RESUMEN

BACKGROUND: Heart 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. METHODS: Circulatory 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. RESULTS: Circulating 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. CONCLUSIONS: In 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.

RESUMEN

The isolated heart perfusion model, a fundamental tool in cardiovascular research, has evolved significantly since its inception in the late 19th century. This review traces the development of the isolated heart model, from its early adaptations by pioneers such as Langendorff and Starling to modern advancements by researchers like Morgan and Neely. We discuss the various applications of the model in pharmacological testing, disease modeling, and educational settings, emphasizing its crucial role in understanding cardiac function and disease mechanisms. Recent technological enhancements, including high-resolution imaging, integration with bioengineering, and advanced genomic and proteomic analyses, have significantly broadened the capabilities of these models. Looking forward, we explore potential future developments such as the integration of precision medicine, stem cell research, and artificial intelligence, which promise to revolutionize the use of isolated heart perfusion models. This review highlights the model's crucial role in bridging experimental research and clinical applications.

RESUMEN

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 60 min and 120 min was 2.8 ± 1.8 mmHg/mL and 2.7 ± 0.7 mmHg/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.

Asunto(s)

RESUMEN

AIMS: Cardiac energy metabolism is perturbed in ischaemic heart failure and is characterized by a shift from mitochondrial oxidative metabolism to glycolysis. Notably, the failing heart relies more on ketones for energy than a healthy heart, an adaptive mechanism that improves the energy-starved status of the failing heart. However, whether this can be implemented therapeutically remains unknown. Therefore, our aim was to determine if increasing ketone delivery to the heart via a ketogenic diet can improve the outcomes of heart failure. METHODS AND RESULTS: C57BL/6J male mice underwent either a sham surgery or permanent left anterior descending coronary artery ligation surgery to induce heart failure. After 2 weeks, mice were then treated with either a control diet or a ketogenic diet for 3 weeks. Transthoracic echocardiography was then carried out to assess in vivo cardiac function and structure. Finally, isolated working hearts from these mice were perfused with appropriately 3H or 14C labelled glucose (5 mM), palmitate (0.8 mM), and ß-hydroxybutyrate (ß-OHB) (0.6 mM) to assess mitochondrial oxidative metabolism and glycolysis. Mice with heart failure exhibited a 56% drop in ejection fraction, which was not improved with a ketogenic diet feeding. Interestingly, mice fed a ketogenic diet had marked decreases in cardiac glucose oxidation rates. Despite increasing blood ketone levels, cardiac ketone oxidation rates did not increase, probably due to a decreased expression of key ketone oxidation enzymes. Furthermore, in mice on the ketogenic diet, no increase in overall cardiac energy production was observed, and instead, there was a shift to an increased reliance on fatty acid oxidation as a source of cardiac energy production. This resulted in a decrease in cardiac efficiency in heart failure mice fed a ketogenic diet. CONCLUSION: We conclude that the ketogenic diet does not improve heart function in failing hearts, due to ketogenic diet-induced excessive fatty acid oxidation in the ischaemic heart and a decrease in insulin-stimulated glucose oxidation.

Asunto(s)

RESUMEN

In modern cardiovascular research, isolated perfused hearts have become cost-effective and highly reproducible tools to investigate the mechanisms of cardiovascular diseases (CVDs). Since they were first introduced in the nineteenth century, isolated perfused hearts have been extensively used for testing novel therapies, elucidating cardiac metabolic and electrophysiological activities, and modeling CVDs, including ischemic heart disease, arrhythmias, and hyperacute rejection. In recent years, ex vivo heart perfusion (EVHP) has shown potential in cardiac transplantation by allowing prolonged preservation and reconditioning of donor hearts. In this review, we summarize the evolution of the isolated perfused heart technique and its applications in cardiovascular research to help researchers comprehensively understand the capabilities of isolated heart models and provide guidance to use them to investigate various CVDs.

