Adult heart transplantation with distant procurement and ex-vivo preservation of donor hearts after circulatory death: a case series

Hypothermic and cryogenic preservation of cardiac tissue-engineered constructs

Cardiac tissue engineering (cTE) has already advanced towards the first clinical trials, investigating safety and feasibility of cTE construct transplantation in failing hearts. However, the lack of well-established preservation methods poses a hindrance to further scalability, commercialization, and transportation, thereby reducing their clinical implementation. In this study, hypothermic preservation (4 °C) and two methods for cryopreservation (i.e., a slow and fast cooling approach to -196 °C and -150 °C, respectively) were investigated as potential solutions to extend the cTE construct implantation window. The cTE model used consisted of human induced pluripotent stem cell-derived cardiomyocytes and human cardiac fibroblasts embedded in a natural-derived hydrogel and supported by a polymeric melt electrowritten hexagonal scaffold. Constructs, composed of cardiomyocytes of different maturity, were preserved for three days, using several commercially available preservation protocols and solutions. Cardiomyocyte viability, function (beat rate and calcium handling), and metabolic activity were investigated after rewarming. Our observations show that cardiomyocytes' age did not influence post-rewarming viability, however, it influenced construct function. Hypothermic preservation with HypoThermosol® ensured cardiomyocyte viability and function. Furthermore, fast freezing outperformed slow freezing, but both viability and function were severely reduced after rewarming. In conclusion, whereas long-term preservation remains a challenge, hypothermic preservation with HypoThermosol® represents a promising solution for cTE construct short-term preservation and potential transportation, aiding in off-the-shelf availability, ultimately increasing their clinical applicability.

Organ Donation by the Imminently Dead: Addressing the Organ Shortage and the Dead Donor Rule

The dead donor rule (DDR) has facilitated the saving of hundreds of thousands of lives. Recent advances in heart donation, however, have exposed how DDR has limited donation of all organs. We propose advancing the moment in the dying process at which death can be determined to increase substantially the supply of organs for transplantation. We justify this approach by identifying certain flaws in the Uniform Determination of Death Act and proposing a modification of that law that permits earlier procurement of healthier organs in greater numbers.

Donation after circulatory death improves probability of heart transplantation in waitlisted candidates and results in post-transplant outcomes similar to those achieved with brain-dead donors

OBJECTIVE

To quantitate the impact of heart donation after circulatory death (DCD) donor utilization on both waitlist and post-transplant outcomes in the United States.

METHODS

The United Network for Organ Sharing database was queried to identify all adult waitlisted and transplanted candidates between October 18, 2018, and December 31, 2022. Waitlisted candidates were stratified according to whether they had been approved for donation after brain death (DBD) offers only or also approved for DCD offers. The cumulative incidence of transplantation was compared between the 2 cohorts. In a post-transplant analysis, 1-year post-transplant survival was compared between unmatched and propensity-score-matched cohorts of DBD and DCD recipients.

RESULTS

A total of 14,803 candidates were waitlisted, including 12,287 approved for DBD donors only and 2516 approved for DCD donors. Overall, DCD approval was associated with an increased sub-hazard ratio (HR) for transplantation and a lower sub-HR for delisting owing to death/deterioration after risk adjustment. In a subgroup analysis, candidates with blood type B and status 4 designation received the greatest benefit from DCD approval. A total of 12,238 recipients underwent transplantation, 11,636 with DBD hearts and 602 with DCD hearts. Median waitlist times were significantly shorter for status 3 and status 4 recipients receiving DCD hearts. One-year post-transplant survival was comparable between unmatched and propensity score-matched cohorts of DBD and DCD recipients.

CONCLUSIONS

The use of DCD hearts confers a higher probability of transplantation and a lower incidence of death/deterioration while on the waitlist, particularly among certain subpopulations such as status 4 candidates. Importantly, the use of DCD donors results in similar post-transplant survival as DBD donors.

Cost-Effectiveness of Cardiovascular Magnetic Resonance for Rejection Surveillance After Cardiac Transplantation in the Australian Health Care System

BACKGROUND

Heart transplantation is an effective treatment for end-stage congestive heart failure, however, achieving the right balance of immunosuppression to maintain graft function while minimising adverse effects is challenging. Serial endomyocardial biopsies (EMBs) are currently the standard for rejection surveillance, despite being invasive. Replacing EMB-based surveillance with cardiac magnetic resonance (CMR)-based surveillance for acute cardiac allograft rejection has shown feasibility. This study aimed to assess the cost-effectiveness of CMR-based surveillance in the first year after heart transplantation.

METHOD

A prospective clinical trial was conducted with 40 orthotopic heart transplant (OHT) recipients. Participants were randomly allocated into two surveillance groups: EMB-based, and CMR-based. The trial included economic evaluations, comparing the frequency and cost of surveillance modalities in relation to quality-adjusted life years (QALYs) within the first year post-transplantation. Sensitivity analysis encompassed modelled data from observed EMB and CMR arms, integrating two hypothetical models of expedited CMR-based surveillance.

RESULTS

In the CMR cohort, 238 CMR scans and 15 EMBs were conducted, versus (vs) 235 EMBs in the EMB group. CMR surveillance yielded comparable rejection rates (CMR 74 vs EMB 94 events, p=0.10) and did not increase hospitalisation risk (CMR 32 vs EMB 46 events, p=0.031). It significantly reduced the necessity for invasive EMBs by 94%, lowered costs by an average of AUD$32,878.61, and enhanced cumulative QALY by 0.588 compared with EMB. Sensitivity analysis showed that increased surveillance with expedited CMR Models 1 and 2 were more cost-effective than EMB (all p<0.01), with CMR Model 1 achieving the greatest cost savings (AUD$34,091.12±AUD$23,271.86 less) and utility increase (+0.62±1.49 QALYs, p=0.011), signifying an optimal cost-utility ratio. Model 2 showed comparable utility to the base CMR model (p=0.900) while offering the benefit of heightened surveillance frequency during periods of elevated rejection risk.

CONCLUSIONS

CMR-based rejection surveillance in orthotopic heart transplant recipients provides a cost-effective alternative to EMB-based surveillance. Furthermore, it reduces the need for invasive procedures, without increased risk of rejection or hospitalisation for patients, and can be incorporated economically for expedited surveillance. These findings have important implications for improving patient care and optimising resource allocation in post-transplant management.

Metabolic Considerations in Direct Procurement and Perfusion Protocols with DCD Heart Transplantation

Heart transplantation with donation after circulatory death (DCD) provides excellent patient outcomes and increases donor heart availability. However, unlike conventional grafts obtained through donation after brain death, DCD cardiac grafts are not only exposed to warm, unprotected ischemia, but also to a potentially damaging pre-ischemic phase after withdrawal of life-sustaining therapy (WLST). In this review, we aim to bring together knowledge about changes in cardiac energy metabolism and its regulation that occur in DCD donors during WLST, circulatory arrest, and following the onset of warm ischemia. Acute metabolic, hemodynamic, and biochemical changes in the DCD donor expose hearts to high circulating catecholamines, hypoxia, and warm ischemia, all of which can negatively impact the heart. Further metabolic changes and cellular damage occur with reperfusion. The altered energy substrate availability prior to organ procurement likely plays an important role in graft quality and post-ischemic cardiac recovery. These aspects should, therefore, be considered in clinical protocols, as well as in pre-clinical DCD models. Notably, interventions prior to graft procurement are limited for ethical reasons in DCD donors; thus, it is important to understand these mechanisms to optimize conditions during initial reperfusion in concert with graft evaluation and re-evaluation for the purpose of tailoring and adjusting therapies and ensuring optimal graft quality for transplantation.

