Faculty Bibliography

BACKGROUND:Heart utilization from donation after circulatory death (DCD) donors remains highly variable across the United States, potentially resulting in missed transplantation opportunities. This study aimed to quantify the frequency of clinically viable, non-utilized DCD hearts and identify usage barriers. METHODS:We conducted a retrospective, national registry analysis of donors ≤55 years old who donated ≥1 organ, focusing primarily on DCDs. Donor characteristics, particularly age, warm ischemic time (WIT), and EF, as well as reasons for non-recovery and offer refusal, were analyzed. SRTR's heart yield model was employed to identify non-utilized DCD hearts clinically comparable to transplanted DCD hearts. RESULTS:In 2023, 613 DCD hearts were transplanted, accounting for 13.5% of all heart transplants. Only 15.5% of DCD hearts from donors ≤55 years old were utilized. Marked variation in risk-adjusted DCD heart yield was observed between states, OPOs, and Regions. Donors of transplanted DCD hearts had a median age of 32, WIT 24 minutes, and EF 63%. The yield model identified between 701-1,243 non-utilized DCD hearts with characteristics comparable to transplanted cases. Concerns about delayed progression to circulatory arrest after life support withdrawal was a key reason for non-utilization. CONCLUSIONS:Despite wider acceptance of DCD heart transplantation, an increasing proportion of DCD hearts remain unused despite favorable characteristics. Concerns related to delayed progression to circulatory arrest are a significant barrier to heart utilization. Addressing geographic variability and improving predictive models for donor viability could double DCD heart utilization and expand heart transplantation volume by approximately 700-1,200 (15-27%) annually.

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.

The increasing demand for donor hearts presents both a critical challenge and a significant opportunity for innovation in cardiac transplantation. Advancements in immunosuppressive regimens and genetic engineering have reignited recent interest in xenotransplantation. Notably, 2 human patients have received genetically modified pig hearts under expanded-access authorization. They survived for 40 and 60 days, with xenograft failure preceding death in both cases. Concurrently, decedent studies have focused on monitoring the short-term physiological function of genetically modified cardiac xenografts in legally brain-dead recipients, representing a novel experimental paradigm for preclinical testing to help bridge the gap between nonhuman primate studies and clinical trials. These contemporary achievements build on a large body of exploratory efforts in cardiac xenotransplantation in nonhuman primates. Despite significant progress in overcoming hyperacute rejection, adaptive cellular and humoral immunological barriers remain. This review aims to critically evaluate the current advancements in xenotransplantation, to explore ongoing challenges, and to discuss the future potential of this innovative approach in addressing the growing demand for donor organs in cardiac transplantation.

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.

HeartMate 3 is the only durable left ventricular assist devices (LVAD) currently implanted in the United States. The purpose of this study was to develop a predictive model for 1 year mortality of HeartMate 3 implanted patients, comparing standard statistical techniques and machine learning algorithms. Adult patients registered in the Society of Thoracic Surgeons, Interagency Registry for Mechanically Assisted Circulatory Support (STS-INTERMACS) database, who received primary implant with a HeartMate 3 between January 1, 2017, and December 31, 2019, were included. Epidemiological, clinical, hemodynamic, and echocardiographic characteristics were analyzed. Standard logistic regression and machine learning (elastic net and neural network) were used to predict 1 year survival. A total of 3,853 patients were included. Of these, 493 (12.8%) died within 1 year after implantation. Standard logistic regression identified age, Model End Stage Liver Disease (MELD)-XI score, right arterial (RA) pressure, INTERMACS profile, heart rate, and etiology of heart failure (HF), as important predictor factors for 1 year mortality with an area under the curve (AUC): 0.72 (0.66-0.77). This predictive model was noninferior to the ones developed using the elastic net or neural network. Standard statistical techniques were noninferior to neural networks and elastic net in predicting 1 year survival after HeartMate 3 implantation. The benefit of using machine-learning algorithms in the prediction of outcomes may depend on the type of dataset used for analysis.

The last several years have seen a rise in use of mechanical circulatory support (MCS) to bridge heart transplant recipients. A controlled hypothermic organ preservation system, the SherpaPak Cardiac Transport System (SCTS), was introduced in 2018 and has grown in utilization with reports of improved posttransplant outcomes. The Global Utilization And Registry Database for Improved heArt preservatioN (GUARDIAN)-Heart registry is an international, multicenter registry assessing outcomes after transplant using the SCTS. This analysis examines outcomes in recipients bridged with various MCS devices in the GUARDIAN-Heart Registry. A total of 422 recipients with donor hearts transported using SCTS were included and identified. Durable ventricular assist devices (VADs) were used exclusively in 179 recipients, temporary VADs or intra-aortic balloon pump (IABP) in 197, and extracorporeal membrane oxygenation (ECMO) in 14 recipients. Average ischemic times were over 3.5 hours in all cohorts. Severe primary graft dysfunction (PGD) posttransplant increased across groups (4.5% VAD, 5.1% temporary support, 21.4% ECMO), whereas intensive care unit (ICU) length of stay (18.2 days) and total hospital stay (39.4 days) was longer in the ECMO cohort than the VAD and IABP groups. A comparison of outcomes of MCS bridging in SCTS versus traditional ice revealed significantly lower rates of both moderate/severe right ventricular (RV) dysfunction and severe PGD in the SCTS cohort; however, upon propensity matching only the reductions in moderate/severe RV dysfunction were statistically significant. Use of SCTS in transplant recipients with various bridging strategies results in excellent outcomes.