RESUMEN

Objective: Functional assessment of hearts during ex-vivo heart perfusion is not well-established. Conventional intraventricular balloon methods for large animals sacrifice the mitral valve. This study assessed the effectiveness of the modified intraventricular balloon method in comparison with other modalities used during working mode in juvenile pigs. Methods: Following asphyxia circulatory arrest, hearts were ischemic for 15 minutes and then reperfused on an ex-vivo device for 2 hours before switching to working mode. Left ventricular pressure was continuously measured during reperfusion by a saline-filled balloon fixated in the left atrium. Spearman Correlation Coefficients with linear regression lines with confidence intervals were analyzed. Results: Maximum dp/dt at 90 minutes of reperfusion and minimum dp/dt at 60 minutes of reperfusion showed a moderate positive correlation to that in working mode, respectively (Rs = 0.61, P = .04 and Rs = 0.60, P = .04). At 60 minutes of reperfusion, minimum dp/dt showed moderate positive correlation to tau (Rs = 0.52, P = .08). Myocardial oxygen consumption during reperfusion consistently decreased at least 30% compared to working mode (at 90 minutes as the highest during reperfusion, 3.3 ± 0.8; in working mode, 5.6 ± 1.4, mLO2/min/100 g, P < .001). Conclusions: Functional parameters of contractility and relaxation measured during reperfusion by the modified balloon method showed significant correlations to respective parameters in working mode. This mitral valve sparing technique can be used to predict viability and ventricular function in the early phase of ex-vivo heart perfusion without loading the heart during working mode.

RESUMEN

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.

RESUMEN

Conditions to which the cardiac graft is exposed during transplantation with donation after circulatory death (DCD) can trigger the recruitment of macrophages that are either unpolarized (M0) or pro-inflammatory (M1) as well as the release of extracellular vesicles (EV). We aimed to characterize the effects of M0 and M1 macrophage-derived EV administration on post-ischaemic functional recovery and glucose metabolism using an isolated rat heart model of DCD. Isolated rat hearts were subjected to 20 min aerobic perfusion, followed by 27 min global, warm ischaemia or continued aerobic perfusion and 60 min reperfusion with or without intravascular administration of EV. Four experimental groups were compared: (1) no ischaemia, no EV; (2) ischaemia, no EV; (3) ischaemia with M0-macrophage-dervied EV; (4) ischaemia with M1-macrophage-derived EV. Post-ischaemic ventricular and metabolic recovery were evaluated. During reperfusion, ventricular function was decreased in untreated ischaemic and M1-EV hearts, but not in M0-EV hearts, compared to non-ischaemic hearts (p < 0.05). In parallel with the reduced functional recovery in M1-EV versus M0-EV ischaemic hearts, rates of glycolysis from exogenous glucose and oxidative metabolism tended to be lower, while rates of glycogenolysis and lactate release tended to be higher. EV from M0- and M1-macrophages differentially affect post-ischaemic cardiac recovery, potentially by altering glucose metabolism in a rat model of DCD. Targeted EV therapy may be a useful approach for modulating cardiac energy metabolism and optimizing graft quality in the setting of DCD.

Asunto(s)

RESUMEN

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.

Asunto(s)

RESUMEN

BACKGROUND: Cardiac donation after circulatory death is a promising option to increase graft availability. Graft preservation with 30 minutes of hypothermic oxygenated perfusion (HOPE) before normothermic machine perfusion may improve cardiac recovery as compared with cold static storage, the current clinical standard. We investigated the role of preserved nitric oxide synthase activity during HOPE on its beneficial effects. METHODS AND RESULTS: Using a rat model of donation after circulatory death, hearts underwent in situ ischemia (21 minutes), were explanted for a cold storage period (30 minutes), and then reperfused under normothermic conditions (60 minutes) with left ventricular loading. Three cold storage conditions were compared: cold static storage, HOPE, and HOPE with Nω-nitro-L-arginine methyl ester (nitric oxide synthase inhibitor). To evaluate potential confounding effects of high coronary flow during early reperfusion in HOPE hearts, bradykinin was administered to normalize coronary flow to HOPE levels in 2 additional groups (cold static storage and HOPE with Nω-nitro-L-arginine methyl ester). Cardiac recovery was significantly improved in HOPE versus cold static storage hearts, as determined by cardiac output, left ventricular work, contraction and relaxation rates, and coronary flow (P<0.05). Furthermore, HOPE attenuated postreperfusion calcium overload. Strikingly, the addition of Nω-nitro-L-arginine methyl ester during HOPE largely abolished its beneficial effects, even when early reperfusion coronary flow was normalized to HOPE levels. CONCLUSIONS: HOPE provides superior preservation of ventricular and vascular function compared with the current clinical standard. Importantly, HOPE's beneficial effects require preservation of nitric oxide synthase activity during the cold storage. Therefore, the application of HOPE before normothermic machine perfusion is a promising approach to optimize graft recovery in donation after circulatory death cardiac grafts.