Outcomes of Heart Transplantation From Donation After Circulatory Death: An Up-to-Date Systematic Meta-analysis

BACKGROUND

Donation after circulatory death (DCD) heart transplantation (HTx) significantly expands the donor pool and reduces waitlist mortality. However, high-level evidence-based data on its safety and effectiveness are lacking. This meta-analysis aimed to compare the outcomes between DCD and donation after brain death (DBD) HTxs.

METHODS

Databases, including MEDLINE, Embase, CINAHL, and the Cochrane Central Register of Controlled Trials, were systematically searched for randomized controlled trials and observational studies reporting the outcomes of DCD and DBD HTxs published from 2014 onward. The data were pooled using random-effects models. Risk ratios (RRs) with 95% confidence intervals (CIs) were used as the summary measures for categorical outcomes and mean differences were used for continuous outcomes.

RESULTS

Twelve eligible studies were included in the meta-analysis. DCD HTx was associated with lower 1-y mortality rate (DCD 8.13% versus DBD 10.24%; RR = 0.75; 95% CI, 0.59-0.96; P = 0.02) and 5-y mortality rate (DCD 14.61% versus DBD 20.57%; RR = 0.72; 95% CI, 0.54-0.97; P = 0.03) compared with DBD HTx.

CONCLUSIONS

Using the current DCD criteria, HTx emerges as a promising alternative to DBD transplantation. The safety and feasibility of DCD hearts deserve further exploration and investigation.

Bruton's tyrosine kinase ablation inhibits B cell responses and antibody production for the prevention of chronic rejection in cardiac transplantation

Chronic rejection is the primary cause of late allograft failure, however, the current treatments for chronic rejection have not yielded desirable therapeutic effects. B cell activation and donor-specific antibody (DSA) production are the primary factors leading to chronic rejection. Bruton's tyrosine kinase (BTK) plays a key role in the activation and differentiation of B cells and in antibody production. This study investigated the efficacy of blocking BTK signalling in the prevention of chronic rejection. BTK signalling was blocked using the BTK inhibitor ibrutinib and gene knockout. In vitro assays were conducted to examine the consequences and underlying mechanisms of BTK blockade in regards to B cell activation, differentiation, and antibody secretion. Additionally, we established a cardiac transplantation mouse model of chronic rejection to explore the preventive effects and mechanisms of BTK ablation on chronic rejection. Ablating BTK signalling in vitro resulted in the inhibition of B cell activation, differentiation, and antibody production. In vivo experiments provided evidence that ablating BTK signalling alleviated chronic rejection, leading to reduced damage in myocardial tissue, neointimal hyperplasia, interstitial fibrosis, inflammatory cell infiltration, and C4d deposition. Allograft survival was prolonged, and B cell responses and DSA production were inhibited as a result. We confirmed that ablation of BTK signalling inhibited B cell response by blocking downstream PLCγ2 phosphorylation and inhibiting the NF-κB, NFAT, and ERK pathways. Our findings demonstrated that ablation of BTK signalling inhibited B cell activation and differentiation, reduced DSA production, and effectively prevented chronic rejection.

Outcomes following concomitant multiorgan heart transplantation from circulatory death donors: The United States experience

BACKGROUND

Donation after circulatory death (DCD) has reemerged as a method of expanding the donor heart pool. Given the high waitlist mortality of multiorgan heart candidates, we evaluated waitlist outcomes associated with willingness to consider DCD offers and post-transplant outcomes following DCD transplant for these candidates.

METHODS

We identified adult multiorgan heart candidates and recipients between January 1, 2020 and March 31, 2023 nationally. Among candidates that met inclusion criteria, we compared the cumulative incidence of transplant, with waitlist death/deterioration as a competing risk, by willingness to consider DCD offers. Among recipients of DCD versus brain death (DBD) transplants, we compared perioperative outcomes and post-transplant survival.

RESULTS

Of 1,802 heart-kidney, 266 heart-liver, and 440 heart-lung candidates, 15.8%, 12.4%, and 31.1%, respectively, were willing to consider DCD offers. On adjusted analysis, willingness to consider DCD offers was associated with higher likelihood of transplant for all multiorgan heart candidates and decreased likelihood of waitlist deterioration for heart-lung candidates. Of 1,100 heart-kidney, 173 heart-liver, and 159 heart-lung recipients, 5.4%, 2.3%, and 2.5%, respectively, received DCD organs. Recipients of DCD and DBD heart-kidney transplants had a similar likelihood of perioperative outcomes and 1-year survival. All other DCD multiorgan heart recipients have survived to the last follow-up.

CONCLUSIONS

Multiorgan heart candidates who were willing to consider DCD offers had favorable waitlist outcomes, and heart-kidney recipients of DCD transplants had similar post-transplant outcomes to recipients of DBD transplants. We recommend the use of DCD organs to increase the donor pool for these high-risk candidates.

Association of procurement technique with organ yield and cost following donation after circulatory death

Donation after circulatory death (DCD) could account for the largest expansion of the donor allograft pool in the contemporary era. However, the organ yield and associated costs of normothermic regional perfusion (NRP) compared to super-rapid recovery (SRR) with ex-situ normothermic machine perfusion, remain unreported. The Organ Procurement and Transplantation Network (December 2019 to June 2023) was analyzed to determine the number of organs recovered per donor. A cost analysis was performed based on our institution's experience since 2022. Of 43 502 donors, 30 646 (70%) were donors after brain death (DBD), 12 536 (29%) DCD-SRR and 320 (0.7%) DCD-NRP. The mean number of organs recovered was 3.70 for DBD, 3.71 for DCD-NRP (P < .001), and 2.45 for DCD-SRR (P < .001). Following risk adjustment, DCD-NRP (adjusted odds ratio 1.34, confidence interval 1.04-1.75) and DCD-SRR (adjusted odds ratio 2.11, confidence interval 2.01-2.21; reference: DBD) remained associated with greater odds of allograft nonuse. Including incomplete and completed procurement runs, the total average cost of DCD-NRP was $9463.22 per donor. By conservative estimates, we found that approximately 31 donor allografts could be procured using DCD-NRP for the cost equivalent of 1 allograft procured via DCD-SRR with ex-situ normothermic machine perfusion. In conclusion, DCD-SRR procurements were associated with the lowest organ yield compared to other procurement methods. To facilitate broader adoption of DCD procurement, a comprehensive understanding of the trade-offs inherent in each technique is imperative.

Impact of Hemoglobin Level in Ex Vivo Heart Perfusion on Donation After Circulatory Death Hearts: A Juvenile Porcine Experimental Model

BACKGROUND

Ex vivo heart perfusion (EVHP) of donation after circulatory death (DCD) hearts has become an effective strategy in adults; however, the small circulating volume in pediatrics poses the challenge of a low-hemoglobin (Hb) perfusate. We aimed to determine the impact of perfusate Hb levels during EVHP on DCD hearts using a juvenile porcine model.

