Search

Donation after circulatory death (DCD) could significantly improve cardiac graft availability. However, DCD hearts undergo potentially deleterious warm ischemia/reperfusion (I/R). As endothelial damage is a key factor in cardiac I/R injury, we aimed to investigate the tolerance of cardiac and endothelial function after various durations of warm ischemia to improve the timing and choice of cardioprotective therapies.Isolated, working rat hearts were perfused for 20 minutes aerobically, then underwent various periods of warm global ischemia and either 30 or 60 minutes of reperfusion.Compared with non-ischemic hearts, recovery of left ventricular work (heart rate-developed pressure product) was significantly reduced at 60 minutes of reperfusion with ≥27 minutes of ischemia (p0.05 for all), but was unchanged after 21 or 24 minutes of ischemia. Markers of cell death and edema significantly increased with ≥27-minute ischemia compared with non-ischemic hearts (p0.05 for all). Endothelial-dependent vasodilation was significantly impaired compared with non-ischemic hearts with ≥24 minutes of ischemia, whereas endothelial-independent vasodilation was impaired with ≥27 minutes of ischemia (p0.05 for all). Furthermore, with ≥24 minutes of ischemia, superoxide production by nitric oxide synthase and peroxynitrite levels were significantly increased compared with non-ischemic hearts, suggesting endothelial nitric oxide synthase (eNOS) uncoupling (p0.05 for both).The first signs of endothelial dysfunction after cardiac ischemia occur with less ischemia than cardiac functional alterations, and may result from increased eNOS uncoupling. Strategies aimed at improving eNOS coupling may thus help to optimize both endothelial and myocardial recovery, ultimately facilitating DCD heart transplantation.

BACKGROUND Cardioprotection and graft evaluation after ischemia-reperfusion (IR) are essential in facilitating heart transplantation with donation after circulatory death. Given the key role of mitochondria in IR, we aimed to investigate the tolerance of cardiac mitochondria to warm, global ischemia and to determine the predictive value of early reperfusion mitochondria-related parameters for post-ischemic cardiac recovery. METHODS Isolated, working rat hearts underwent 0, 21, 24, 27, 30, or 33 minutes of warm, global ischemia, followed by 60 minutes of reperfusion. Functional recovery (developed pressure × heart rate) was determined at 60 minutes of reperfusion, whereas mitochondrial integrity was measured at 10 minutes of reperfusion. RESULTS Functional recovery at 60 minutes of reperfusion decreased with ≥ 27 minutes of ischemia vs no ischemia (n = 7-8/group; p < 0.01). Cytochrome c, succinate release, and mitochondrial Ca content increased with ≥ 27 minutes of ischemia vs no ischemia (p < 0.05). Ischemia at ≥ 21 minutes decreased mitochondrial coupling, adenosine 5'-triphosphate content, mitochondrial Ca retention capacity, and increased oxidative damage vs no ischemia (p < 0.05). Reactive oxygen species (ROS) from reverse electron transfer increased with 21 and 27 minutes of ischemia vs no ischemia and 33 minutes of ischemia (p < 0.05), whereas ROS from forward electron transfer increased only with 33 minutes of ischemia vs no ischemia (p < 0.05). Mitochondrial coupling and adenosine 5'-triphosphate content correlated positively and cytochrome c, succinate, oxidative damage, and mitochondrial Ca content correlated negatively with cardiac functional recovery (p < 0.05). CONCLUSIONS Mitochondrial dysfunction occurs with shorter periods of ischemia than cardiac dysfunction. Mitochondrial coupling, ROS emission from reverse electron transfer, and calcium retention are particularly sensitive to early reperfusion injury, reflecting potential targets for cardioprotection. Indicators of mitochondrial integrity may be of aid in evaluating suitability of donation after circulatory death grafts for transplantation.