Asunto(s)

RESUMEN

Ex vivo working porcine heart models allow for the study of a heart's function and physiology outside the living organism. These models are particularly useful due to the anatomical and physiological similarities between porcine and human hearts, providing an experimental platform to investigate cardiac disease or assess donor heart viability for transplantation. This chapter presents an in-depth discussion of the model's components, including the perfusate, preload, and afterload. We explore the challenges of emulating cardiac afterload and present a historical perspective on afterload modeling, discussing various methodologies and their respective limitations. An actively controlled afterload device is introduced to enhance the model's ability to rapidly adjust pressure in the large arteries, thereby providing a more accurate and dynamic experimental model. Finally, we provide a comprehensive experimental protocol for the ex vivo working porcine heart model.

Asunto(s)

Asunto(s)

RESUMEN

BACKGROUND: Our team previously identified a stem cell-derived cardioprotective additive that can be added to standard cardioplegia to extend myocardial viability during prolonged myocardial cold ischemic time (CIT) in rodent models. The purpose of this study was to utilize a porcine model to compare in-vivo versus ex-vivo porcine simulation of CIT that accompanies cardiac transplantation in humans, in order to determine an optimal method for translation of our studies to larger animals. METHODS: Eight 39-55 kg Yorkshire X pigs were randomly assigned to either in-vivo or ex-vivo simulation. After administration of general anesthesia and endotracheal intubation, baseline measurement of left ventricular performance was obtained via transesophageal echocardiography (TEE). After midline sternotomy and heparin administration, the aorta was cross-clamped and two liters of HTK-Custodiol were introduced via the aortic root. The in-vivo method utilized cold ischemic heart storage in the chest cavity while supporting the experimental animal with cardiopulmonary bypass (CPB). The ex-vivo method involved standard cardiac procurement, cold ischemic storage outside of the body, and subsequent cardiac reperfusion utilizing cardiac reanimation in a Langendorff heart perfusion mode. After CIT, measurements of post-ischemic left ventricular performance were obtained via echocardiography. Results are presented as: Mean ± Standard Deviation (Median, Minimum-Maximum). RESULTS: Weight (kilograms) was similar in the in-vivo group and the ex-vivo group: 44 ± 1.8 (44, 42-46) versus 44 ± 5.1 (43.5, 39-51), respectively. Cold ischemic time (minutes) was longer in the ex-vivo group: 360 ± 0 (360, 360-360) versus 141 ± 26.7 (149, 102-163). Temperature (degrees Celsius) was colder in the ex-vivo group: 8 ± 0 (8, 8-8) versus 16.5 ± 4.2 (16, 12-16).In the in-vivo group, baseline ejection fraction and ejection fraction after CIT were: 48.25% ± 14.95% (48.5%, 33%-63%) and 41.25% ± 22.32% (41.5%, 20%-62%), respectively. In the ex-vivo group, baseline ejection fraction and ejection fraction after CIT were: 56.4% ± 5.9% (57%, 50%-67%) and 60.4% ± 7.7% (61.5%, 51.9%-67%), respectively. CONCLUSION: The ex-vivo technique is suitable to evaluate cardioplegia additives that may substantially extend myocardial tolerance to cold ischemia.

RESUMEN

BACKGROUND: Extended criteria donor (ECD) hearts available with donation after brain death (DBD) are underutilized for transplantation due to limitations of cold storage. OBJECTIVES: This study evaluated use of an extracorporeal perfusion system on donor heart utilization and post-transplant outcomes in ECD DBD hearts. METHODS: In this prospective, single-arm, multicenter study, adult heart transplant recipients received ECD hearts using an extracorporeal perfusion system if hearts met study criteria. The primary outcome was a composite of 30-day survival and absence of severe primary graft dysfunction (PGD). Secondary outcomes were donor heart utilization rate, 30-day survival, and incidence of severe PGD. The safety outcome was the mean number of heart graft-related serious adverse events within 30 days. Additional outcomes included survival through 2 years benchmarked to concurrent nonrandomized control subjects. RESULTS: A total of 173 ECD DBD hearts were perfused; 150 (87%) were successfully transplanted; 23 (13%) did not meet study transplantation criteria. At 30 days, 92% of patients had survived and had no severe PGD. The 30-day survival was 97%, and the incidence of severe PGD was 6.7%. The mean number of heart graft-related serious adverse events within 30 days was 0.17 (95% CI: 0.11-0.23). Patient survival was 93%, 89%, and 86% at 6, 12, and 24 months, respectively, and was comparable with concurrent nonrandomized control subjects. CONCLUSIONS: Use of an extracorporeal perfusion system resulted in successfully transplanting 87% of donor hearts with excellent patient survival to 2 years post-transplant and low rates of severe PGD. The ability to safely use ECD DBD hearts could substantially increase the number of heart transplants and expand access to patients in need. (International EXPAND Heart Pivotal Trial [EXPANDHeart]; NCT02323321; Heart EXPAND Continued Access Protocol; NCT03835754).