METHODS

Sixteen DCD piglet hearts (11-14 kg) were reperfused for 4 h in unloaded mode followed by working mode. Metabolism, cardiac function, and cell damage were compared between the low-Hb (Hb, 5.0-5.9 g/dL; n = 8) and control (Hb, 7.5-8.4 g/dL; n = 8) groups. Between-group differences were evaluated using 2-sample t-tests or Fisher's Exact tests.

RESULTS

During unloaded mode, the low-Hb group showed lower myocardial oxygen consumption (P < 0.001), a higher arterial lactate level (P = 0.001), and worse systolic ventricular function (P < 0.001). During working mode, the low-Hb group had a lower cardiac output (mean, 71% versus 106% of normal cardiac output, P = 0.010) and a higher arterial lactate level (P = 0.031). Adjusted cardiac troponin-I (P = 0.112) did not differ between the groups. Morphological myocyte injury in the left ventricle was more severe in the low-Hb group (P = 0.028).

CONCLUSIONS

Low-Hb perfusate with inadequate oxygen delivery induced anaerobic metabolism, resulting in suboptimal DCD heart recovery and declined cardiac function. Arranging an optimal perfusate is crucial to organ protection, and further endeavors to refine the priming volume of EVHP or the transfusion strategy are required.

Donor Heart Recovery and Preservation Modalities in 2024

Historically, heart transplantation (HT) has relied on the use of traditional cold storage for donor heart preservation. This organ preservation modality has several limitations, including the risk for ischemic and cold-induced graft injuries that may contribute to primary graft dysfunction and poor post-HT outcomes. In recent years, several novel donor heart preservation modalities have entered clinical practice, including the SherpaPak Cardiac Transport System of controlled hypothermic preservation, and the Transmedics Organ Care System of ex vivo perfusion. Such technologies are altering the landscape of HT by expanding the geographic reach of procurement teams and enabling both donation after cardiac death and the use of expanded criteria donor hearts. This paper will review the emerging evidence on the association of these modalities with improved post-HT outcomes, and will also suggest best practices for selecting between donor heart preservation techniques.

NADPH oxidase overexpression and mitochondrial OxPhos impairment are more profound in human hearts donated after circulatory death than brain death

This study investigated cardiac stress and mitochondrial oxidative phosphorylation (OxPhos) in human donation after circulatory death (DCD) hearts regarding warm ischemic time (WIT) and subsequent cold storage and compared them with that of human brain death donor (DBD) hearts. A total of 24 human hearts were procured for the research study-6 in the DBD group and 18 in the DCD group. DCD group was divided into three groups (n = 6) based on different WITs (20, 40, and 60 min). All hearts received del Nido cardioplegia before being placed in normal saline cold storage for 6 h. Left ventricular biopsies were performed at hours 0, 2, 4, and 6. Cardiac stress [nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits: 47-kDa protein of phagocyte oxidase (p47phox), 91-kDa glycoprotein of phagocyte oxidase (gp91phox)] and mitochondrial oxidative phosphorylation [OxPhos, complex I (NADH dehydrogenase) subunit of ETC (CI)-complex V (ATP synthase) subunit of ETC (CV)] proteins were measured in cardiac tissue and mitochondria respectively. Modulation of cardiac stress and mitochondrial dysfunction were observed in both DCD and DBD hearts. However, DCD hearts suffered more cardiac stress (overexpressed NADPH oxidase subunits) and diminished mitochondrial OxPhos than DBD hearts. The severity of cardiac stress and impaired oxidative phosphorylation in DCD hearts correlated with the longer WIT and subsequent cold storage time. More drastic changes were evident in DCD hearts with a WIT of 60 min or more. Activation of NADPH oxidase via overproduction of p47phox and gp91phox proteins in cardiac tissue may be responsible for cardiac stress leading to diminished mitochondrial oxidative phosphorylation. These protein changes can be used as biomarkers for myocardium damage and might help assess DCD and DBD heart transplant suitability.NEW & NOTEWORTHY First human DCD heart research studied cardiac stress and mitochondrial dysfunction concerning WIT and the efficacy of del Nido cardioplegia as an organ procurement solution and subsequent cold storage. Mild to moderate cardiac stress and mitochondrial dysfunction were noticed in DCD hearts with WIT 20 and 40 min and cold storage for 4 and 2 h, respectively. These changes can serve as biomarkers, allowing interventions to preserve mitochondria and extend WIT in DCD hearts.

Donation after circulatory death significantly reduces waitlist times while not changing post-heart transplant outcomes: A United Network for Organ Sharing Analysis

BACKGROUND

Recently, several centers in the United States have begun performing donation after circulatory death (DCD) heart transplants (HTs) in adults. We sought to characterize the recent use of DCD HT, waitlist time, and outcomes compared to donation after brain death (DBD).

METHODS

Using the United Network for Organ Sharing database, 10,402 adult (aged >18 years) HT recipients from January 2019 to June 2022 were identified: 425 (4%) were DCD and 9,977 (96%) were DBD recipients. Posttransplant outcomes in matched and unmatched cohorts and waitlist times were compared between groups.

RESULTS

DCD and DBD recipients had similar age (57 years for both, p = 0.791). DCD recipients were more likely White (67% vs 60%, p = 0.002), on left ventricular assist device (LVAD; 40% vs 32%, p < 0.001), and listed as status 4 to 6 (60% vs 24%, p < 0.001); however, less likely to require inotropes (22% vs 40%, p < 0.001) and preoperative extracorporeal membrane oxygenation (0.9% vs 6%, p < 0.001). DCD donors were younger (29 vs 32 years, p < 0.001) and had less renal dysfunction (15% vs 39%, p < 0.001), diabetes (1.9% vs 3.8%, p = 0.050), or hypertension (9.9% vs 16%, p = 0.001). In matched and unmatched cohorts, early survival was similar (p = 0.22). Adjusted waitlist time was shorter in DCD group (21 vs 31 days, p < 0.001) compared to DBD cohort and 5-fold shorter (DCD: 22 days vs DBD: 115 days, p < 0.001) for candidates in status 4 to 6, which was 60% of DCD cohort.

CONCLUSIONS

The community is using DCD mostly for those recipients who are expected to have extended waitlist times (e.g., durable LVADs, status >4). DCD recipients had similar posttransplant early survival and shorter adjusted waitlist time compared to DBD group. Given this early success, efforts should be made to expand the donor pool using DCD, especially for traditionally disadvantaged recipients on the waitlist.

End-stage heart failure: The future of heart transplant and artificial heart

In the last decades, outcomes significantly improved for both heart transplantation and LVAD. Heart transplantation remains the gold standard for the treatment of end stage heart failure and will remain for many years to come. The most relevant limitations are the lack of grafts and the effects of long-term immunosuppressive therapy that involve infectious, cancerous and metabolic complications despite advances in immunosuppression management. Mechanical circulatory support has an irreplaceable role in the treatment of end-staged heart failure, as bridge to transplant or as definitive implantation in non-transplant candidates. Although clinical results do not overcome those of HTx, improvement in the new generation of devices may help to reach the equipoise between the two therapies. This review will go through the evolution, current status and perspectives of both therapeutics.

Normothermic Machine Perfusion Systems: Where Do We Go From Here?