Donation after circulatory death (DCD) holds great promise for improving cardiac graft availability, however concerns persist regarding injury following warm ischemia, after donor circulatory arrest, and subsequent reperfusion. Application of pre-ischemic treatments is limited for ethical reasons, thus cardioprotective strategies applied at graft procurement (reperfusion) are of particular importance in optimizing graft quality. Given the key role of mitochondria in cardiac ischemia-reperfusion injury, we hypothesize that three reperfusion strategies: mild hypothermia, mechanical post-conditioning and hypoxia, when briefly applied at reperfusion onset, provoke mitochondrial changes that may underlie their cardioprotective effects. Using an isolated, working rat heart model of DCD, we demonstrate that all three strategies improve oxygen-consumption-cardiac-work coupling and increase tissue ATP content, in parallel with increased functional recovery. These reperfusion strategies, however, differentially affect mitochondria; mild hypothermia also increases phosphocreatine content, while mechanical post-conditioning stimulates mitochondrial complex I activity and reduces cytochrome c release (marker of mitochondrial damage), whereas hypoxia up-regulates the expression of Pgc-1α (regulator of mitochondrial biogenesis). Characterisation of the role of mitochondria in cardioprotective reperfusion strategies should aid in the identification of new, mitochochondrial-based therapeutic targets and the development of effective reperfusion strategies that could ultimately facilitate DCD heart transplantation. This article is protected by copyright. All rights reserved.

In donation after circulatory death (DCD), cardiac grafts are subjected to warm ischemia in situ, prior to a brief period of cold, static storage (CSS) at procurement, and ex situ, normothermic, machine perfusion (NMP) for transport and graft evaluation. Cold ischemia and normothermic reoxygenation during NMP could aggravate graft injury through continued accumulation and oxidation, respectively, of mitochondrial succinate, and the resultant oxidative stress. We hypothesized that replacing CSS with hypothermic, oxygenated perfusion (HOPE) could provide cardioprotection by reducing cardiac succinate levels before NMP. DCD was simulated in male Wistar rats. Following 21 minutes in situ ischemia, explanted hearts underwent 30 minutes hypothermic storage with 1 of the following: (1) CSS, (2) HOPE, (3) hypothermic deoxygenated perfusion (HNPE), or (4) HOPE + AA5 (succinate dehydrogenase inhibitor) followed by normothermic reperfusion to measure cardiac and metabolic recovery. After hypothermic storage, tissue ATP/ADP levels were higher and succinate concentration was lower in HOPE vs CSS, HNPE, and HOPE + AA5 hearts. After 60 minutes reperfusion, cardiac function was increased and cellular injury was decreased in HOPE compared with CSS, HNPE, and HOPE + AA5 hearts. HOPE provides improved cardioprotection via succinate oxidation prior to normothermic reperfusion compared with CSS, and therefore is a promising strategy for preservation of cardiac grafts obtained with DCD.

Introduction: Donation after circulatory death (DCD) could substantially improve donor heart availability. However, warm ischemia prior to procurement is of particular concern for cardiac graft quality. We describe a rat model of DCD with in-situ ischemia in order to characterize the physiologic changes during the withdrawal period before graft procurement, to determine effects of cardioplegic graft storage, and to evaluate the post-ischemic cardiac recovery in comparison with an established ex-situ ischemia model.Methods: Following general anesthesia in male, Wistar rats (404 ± 24 g, n = 25), withdrawal of life-sustaining therapy was simulated by diaphragm transection. Hearts underwent no ischemia or 27 min in-situ ischemia and were explanted. Ex situ, hearts were subjected to a cardioplegic flush and 15 min cold storage or not, and 60 min reperfusion. Cardiac recovery was determined and compared to published results of an entirely ex-situ ischemia model (n = 18).Results: In donors, hearts were subjected to hypoxia and hemodynamic changes, as well as increased levels of circulating catecholamines and free fatty acids prior to circulatory arrest. Post-ischemic contractile recovery was significantly lower in the in-situ ischemia model compared to the ex-situ model, and the addition of cardioplegic storage improved developed pressure-heart rate product, but not cardiac output.Conclusion: The in-situ model provides insight into conditions to which the heart is exposed before procurement. Compared to an entirely ex-situ ischemia model, hearts of the in-situ model demonstrated a lower post-ischemic functional recovery, potentially due to systemic changes prior to ischemia, which are partially abrogated by cardioplegic graft storage.

