronic kidney disease (CKD) are associated with short- and long-term morbidity and mortality following heart transplantation (HT). We investigated the incidence and risk factors for developing ARF requiring hemodialysis (HD) and CKD following HT specifically in patients with a left ventricular assist device (LVAD). We examined the International Society for Heart and Lung Transplantation (ISHLT) Thoracic Transplant Registry for heart transplant patients between January 2000 and June 2015. We compared patients bridged with durable continuous-flow LVAD to those without LVAD support. Primary outcomes were ARF requiring HD before discharge following HT and CKD (defined as creatinine >2.5 mg/dl, permanent dialysis, or renal transplant) within 3 years. There were 18,738 patients, with 4,535 (24%) bridged with LVAD support. Left ventricular assist device patients had higher incidence of ARF requiring HD and CKD at 1 year, but no significant difference in CKD at 3 years compared to non-LVAD patients. Among LVAD patients, body mass index (BMI) (odds ratio [OR] = 1.79, p < 0.001), baseline estimated glomerular filtration rate (eGFR) (OR = 0.43, p < 0.001), and ischemic time (OR = 1.28, p = 0.014) were significantly associated with ARF requiring HD. Similarly, BMI (hazard ratio [HR] = 1.49, p < 0.001), baseline eGFR (HR = 0.41, p < 0.001), pre-HT diabetes mellitus (DM) (HR = 1.37, p = 0.011), and post-HT dialysis before discharge (HR = 3.93, p < 0.001) were significantly associated with CKD. Left ventricular assist device patients have a higher incidence of ARF requiring HD and CKD at 1 year after HT compared with non-LVAD patients, but incidence of CKD is similar by 3 years. Baseline renal function, BMI, ischemic time, and DM can help identify LVAD patients at risk of ARF requiring HD or CKD following HT.

Heart transplantation: focus on donor recovery strategies, left ventricular assist devices, and novel therapies

Heart transplantation is advocated in selected patients with advanced heart failure in the absence of contraindications. Principal challenges in heart transplantation centre around an insufficient and underutilized donor organ pool, the need to individualize titration of immunosuppressive therapy, and to minimize late complications such as cardiac allograft vasculopathy, malignancy, and renal dysfunction. Advances have served to increase the organ donor pool by advocating the use of donors with underlying hepatitis C virus infection and by expanding the donor source to use hearts donated after circulatory death. New techniques to preserve the donor heart over prolonged ischaemic times, and enabling longer transport times in a safe manner, have been introduced. Mechanical circulatory support as a bridge to transplantation has allowed patients with advanced heart failure to avoid progressive deterioration in hepato-renal function while awaiting an optimal donor organ match. The management of the heart transplantation recipient remains a challenge despite advances in immunosuppression, which provide early gains in rejection avoidance but are associated with infections and late-outcome challenges. In this article, we review contemporary advances and challenges in this field to focus on donor recovery strategies, left ventricular assist devices, and immunosuppressive monitoring therapies with the potential to enhance outcomes. We also describe opportunities for future discovery to include a renewed focus on long-term survival, which continues to be an area that is under-studied and poorly characterized, non-human sources of organs for transplantation including xenotransplantation as well as chimeric transplantation, and technology competitive to human heart transplantation, such as tissue engineering.

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.

Evolving Characteristics of Heart Transplantation Donors and Recipients: JACC Focus Seminar

Although the burden of end-stage heart failure continues to increase, the number of available organs for heart transplantation (HT) remains inadequate. The HT community has been challenged to find ways to expand the number of donor hearts available. Recent advances include use of hearts from donors infected with hepatitis C virus as well as other previously underutilized donors, including those with left ventricular dysfunction, of older age, and with a history of cocaine use. Concurrently, emerging trends in HT surgery include donation after circulatory death, ex vivo normothermic heart perfusion, and controlled hypothermic preservation, which may enable procurement of organs from farther distances and prevent early allograft dysfunction. Contemporary HT recipients have also evolved in light of the 2018 revision to the U.S. heart allocation policy. This focus seminar discusses recent trends in donor and recipient phenotypes and management strategies for successful HT, as well as evolving areas and future directions.

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.

Prognostic value of comprehensive intracoronary physiology assessment early after heart transplantation

AIMS

We evaluated the long-term prognostic value of invasively assessing coronary physiology after heart transplantation in a large multicentre registry.