Normothermic machine perfusion (NMP) aims to preserve organs ex vivo by simulating physiological conditions such as body temperature. Recent advancements in NMP system design have prompted the development of clinically effective devices for liver, heart, lung, and kidney transplantation that preserve organs for several hours/up to 1 d. In preclinical studies, adjustments to circuit structure, perfusate composition, and automatic supervision have extended perfusion times up to 1 wk of preservation. Emerging NMP platforms for ex vivo preservation of the pancreas, intestine, uterus, ovary, and vascularized composite allografts represent exciting prospects. Thus, NMP may become a valuable tool in transplantation and provide significant advantages to biomedical research. This review recaps recent NMP research, including discussions of devices in clinical trials, innovative preclinical systems for extended preservation, and platforms developed for other organs. We will also discuss NMP strategies using a global approach while focusing on technical specifications and preservation times.

Heart transplantation: advances in expanding the donor pool and xenotransplantation

Approximately 65 million adults globally have heart failure, and the prevalence is expected to increase substantially with ageing populations. Despite advances in pharmacological and device therapy of heart failure, long-term morbidity and mortality remain high. Many patients progress to advanced heart failure and develop persistently severe symptoms. Heart transplantation remains the gold-standard therapy to improve the quality of life, functional status and survival of these patients. However, there is a large imbalance between the supply of organs and the demand for heart transplants. Therefore, expanding the donor pool is essential to reduce mortality while on the waiting list and improve clinical outcomes in this patient population. A shift has occurred to consider the use of organs from donors with hepatitis C virus, HIV or SARS-CoV-2 infection. Other advances in this field have also expanded the donor pool, including opt-out donation policies, organ donation after circulatory death and xenotransplantation. We provide a comprehensive overview of these various novel strategies, provide objective data on their safety and efficacy, and discuss some of the unresolved issues and controversies of each approach.

Modern advances in heart transplantation

Heart transplantation (HTx) is the only definitive therapy for patients with end stage heart disease. With the increasing global prevalence of heart failure, the demand for HTx has continued to grow and outpace supply. In this paper, we will review advances in the field of HTx along the clinical journey of a HTx recipient. Starting with the sensitized patient, we discuss current methods to define sensitization, and assays to help identify clinically relevant anti-HLA antibodies. Desensitization strategies targeting all levels of the adaptive immune system are discussed with emphasis on novel techniques such as anti-CD 38 blockade and use of the Immunoglobulin G-Degrading Enzyme of Streptococcus Pyogenes. We next discuss donor procurement and the resurgence of donation after circulatory death as a viable strategy to significantly and safely increase the donor pool. Post-transplant, we evaluate non-invasive surveillance techniques including gene expression profiling and donor-derived cell-free DNA. Last, we discuss the ground-breaking developments in the field of xenotransplantation.

Cardioprotective effect of Interleukin-11 against warm ischemia-reperfusion injury in a rat heart donor model

Shortage of donor organs for heart transplantation is a worldwide problem. Donation after circulatory death (DCD) has been proposed to expand the donor pool. However, in contrast to the donation after brain death that undergoes immediate cold preservation, warm ischemia and subsequent reperfusion injury are inevitable in DCD. It has been reported that interleukin-11 (IL-11) mitigates ischemia-reperfusion injury in rodent models of myocardial infarction and donation after brain death heart transplantation. We hypothesized that IL-11 also offers benefit to warm ischemia in an experimental model of cardiac transplantation that resembles DCD. The hearts of naïve male Sprague Dawley rats (n = 15/group) were procured, subjected to 25-min warm ischemia, and reperfused for 60 min using Langendorff apparatus. IL-11 or saline was administered intravenously before the procurement, added to maintenance buffer, and infused via perfusion during reperfusion. IL-11 group exhibited significantly better cardiac function post-reperfusion. Severely damaged mitochondria was found in the electron microscopic analysis of control hearts whereas the mitochondrial structure was better preserved in the IL-11 treated hearts. Immunoblot analysis using neonatal rat cardiomyocytes revealed increased signal transducer and activator of transcription 3 (STAT3) phosphorylation at Ser727 after IL-11 treatment, suggesting its role in mitochondrial protection. Consistent with expected activation of mitochondrial respiration by mitochondrial STAT3, immunohistochemical staining demonstrated a higher mitochondrial cytochrome c oxidase subunit 2 expression. In summary, IL-11 protects the heart from warm ischemia reperfusion injury by alleviating mitochondrial injury and could be a viable therapeutic option for DCD heart transplantation.

Getting out of the box: the future of the UK donation after circulatory determination of death heart programme

Heart failure imposes a significant burden on all health care systems and has a 5-year mortality of 50%. Heart transplantation and ventricular assist device (VAD) implantation are the definitive therapies for end stage heart disease, although transplantation appears to offer superior long-term survival and quality of life over VAD implantation. Transplantation is limited by a shortage in donor hearts, resulting in considerable waiting list mortality. Donation after circulatory determination of death (DCD) offers a significant uplift in the number of donors for heart transplantation. The outcomes both from the UK and internationally have been exciting, with outcomes at least as good as conventional donation after brain death (DBD) transplantation. Currently, DCD hearts are reperfused using ex-situ machine perfusion (ESMP). Whilst ESMP has enabled the development of DCD transplantation, it comes at significant cost, with the per run cost of approximately GBP £90,000. In-situ perfusion of the heart, otherwise known as thoraco-abdominal normothermic regional perfusion (taNRP) is cheaper, but there are ethical concerns regarding the potential to restore cerebral perfusion in the donor. We must determine whether there is any cerebral circulation during in-situ perfusion of the heart to ensure that it does not invalidate the diagnosis of death and potentially violate the dead donor rule. Besides this, there is a need for a randomised controlled trial to definitively determine whether taNRP offers any clinical advantages over ex-situ machine perfusion. This viewpoint article explores these issues in more detail.

Heart Transplant and Donors After Circulatory Death: A Clinical-Preclinical Systematic Review

INTRODUCTION

Heart transplantation is the treatment of choice for end-stage heart failure. There is a mismatch between the number of donor hearts available and the number of patients awaiting transplantation. Expanding the donor pool is critically important. The use of hearts donated following circulatory death is one approach to increasing the number of available donor hearts.

MATERIALS AND METHODS

A systematic review was performed according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines utilizing Pubmed/MEDLINE and Embase. Articles including adult human studies and preclinical animal studies of heart transplantation following donation after circulatory death were included. Studies of pediatric populations or including organs other than heart were excluded.

RESULTS

Clinical experience and preclinical studies are reviewed. Clinical experience with direct procurement, normothermic regional perfusion, and machine perfusion are included. Preclinical studies addressing organ function assessment and enhancement of performance of marginal organs through preischemic, procurement, preservation, and reperfusion maneuvers are included. Articles addressing the ethical considerations of thoracic transplantation following circulatory death are also reviewed.

CONCLUSIONS

Heart transplantation utilizing organs procured following circulatory death is a promising method to increase the donor pool and offer life-saving transplantation to patients on the waitlist living with end-stage heart failure. There is robust ongoing preclinical and clinical research to optimize this technique and improve organ yield. There are also ongoing ethical considerations that must be addressed by consensus before wide adoption of this approach.

