Faculty Bibliography

UNLABELLED:Noninvasive rejection biomarkers (AlloMap, AlloSure) demonstrate high negative predictive value but positive predictive values of only 10-30%, driving avoidable endomyocardial biopsies. We developed a multi-modal AI model integrating electrocardiography with molecular biomarkers in 389 heart transplant recipients (5338 ECG-biopsy pairs), performing the first head-to-head comparison of AI-ECG, AlloMap, AlloSure, and their integration against biopsy-proven rejection. Individual modalities showed modest discrimination (AI-ECG AUC 0.65; AlloSure 0.67; AlloMap 0.56), while combining biomarkers alone did not improve performance (AUC 0.65). In the multi-modal test subset of ECGs (n=38, 2 rejection events), the integrated model achieved AUC 0.81 with 100% specificity (0/36 false positives) and 97% negative predictive value, eliminating all 19 false-positive combined-biomarker referrals. These hypothesis-generating results support prospective multi-center validation to determine whether requiring concordance across electrical and biomarker signals reduces unnecessary biopsies while preserving high negative predictive value. BACKGROUND/UNASSIGNED:Noninvasive rejection biomarkers (AlloMap gene-expression profiling (GEP); AlloSure donor-derived cell-free DNA (dd-cfDNA)) deliver high negative predictive value but positive predictive values of only 10-30%, driving avoidable endomyocardial biopsies. Each biomarker interrogates a single biological compartment. Whether integrating AI-enabled electrocardiography (AI-ECG) with these molecular assays improves specificity has not been tested. METHODS/UNASSIGNED:We retrospectively assembled 5338 unique ECG-endomyocardial-biopsy pairs from 389 adult heart transplant recipients at a single center (2018-2024). A ResNet-18 convolutional neural network was trained on 8-lead ECG waveforms with clinical covariates. In the 340-patient subset with same encounter AlloMap and AlloSure testing (405 ECG-biomarker-biopsy triplets), an integrated model fused the ECG embedding with biomarker values via late concatenation. We performed the first head-to-head, same-cohort comparison of AI-ECG, AlloMap, AlloSure, and their integration against biopsy-proven rejection (ISHLT ≥2R ACR or pAMR ≥2). Discrimination was evaluated with bootstrap 95% confidence intervals. RESULTS/UNASSIGNED:Individual modalities showed modest discrimination (AI-ECG AUC 0.65, 95% CI 0.58-0.72; AlloSure 0.67, 0.56-0.78; AlloMap 0.56, 0.46-0.67); combining biomarkers alone did not improve performance (AUC 0.65). In the multi-modal test subset (n=38 ECG-biopsy pairs, 2 rejection events), the integrated model achieved AUC 0.81 (0.50-1.00), 100% specificity (36/36; Clopper-Pearson 90-100%), and 97% NPV. At the same NPV threshold, all 19 false-positive combined-biomarker referrals in this subset would have been avoided, though this estimate reflects a single operating point in a small sample. AUC gains over single modalities did not reach statistical significance (DeLong p=0.31-0.34) given the limited event count. CONCLUSIONS/UNASSIGNED:A multi-modal AI model that requires concordance across electrical, immune-transcriptional, and donor-DNA signals showed numerically higher specificity for cardiac allograft rejection than any single modality, although the corresponding AUC differences did not reach statistical significance. These hypothesis-generating findings suggest that cross-compartment concordance may help discriminate true rejection from biomarker noise, but the small multi-modal test set precludes definitive conclusions; a pre-specified prospective multi-center trial powered for ≥50 rejection events is the necessary next step to test this hypothesis.

We aimed to investigate myocardial temperatures of allografts after removal from cold static storage (CSS) and the relationship between temperature and early outcomes of heart transplantation (HT). Between January and September 2024, 22 allografts preserved with CSS underwent prospective temperature measurements at the left ventricular free wall (LVFW) and interventricular septum; preservation solution temperatures were also measured. Median LVFW temperature was 4.0°C, septal temperature was 3.9°C, and solution temperature was 3.7°C. LVFW and septal temperatures were significantly correlated (p < 0.001), as were septal and solution temperatures (p = 0.03). Ischemic time inversely correlated with solution temperature (p = 0.021), and septal thickness correlated with septal temperature (p = 0.04). One patient developed severe primary graft dysfunction, and 30-day recipient and graft survival were 100% (22/22). We conclude that CSS maintains myocardial temperatures near 4°C, and it can achieve excellent post-HT outcomes with a low incidence of PGD.

