Ex Situ Heart Perfusion Research Articles

Myocardial oxygen handling and metabolic function of ex-situ perfused human hearts from circulatory death donors

BackgroundThis study investigated oxygen handling of human hearts donated after circulatory death (DCD) on normothermic ex-situ heart perfusion (ESHP) and evaluated oxygen handling markers as adjuncts to cardiac viability assessment. MethodsThis single-center retrospective study included human DCD heart transplantation procedures using ESHP. Lactate concentrations, blood gas, myocardial oxygen consumption (MVO2), delivery (MDO2) and extraction (MEO2), coronary blood flow (CBF), coronary vascular resistance (CVR), and adenosine infusion were reported over time. Correlation between parameters was assessed, and statistical testing compared patients who did and did not require extracorporeal membrane oxygenation (ECMO) support after transplantation. ResultsLactate concentrations decreased during ESHP in all transplanted hearts (n=25) and increased in 1 rejected heart. Arterial PO2 was 75.2±2.9 kPa, with an arteriovenous ΔPO2 of 44.8±10.4 kPa. Oxygen saturation was 100% in most arterial and venous samples. Average MVO2 was 2.7±0.6 mL·min-1·100·g-1 myocardium, MDO2 98.5±20.4 mL·min-1, and MEO2 8.6±1.8%. Average CVR was 0.025±0.006 mmHg∙min∙mL-1∙100 g-1 and increased over time. ΔPO2 correlated strongly with MVO2 (R=0.797, p<0.001) and lactate trend (R=0.799, p<0.001) in transplanted hearts, without differences compared to the rejected heart with increasing lactate. Adenosine infusion on ESHP was significantly higher in patients requiring ECMO post-transplantation versus non-ECMO cases (11.7 (4.5-21.0) vs. 2.2 (1.5-6.7) mL·h-1, p=0.039). ConclusionsHearts on normothermic ESHP receive excessive MDO2, due to high PO2 and CBF, while the MVO2 is relatively low. Thus, CBF and PO2 can potentially be lowered. Furthermore, ΔPO2 could serve as additional marker of metabolic function under these hyperoxic circumstances. The adenosine infusion rate might predict post-transplantation ECMO requirement.

Circulating factors, in both donor and ex-vivo heart perfusion, correlate with heart recovery in a pig model of DCD

BackgroundHeart transplantation with donation after circulatory death and ex-situ heart perfusion offers excellent outcomes and increased transplantation rates. However, improved graft evaluation techniques are required to ensure effective utilization of grafts. Therefore, we investigated circulating factors, both in-situ and ex-situ, as potential biomarkers for cardiac graft quality. MethodsCirculatory death was simulated in anesthetized male pigs with warm ischemic durations of 0, 10, 20, or 30 min. Hearts were explanted and underwent ex-situ perfusion for 3h in an unloaded mode, followed by left ventricular loading for 1h, to evaluate cardiac recovery (outcomes). Multiple donor blood and ex-situ perfusate samples were used for biomarker evaluation with either standard biochemical techniques or nuclear magnetic resonance spectroscopy. ResultsCirculating adrenaline, both in the donor and at 10 min ex-situ heart perfusion, negatively correlated with cardiac recovery (p <0.05 for all). We identified several new potential biomarkers for cardiac graft quality that can be measured rapidly and simultaneously with nuclear magnetic resonance spectroscopy. At multiple timepoints during unloaded ex-situ heart perfusion, perfusate levels of acetone, betaine, creatine, creatinine, fumarate, hypoxanthine, lactate, pyruvate and succinate (p <0.05 for all) significantly correlated with outcomes; the optimal timepoint being 60 min. ConclusionsIn heart donation after circulatory death, circulating adrenaline levels are valuable for cardiac graft evaluation. Nuclear magnetic resonance spectroscopy is of particular interest, as it measures multiple metabolites in a short timeframe. Improved biomarkers may allow more precision and therefore better support clinical decisions about transplantation suitability.

Coronary Angiography During Ex-Situ Heart Perfusion in a Porcine Model.

