Normothermic Regional Perfusion is an Emerging Cost-Effective Alternative in Donation After Circulatory Death (DCD) in Heart Transplantation

Severe primary graft dysfunction in heart transplant recipients using donor hearts after circulatory death: United States experience

OBJECTIVE

This study compares the incidence of severe Primary Graft Dysfunction (PGD) in a contemporaneous cohort of donors after circulatory death (DCD) and brain death (DBD) heart transplant recipients.

METHOD

The United Network for Organ Sharing database was queried for isolated adult heart transplant recipients from 9/2023 to 6/2024. Heart recipients were stratified based on the organ donation type (DCD vs DBD). DCD heart recipients were further categorized based on the procurement method: time between circulatory death to cross-clamp: ≤ 30 minutes (Direct Procurement and Preservation, DPP), >30 minutes (Normothermic Regional Perfusion, NRP). Outcomes of interest included: severe PGD (Left/Bi-Ventricular; LV/BiV) at 24 hours and Severe Graft Dysfunction at 72 hours (patients with severe PGD at 24 hours that remain on mechanical support at 72 hours).

RESULTS

A total of 2590 adult heart transplant recipients were identified, of which 17.1% underwent DCD heart transplantation. DCD heart recipients were less likely to be on inotrope (36.7% vs 41.6%, p=0.046) and ECMO (4.1% vs 9.9%, p<0.001) prior to transplant than DBD heart recipients. DCD heart recipients were more likely than DBD heart recipients to develop severe PGD (LV/BiV) at 24 hours (9.5% vs 5.1%, p<0.001). The Severe Graft Dysfunction at 72 hours (2.3% vs 2.9%, p=0.67) and 30-day mortality were similar between the 2 groups. Recipients of DCD heart procured with DPP or NRP had similar severe PGD (LV/BiV) at 24 hours (9.4% vs 9.7%, p=0.93).

CONCLUSION

Severe PGD at 24 hours is higher among the DCD than DBD heart recipients, but Graft Dysfunction improves by 72 hours.

On the ethical permissibility of in situ reperfusion in cardiac transplantation after the declaration of circulatory death

Transplant surgeons in the USA have begun performing a novel organ procurement protocol in the setting of circulatory death. Unlike traditional donation after circulatory death (DCD) protocols, in situ normothermic perfusion DCD involves reperfusing organs, including the heart, while still contained in the donor body. Some commentators, including the American College of Physicians, have claimed that in situ reperfusion after circulatory death violates the widely accepted Dead Donor Rule (DDR) and conclude that in situ reperfusion is ethically impermissible. In this paper I argue that, in terms of respecting the DDR, in situ reperfusion cardiac transplantation does not differ from traditional DCD cardiac transplantation. I do this by introducing and defending a refined conception of circulatory death, namely vegetative state function permanentism I also argue against the controversial brain occlusion feature of the in situ reperfusion DCD protocol, on the basis that it is ethically unnecessary and generates the problematic appearance of ethical dubiousness.

Global transplantation: Lessons from organ transplantation organizations worldwide

Although national transplant organizations share common visions and goals, the creation of a unified global organization remains impractical. Differences in ethnicity, culture, religion, and education shape local practices and infrastructure, making the establishment of a single global entity unfeasible. Even with these social disparities aside, logistical factors such as time and distance between organ procurement and transplantation sites pose significant challenges. While technological advancements have extended organ preservation times, they have yet to support the demands of transcontinental transplantations effectively. This review presents a comparative analysis of the structures, operational frameworks, policies, and legislation governing various transplant organizations around the world. Key differences pertain to the administration of these organizations, trends in organ donation, and organ allocation policies, which reflect the financial, cultural, and religious diversity across different regions. While a global transplant organization may be out of reach, agreeing on best practices for the benefit of patients is essential.

Challenges and opportunities in organ donation after circulatory death

In recent years, there has been resurgence in donation after circulatory death (DCD). Despite that, the number of organs transplanted from these donors remains low due to concerns about their function and a lack of an objective assessment at the time of donation. This overview examines the current DCD practices and the classification modifications to accommodate regional perspectives. Several risk factors underscore the reluctance to accept DCD organs, and we discuss the modern strategies to mitigate them. The advent of machine perfusion technology has revolutionized the field of DCD transplantation, leading to improved outcomes and better organ usage. With many strategies at our disposal, there is an urgent need for comparative trials to determine the optimal use of perfusion technologies for each donated organ type. Additional progress in defining therapeutic strategies to repair the damage sustained during the dying process should further improve DCD organ utilization and outcomes. However, there remains wide variability in access to DCD donation and transplantation, and organizational efforts should be doubled up with consensus on key ethical issues that still surround DCD donation in the era of machine perfusion.