Background: Use of cardiac grafts obtained with donation after circulatory death (DCD) could significantly improve donor heart availability. As DCD hearts undergo potentially deleterious warm ischemia and reperfusion, clinical protocols require optimization to ensure graft quality. Thus, we investigated effects of alternative preservation conditions on endothelial and/or vascular and contractile function in comparison with the current clinical standard. Methods: Using a rat DCD model, we compared currently used graft preservation conditions, St. Thomas n°2 (St. T) at 4°C, with potentially more suitable conditions for DCD hearts, adenosine-lidocaine preservation solution (A-L) at 4°C or 22°C. Following general anesthesia and diaphragm transection, hearts underwent either 0 or 18 min of in-situ warm ischemia, were explanted, flushed and stored for 15 min with either St. T at 4°C or A-L at 4°C or 22°C, and then reperfused under normothermic, aerobic conditions. Endothelial integrity and contractile function were determined. Results: Compared to 4°C preservation, 22°C A-L significantly increased endothelial nitric oxide synthase (eNOS) dimerization and reduced oxidative tissue damage (p < 0.05 for all). Furthermore, A-L at 22°C better preserved the endothelial glycocalyx and coronary flow compared with St. T, tended to reduce tissue calcium overload, and stimulated pro-survival signaling. No significant differences were observed in cardiac function among ischemic groups. Conclusions: Twenty-two-degree Celsius A-L solution better preserves the coronary endothelium compared to 4°C St. T, which likely results from greater eNOS dimerization, reduced oxidative stress, and activation of the reperfusion injury salvage kinase (RISK) pathway. Improving heart preservation conditions immediately following warm ischemia constitutes a promising approach for the optimization of clinical protocols in DCD heart transplantation. Keywords: coronary vascular function; donation after circulatory death (DCD); heart transplantation; ischemia-reperfusion; preservation conditions.

Heart transplantation remains the treatment of reference for patients experiencing end‐stage heart failure; unfortunately, graft availability through conventional donation after brain death is insufficient to meet the demand. Use of extended‐criteria donors or donation after circulatory death has emerged to increase organ availability; however, clinical protocols require optimization to limit or prevent damage in hearts possessing greater susceptibility to injury than conventional grafts. The emergence of cardiac ex situ machine perfusion not only facilitates the use of extended‐criteria donor and donation after circulatory death hearts through the avoidance of potentially damaging ischemia during graft storage and transport, it also opens the door to multiple opportunities for more sensitive monitoring of graft quality. With this review, we aim to bring together the current knowledge of biomarkers that hold particular promise for cardiac graft evaluation to improve precision and reliability in the identification of hearts for transplantation, thereby facilitating the safe increase in graft availability. Information about the utility of potential biomarkers was categorized into 5 themes: (1) functional, (2) metabolic, (3) hormone/prohormone, (4) cellular damage/death, and (5) inflammatory markers. Several promising biomarkers are identified, and recommendations for potential improvements to current clinical protocols are provided.

Purpose Although heart donation after circulatory death (DCD) is a promising option to increase graft availability, hearts undergo warm, global ischemia prior to procurement, which is a concern for graft quality. In clinical DCD, hearts are commonly procured and subjected to cold, static storage (CSS) prior to ex-situ normothermic machine perfusion for transport and graft evaluation. Cold ischemia induced by CSS and reoxygenation at normothermic temperatures, however, may aggravate graft injury, especially in endothelial cells. We hypothesized that replacing CSS with hypothermic, oxygenated perfusion (HOPE) provides cardioprotection by preserving the vasculature through the production of nitric oxide. Methods Following anaesthesia, diaphragm transection and circulatory arrest in male Wistar rats to simulate DCD conditions, hearts underwent 21 min of warm, in-situ ischemia. Hearts were then subjected to either 30 min of CSS, HOPE, or HOPE with the presence of L-NAME (nitric oxide synthase inhibitor). Afterwards, hearts were reperfused ex-situ for 60 min under oxygenated, normothermic conditions. Results Compared to CSS, HOPE hearts demonstrated higher cardiac function (determined by cardiac output, left ventricular work, as well as contraction and relaxation rates) after 60 min of reperfusion. Furthermore, preliminary results indicate a higher coronary vascular resistance at the end of the hypothermic perfusion period in hearts with L-NAME compared to HOPE alone. Early reperfusion coronary flow, an indicator of vascular function, tended to be higher in hearts subjected to HOPE compared to hearts treated with L-NAME or to the current clinical scenario (CSS). Conclusion Preservation of vascular and contractile function with HOPE appears superior to the current clinical protocol (CSS). The increase in coronary flow during early reperfusion in HOPE hearts was abolished with the addition of L-NAME, indicating that the beneficial vascular effects of HOPE could be mediated by the production of nitric oxide. Consequently, we believe that HOPE holds great potential for preservation of cardiac grafts obtained with DCD.