BACKGROUND/UNASSIGNED:Pyridostigmine bromide is a short-acting carbamate acetylcholinesterase inhibitor that has been shown to acutely augment parasympathetic signaling in cardiovascular disease populations. OBJECTIVE/UNASSIGNED:This study was undertaken to characterize pharmacodynamics, safety, and tolerability of pyridostigmine during repeated dosing in patients with heart failure. METHODS/UNASSIGNED:A prospective ascending-dose, forced titration, double-blind Phase II randomized clinical trial was conducted to compare the effects of pyridostigmine bromide (15, 30, and 60 mg TID over 8 weeks) versus matching placebo on red blood cell (RBC) acetylcholinesterase activity, cholinergic side effects, and physiologic measures of parasympathetic heart rate modulation and sympathovagal balance in ambulatory patients with chronic systolic heart failure. RESULTS/UNASSIGNED:< 0.001 vs placebo). Physiologic measures of parasympathetic heart rate modulation and sympathovagal balance did not differ between treatment groups. In the pyridostigmine bromide group, RBC acetylcholinesterase activity was not significantly associated with postexercise parasympathetic heart modulation. CONCLUSIONS/UNASSIGNED:Pyridostigmine bromide administered over 8 weeks was associated with a significant reduction of RBC acetylcholinesterase activity and relatively mild symptoms of cholinergic excess, but changes in parasympathetic signaling in the sinoatrial node previously reported after acute administration were not observed. Further investigations are needed to delineate pharmacodynamic and pathobiological factors contributing to these findings. ClinicalTrials.gov identifier: NCT01415921.

BACKGROUND:Despite the goal of the 2018 revision to the heart allocation policy to reduce reliance on exception requests through improved granularity in status criteria, there has been a dramatic rise in exception requests. OBJECTIVES/OBJECTIVE:This study evaluated trends in exception use over the first 6 years of the updated policy, assessing associated clinical factors, temporal changes, and impact on waitlist outcomes. METHODS:This retrospective transplant registry analysis included all adult isolated heart transplant candidates from October 18, 2018, to September 30, 2024. Candidates were stratified by exception use, listing era, and region. Exception use was compared using Wilcoxon rank-sum and chi-squared tests, with multilevel logistic regression assessing independent associations. Trends over time and across UNOS (United Network for Organ Sharing) regions were evaluated, and a competing risks framework examined time to transplant and waitlist mortality. RESULTS:Among 26,330 candidates, 38.6% used exception requests, with a statistically significant increase over time, particularly in higher priority statuses. Exception use was more common among Black, non-Hispanic candidates, and candidates with blood type O, and less likely for patients with blood type A (P < 0.001). Additionally, pretransplant isolated durable left ventricular assist devices were less common in candidates who requested exceptions (19.0% vs 31.6%; P < 0.001). Overall, 39.9% of exception candidates were listed at status 1 or 2 compared to 29% of nonexception candidates, and 69.2% of exception candidates were removed from the waitlist at status 1 or 2 compared with 37% of nonexception candidates. CONCLUSIONS:The rising use of exceptions underscores ongoing limitations in allocation criteria, and disparities suggesting inequities in access to higher listing status. Policy refinements are needed to ensure a balance between medical urgency and equitable allocation.