Adult cardiac transplantation utilizing donors after circulatory death

Donation after circulatory death (DCD) presents both opportunities and challenges in the realm of heart transplantation. Its emergence holds promise for narrowing the gap between patients in need of organs and the available donor pool. The rapid emergence of DCD use has allowed heart transplant volume to increase worldwide. Long-term outcomes and best practices remain to be defined and are important considerations in the wider use of these techniques in a broad selection of patients to understand best use and practice moving forward. Expanding DCD donation entails substantial resource allocation, coordination efforts, and training initiatives. Moving forward, standardization is imperative, particularly in aspects such as "stand-off" time, warm ischemic time (WIT), and perfusate composition.

European Society of Organ Transplantation (ESOT) Consensus Statement on Machine Perfusion in Cardiothoracic Transplant

The machine perfusion (MP) of transplantable grafts has emerged as an upcoming field in Cardiothoracic (CT) transplantation during the last decade. This technology carries the potential to assess, preserve, and even recondition thoracic grafts before transplantation, so it is a possible game-changer in the field. This technology field has reached a critical turning point, with a growing number of publications coming predominantly from a few leading institutions, but still need solid scientific evidence. Due to the increasing need to expand the donor pool, especially in Europe, where the donor age is steeply increased, a consensus has been established to address the growing need and knowledge of machine perfusion in cardiothoracic transplantation, targeting the unmet scientific need in this growing field but also, priorities for development, and regional differences in utilization rates and organizational issues. To address MP in CT, the European Society of Organ Transplantation (ESOT) convened a dedicated Working group comprised of experts in CT to review literature about MP to develop guidelines that were subsequently discussed and voted on during the Consensus Conference that took place in person in Prague during the TLJ 3.0 in November 2022. The findings and recommendations of the Cardiothoracic Working Group on MP are presented in this article.

Cardiac Loading using Passive Left Atrial Pressurization and Passive Afterload for Graft Assessment

Ex vivo machine perfusion or normothermic machine perfusion is a preservation method that has gained great importance in the transplantation field. Despite the immense opportunity for assessment due to the beating state of the heart, current clinical practice depends on limited metabolic trends for graft evaluation. Hemodynamic measurements obtained from left ventricular loading have garnered significant attention within the field due to their potential as objective assessment parameters. In effect, this protocol provides an easy and effective manner of incorporating loading capabilities to established Langendorff perfusion systems through the simple addition of an extra reservoir. Furthermore, it demonstrates the feasibility of employing passive left atrial pressurization for loading, an approach that, to our knowledge, has not been previously demonstrated. This approach is complemented by a passive Windkessel base afterload, which acts as a compliance chamber to maximize myocardial perfusion during diastole. Lastly, it highlights the capability of capturing functional metrics during cardiac loading, including left ventricular pulse pressure, contractility, and relaxation, to uncover deficiencies in cardiac graft function after extended periods of preservation times (˃6 h).

Neither Ethical nor Prudent: Why Not to Choose Normothermic Regional Perfusion

In transplant medicine, the use of normothermic regional perfusion (NRP) in donation after circulatory determination of death raises ethical difficulties. NRP is objectionable because it restores the donor's circulation, thus invalidating a death declaration based on the permanent cessation of circulation. NRP's defenders respond with arguments that are tortuous and factually inaccurate and depend on introducing extraneous concepts into the law. However, results comparable to NRP's-more and higher-quality organs and more efficient allocation-can be achieved by removing organs from deceased donors and using normothermic machine perfusion (NMP) to support the organs outside the body, without jeopardizing confidence in transplantation's legal and ethical foundations. Given the controversy that NRP generates and the convoluted justifications made for it, we recommend a prudential approach we call "ethical parsimony," which holds that, in the choice between competing means of achieving a result, the ethically simpler one is to be preferred. This approach makes clear that policy-makers should favor NMP over NRP.

Novel portable hypothermic machine perfusion preservation device enhances cardiac viability of donated human hearts

Introduction

Heart transplant remains the gold standard treatment for patients with advanced heart failure. However, the list of patients waiting for a heart transplant continues to increase. We have developed a portable hypothermic oxygenated machine perfusion device, the VP.S ENCORE®, to extend the allowable preservation time. The purpose of this study was to test the efficacy of the VP.S. ENCORE® using deceased donors derived hearts.

Methods

Hearts from brain-dead donors not utilized for transplant (n = 11) were offered for research from the Texas Organ Sharing Alliance (TOSA), South and Central Texas' Organ Procurement Organization (OPO) and were preserved in the VP.S ENCORE® for 4 (n = 2), 6 (n = 3), and 8 (n = 3) hours or were kept in static cold storage (SCS) (n = 3). After preservation, the hearts were placed in an isolated heart Langendorff model for reperfusion and evaluated for cardiac function.