Heart transplantation is the gold standard treatment for advanced heart failure. The procurement of extended criteria donors (ECD) increases due to the current organ shortage. Coronary angiography is recommended in ECD at risk for coronary artery disease but is not systematically performed. These hearts are, therefore, either declined for transplant or procured without screening for coronary artery disease. Coronary angiography during normothermic ex-situ heart perfusion (NESP) could be an interesting approach to enhance the rate of ECD procurement and to reduce the risk of primary graft failure in the absence of coronary angiography in ECD. The present protocol aims to provide material details along with optimal imaging views for coronary angiography during NESP. Reproducible angiographic views were observed, including one dedicated to the right coronary artery, two for the left anterior descending artery, two for the circumflex artery, and a spider view. Continuous lactate extraction was observed in all procedures with a final median concentration of 1.10 mmol/L (0.61-1.75 mmol/L) two hours after coronary angiography, consistent with myocardial viability. The median contrast agent volume used for ex-situ imaging of the isolated perfused heart was 48 mL (38-108 mL). This protocol was reproducible for coronary artery imaging and did not impair myocardial viability during NESP.

Optimizing Resuscitation of the Donation after Circulatory Death Heart by Mitochondrial Protection in a Female Porcine Model.

Due to the shortage of donor organs, an increasing number of transplant organs are harvested after circulatory arrest (donation after circulatory death [DCD]). Using a translational porcine model of DCD, this study developed and evaluated a protocol based on cardioprotection by multidrug postconditioning to optimize resuscitation of DCD hearts during ex situ heart perfusion (ESHP). Hearts of female pigs (45.0 ± 4.5 kg) were procured following a clinically identical DCD protocol, consisting of the termination of ventilator support and confirmation of circulatory arrest, followed by a 15-min standoff period. DCD hearts were randomly allocated to ESHP (38.4°C) in the absence (untreated, N = 5) or presence (treated, N = 5) of a postconditioning treatment added to the perfusate, consisting of Intralipid (1%), sevoflurane (2% v/v), and remifentanil (3 nM). All hearts were perfused with blood and Krebs-Henseleit solution (1:1) for 60 min in Langendorff mode and for an additional 300 min in working mode for a total perfusion time of 6 h. Oxidative capacity and detailed left ventricular mechanical function under an increasing workload (left atrial pressure, 6 to 12 mmHg) were assessed hourly. Left ventricular tissue was snap-frozen at the end of ESHP and used for molecular analyses. Left ventricular inotropy (LVdP/dtmax) did not decline over time in treated DCD hearts and was significantly higher at the end of the protocol as compared with untreated DCD hearts (ΔLVdP/dtmax = 440 mmHg/s; P = 0.009). Treated DCD hearts exhibited persistently higher left ventricular stroke work index during the 6-h period of ESHP, whereas untreated DCD hearts displayed a significant decline (change in left ventricular stroke work index = -3.10 ml · mmHg/g; P(time within untreated group) < 0.001). Treated DCD hearts displayed higher metabolic activity as measured by oxygen consumption (ΔO2 = 3.11 ml O2 · min-1 · 100 g-1; P = 0.004) and released lower amounts of cell-free mitochondrial DNA into the perfusate, a marker of potential graft dysfunction. Treated hearts also used fatty acids from Intralipid as an energy source, whereas untreated DCD hearts showed glyceroneogenesis with triglyceride accumulation and depletion of tricarboxylic acid cycle intermediates; reduced mitochondrial complex I, II, and III activities with accumulation of mitochondrial NADH, and signs of ultrastructural damage. A translationally relevant protective ESHP protocol consisting of treatment with Intralipid, sevoflurane, and remifentanil markedly accelerated functional recovery and improved viability of DCD hearts.

The Effects of Oxygen-Derived Free-Radical Scavengers During Normothermic Ex-Situ Heart Perfusion.