BACKGROUND:Porcine genome editing has revolutionized xenotransplantation, recently enabling the first pig-to-human heart xenotransplants. However, the xeno-immune response in heart xenografts remains largely unexplored. This study aimed to precisely characterize the xeno-immune response and injury in two heart xenografts, transplanted from 10-gene-edited pigs into brain-dead human recipients. METHODS:We analyzed xenograft biopsies at 66-hour post-reperfusion using a multimodal phenotyping approach combining: morphological evaluation, immunophenotyping, ultrastructural assessment, automated quantification of multiplex immunofluorescence staining and gene expression profiling. Xenografts before implantation and wild-type pig hearts with and without ischemia reperfusion injury and brain death were used as controls. RESULTS:Both xenografts showed evidence of endothelial activation and mild microvascular inflammation without capillary C4d deposition. Immune infiltrates were mainly composed of CD15+ and CD68+ innate immune cells. Ultrastructural assessment showed endothelial swelling with occasional intravascular leucocytes. Deep-learning based automated multiplex immunofluorescence analysis confirmed that microvascular inflammation was primarily associated with CD15+ and CD68+ innate immune cells. Both xenografts showed increased expression of genes and pathways associated with monocyte/macrophage activation, neutrophil activation, interferon-gamma response, natural killer cell burden, endothelial activation, apoptosis and injury repair. This phenotype was absent in all control pig hearts, independently from ischemia reperfusion injury and brain death. CONCLUSIONS:Multimodal phenotyping of pig-to-human heart xenografts revealed early signs of xeno-immune response, characterized by mild innate microvascular inflammation, endothelial activation, and molecular signature characteristic of antibody-mediated rejection. Developing such precision diagnostic system could improve graft monitoring in future clinical settings.

BACKGROUND:The diagnosis of cardiac sarcoidosis (CS) is often challenging, particularly in atypical cases. CASE SUMMARY/METHODS:This case involves a previously healthy 33-year-old woman who was found to have a biatrial mass and evidence of a diffuse inflammatory or neoplastic process on multimodality imaging. Percutaneous biopsy of the cardiac mass was performed, and histopathologic examination revealed granulomas consistent with CS. DISCUSSION/CONCLUSIONS:This case adds to the growing number of reports of CS manifesting as an intracardiac mass. TAKE-HOME MESSAGES/CONCLUSIONS:The clinical presentation of CS is highly variable, and it may rarely manifest as an intracardiac mass. The diagnosis of cardiac sarcoidosis is often challenging, particularly in patients with atypical presentations. Indeterminate cardiac masses often require direct tissue sampling because the changes in treatment and prognosis are substantial.

CLINICAL CONDITION/UNASSIGNED:The authors present the case of a young man who presented with cardiogenic shock requiring venoarterial extracorporeal membrane oxygenation and microaxial flow pump complicated by acute spinal cord infarction (SCI) leading to bilateral lower extremity paraplegia. KEY QUESTIONS/UNASSIGNED:The key questions included the following: 1) What is the incidence and pathophysiology for SCI with mechanical circulatory support (MCS)?; 2) Which configurations of MCS carry a greater risk of SCI? How do we approach MCS escalation, recognizing that with each device we carry additive risk of complications?; 3) What data guide anticoagulation strategies for MCS?; and 4) What strategies can we implement to support patients who have suffered SCI from MCS? OUTCOME/RESULTS:Our patient was transitioned to a right ventricular assist device with Impella 5.5 as a bridge to therapy, and underwent cardiac transplantation 4 weeks after presentation with ongoing inpatient rehabilitation. TAKE-HOME MESSAGES/CONCLUSIONS:Contemporary MCS carries a small but significant risk of SCI which is often irreversible. More data are required to guide anticoagulation strategies for MCS and mitigate risk.

BACKGROUND/UNASSIGNED:Donation after circulatory death (DCD) with cardiopulmonary bypass for thoracoabdominal normothermic regional perfusion (TA-NRP) has led to increased use of donor hearts. Rejection rates and long-term survival outcomes are not known. METHODS/UNASSIGNED:A single-center retrospective cohort review of patients who underwent DCD heart transplantation from January 2020 to December 2023 was performed. Donor and recipient characteristics, operative characteristics, and posttransplantation outcomes were analyzed. Subgroup analysis comparing co-localized vs distant donors and recipients was performed. The primary end point was 1-year survival. Secondary end points included incidences of primary graft dysfunction (PGD), cardiac allograft vasculopathy (CAV), rejection rate, and overall mortality. Our TA-NRP protocol has remained the same, consisting of sternotomy, ligation of aortic arch vessels, establishment of cardiopulmonary bypass, reintubation, resuscitation of the heart, and cold static storage during transport. RESULTS/UNASSIGNED:< .005) ischemia times, without any other differences. CONCLUSIONS/UNASSIGNED:Outcomes after DCD heart transplantation using TA-NRP remain encouraging with acceptable rates of rejection, PGD, CAV, and survival at 1 year.