Donation after circulatory death (DCD) could improve donor heart availability, however, warm ischemia-reperfusion injury raises concerns about graft quality. Mechanical postconditioning (MPC) may limit injury, but mechanisms remain incompletely characterized. Therefore, we investigated the roles of glucose metabolism and key signaling molecules in MPC using an isolated rat heart model of DCD. Hearts underwent 20 minutes perfusion, 30 minutes global ischemia, and 60 minutes reperfusion with or without MPC (two cycles: 30 seconds reperfusion&mdash, 30 seconds ischemia). Despite identical perfusion conditions, MPC either significantly decreased (low recovery = LoR, 32 &plusmn, 5%, p &lt, 0.05), or increased (high recovery = HiR, 59 &plusmn, 7%, 0.05) the recovery of left ventricular work compared with no MPC (47 &plusmn, 9%). Glucose uptake and glycolysis were increased in HiR vs. LoR hearts (p &lt, 0.05), but glucose oxidation was unchanged. Furthermore, in HiR vs. LoR hearts, phosphorylation of raptor, a downstream target of AMPK, increased (p &lt, 0.05), cytochrome c release (p &lt, 0.05) decreased, and TNF&alpha, content tended to decrease. Increased glucose uptake and glycolysis, lower mitochondrial damage, and a trend towards decreased pro-inflammatory cytokines occurred specifically in HiR vs. LoR MPC hearts, which may result from greater AMPK activation. Thus, we identify endogenous cellular mechanisms that occur specifically with cardioprotective MPC, which could be elicited in the development of effective reperfusion strategies for DCD cardiac grafts.

Low molecular weight heparin is currently the standard therapy for the primary prevention of thromboembolic disease in cancer patients. The use of direct-acting anticoagulants could be an alternative, but its efficacy and safety profile in these types of patients remains unclear.We searched in Epistemonikos, the largest database of systematic reviews in health, which is maintained by screening multiple sources of information, including MEDLINE, EMBASE, Cochrane, among others. We extracted data from identified reviews, analyzed data from primary studies, performed a meta-analysis, and prepared a summary table of results using the GRADE method.We identified four systematic reviews that together included two primary studies, of which both correspond to trials. We conclude that the use of direct-acting oral anticoagulants probably increases the outcome of major bleeding and likely slightly increases the risk of thromboembolic disease. No studies were found that evaluated the outcome of quality of life or mortality.El uso de heparina de bajo peso molecular es actualmente la terapia estándar para prevención primaria de enfermedad tromboembólica en pacientes con cáncer. El uso de los anticoagulantes de acción directa podría ser una alternativa pero su perfil de eficacia y seguridad en este tipo de pacientes sigue siendo aún poco claro.Realizamos una búsqueda en Epistemonikos, la mayor base de datos de revisiones sistemáticas en salud, la cual es mantenida mediante el tamizaje de múltiples fuentes de información, incluyendo MEDLINE/PubMed, EMBASE, Cochrane, entre otras. Extrajimos los datos desde las revisiones identificadas, analizamos los datos de los estudios primarios, realizamos un metanálisis y preparamos una tabla de resumen de los resultados utilizando el método GRADE.Identificamos cuatro revisiones sistemáticas que, en conjunto, incluyeron dos estudios primarios, los que corresponden a ensayos. Concluimos que el uso de anticoagulantes orales de acción directa probablemente aumenta el desenlace hemorragia mayor y probablemente aumenta levemente el riesgo de enfermedad tromboembólica. No se encontraron estudios que evaluaran el desenlace calidad de vida ni de mortalidad.