Oxidative stress occurs during ex-situ heart perfusion (ESHP) and may negatively affect functional preservation of the heart. We sought to assess the status of key antioxidant enzymes during ESHP, and the effects of augmenting these antioxidants on the attenuation of oxidative stress and improvement of myocardial and endothelial preservation in ESHP. Porcine hearts were perfused for 6 hours with oxygen-derived free-radical scavengers polyethylene glycol (PEG)-catalase or PEG-superoxide dismutase (SOD) or with naive perfusate (control). The oxidative stress-related modifications were determined in the myocardium and coronary vasculature, and contractile function, injury, and endothelial integrity were compared between the groups. The activity of key antioxidant enzymes decreased and adding catalase and SOD restored the enzyme activity. Cardiac function and endothelial integrity were preserved better with restored catalase activity. Catalase and SOD both decreased myocardial injury and catalase reduced ROS production and oxidative modification of proteins in the myocardium and coronary vasculature. The activity of antioxidant enzymes decrease in ESHP. Catalase may improve the preservation of cardiac function and endothelial integrity during ESHP. While catalase and SOD may both exert cardioprotective effects, unbalanced SOD and catalase activity may paradoxically increase the production of reactive species during ESHP.

Ex Situ Left Ventricular Pressure-Volume Loop Analyses for Donor Hearts: Proof of Concept in an Ovine Experimental Model.

Ex situ heart perfusion (ESHP) has emerged as an important strategy to preserve donation after brain death (DBD) and donation after circulatory death (DCD) donor hearts. Clinically, both DBD and DCD hearts are successfully preserved using ESHP. Viability assessment is currently based on biochemical values, while a reliable method for graft function assessment in a physiologic working mode is unavailable. As functional assessment during ESHP has demonstrated the highest predictive value of outcome post-transplantation, this is an important area for improvement. In this study, a novel method for ex situ assessment of left ventricular function with pressure-volume loop analyses is evaluated. Ovine hearts were functionally evaluated during normothermic ESHP with the novel pressure-volume loop system. This system provides an afterload and adjustable preload to the left ventricle. By increasing the preload and measuring end-systolic elastance, the system could successfully assess the left ventricular function. End-systolic elastance at 60min and 120min was 2.8 ± 1.8mmHg/mL and 2.7 ± 0.7mmHg/mL, respectively. In this study we show a novel method for functional graft assessment with ex situ pressure-loop analyses during ESHP. When further validated, this method for pressure-volume assessments, could be used for better graft selection in both DBD and DCD donor hearts.

The Impact of Ex Situ Heart Perfusion in Pediatric Transplantation: An Analysis of the OPTN Database.

Ex situ heart perfusion (ESHP) has increased the pool of donors in adults. However, this is not true in pediatrics due to lack of devices. Therefore, we sought to understand organ refusal in pediatrics and estimate donor heart usage with ESHP. Donor hearts offered to pediatrics were identified from the Organ Procurement and Transplantation Network Database (2000-2019). A linear regression model was built to predict average travel speed, and the extended maximum permitted distance with ESHP was calculated. This extended distance was compared with the policy for maximum travel distance. There were 33,708 donor offers (n = 10,807 hearts) to pediatric programs [24.1% (n = 2,604) transplanted]. Six percent of the offers (n = 1,832) (n = 771 hearts) were turned down due to distance, with 676 of the hearts never transplanted. Based on the modeling and using an ESHP time of 5.5 hours, 84% (n = 570/676) of hearts turned down due to distance could be utilized by pediatric programs. This proportion increased to 100% with 10 hours of support time. By addressing prolonged ischemic time due to distance, ESHP has the potential to increase the number of donors utilized in pediatric candidates. Although no device exists for pediatrics, this analysis lends support to the importance of developing this technology.