50-years journey of heart transplant

Heart transplant is an established modality for the treatment of heart disease refractory to medical therapy. The last 50 years have seen the evolution of immune suppression therapy and standardization of protocols which have significantly improved outcomes following cardiac transplants. Donor availability is the main limiting factor and has restricted the number of heart transplants worldwide. Simultaneously, left ventricular assist devices have evolved to provide a "bridge" for recovery and transplant and alternatively as destination therapy to those waiting for the availability of a donor. This review article provides an overview of the current status of heart transplants after half a century and specific issues pertaining to our country.

Pushing the boundaries of innovation: the potential of ex vivo organ perfusion from an interdisciplinary point of view

Ex vivo machine perfusion (EVMP) is an emerging technique for preserving explanted solid organs with primary application in allogeneic organ transplantation. EVMP has been established as an alternative to the standard of care static-cold preservation, allowing for prolonged preservation and real-time monitoring of organ quality while reducing/preventing ischemia-reperfusion injury. Moreover, it has paved the way to involve expanded criteria donors, e.g., after circulatory death, thus expanding the donor organ pool. Ongoing improvements in EVMP protocols, especially expanding the duration of preservation, paved the way for its broader application, in particular for reconditioning and modification of diseased organs and tumor and infection therapies and regenerative approaches. Moreover, implementing EVMP for in vivo-like preclinical studies improving disease modeling raises significant interest, while providing an ideal interface for bioengineering and genetic manipulation. These approaches can be applied not only in an allogeneic and xenogeneic transplant setting but also in an autologous setting, where patients can be on temporary organ support while the diseased organs are treated ex vivo, followed by reimplantation of the cured organ. This review provides a comprehensive overview of the differences and similarities in abdominal (kidney and liver) and thoracic (lung and heart) EVMP, focusing on the organ-specific components and preservation techniques, specifically on the composition of perfusion solutions and their supplements and perfusion temperatures and flow conditions. Novel treatment opportunities beyond organ transplantation and limitations of abdominal and thoracic EVMP are delineated to identify complementary interdisciplinary approaches for the application and development of this technique.

A Case Report of Triple Organ Transplantation From a Donor After Circulatory Death Using Thoraco-Abdominal Normothermic Regional Perfusion

Organ transplantation with donation after circulatory death can potentially increase the donor pool. Here, we report the rare case of triple-organ (heart/liver/kidney) transplantation from a donor after circulatory death using thoraco-abdominal normothermic regional perfusion. The recipient was a 61-year-old man with end-stage heart failure, liver failure, and kidney failure secondary to arrhythmogenic right ventricular dysplasia. He received a heart/liver/kidney transplantation from a donor after circulatory death. The course was complicated with primary graft dysfunction of the heart that resolved on postoperative day 3. The patient was discharged on postoperative day 39. He has no evidence for rejection on heart biopsy, and all 3 organs exhibit stable function. The use of donation after cardiac death donors greatly increases the donor pool and should be considered for patients requiring multiorgan transplantation. The use of thoraco-abdominal normothermic reperfusion is not only a feasible method for multiorgan procurement but also provides enhanced protection for all transplanted organs.

Impact of Donor Hemodynamics on Recipient Survival in Heart Transplantation

BACKGROUND

Heart transplantation is the gold-standard therapy for end-stage heart failure, but rates of donor-heart use remain low due to various factors that are often not evidence based. The impact of donor hemodynamics obtained via right-heart catheterization on recipient survival remains unclear.

METHODS

The United Network for Organ Sharing registry was used to identify donors and recipients from September 1999-December 2019. Donor hemodynamics data were obtained and analyzed using univariate and multivariable logistical regression, with the primary endpoints being 1- and 5-year post-transplant survival.

RESULTS

Of the 85,333 donors who consented to heart transplantation during the study period, 6573 (7.7%) underwent right-heart catheterization, of whom 5531 eventually underwent procurement and transplantation. Donors were more likely to undergo right-heart catheterization if they had high-risk criteria. Recipients who had donor hemodynamic assessment had 1- and 5-year survival rates similar to those without donor hemodynamic assessment (87% vs 86%, 1 year). Abnormal hemodynamics were common in donor hearts but did not impact recipient survival rates, even when risk-adjusted in multivariable analysis.

CONCLUSIONS

Donors with abnormal hemodynamics may represent an opportunity to expand the pool of viable donor hearts.

Graft preservation in heart transplantation: current approaches

Heart transplantation (HTx) represents the current best surgical treatment for patients affected by end-stage heart failure. However, with the improvement of medical and interventional therapies, the population of HTx candidates is increasingly old and at high-risk for mortality and complications. Moreover, the use of "extended donor criteria" to deal with the shortage of donors could increase the risk of worse outcomes after HTx. In this setting, the strategy of donor organ preservation could significantly affect HTx results. The most widely used technique for donor organ preservation is static cold storage in ice. New techniques that are clinically being used for donor heart preservation include static controlled hypothermia and machine perfusion (MP) systems. Controlled hypothermia allows for a monitored cold storage between 4°C and 8°C. This simple technique seems to better preserve the donor heart when compared to ice, probably avoiding tissue injury due to sub-zero °C temperatures. MP platforms are divided in normothermic and hypothermic, and continuously perfuse the donor heart, reducing ischemic time, a well-known independent risk factor for mortality after HTx. Also, normothermic MP permits to evaluate marginal donor grafts, and could represent a safe and effective technique to expand the available donor pool. However, despite the increasing number of donor hearts preserved with these new approaches, whether these techniques could be considered superior to traditional CS still represents a matter of debate. The aim of this review is to summarize and critically assess the available clinical data on donor heart preservation strategies employed for HTx.

Case report: Heart retransplant from a donor after circulatory death and extended transport period with normothermic perfusion

A 55-year-old man with end-stage heart failure, who had an orthotopic heart transplant 21 years prior, underwent heart retransplantation using a heart from a donor with circulatory death in a distant location and an extended transport period with normothermic ex vivo perfusion. Owing to the persistent and worsening shortage of donor hearts, this case illustrates that expanding the donor acceptance criteria to include more distant donor locations and enrolling recipients with extended criteria (e.g., heart retransplantation) is feasible.

A national pilot of donation after circulatory death (DCD) heart transplantation within the United Kingdom

BACKGROUND

The United Kingdom (UK) was one of the first countries to pioneer heart transplantation from donation after circulatory death (DCD) donors. To facilitate equity of access to DCD hearts by all UK heart transplant centers and expand the retrieval zone nationwide, a Joint Innovation Fund (JIF) pilot was provided by NHS Blood and Transplant (NHSBT) and NHS England (NHSE). The activity and outcomes of this national DCD heart pilot program are reported.

METHODS

This is a national multi-center, retrospective cohort study examining early outcomes of DCD heart transplants performed across 7 heart transplant centers, adult and pediatric, throughout the UK. Hearts were retrieved using the direct procurement and perfusion (DPP) technique by 3 specialist retrieval teams trained in ex-situ normothermic machine perfusion. Outcomes were compared against DCD heart transplants before the national pilot era and against contemporaneous donation after brain death (DBD) heart transplants, and analyzed using Kaplan-Meier analysis, chi-square test, and Wilcoxon's rank-sum.

