Heart transplant outcomes in patients with mechanical circulatory support: cold storage versus normothermic perfusion organ preservation

Single-center experience of extended brain-death donor heart preservation with the organ care system

BACKGROUND

The Organ Care System (OCS) (Transmedics, Andover, MA) reduces cold ischemic time of donor hearts by producing a normothermic beating state during ex vivo perfusion, enabling extended ex situ intervals, which potentially increases donor pool. We aimed to compare outcomes in utilization of OCS and conventional cold storage technique.

METHODS

Consecutive heart transplants following brain death at our institution between May 2022 and July 2023 were analyzed. Recipients were divided into those receiving hearts preserved with OCS [N = 15] and those with conventional cold storage (Control, N = 27), with OCS utilization when anticipated ischemic time was more than 4 h. Pre-transplant characteristics and transplant outcomes were compared.

RESULTS

OCS utilization allowed a significant increase in distance traveled for heart retrieval (OCS, 624 ± 269 vs. Control, 153 ± 128 miles, p < 0.001), with longer mean total preservation times (6.2 ± 1.1 vs 2.6 ± 0.6 h, p < 0.001). All but one patient displayed a general decrease or plateau in lactate throughout perfusion time by OCS. Both groups experienced similar rates of severe primary graft dysfunction (OCS, 6.7% [N = 1] vs. Control, 11.1% [N = 3], p = 0.63), with 100% in-hospital survival in the OCS group compared to 96.3% in the Control group (p = 0.34). Kaplan-Meier survival analysis showed that estimated one-year survival were comparable (OCS, 93.3 ± 6.4% vs. Control, 88.9 ± 6.0%, p = 0.61).

CONCLUSION

With a mean preservation time of around 6 h and distance covered of over 600 miles, our results using OCS indicate a potential to safely increase the quantity and viability of accessible organs, thus broadening the donor pool without negatively affecting outcomes.

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.

Impact of machine perfusion on transplant infectious diseases: New challenges and opportunities

Preservation techniques that maintain the viability of an organ graft between retrieval from the donor and implantation into the recipient remain a critical aspect of solid organ transplantation. While traditionally preservation is accomplished with static cold storage, advances in ex vivo dynamic machine perfusion, both hypothermic and normothermic, have allowed for prolongation of organ viability and recovery of marginal organs effectively increasing the usable donor pool. However, the use of these novel machine perfusion technologies likely exposes the recipient to additional infectious risk either through clonal expansion of pathogens derived during organ recovery or de novo exogenous acquisition of pathogens while the organ remains on the machine perfusion circuit. There is a paucity of high-quality studies that have attempted to quantify infection risk, although it appears that prolonging the time on the machine perfusion circuit and normothermic parameters increases the risk of infection. Conversely, the use of ex vivo machine perfusion unlocks new opportunities to detect and treat donor-derived infections before implantation into the recipient. This review seeks to reveal how the use of ex vivo machine perfusion strategies may augment the risk of infection in the organ recipient as well as outline ways that this technology could be leveraged to enhance our ability to manage donor-derived infections.

Ex vivo heart perfusion: an updated systematic review

Due to the discrepancy between patients awaiting a heart transplant and the availability of donor hearts, strategies to expand the donor pool and improve the transplant's success are crucial. This review aims to summarize current knowledge on the ex vivo heart preservation (EVHP) experience as an alternative to standard cold static storage (CSS). EVHP techniques can improve the preservation of the donor's heart before transplantation and allow for pre-transplant organ evaluation.

Introduction of ex vivo perfusion of extended-criteria donor hearts in a single center in Asia

The shortage of organs for heart transplantation has created a need to explore the use of extended-criteria organs. We report the preliminary use of normothermic TransMedics Organ Care System-an ex vivo approach to preserve extended-criteria brain-dead donor hearts. This System maintains a normal temperature, provides continuous perfusion and oxygenation, reduces ischemic time, and enables additional viability assessment options. In a retrospective single-centre study conducted from April 2020 to March 2023, four extended criteria brain-dead donor hearts were perfused and monitored using the Organ Care System. Suitability for transplantation was assessed based on stable or decreasing lactate levels, along with appropriate perfusion parameters. The Organ Care for use of the Organ Care System were coronary artery disease, left ventricular hypertrophy, high-dose inotrope use in the donor, a downtime exceeding 20 min, and a left ventricular ejection fraction of 40-50%. Three out of the four donor hearts were transplanted, while one was discarded due to rising lactate concentration. The three recipients had a higher surgical risk profile for heart transplant. All showed normal cardiac function and no primary graft dysfunction postoperatively. At 2-3 years post-transplant, all recipients have a ventricular function of > 60%, with only one showing evidence of mild rejection. The Organ Care System enables the successful transplantation of marginal donor organs in high-risk recipients, showcasing the feasibility of recruiting donors with extended criteria. This technique is safe and promising, expanding the donor pool and addressing the organ shortage in heart transplantation in Hong Kong.