CARD15: Parent Perceptions of Ex-Situ Heart Perfusion

Introduction: Pediatric heart transplant (HTx) candidates continue to have high waitlist mortality due to donor availability. Ex-situ heart perfusion (ESHP) has the potential to increase the donor pool, yet has been used sparingly in pediatrics due to size restrictions of the current technology. Previous work has shown that for ESHP to be accepted by pediatric healthcare providers (HCP), the risks to the donor heart and the costs need to be better understood and that rigorous research and implementation oversight is essential. Perspectives from caregivers about ESHP has not been assessed and forms the basis of this qualitative study. Methods: Virtual, semi-structured interviews were conducted with caregivers of children who are awaiting or received HTx. Data were analyzed using qualitative content analysis. Results: Twelve participants from 2 countries participated in this study. Awareness about and understanding of ESHP varied among participants from complete unawareness to understanding specifics. Independent of their awareness, all purported that it was an excellent and innovative technology, and supported ESHP implementation in pediatrics. No ethical issues or concerns about the use were identified that differed from other medical technologies, although participants did state that understanding the length of time the heart can be mounted and risks to donor and recipient were important. Participants expressed various views on how to approach parents regarding ESHP. Overall, most participants stated that the consent processes should be like other medical procedure and some commented that deferred or waived consent would be acceptable, especially if ESHP became part of routine clinical practice. Even if consent was waived, participants agreed that the use of ESHP should be disclosed just like other information is disclosed about the donor heart and that introduction of ESHP should come early in the HTx journey. Conclusion: Families are supportive of the use of ESHP. Like HCPs, they endorse the need to understand the potential risks and that information should be presented early in the transplant process.

CARD27: Morphologic and functional assessment of beating heart in normothermic ex-situ preservation

Background: Heart transplantation remains the treatment of choice for patients experiencing end-stage heart failure. The emergence of cardiac ex situ machine perfusion not only facilitates the use of donor heart through the avoidance of potentially damaging ischemia during graft storage, it also opens new horizons for more sensitive monitoring of graft quality in the transplant field, and morphologic-functional assessment. Methods: Twenty-five domestic adult pigs, weighing 93.1±13.1kg were selected for this study. Until cardiectomy, all pigs received Principles of Laboratory Animal Care. The pig heart were cannulated, and then connected to the Portable System for Normothermic Ex-Situ HeartPreservation (our made). In the Heart Preservation System (HPS), oxygenated blood is perfused by a centrifugal pump into the aorta, perfusing the coronary arteries. After the end of experiment, (6-14 hour) pig heart was arrested with normothermic blood cardioplegia and disconnected. The pig isolated heart was conditioned with Levosimendan while in the system and hemofiltration was applied in the HPS in order to protect and improve donor heart function. Ex-Situ Heart Perfusion process was accompanied with morphologic-functional assessment such as echocardiography, contrast-enhanced magnetic resonance, thermodilution technique and biochemistry. Results: Mean (SD) ischemic time was 19.2 (±3.3) min. Mean ex vivo perfusion time was 560 (±143) min. Time of sinus rhythm restoration was 2.3 (5.7) min. All isolated hearts had stable perfusion, biochemical, as well as myocardial functional parameters measured by echocardiography and thermodilution technique, and histological characteristics in the perfusion system. MRI structural images showed no infiltrates alterations in myocardium. Mean venous lactate trend are with normal levels at the end of perfusion 1.6 (±0.6). Conclusion: Normothermic Ex-Situ Heart Perfusion provides near to physiologic, reproducible approach to sustain the isolated heart for long period of time. Multiparametric assessment of organ morphology and function is feasible in Ex-Situ Heart Perfusion, and may improve organ assessment, leading to a better selection for transplant.Figure 1. Simplified schema of the experimental design and protocol.

Mitochondrial transplantation preserves myocardial function and viability in pediatric and neonatal pig hearts donated after circulatory death