RESULTS

From September 7, 2020 to February 28, 2022, 215 potential DCD hearts were offered of which 98 (46%) were accepted and attended. There were 77 potential donors (36%) which proceeded to death within 2 hours, with 57 (27%) donor hearts successfully retrieved and perfused ex situ and 50 (23%) DCD hearts going on to be transplanted. During this same period, 179 DBD hearts were transplanted. Overall, there was no difference in the 30-day survival rate between DCD and DBD (94% vs 93%) or 90 day survival (90% vs 90%) respectively. There was a higher rate of ECMO use post-DCD heart transplants compared to DBD (40% vs 16%, p = 0.0006), and DCD hearts in the pre pilot era, (17%, p = 0.002). There was no difference in length of ICU stay (9 DCD vs 8 days DBD, p = 0.13) nor hospital stay (28 DCD vs 27 DBD days, p = 0.46).

CONCLUSION

During this pilot study, 3 specialist retrieval teams were able to retrieve DCD hearts nationally for all 7 UK heart transplant centers. DCD donors increased overall heart transplantation in the UK by 28% with equivalent early posttransplant survival compared with DBD donors.

Donor heart ischemic time can be extended beyond 9 hours using hypothermic machine perfusion in sheep

BACKGROUND

The global shortage of donor hearts available for transplantation is a major problem for the treatment of end-stage heart failure. The ischemic time for donor hearts using traditional preservation by standard static cold storage (SCS) is limited to approximately 4 hours, beyond which the risk for primary graft dysfunction (PGD) significantly increases. Hypothermic machine perfusion (HMP) of donor hearts has been proposed to safely extend ischemic time without increasing the risk of PGD.

METHODS

Using our sheep model of 24 hours brain death (BD) followed by orthotopic heart transplantation (HTx), we examined post-transplant outcomes in recipients following donor heart preservation by HMP for 8 hours, compared to donor heart preservation for 2 hours by either SCS or HMP.

RESULTS

Following HTx, all HMP recipients (both 2 hours and 8 hours groups) survived to the end of the study (6 hours after transplantation and successful weaning from cardiopulmonary bypass), required less vasoactive support for hemodynamic stability, and exhibited superior metabolic, fluid status and inflammatory profiles compared to SCS recipients. Contractile function and cardiac damage (troponin I release and histological assessment) was comparable between groups.

CONCLUSIONS

Overall, compared to current clinical SCS, recipient outcomes following transplantation are not adversely impacted by extending HMP to 8 hours. These results have important implications for clinical transplantation where longer ischemic times may be required (e.g., complex surgical cases, transport across long distances). Additionally, HMP may allow safe preservation of "marginal" donor hearts that are more susceptible to myocardial injury and facilitate increased utilization of these hearts for transplantation.

Heart transplantation from donation after circulatory death: Impact on waitlist time and transplant rate

The effect of using donation after circulatory death (DCD) hearts on waitlist outcomes has not been substantiated. We retrospectively analyzed 184 heart transplant (HT) candidates at our institution from 2019 to 2021. Patients were stratified into 2 observation periods centered on September 12, 2020, when the adult DCD HT program officially began. The primary outcome was a comparison of transplant rate between period 1 (pre-DCD) and period 2 (post-DCD). Secondary outcomes included waitlist time-to-transplant, waitlist mortality rate, independent predictors of incidence of HT, and posttransplant outcomes. A total of 165 HTs (n = 92 in period 1 and n = 73 in period 2) were performed. The median waitlist time-to-transplant decreased from 47.5 to 19 days in periods 1 and 2, respectively (P = .004). The transplant rate increased from 181 per 100 patient-years in period 1 to 579 per 100 patient-years in period 2 (incidence rate ratio, 1.87; 95% CI, 1.04-3.38; P = .038). There were no statistical differences in waitlist mortality rate (P = .566) and 1-year survival (P = .699) between the 2 periods. DCD HTs (n = 36) contributed to 49.3% of overall HT activity in period 2. We concluded that utilization of DCD hearts significantly reduced waitlist time and increased transplant rate. Short-term posttransplant outcomes were comparable between the pre-DCD and post-DCD periods.

Dilemmas concerning heart procurement in controlled donation after circulatory death

With an expanding population at risk for heart failure and the resulting increase in patients admitted to the waiting list for heart transplantation, the demand of viable organs exceeds the supply of suitable donor hearts. Use of hearts after circulatory death has reduced this deficit. Two primary techniques for heart procurement in circulatory death donors have been described: direct procurement and perfusion and thoraco-abdominal normothermic regional perfusion. While the former has been accepted as an option for heart procurement in circulatory death donors, the latter technique has raised some ethical questions in relation to the dead donor rule. In this paper we discuss the current dilemmas regarding these heart procurement protocols in circulatory death donors.

Metabolomic profiling of cardiac allografts after controlled circulatory death

BACKGROUND

Assessment of myocardial viability during ex situ heart perfusion (ESHP) is based on the measurement of lactate concentrations. As this provides with limited information, we sought to investigate the metabolic signature associated with donation after circulatory death (DCD) and the impact of ESHP on the myocardial metabolome.

METHODS

Porcine hearts were retrieved either after warm ischemia (DCD group, N = 6); after brain-stem death (BSD group, N = 6); or without DCD nor BSD (Control group, N = 6). Hearts were perfused using normothermic oxygenated blood for 240 minutes. Plasma and myocardial samples were collected respectively every 30 and 60 minutes, and analyzed by an untargeted metabolomic approach using liquid chromatography coupled to high-resolution mass spectrometry.

RESULTS

Median duration of warm ischemia was 23 minutes [19-29] in DCD animals. Lactate level within myocardial biopsies was not significantly different between groups at T0 (p = 0.281), and remained stable over the 4-hour period of ESHP. More than 300 metabolites were detected in plasma and heart biopsy samples. Compared to BSD animals, metabolomics changes involving energy and nucleotide metabolisms were observed in plasma samples of DCD animals before initiation of ESHP, whereas 2 metabolites (inosine monophosphate and methylbutyrate) exhibited concentration changes in biopsy samples. Normalization of DCD metabolic profile was remarkable after 4 hours of ESHP.

CONCLUSION

A specific metabolic profile was observed in DCD hearts, mainly characterized by an increased nucleotide catabolism. DCD and BSD metabolomes proved normalized during ESHP. Complementary investigations are needed to correlate these findings to cardiac performances.

Ethical Issues in Donation following Circulatory Death: A Scoping Review Examining Changes over Time from 1993 to 2022

Background: Ethical frameworks for organ donation following circulatory death (DCD) were established >20 years ago. However, considerable variation exists among these, indicating consensus has not been reached on all issues. Additionally, advances such as cardiac DCD transplants and normothermic regional perfusion (NRP) may have reignited old debates.Methods: We reviewed the English-language literature addressing ethical issues in DCD from 1993 to 2022, examining changes in frequency with which ethical principles and their sub-themes identified within each, were addressed.Results: Non-maleficence was the most frequently addressed principle (192 of 199 articles), as well as the most varied, with 9 subthemes (versus 2-4 within each of the other bioethical principles).Conclusions: There were several changes in the terminology used to refer to DCD over time, and substantial interest in cardiac DCD and NRP in recent publications, arising in 11 and 19 of the 30 publications from 2018 to 2022.