METHODS AND RESULTS

Comprehensive intracoronary physiology assessment measuring fractional flow reserve (FFR), the index of microcirculatory resistance (IMR), and coronary flow reserve (CFR) was performed in 254 patients at baseline (a median of 7.2 weeks) and in 240 patients at 1 year after transplantation (199 patients had both baseline and 1-year measurement). Patients were classified into those with normal physiology, reduced FFR (FFR ≤ 0.80), and microvascular dysfunction (either IMR ≥ 25 or CFR ≤ 2.0 with FFR > 0.80). The primary outcome was the composite of death or re-transplantation at 10 years. At baseline, 5.5% had reduced FFR; 36.6% had microvascular dysfunction. Baseline reduced FFR [adjusted hazard ratio (aHR) 2.33, 95% confidence interval (CI) 0.88-6.15; P = 0.088] and microvascular dysfunction (aHR 0.88, 95% CI 0.44-1.79; P = 0.73) were not predictors of death and re-transplantation at 10 years. At 1 year, 5.0% had reduced FFR; 23.8% had microvascular dysfunction. One-year reduced FFR (aHR 2.98, 95% CI 1.13-7.87; P = 0.028) and microvascular dysfunction (aHR 2.33, 95% CI 1.19-4.59; P = 0.015) were associated with significantly increased risk of death or re-transplantation at 10 years. Invasive measures of coronary physiology improved the prognostic performance of clinical variables (χ2 improvement: 7.41, P = 0.006). However, intravascular ultrasound-derived changes in maximal intimal thickness were not predictive of outcomes.

CONCLUSION

Abnormal coronary physiology 1 year after heart transplantation was common and was a significant predictor of death or re-transplantation at 10 years.

Impact of using higher-risk donor hearts for candidates with pre-transplant mechanical circulatory support

BACKGROUND

We evaluated post-heart transplant (HTx) outcomes after use of higher-risk donor hearts for candidates supported with pre-HTx mechanical circulatory support (MCS).

METHODS

In this retrospective analysis of the national United Network for Organ Sharing registry, a total of 9,915 adult candidates on MCS underwent HTx from January 1, 2010 to March 31, 2019. Multi-organ, re-transplant, and congenital heart disease patients were excluded. Higher-risk donor organs met at least one of the following criteria: left ventricular ejection fraction <50%, donor to recipient predicted heart mass ratio <0.86, donor age >55 years, or ischemic time >4 hours. Primary outcome was 1 year post-transplant survival.

RESULTS

Among HTx recipients, 3688 (37.2%) received higher-risk donor hearts. Candidates supported with pre-HTx extracorporeal membrane oxygenation or biventricular assist device (n = 374, 3.8%) who received higher-risk donor hearts had comparable 1 year survival (HR: 1.14, 95% CI: [0.67-1.93], p = 0.64) to recipients of standard-risk donor hearts, when adjusted for recipient age and sex. In candidates supported with intra-aortic balloon pump (n = 1391, 14.6%), transplantation of higher-risk donor hearts did not adversely affect 1 year survival (HR: 0.80, 95% CI: [0.52-1.22], p = 0.30). Patients on durable left ventricular assist devices (LVAD) who received higher-risk donor hearts had comparable 1 year survival to continued LVAD support on the waitlist, but mortality was increased compared to those who received standard-risk donor hearts (HR: 1.37, 95% CI: [1.11-1.70], p = 0.004).

CONCLUSIONS

Patients requiring pre-HTx temporary MCS who received higher-risk donor hearts had comparable 1 year post-transplant survival to those who received standard-risk donor hearts. Stable patients on durable LVADs may benefit from waiting for standard-risk donor hearts.

Cardiopulmonary Exercise Testing With Echocardiography to Assess Recovery in Patients With Ventricular Assist Devices

The left ventricular assist device (LVAD) is an established treatment for select patients with end-stage heart failure. Some patients recovered and are considered for explantation. Assessing recovery involves exercise testing and echo ramping on full and minimal LVAD support. Combined cardiopulmonary exercise testing with simultaneous echo ramping (CPET-R) has not been well studied. Patients were included if they had CPET within the previous 6 months, were clinically stable, and had an INR >2.0 on the day of examination. Patients had CPET-R on two occasions within 14 days: (a) with LVAD at therapeutic speed and (b) with LVAD at the lowest speed possible. Six patients were between 29 and 75 years (two female). One patient did not complete a turn-down test due to evidence of ischemia on initial CPET-R subsequently confirmed as a significant coronary artery stenosis on angiography. There were no significant differences in CPET or echo metrics between LVAD speeds. Two patients were explanted due to presumed LV recovery and remained event free for 30 and 47 months, respectively. Serial CPET-R seems safe and feasible for the evaluation of LV and global function and may result in improved clinical decision making for LVAD explantation.