ObjectiveMitochondrial transplantation has been shown to preserve myocardial function and viability in adult porcine hearts donated after circulatory death (DCD) . Herein, we investigate the efficacy of mitochondrial transplantation for the preservation of myocardial function and viability in neonatal and pediatric porcine DCD heart donation. MethodsCirculatory death was induced in neonatal and pediatric Yorkshire pigs by cessation of mechanical ventilation. Hearts underwent 20 or 36 minutes of warm ischemia time (WIT), 10 minutes of cold cardioplegic arrest, and then were harvested for ex situ heart perfusion (ESHP). Following 15 minutes of ESHP, hearts received either vehicle (VEH) or vehicle containing isolated autologous mitochondria (MITO). A sham nonischemic group (SHAM) did not undergo WIT, mimicking donation after brain death heart procurement. Hearts underwent 2 hours each of unloaded and loaded ESHP perfusion. ResultsFollowing 4 hours of ESHP perfusion, left ventricle developed pressure, dP/dt max, and fractional shortening were significantly decreased (P < .001) in DCD hearts receiving VEH compared with SHAM hearts. In contrast, DCD hearts receiving MITO exhibited significantly preserved left ventricle developed pressure, dP/dt max, and fractional shortening (P < .001 each vs VEH, not significant vs SHAM). Infarct size was significantly decreased in DCD hearts receiving MITO as compared with VEH (P < .001). Pediatric DCD hearts subjected to extended WIT demonstrated significantly preserved fractional shortening and significantly decreased infarct size with MITO (P < .01 each vs VEH). ConclusionsMitochondrial transplantation in neonatal and pediatric pig DCD heart donation significantly enhances the preservation of myocardial function and viability and mitigates against damage secondary to extended WIT.

Ex situ heart perfusion for optimization of pediatric donor organ utilization: Attitudes and perceptions.

Children with heart failure have the highest mortality while awaiting transplantation. Ex situ heart perfusion (ESHP), a method for continuous perfusion of the donor heart, has the potential to improve access to transplant by increasing travel distance between donor and recipient. An adult ESHP device is currently available, but as of yet there is no pediatric device. The aim of this study was to evaluate current knowledge of ESHP among pediatric heart transplant practitioners, define potential barriers, and identify uses of this novel technology. An electronic survey was developed to assess perspectives of international pediatric heart transplant stakeholders (n=68) on ESHP. Select questions were analyzed to evaluate for associations between groups of respondents and patterns of response. Most respondents were familiar but <10% had clinically utilized ESHP. There was optimism that ESHP could decrease waitlist mortality. Respondents were concerned about potential device malfunction and lack of long-term outcomes. There were no differences found in terms of ESHP familiarity among age groups, practitioner center volume, country of work, or discipline. ESHP has the potential to expand the pediatric heart donor pool and decrease waitlist mortality. More education on outcomes and risks/benefits is needed in order to promote widespread adoption.

Metabolomic profiling of cardiac allografts after controlled circulatory death

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. 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. 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. 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.

The Impact of Ex Situ Heart Perfusion in Pediatric Transplantation: An Analysis of the United Network for Organ Sharing Registry.

Ex situ heart perfusion (ESHP) has increased the pool of donors in adults. However, this is not true in pediatrics due to lack of devices. Therefore, we sought to understand organ refusal in pediatrics and estimate donor heart usage with ESHP. Donor hearts offered to pediatrics were identified from the United Network for Organ Sharing (UNOS) Database (2000-2019). A linear regression model was built to predict average travel speed, and the extended maximum permitted distance with ESHP was calculated. This extended distance was compared with the policy for maximum travel distance. There were 33,708 donor offers (n = 10,807 hearts) to pediatric programs (24.1% [n = 2,604] transplanted). Six percent of the offers (n = 1,832) (n = 771 hearts) were turned down due to distance, with 676 of the hearts never transplanted. Based on the modeling and using an ESHP time of 5.5 hours, 84% (n = 570/676) of hearts turned down as distance could be utilized by pediatric programs. This proportion increased to 100% with 10 hours of support time. By addressing prolonged ischemic time due to distance, ESHP has the potential to increase the number of donors utilized in pediatric candidates. While no device exists for pediatrics, this analysis lends support to the importance of developing this technology.

Validation of the slaughterhouse porcine heart model for ex-situ heart perfusion studies.