Short-term outcomes after heart transplantation using donor hearts preserved with ex vivo perfusion

The standard Conventional Cold Storage (CCS) during heart transplantation procurement is associated with time-dependent ischemic injury to the graft, which is a significant independent risk factor for post-transplant early morbidity and mortality - especially when cold ischemic time exceeds four hours. Since 2018, Rigshospitalet (Copenhagen, Denmark) has been utilising ex vivo perfusion (Organ Care System, OCS) in selected cases. The objective of this study was to compare the short-term clinical outcomes of patients transplanted with OCS compared to CCS. Methods: This retrospective single-centre study was based on consecutive patients undergoing a heart transplant between January 2018 and April 2021. Patients were selected for the OCS group when the cold ischemic time was expected to exceed four hours. The primary outcome measure was six-month event-free survival. Results: In total, 48 patients were included in the study; nine were transplanted with an OCS heart. The two groups had no significant differences in baseline characteristics. Six-month event-free survival was 77.8% [95% CI: 54.9-100%] in the OCS group and 79.5% [95% CI: 67.8-93.2%] in the CCS group (p = 0.91). While the OCS group had a median out-of-body time that was 183 min longer (p < 0.0001), the cold ischemic time was reduced by 51 min (p = 0.007). Conclusion: In a Scandinavian setting, our data confirms that utilising OCS in heart procurement allows for a longer out-of-body time and a reduced cold ischemic time without negatively affecting safety or early post-transplant outcomes.

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.

Heart Transplantation in High-Risk Recipients Employing Donor Marginal Grafts Preserved With Ex-Vivo Perfusion

Extending selection criteria to face donor organ shortage in heart transplantation (HTx) may increase the risk of mortality. Ex-vivo normothermic perfusion (EVP) limits ischemic time allowing assessment of graft function. We investigated the outcome of HTx in 80 high-risk recipients transplanted with marginal donor and EVP-preserved grafts, from 2016 to 2021. The recipients median age was 57 years (range, 13-75), with chronic renal failure in 61%, impaired liver function in 11% and previous cardiac surgery in 90%; 80% were mechanically supported. Median RADIAL score was 3. Mean graft ischemic time was 118 ± 25 min, "out-of-body" time 420 ± 66 min and median cardiopulmonary bypass (CPB) time 228 min (126-416). In-hospital mortality was 11% and ≥moderate primary graft dysfunction 16%. At univariable analysis, CPB time and high central venous pressure were risk factors for mortality. Actuarial survival at 1 and 3 years was 83% ± 4%, and 72% ± 7%, with a median follow-up of 16 months (range 2-43). Recipient and donor ages, pre-HTx extracorporeal life support and intra-aortic balloon pump were risk factors for late mortality. In conclusion, the use of EVP allows extension of the graft pool by recruitment of marginal donors to successfully perform HTx even in high-risk recipients.

The Year in Cardiothoracic Transplant Anesthesia: Selected Highlights From 2021 Part II: Cardiac Transplantation

This article spotlights the research highlights of this year that specifically pertain to the specialty of anesthesia for heart transplantation. This includes the research on recent developments in the selection and optimization of donors and recipients, including the use of donation after cardiorespiratory death and extended criteria donors, the use of mechanical circulatory support and nonmechanical circulatory support as bridges to transplantation, the effect of COVID-19 on heart transplantation candidates and recipients, and new advances in the perioperative management of these patients, including the use of echocardiography and postoperative outcomes, focusing on renal and cerebral outcomes.

Pre-Treatment of Transplant Donors with Hydrogen Sulfide to Protect against Warm and Cold Ischemia-Reperfusion Injury in Kidney and Other Transplantable Solid Organs

Ischemia-reperfusion injury (IRI), a pathological condition resulting from prolonged cessation and subsequent restoration of blood flow to a tissue, is an inevitable consequence of solid organ transplantation. Current organ preservation strategies, such as static cold storage (SCS), are aimed at reducing IRI. However, prolonged SCS exacerbates IRI. Recent research has examined pre-treatment approaches to more effectively attenuate IRI. Hydrogen sulfide (H₂S), the third established member of a family of gaseous signaling molecules, has been shown to target the pathophysiology of IRI and thus appears to be a viable candidate that can overcome the transplant surgeon's enemy. This review discusses pre-treatment of renal grafts and other transplantable organs with H₂S to mitigate transplantation-induced IRI in animal models of transplantation. In addition, ethical principles of pre-treatment and potential applications of H₂S pre-treatment in the prevention of other IRI-associated conditions are discussed.

Expanding Donor Heart Utilization Through Machine Perfusion Technologies

Purpose of Review

Recent advances in donor heart preservation have allowed the utilization of hearts that would typically be discarded due to prolonged ischemic times or donation via the circulatory death pathway. This review will discuss recent advances in donor heart preservation including optimization of machine perfusion technologies and future strategies of potential benefit for the donor heart and transplant outcomes.