Left ventricular assist devices (LVAD) are surgically implanted mechanical support devices utilized with increasing frequency as a bridge to myocardial recovery, destination therapy, and heart transplantation. While the use of such devices in patients with advanced heart failure has shown significant survival benefits and improved quality of life, they bear their own risks and complications.¹ Bleeding, infection, pump thrombosis, and stroke are just some of the serious complications associated with LVADs.² LVAD-associated pseudoaneurysms are rare, with prior reports of occurrence at the left ventricular apex and at the anastomosis site of the outflow graft to the ascending aorta.^3,4 Typically, this device-related complication requires surgical repair and, if at all feasible, heart transplantation. However, in cases of difficult anatomy, unfavorable position, and significant comorbidities, surgery may be contraindicated due to high surgical risk. This case portrays a patient suffering from a left ventricular pseudoaneurysm after HeartMate-III implantation that was not amenable to surgical repair due to heightened surgical risk. We document the first pseudoaneurysm associated with the HeartMate-III in available literature and describe a novel management strategy of documented nonoperative course of LVAD-associated pseudoaneurysm, with the patient surviving 56+ months with medical optimization and management.

To evaluate outcomes of patients undergoing heart transplants (HTs) using an intra-aortic balloon pump (IABP) under exception status. Adult patients supported by an IABP who underwent HT between November 18, 2018, and December 31, 2020, as documented in the United Network for Organ Sharing, were included. Patients were stratified according to requests for exception status. Kaplan-Meier methodology was used to look for differences in survival between groups. A total of 1284 patients were included; 492 (38.3%) were transplanted with an IABP under exception status. Exception status patients had higher body mass index, were more likely to be Black, and had longer waitlist times. Exception status patients received organs from younger donors, had a shorter ischemic time, and had a higher frequency of sex mismatch. The 1-year posttransplant survival was 93% for the nonexception and 88% for the exception IABP patients (hazard ratio: 1.85 [95% confidence interval: 1.12-2.86, P = .006]). The most common reason for requesting an exception status was inability to meet blood pressure criteria for extension (37% of patients). The most common reason for an extension request for an exception status was right ventricular dysfunction (24%). IABP patients transplanted under exception status have an increased 1-year mortality rate posttransplant compared with those without exception status.

OBJECTIVES/OBJECTIVE:The HeartMate 3 (Abbott) left ventricular assist device provides substantial improvement in long-term morbidity and mortality in patients with advanced heart failure. The Implantation of the HeartMate 3 in Subjects With Heart Failure Using Surgical Techniques Other Than Full Median Sternotomy study compares thoracotomy-based implantation clinical outcomes with standard median sternotomy. METHODS:We conducted a prospective, multicenter, single-arm study in patients eligible for HeartMate 3 implantation with thoracotomy-based surgical technique (bilateral thoracotomy or partial upper sternotomy with left thoracotomy). The composite primary end point was survival free of disabling stroke (modified Rankin score >3), or reoperation to remove or replace a malfunctioning device, or conversion to median sternotomy at 6-months postimplant (elective transplants were treated as a success). The primary end point (noninferiority, -15% margin) was assessed with >90% power compared with a propensity score-matched cohort (ratio 1:2) derived from the Multi-Center Study of MagLev Technology in Patients Undergoing Mechanical Circulatory Support Therapy With HeartMate 3 continued access protocol. RESULTS:The study enrolled 102 patients between December 2020 and July 2022 in the thoracotomy-based arm at 23 North American centers. Follow-up concluded in December 2022. In the Implantation of the HeartMate 3 in Subjects With Heart Failure Using Surgical Techniques Other Than Full Median Sternotomy study group, noninferiority criteria was met (absolute between-group difference, -1.2%; Farrington Manning lower 1-sided 95% CI, -9.3%; P < .0025) and event-free survival was not different (85.0% vs 86.2%; hazard ratio, 1.01; 95% CI, 0.58-2.10). Length of stay with thoracotomy-based implant was longer (median, 20 vs 17 days; P = .03). No differences were observed for blood product utilization, adverse events (including right heart failure), functional status, and quality of life between cohorts. CONCLUSIONS:Thoracotomy-based implantation of the HeartMate 3 left ventricular assist device is noninferior to implantation via standard full sternotomy. This study supports thoracotomy-based implantation as an additional standard for surgical implantation of the HeartMate 3 left ventricular assist device.