To validate slaughterhouse hearts for ex-situ heart perfusion studies, we compared cold oxygenated machine perfusion in less expensive porcine slaughterhouse hearts (N = 7) to porcine hearts that are harvested following the golden standard in laboratory animals (N = 6). All hearts received modified St Thomas 2 crystalloid cardioplegia prior to 4hours of cold oxygenated machine perfusion. Hearts were perfused with homemade modified Steen heart solution with a perfusion pressure of 20-25mmHg to achieve a coronary flow between 100-200mL/min. Reperfusion and testing was performed for 4 hours on a normothermic, oxygenated diluted whole blood loaded heart model. Survival was defined by a cardiac output above 3L with a mean aortic pressure above 60mmHg. Both groups showed 100% functional survival, with laboratory hearts displaying superior cardiac function. Both groups showed similar decline in function over time. We conclude that the slaughterhouse heart can be used as an alternative to laboratory hearts and provides a cost-effective method for future ex-situ heart perfusion studies.

Oxidative stress and related metabolic alterations are induced in ex situ perfusion of donated hearts regardless of the ventricular load or leukocyte depletion

We sought to determine the role of donor blood circulating leukocytes in mediating oxidative stress and inflammation during normothermic ex situ heart perfusion (ESHP). Normothermic ESHP allows preservation of donated heart in a perfused, dynamic state, preventing ischemia. However, the cardiac function declines during ESHP, limiting the potential of this method for improvement of the outcomes of transplantation and expanding the donor pool. Extracorporeal circulation-related oxidative stress plays a critical role in the functional decline of the donor heart. Hearts from domestic pigs were perfused in working mode (WM, whole blood-based or leukocyte-depleted blood-based perfusate) or nonworking mode. Markers of oxidative stress and responsive glucose anabolic pathways were induced in the myocardium regardless of left ventricular load. Myocardial function during ESHP as well as cardioprotective mechanisms were preserved better in WM. Leukocyte-depleted perfusate did not attenuate tissue oxidative stress or perfusate proinflammatory cytokines and did not improve functional preservation. Although ESHP is associated with ongoing oxidative stress and metabolic alteration in the myocardium, preserved cardioprotective mechanisms in WM may exert beneficial effects. Leukocyte depletion of the perfusate may not attenuate inflammation and oxidative stress effectively or improve the functional preservation of the heart during ESHP.

Lactate during ex-situ heart perfusion does not predict the requirement for mechanical circulatory support following donation after circulatory death (DCD) heart transplants.

Ex-situ heart perfusion (ESHP) is commonly used for the reanimation and preservation of hearts following donation after circulatory determined death (DCD). The only commercially available existing ESHP device promotes perfusate lactate levels for assessment of heart viability. The reliability of this marker is yet to be confirmed for DCD heart transplantation. This is a single center, retrospective study examining DCD heart transplants from March 1, 2015 to June 30, 2020. Recipients were divided into 2 groups dependent upon their requirement for or absence of mechanical circulatory support post-transplant. Lactate profiles obtained during ESHP were analyzed. Hearts were procured using the direct procurement and perfusion (DPP) method. Fifty-one DCD heart transplant recipients were studied, of which 20 (39%) were dependent on mechanical circulatory support (MCS) following transplantation, (2% Ventricular Assist Device (VAD), 16% Extra Corporeal Membrane Oxygenation (ECMO) and 21% Intra-aortic balloon pumps (IABP). There was no difference in arterial lactate profiles on ESHP at any time point for those dependent upon MCS support (MCS) and those that were not (no MCS) post-transplant. After 3 hours of ESHP, the arterial lactate was >5mmol/L in 80% upon MCS vs 62% no MCS, p=.30. There was also no difference in ESHP rising arterial lactate concentrations, (15% MCS vs 13% non MCS, p=1.00). For DCD hearts transplants retrieved using the DPP technique, lactate profiles do not seem to be a reliable predictor of mechanical circulatory support requirement post-transplant.

Pediatric heart transplantation following donation after circulatory death, distant procurement, and ex-situ perfusion.