Recent Findings

Improvements in organ preservation strategies have enabled retrieval of donor hearts that were not ideal for static cold storage. Machine perfusion (normothermic and hypothermic) and normothermic regional perfusion have ultimately expanded the donor pool for adult heart transplantation. Xenotransplantation has also incorporated machine perfusion for porcine donor heart preservation.

Summary

Traditional static cold storage is feasible for non-complex donors and transplants. Machine perfusion has enabled increased donor heart utilization however optimal preservation strategies are dependent on the donor criteria, predicted ischemic times and surgical complexity.

Strategies for Expanding Donors Pool in Heart Transplantation

Heart transplant remains the criterion standard treatment for patients in end-stage heart failure. Improvement in the post-heart transplant outcomes in the last decade has contributed to increased demand for organs. Worldwide each year, more than 5000 heart transplants are performed and 50,000 people become candidates for heart transplant. In the last 50 years, there have been several attempts to expand donor criteria to increase the donor pool. Despite making hepatitis C virus, opioid overdose death, old age allowable and changing the allocation system, the gap between supply and demand is widening and unfortunately, thousands die every year waiting due to the critical shortage of organs. New technologies for heart donation after circulatory death have emerged, particularly normothermic regional organ perfusion and ex-vivo heart perfusion using organ care systems. However, these technologies still do not fill the gap. Continuous advancements in areas such as regenerative medicine and xenotransplantation, among others, are needed to overcome the shortage of heart donors for heart transplantation.

Normothermic Ex Situ Heart Perfusion With the Organ Care System for Cardiac Transplantation: A Meta-analysis

BACKGROUND

Heart transplantation (HTx) is, at present, the most effective therapy for end-stage heart failure patients; however, the number of patients on the waiting list is rising globally, further increasing the gap between demand and supply of donors for HTx. First studies using the Organ Care System (OCS) for normothermic machine perfusion show promising results yet are limited in sample size. This article presents a meta-analysis of heart donation either after brain death (OCS-DBD) or circulatory death (OCS-DCD) on using OCS versus static cold storage used for HTx.

METHODS

A systematic literature search was performed for articles discussing the use of normothermic ex situ heart perfusion in adult patients. Thirty-day survival outcomes were pooled, and odds ratios were calculated using random-effects models. Long-term survival was visualized with Kaplan-Meier curves, hazard ratios were calculated and pooled using fixed-effects models, and secondary outcomes were analyzed.

RESULTS

A total of 12 studies were included, with 741 patients undergoing HTx, of which 260 with the OCS (173 DBD and 87 DCD). No differences were found between the 3 groups for early and late survival outcomes or for secondary outcomes.

CONCLUSIONS

OCS outcomes, for both DBD and DCD hearts, appeared similar as for static cold storage. Therefore, OCS is a safe and effective technique to enlarge the cardiac donor pool in both DBD and DCD, with additional benefits for long-distance transport and surgically complex procedures.

Ex vivo perfusion of the donor heart: Preliminary experience in high-risk transplantations

BACKGROUND

The number of heart transplantations (HTs) has decreased in France since 2017 (-5%/year) despite a stable rate of patients referred on the waiting list. Ex vivo heart perfusion (EVHP) is an innovative approach for organ preservation, reducing graft ischaemic time and facilitating continuous organ monitoring before transplantation.

AIM

To report our preliminary experience of seven donor hearts preserved with EVHP, including the first heart resuscitated after circulatory-determined death in France.

METHODS

Seven hearts were procured from donation after brain death (DBD) for HT or donation after circulatory-determined death (DCD) for research purposes (Protocol PFS20-004, Agence de la Biomédecine, La Plaine Saint-Denis, France). All grafts were preserved using the Organ Care System® (TransMedics Inc., Andover, MA, USA) for normothermic EVHP. Perfusion parameters were adjusted to achieve stable or decreasing arterial lactate trend consistent with suitability for organ transplantation.

RESULTS

Indications for EVHP were assessment of a marginal graft in four cases, prolonged preservation in two cases (anticipated duration for retrieval of recipient's heart>3hours) and resuscitation after circulatory-determined death in one case. Median duration of EVHP was 270 (interquartile range 216-343) minutes. five were transplanted, with a median ex situ preservation time (ischaemic time+EVHP time) of 334 (interquartile range 326-444) minutes. The two other grafts were discarded for HT. Three recipients had extracorporeal life support after HT, and presented complete cardiac recovery within a week after HT. One patient died at day 11 because of septic shock. The 3-month survival rate was 75% among recipients. Three months after HT, the left ventricular ejection fraction was>60% in all cases.

CONCLUSIONS

EVHP enabled safe prolonged preservation and assessment of marginal grafts. This approach provides an opportunity to expand the donor pool by resuscitating grafts from donors with extended criteria, including controlled DCD.