Results

The mean donor age was 37.82 ± 12.67 with the youngest donor being 19 and the oldest donor being 58 years old. SCS hearts mean weight gain (%) was -1.4 ± 2.77, while perfused at 4 h was 5.6 ± 6.04, perfused at 6 h 2.1 ± 6.04, and 8 h was 7.2 ± 10.76. Venous and arterial lactate concentrations were less than 2.0 mmol/L across all perfused hearts. Left ventricular contractility (+dPdT, mmHg/s) for 4 h (1,214 ± 1,064), 6 (1,565 ± 141.3), and 8 h (1,331 ± 403.6) were within the range of healthy human heart function. Thus, not significant as compared to the SCS group (1,597 ± 342.2). However, the left ventricular relaxation (mmHg/s) was significant in 6-hour perfused heart (p < 0.05) as compared to SCS. Gene expression analysis of inflammation markers (IL-6, IL-1β) showed no significant differences between SCS and perfused hearts, but a 6-hour perfusion led to a downregulated expression of these markers.

Discussion

The results demonstrate that the VP.S ENCORE® device enhances cardiac viability and exhibits comparable cardiac function to a healthy heart. The implications of these findings suggest that the VP.S ENCORE® could introduce a new paradigm in the field of organ preservation, especially for marginal hearts.

Single center utilization and post-transplant outcomes of thoracoabdominal normothermic regional perfusion deceased cardiac donor organs

INTRODUCTION

Thoracoabdominal normothermic regional perfusion (TA-NRP) following cardiac death is an emerging multivisceral organ procurement technique. Recent national studies on outcomes of presumptive TA-NRP-procured organs are limited by potential misclassification since TA-NRP is not differentiated from donation after cardiac death (DCD) in registry data.

METHODS

We studied 22 donors whose designees consented to TA-NRP and organ procurement performed at our institution between January 20, 2020 and July 3, 2022. We identified these donors in SRTR to describe organ utilization and recipient outcomes and compared them to recipients of traditional DCD (tDCD) and donation after brain death (DBD) organs during the same timeframe.

RESULTS

All 22 donors progressed to cardiac arrest and underwent TA-NRP followed by heart, lung, kidney, and/or liver procurement. Median donor age was 41 years, 55% had anoxic brain injury, 45% were hypertensive, 0% were diabetic, and median kidney donor profile index was 40%. TA-NRP utilization was high across all organ types (88%-100%), with a higher percentage of kidneys procured via TA-NRP compared to tDCD (88% vs. 72%, p = .02). Recipient and graft survival ranged from 89% to 100% and were comparable to tDCD and DBD recipients (p ≥ .2). Delayed graft function was lower for kidneys procured from TA-NRP compared to tDCD donors (27% vs. 44%, p = .045).

CONCLUSION

Procurement from TA-NRP donors yielded high organ utilization, with outcomes comparable to tDCD and DBD recipients across organ types. Further large-scale study of TA-NRP donors, facilitated by its capture in the national registry, will be critical to fully understand its impact as an organ procurement technique.

Donor and recipient risk factors for the development of primary graft dysfunction following lung transplantation

Primary Graft Dysfunction (PGD) is a major cause of both short-term and long-term morbidity and mortality following lung transplantation. Various donor, recipient, and technical risk factors have been previously identified as being associated with the development of PGD. Here, we present a comprehensive review of the current literature as it pertains to PGD following lung transplantation, as well as discussing current strategies to mitigate PGD and future directions. We will pay special attention to recent advances in lung transplantation such as ex-vivo lung perfusion, thoracoabdominal normothermic regional perfusion, and up-to-date literature published in the interim since the 2016 ISHLT consensus statement on PGD and the COVID-19 pandemic.

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.

Thoracic organ machine perfusion: A review of concepts with a focus on reconditioning therapies

Thoracic organ transplantation, including lung, heart, and heart-lung transplants are highly regarded as gold standard treatments for patients suffering from heart failure or chronic end stage lung conditions. The relatively high prevalence of conditions necessitating thoracic organ transplants combined with the lack of available organs has resulted in many either dying or becoming too ill to receive a transplant while on the waiting list. There is a dire need to increase both the number of organs available and the utilization of such organs. Improved preservation techniques beyond static storage have shown great potential to lengthen the current period of viability of thoracic organs while outside the body, promising better utilization rates, increased donation distance, and improved matching of donors to recipients. Ex-situ organ perfusion (ESOP) can also make some novel therapeutic strategies viable, and the combination of the ESOP platform with such reconditioning therapies endeavors to better improve functional preservation of organs in addition to making more organs viable for transplantation. Given the abundance of clinical and pre-clinical studies surrounding reconditioning of thoracic organs in combination with ESOP, we summarize in this review important concepts and research regarding thoracic organ machine perfusion in combination with reconditioning therapies.