Limited availability of suitable donor hearts remains a challenge to pediatric heart transplantation, contributing to waitlist mortality. Controlled donation after circulatory death (DCD) has demonstrated success in adults. Early series of pediatric DCD heart transplantation using cold storage alone reported significant early mortality. We report a collaboration between 2 centers in the United Kingdom, combining expertise in adult DCD organ retrieval and pediatric transplantation. This retrospective series comprises 6 children (4 male, all >20 kg) undergoing DCD heart transplantation at Great Ormond Street Hospital between 1 February and 30 September 2020, following retrieval with direct procurement and perfusion using portable normothermic machine perfusion by the Royal Papworth Hospital service. Baseline characteristics and 1-year follow-up were compared to 9 children who underwent donation after brain death (DBD) transplants contemporaneously. Mean DCD donor age was 24.67 years and mean DCD recipient age was 13.83 years. Mean functional warm ischemic time was 28.5 minutes and ex-situ heart perfusion time was 280 minutes. Median ICU and hospital stay were 9 and 17 days, respectively. All children survived to 1-year post-transplant. Survival and ICU and hospital stay were similar between the DCD and DBD cohorts. Performing DCD transplants resulted in a 66.7% increase in transplants for children >20 kg at GOSH during the study. This series demonstrates that DCD heart transplant can be performed safely with excellent short-term survival in children. Although the cohort is small, there was no significant difference in major outcomes compared to a DBD cohort.

Dynamic Metabolic Changes During Prolonged Ex Situ Heart Perfusion Are Associated With Myocardial Functional Decline.

Ex situ heart perfusion (ESHP) was developed to preserve and evaluate donated hearts in a perfused beating state. However, myocardial function declines during ESHP, which limits the duration of perfusion and the potential to expand the donor pool. In this research, we combine a novel, minimally-invasive sampling approach with comparative global metabolite profiling to evaluate changes in the metabolomic patterns associated with declines in myocardial function during ESHP. Biocompatible solid-phase microextraction (SPME) microprobes serving as chemical biopsy were used to sample heart tissue and perfusate in a translational porcine ESHP model and a small cohort of clinical cases. In addition, six core-needle biopsies of the left ventricular wall were collected to compare the performance of our SPME sampling method against that of traditional tissue-collection. Our state-of-the-art metabolomics platform allowed us to identify a large number of significantly altered metabolites and lipid species that presented comparable profile of alterations to conventional biopsies. However, significant discrepancies in the pool of identified analytes using two sampling methods (SPME vs. biopsy) were also identified concerning mainly compounds susceptible to dynamic biotransformation and most likely being a result of low-invasive nature of SPME. Overall, our results revealed striking metabolic alterations during prolonged 8h-ESHP associated with uncontrolled inflammation not counterbalanced by resolution, endothelial injury, accelerated mitochondrial oxidative stress, the disruption of mitochondrial bioenergetics, and the accumulation of harmful lipid species. In conclusion, the combination of perfusion parameters and metabolomics can uncover various mechanisms of organ injury and recovery, which can help differentiate between donor hearts that are transplantable from those that should be discarded.

Facilitators and Barriers of Ex Situ Heart Perfusion (ESHP) in Pediatric Donation