Asunto(s)

RESUMEN

INTRODUCTION: 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). METHODS: All hearts received modified St Thomas 2 crystalloid cardioplegia prior to 4 hours of cold oxygenated machine perfusion. Hearts were perfused with homemade modified Steen heart solution with a perfusion pressure of 20-25 mmHg to achieve a coronary flow between 100-200 mL/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 3 L with a mean aortic pressure above 60 mmHg. RESULTS: Both groups showed 100% functional survival, with laboratory hearts displaying superior cardiac function. Both groups showed similar decline in function over time. CONCLUSION: 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.

Asunto(s)

RESUMEN

Ex situ organ preservation by machine perfusion can improve preservation of organs for transplantation. Furthermore, machine perfusion opens up the possibilities for selective immunomodulation, creation of tolerance to ischemia-reperfusion injury and/or correction of a pathogenic genetic defect. The application of gene modifying therapies to treat heart diseases caused by pathogenic mutations during ex situ heart perfusion seems promising, especially given the limitations related to delivery of vectors that were encountered during clinical trials using in vivo cardiac gene therapy. By isolating the heart in a metabolically and immunologically favorable environment and preventing off-target effects and dilution, it is possible to directly control factors that enhance the success rate of cardiac gene therapy. A literature search of PubMed and Embase databases was performed to identify all relevant studies regarding gene therapy during ex situ heart perfusion, aiming to highlight important lessons learned and discuss future clinical prospects of this promising approach.

RESUMEN

INTRODUCTION: We describe successful aortic arch cannulation and perfusion of a heart donated after circulatory death using the Transmedics Organ Care System™. CASE REPORT: A 47-year old man developed advanced heart failure symptoms after prior mustard operation for transposition of the great arteries. He matched a DCD-donor and required an elongated aorta for implantation due to his altered anatomy. The donor heart was retrieved and successfully perfused via aortic arch cannulation for 4.5 h with satisfactory perfusion parameters. DISUSSION: Although Transmedics advises against aortic arch cannulation due to concerns regarding malperfusion, satisfactory and safe perfusion can be achieved by careful positioning of the heart. Awareness and attention to the occurrence of malperfusion is mandatory, especially during transport, to achieve satisfactory outcome. CONCLUSION: Aortic arch cannulation is feasible without compromising quality of perfusion. This is relevant for patient that require an elongated aorta after surgically corrected congenital heart disease.

RESUMEN

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.

RESUMEN

BACKGROUND: Pediatric patients awaiting a heart transplant have high waitlist mortality. Several strategies have been utilized to decrease waiting times, but a mortality risk still exists. New medical technologies may improve waiting times and associated mortality. Ex situ heart perfusion (ESHP) is one such technology, which can decrease the impact of cold ischemia on the donor heart and allow for a longer out-of-body time. Adoption of such technology in pediatric heart transplantation will require support from end users, including patient and families. The aim of this qualitative study was to report the perspectives of families with experience related to pediatric HTx toward ESHP. METHODS: Semistructured interviews were conducted with 12 parents or guardians of children who were awaiting or received heart transplantation. Interviews were transcribed, and data were analyzed using qualitative content analysis. RESULTS: Participants expressed varied awareness and knowledge of ESHP. Independent of their understanding of ESHP, all purported that ESHP was an excellent idea and that this technology should be implemented in the pediatric population. They did not identify fundamentally different ethical issues or concerns for ESHP being used relative to other medical technologies. Overall, most participants described consent processes for ESHP should be like any other procedure. All agreed that the surgeon should continue to describe the overall health of the donor heart, provide their medical recommendations, and allow families to have the final say. CONCLUSIONS: The concepts described by the parents and guardians are important in moving this novel technology forward. This information will serve the basis for knowledge translation that will provide educational resources to broaden the understanding and reach of ESHP.