Vitrification and nanowarming enable long-term organ cryopreservation and life-sustaining kidney transplantation in a rat model

Banking cryopreserved organs could transform transplantation into a planned procedure that more equitably reaches patients regardless of geographical and time constraints. Previous organ cryopreservation attempts have failed primarily due to ice formation, but a promising alternative is vitrification, or the rapid cooling of organs to a stable, ice-free, glass-like state. However, rewarming of vitrified organs can similarly fail due to ice crystallization if rewarming is too slow or cracking from thermal stress if rewarming is not uniform. Here we use "nanowarming," which employs alternating magnetic fields to heat nanoparticles within the organ vasculature, to achieve both rapid and uniform warming, after which the nanoparticles are removed by perfusion. We show that vitrified kidneys can be cryogenically stored (up to 100 days) and successfully recovered by nanowarming to allow transplantation and restore life-sustaining full renal function in nephrectomized recipients in a male rat model. Scaling this technology may one day enable organ banking for improved transplantation.

Transplantation Outcomes with Donor Hearts after Circulatory Death

BACKGROUND

Data showing the efficacy and safety of the transplantation of hearts obtained from donors after circulatory death as compared with hearts obtained from donors after brain death are limited.

METHODS

We conducted a randomized, noninferiority trial in which adult candidates for heart transplantation were assigned in a 3:1 ratio to receive a heart after the circulatory death of the donor or a heart from a donor after brain death if that heart was available first (circulatory-death group) or to receive only a heart that had been preserved with the use of traditional cold storage after the brain death of the donor (brain-death group). The primary end point was the risk-adjusted survival at 6 months in the as-treated circulatory-death group as compared with the brain-death group. The primary safety end point was serious adverse events associated with the heart graft at 30 days after transplantation.

RESULTS

A total of 180 patients underwent transplantation; 90 (assigned to the circulatory-death group) received a heart donated after circulatory death and 90 (regardless of group assignment) received a heart donated after brain death. A total of 166 transplant recipients were included in the as-treated primary analysis (80 who received a heart from a circulatory-death donor and 86 who received a heart from a brain-death donor). The risk-adjusted 6-month survival in the as-treated population was 94% (95% confidence interval [CI], 88 to 99) among recipients of a heart from a circulatory-death donor, as compared with 90% (95% CI, 84 to 97) among recipients of a heart from a brain-death donor (least-squares mean difference, -3 percentage points; 90% CI, -10 to 3; P<0.001 for noninferiority [margin, 20 percentage points]). There were no substantial between-group differences in the mean per-patient number of serious adverse events associated with the heart graft at 30 days after transplantation.

CONCLUSIONS

In this trial, risk-adjusted survival at 6 months after transplantation with a donor heart that had been reanimated and assessed with the use of extracorporeal nonischemic perfusion after circulatory death was not inferior to that after standard-care transplantation with a donor heart that had been preserved with the use of cold storage after brain death. (Funded by TransMedics; ClinicalTrials.gov number, NCT03831048.).

The international experience of in-situ recovery of the DCD heart: a multicentre retrospective observational study

BACKGROUND

Heart transplantation is an effective treatment offering the best recovery in both quality and quantity of life in those affected by refractory, severe heart failure. However, transplantation is limited by donor organ availability. The reintroduction of heart donation after the circulatory determination of death (DCD) in 2014 offered an uplift in transplant activity by 30%. Thoraco-abdominal normothermic regional perfusion (taNRP) enables in-situ reperfusion of the DCD heart. The objective of this paper is to assess the clinical outcomes of DCD donor hearts recovered and transplanted from donors undergoing taNRP.

METHOD

This was a multicentre retrospective observational study. Outcomes included functional warm ischaemic time, use of mechanical support immediately following transplantation, perioperative and long-term actuarial survival and incidence of acute rejection requiring treatment. 157 taNRP DCD heart transplants, performed between February 2, 2015, and July 29, 2022, have been included from 15 major transplant centres worldwide including the UK, Spain, the USA and Belgium. 673 donations after the neurological determination of death (DBD) heart transplantations from the same centres were used as a comparison group for survival.

FINDINGS

taNRP resulted in a 23% increase in heart transplantation activity. Survival was similar in the taNRP group when compared to DBD. 30-day survival was 96.8% ([92.5%-98.6%] 95% CI, n = 156), 1-year survival was 93.2% ([87.7%-96.3%] 95% CI, n = 72) and 5-year survival was 84.3% ([69.6%-92.2%] 95% CI, n = 13).

INTERPRETATION

Our study suggests that taNRP provides a significant boost to heart transplantation activity. The survival rates of taNRP are comparable to those obtained for DBD transplantation in this study. The similar survival may in part be related to a short warm ischaemic time or through a possible selection bias of younger donors, this being an uncontrolled observational study. Therefore, our study suggests that taNRP offers an effective method of organ preservation and procurement. This early success of the technique warrants further investigation and use.

FUNDING

None of the authors have a financial relationship with a commercial entity that has an interest in the subject.

Ex-Vivo Preservation of Heart Allografts—An Overview of the Current State

As heart transplantation continues to be the gold-standard therapy for end-stage heart failure, the supply-demand imbalance of available organs worsens. Until recently, there have been no advances in increasing the donor pool, as prolonged cold ischemic time excludes the use of certain donors. The TransMedics Organ Care System (OCS) allows for ex-vivo normothermic perfusion, which allows for a reduction of cold ischemic time and allows for long-distance procurements. Furthermore, the OCS allows for real-time monitoring and assessment of allograft quality, which can be crucial for extended-criteria donors or donation after cardiac death (DCD) donors. Conversely, the XVIVO device allows for hypothermic perfusion to preserve allografts. Despite their limitations, these devices have the potential to alleviate the supply-demand imbalance in donor availability.

Ex-situ oxygenated hypothermic machine perfusion in donation after circulatory death heart transplantation following either direct procurement or in-situ normothermic regional perfusion

BACKGROUND

Heart transplantation in donation after circulatory death (DCD) relies on warm perfusion using either in situ normothermic regional perfusion (NRP) or ex situ normothermic machine perfusion. In this study, we explore an alternative: oxygenated hypothermic machine perfusion (HMP) using a novel clinically applicable perfusion system, which is compared to NRP with static cold storage (SCS).

METHODS

In a porcine model, a DCD setting was simulated, followed by either (1) NRP and SCS (2) NRP and HMP with the XVIVO Heart preservation system or (3) direct procurement (DPP) and HMP. After preservation, heart transplantation (HTX) was performed. After weaning from cardiopulmonary bypass (CPB), biventricular function was assessed by admittance and Swan-Ganz catheters.

RESULTS

Only transplanted hearts in the HMP groups showed significantly increased biventricular contractility (end-systole elastance) 2 hour post-CPB (left ventricle absolute change: NRP HMP: +1.8 ± 0.56, p = 0.047, DPP HMP: +1.5 ± 0.43, p = 0.045 and NRP SCS: +0.97 ± 0.47 mmHg/ml, p = 0.21; right ventricle absolute change: NRP HMP: +0.50 ± 0.12, p = 0.025, DPP HMP: +0.82 ± 0.23, p = 0.039 and NRP SCS: +0.28 ± 0.26, p = 0.52) while receiving significantly less dobutamine to maintain a cardiac output >4l/min compared to SCS. Diastolic function was preserved in all groups. Post-HTX, both HMP groups showed significantly less increments in plasma troponin T compared to SCS.