Purpose Despite medical advances, pediatric heart transplant (HTx) candidates are at significant risk for morbidity and mortality. Ex Situ Heart Perfusion (ESHP) is a method for continuous perfusion of the donor heart, allowing for extended out-of-body time and functional assessment of the organ. Currently available devices are targeted to adults and have been used in the context of neurological and circulatory determination of death. Pediatric-specific devices are in development, but before adoption, knowledge of stakeholder attitudes towards ESHP is needed. The aim of this study was to explore pediatric HTx stakeholders’ understanding and perspectives of ESHP. Methods A virtual focus group study was conducted international pediatric HTx stakeholders. Data was analyzed using qualitative content analysis. Results There were 17 participants from 12 institutions representing 3 countries. Findings were organized under the topics of: general knowledge, indications, risks, adoption/barriers, and pediatric-specific considerations. Knowledge ranged from limited grasp of the technology to first-hand experience in clinical practice. Discussions encircled the current use of ESHP in adult-sized HTx candidates, and potential future uses in infants and young children. In all focus groups, it was discussed that risks need to be considered regarding ESHP itself, including the potential of damaging the donor heart, subjecting recipients to unquantified risks, and potential adverse impacts on pediatric HTx programs if poor outcomes occur. Concerns surrounding the material costs and human resources associated with ESHP were also discussed. While all discussions highlighted the need for pediatric ESHP devices, participants emphasized the need for rigorous research and implementation oversight of ESHP to navigate ethical issues, program administration, and support best practices in the context of technological innovation. Conclusion For stakeholders to become adopters of ESHP, they must understand the goals, benefits, and risks. This project represents the first step in the adoption of new technology, and the knowledge gained will form the basis for future education, clinical trial design, and rollout of pediatric ESHP technologies. Despite medical advances, pediatric heart transplant (HTx) candidates are at significant risk for morbidity and mortality. Ex Situ Heart Perfusion (ESHP) is a method for continuous perfusion of the donor heart, allowing for extended out-of-body time and functional assessment of the organ. Currently available devices are targeted to adults and have been used in the context of neurological and circulatory determination of death. Pediatric-specific devices are in development, but before adoption, knowledge of stakeholder attitudes towards ESHP is needed. The aim of this study was to explore pediatric HTx stakeholders’ understanding and perspectives of ESHP. A virtual focus group study was conducted international pediatric HTx stakeholders. Data was analyzed using qualitative content analysis. There were 17 participants from 12 institutions representing 3 countries. Findings were organized under the topics of: general knowledge, indications, risks, adoption/barriers, and pediatric-specific considerations. Knowledge ranged from limited grasp of the technology to first-hand experience in clinical practice. Discussions encircled the current use of ESHP in adult-sized HTx candidates, and potential future uses in infants and young children. In all focus groups, it was discussed that risks need to be considered regarding ESHP itself, including the potential of damaging the donor heart, subjecting recipients to unquantified risks, and potential adverse impacts on pediatric HTx programs if poor outcomes occur. Concerns surrounding the material costs and human resources associated with ESHP were also discussed. While all discussions highlighted the need for pediatric ESHP devices, participants emphasized the need for rigorous research and implementation oversight of ESHP to navigate ethical issues, program administration, and support best practices in the context of technological innovation. For stakeholders to become adopters of ESHP, they must understand the goals, benefits, and risks. This project represents the first step in the adoption of new technology, and the knowledge gained will form the basis for future education, clinical trial design, and rollout of pediatric ESHP technologies.

Metabolomic Profiling of Cardiac Allografts After Controlled Circulatory Death

<h3>Purpose</h3> Assessment of myocardial viability during ex situ heart perfusion (ESHP) is only based on lactate trends. Metabolomic profiling of hearts donated after circulatory death (DCD) was performed to investigate new biomarkers of myocardial viability during ESHP. <h3>Methods</h3> Eighteen piglets were randomly allocated in three groups (N=6/per group): donor hearts procured either after 15 minutes of warm ischemia (DCD group); after brain-stem death (BSD group); or without DCD nor BSD (Control group). Blood normothermic ESHP was then initiated for 240 minutes. Plasma and myocardial samples were procured respectively every 30 and 60 minutes, and analyzed by liquid chromatography coupled to high-resolution mass spectrometry. <h3>Results</h3> Median duration of agonal phase was 24 minutes [22-29] in DCD animals, including 15 minutes of functional warm ischemia. Mean coronary flow and mean aortic pressure during ESHP ranged from 720 to 740 mL/min, and from 68 to 73 mmHg respectively, without differences between groups (P=0.544 and P=0.203). At T0, arterial lactate was higher in DCD (7.0±0.9) than in BSD (1.1±0.2) and Control groups (2.0±0.8 mmol/L, P<0.01), and progressively decreased until T240. 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. Three different metabolomic profiles corresponding to DCD, BSD and Control groups were remarkable from T30 to T240, including 300 different metabolites in plasma and tissue samples. Marked nucleotide degradation was observed in DCD group compared to BSD and Control groups (P<0.01). Plasma levels of inosine and guanosine were significantly higher in DCD group and progressively decreased over the time to reach control level after 210 minutes of ESHP (Figure 1). <h3>Conclusion</h3> A specific metabolomic profile was observed in donor hearts exposed to warm ischemia. Considering plasma levels of inosine and guanosine, nucleotides could be relevant biomarkers for viability assessment of DCD hearts.