CONCLUSION

In DCD HTX, increased biventricular contractility post-HTX was only observed in hearts preserved with HMP. In addition, the need for inotropic support and signs of myocardial damage were lower in the HMP groups. DCD HTX can be successfully performed using DPP followed by preservation with HMP in a preclinical setting.

Comparing Cardiac Mechanics and Myocardial Fibrosis in DBD and DCD Heart Transplant Recipients

BACKGROUND

Heart transplantation (HTx) after donation after circulatory death (DCD) is an expanding practice but is associated with increased warm ischemic time. The impact of DCD HTx on cardiac mechanics and myocardial fibrosis has not been reported. We aimed to compare cardiac mechanics and myocardial fibrosis using cardiovascular magnetic resonance (CMR) imaging in donation after brain death (DBD) and DCD HTx recipients and healthy controls.

METHODS AND RESULTS

Consecutive HTx recipients between March 2015 and March 2021 who underwent routine surveillance CMR imaging were included. Cardiac mechanics were assessed using CMR feature tracking to compute global longitudinal strain, global circumferential strain, and right ventricular free-wall longitudinal myocardial strain. Fibrosis was assessed using late gadolinium enhancement imaging and estimation of extracellular volume. There were 82 (DBD n = 42, DCD n = 40) HTx recipients (aged 53 years, interquartile range 41-59 years, 24% female) who underwent CMR imaging at median of 9 months (interquartile range 6-14 months) after transplantation. HTx recipients had increased extracellular volume (29.7 ± 3.6%) compared with normal ranges (25.9%, interquartile range 25.4-26.5). Myocardial strain was impaired after transplantation compared with controls (global longitudinal strain -12.6 ± 3.1% vs -17.2 ± 1.8%, P < .0001; global circumferential strain -16.9 ± 3.1% vs -19.2 ± 2.0%, P = .002; right ventricular free-wall longitudinal strain -15.7 ± 4.5% vs -21.6 ± 4.7%, P < .0001). There were no differences in fibrosis burden (extracellular volume 30.6 ± 4.4% vs 29.2 ± 3.2%; P = .39) or cardiac mechanics (global longitudinal strain -13.1 ± 3.0% vs -12.1 ± 3.1%, P = .14; global circumferential strain -17.3 ± 2.9% vs -16.6 ± 3.1%, P = .27; right ventricular free-wall longitudinal strain -15.9 ± 4.9% vs -15.5 ± 4.1%, P = .71) between DCD and DBD HTx.

CONCLUSIONS

HTx recipients have impaired cardiac mechanics compared with controls, with increased myocardial fibrosis. There were no differences in early CMR imaging characteristics between DBD and DCD heart transplants, providing further evidence that DCD and DBD HTx outcomes are comparable.

Donation after circulatory death heart transplantation using normothermic regional perfusion:The NYU Protocol

Objective

This study aimed to evaluate the impact of cardiopulmonary bypass for thoraco-abdominal normothermic regional perfusion on the metabolic milieu of donation after cardiac death organ donors before transplantation.

Methods

Local donation after cardiac death donor offers are assessed for suitability and willingness to participate. Withdrawal of life-sustaining therapy is performed in the operating room. After declaration of circulatory death and a 5-minute observation period, the cardiac team performs a median sternotomy, ligation of the aortic arch vessels, and initiation of thoraco-abdominal normothermic regional perfusion via central cardiopulmonary bypass at 37 °C. Three sodium chloride zero balance ultrafiltration bags containing 50 mEq sodium bicarbonate and 0.5 g calcium carbonate are infused. Arterial blood gas measurements are obtained every 15 minutes after every zero balance ultrafiltration bag is infused, and blood is transfused as needed to maintain hemoglobin greater than 8 mg/dL. Cardiopulmonary bypass is weaned with concurrent hemodynamic and transesophageal echocardiogram evaluation of the donor heart. The remainder of the procurement, including the abdominal organs, proceeds in a similar controlled fashion as is performed for a standard donation after brain death donor.

Results

Between January 2020 and May 2022, 18 donation after cardiac death transplants using the thoraco-abdominal normothermic regional perfusion protocol were performed at our institution. The median donor age was 42.5 years (range, 20-51 years), and 88.9% (16/18) were male. The mean total donor cardiopulmonary bypass time was 88.8 ± 51.8 minutes. At the beginning of cardiopulmonary bypass, the average donor lactate was 9.4 ± 1.5 mmol/L compared with an average final lactate of 5.3 ± 2.7 mmol/L (P<.0001). The average beginning potassium was 6.5 ± 1.8 mmol/L compared with an average end potassium of 4.2 ± 0.4 mmol/L (P<.0001) . The average beginning hemoglobin was 6.8 ± 0.7 g/dL, and the average end hemoglobin was 8.2 ± 1.3 g/dL (P<.001) . On average, donation after cardiac death donors received transfusions of 2.3 ± 1.5 units of packed red blood cells. Of the 18 donors who underwent normothermic regional perfusion, all hearts were deemed suitable for recovery and successfully transplanted, a yield of 100%. Other organs successfully recovered and transplanted include kidneys (80.6% yield), livers (66.7% yield), and bilateral lungs (27.8% yield).

Conclusions

The use of cardiopulmonary bypass for thoraco-abdominal normothermic regional perfusion is a burgeoning option for improving the quality of organs from donation after cardiac death donors. Meticulous intraoperative management of donation after cardiac death donors with a specific focus on improving their metabolic milieu may lead to improved graft function in transplant recipients.

A Neonatal ABO non-compatible heart transplant from a circulatory-determined death donor using NRP/Cold storage

BACKGROUND

Donation after Circulatory death is gaining worldwide acceptance. Most protocols regard their first cases to be performed with donor and recipient in the same institution. Few records of children or distant procurement have been published.

METHODS

Our institution was offered a heart from a 3-day-old, 3.4-kg child, blood group A, suffering irreversible encephalopathy. Parents accepted withdrawal of life-sustaining therapy and agreed to donation. The donor hospital was located 340 km away. Concomitantly, a 2-month-old, 3.1 kg, blood group type B and with non-compaction ventricles was awaiting for the heart transplant in our unit.

RESULTS

Thirty-seven minutes after withdrawal of life-sustaining therapy, the heart arrested. Five minutes afterwards, a sternotomy was performed. The supra-aortic vessels were clamped altogether. Aorta and right appendage were cannulated and connected to heart-lung machine. The innominate artery above the clamp was severed. The heart resumed spontaneous rhythm in less than 1 min. Ventilation was restored and extracorporeal circulation was maintained for 32 min. Upon cardiologic arrest, the graft was harvested as routinely. The heart was cold-stored and transported by plane to our Hospital. An orthotopic bicaval transplant was performed. Overall cold ischaemia was 245 min. Ten weeks later, the child was discharged home in good condition.

CONCLUSION

Donation in circulatory death could increase the pool in neonates. Extracorporeal circulation proves successful for procurement in neonates. Distant procurement plus cold storage for donation in circulatory death is feasible. Donation in circulatory death and ABO non-compatible strategies are complementary to each other.