Purpose Donation after circulatory death (DCD) could substantially improve donor heart availability. In DCD, the heart is not only exposed to a period of warm ischemia, but also to a damaging pre-ischemic phase after withdrawal of life support. We investigated the effects of different pre-ischemic lactate levels on post-ischemic recovery using an isolated rat heart model of DCD. Methods Isolated, working rat hearts underwent 20’ aerobic perfusion, 28.5’ global ischemia, and 60’ reperfusion. In addition to 11 mM glucose and 1.2 mM palmitate, three pre-ischemic lactate levels were tested: no lactate (0 Lac), physiologic lactate (0.5 mM; 0.5 Lac), or DCD-relevant lactate (1 mM; 1 Lac). Contractile function, mitochondrial integrity and potential mediators of injury were evaluated. Results During reperfusion, left ventricular work (heart rate-developed pressure product) was significantly greater in 0.5 Lac hearts compared to 0 Lac or 1 Lac. In 0.5 Lac vs 0 Lac hearts, in parallel with increased function, cytochrome c release and carbonylated protein levels were significantly reduced, indicating less mitochondrial damage and oxidative stress, respectively. In 1 Lac vs 0.5 Lac hearts, in parallel with decreased function, cytochrome c release tended to increase, but carbonylated protein levels tended to decrease. Conclusion DCD-relevant levels of pre-ischemic lactate (1 mM) reduce contractile recovery during reperfusion compared to physiologic levels. Although increased pre-ischemic lactate tends to lower oxidative stress during reperfusion; this, alone, is insufficient to maintain functional recovery at DCD-relevant levels. Further investigations are ongoing to clarify underlying mechanisms.

RATIONALE Donation after circulatory death (DCD) could improve cardiac graft availability. However, strategies to optimize cardiac graft recovery remain to be established in DCD; these hearts would be expected to be exposed to high levels of circulatory fat immediately prior to the inevitable period of ischemia prior to procurement. OBJECTIVE We investigated whether acute exposure to high fat prior to warm, global ischemia affects subsequent hemodynamic and metabolic recovery in an isolated rat heart model of DCD. METHODS AND RESULTS Hearts of male Wistar rats underwent 20min baseline perfusion with glucose (11mM) and either high fat (1.2mM palmitate; HF) or no fat (NF), 27min global ischemia (37°C), and 60min reperfusion with glucose only (n=7-8 per group). Hemodynamic recovery was 50% lower in HF vs. NF hearts (34±30% vs. 78±8% (60min reperfusion value of peak systolic pressure*heart rate as percentage of mean baseline); p

Aims: Donation after circulatory death (DCD) could improve cardiac graft availability, which is currently insufficient to meet transplant demand. However, DCD organs undergo an inevitable period of warm ischemia and most cardioprotective approaches can only be applied at reperfusion (procurement) for ethical reasons. We investigated whether modifying physical conditions at reperfusion, using four different strategies, effectively improves hemodynamic recovery after warm ischemia. Methods and Results: Isolated hearts of male Wistar rats were perfused in working-mode for 20 min, subjected to 27 min global ischemia (37°C), and 60 min reperfusion (n = 43). Mild hypothermia (30°C, 10 min), mechanical postconditioning (MPC; 2x 30 s reperfusion/30 s ischemia), hypoxia (no O2, 2 min), or low pH (pH 6.8–7.4, 3 min) was applied at reperfusion and compared with controls (i.e., no strategy). After 60 min reperfusion, recovery of left ventricular work (developed pressure*heart rate; expressed as percent of pre-ischemic value) was significantly greater for mild hypothermia (62 ± 7%), MPC (65 ± 8%) and hypoxia (61 ± 11%; p < 0.05 for all), but not for low pH (45 ± 13%), vs. controls (44 ± 7%). Increased hemodynamic recovery was associated with greater oxygen consumption (mild hypothermia, MPC) and coronary perfusion (mild hypothermia, MPC, hypoxia), and with reduced markers of necrosis (mild hypothermia, MPC, hypoxia) and mitochondrial damage (mild hypothermia, hypoxia). Conclusions: Brief modifications in physical conditions at reperfusion, such as hypothermia, mechanical postconditioning, and hypoxia, improve post-ischemic hemodynamic function in our model of DCD. Cardioprotective reperfusion strategies applied at graft procurement could improve DCD graft recovery and limit further injury; however, optimal clinical approaches remain to be characterized.

Gebiet: Chirurgie Biomedizintechnik Biophysik Transplantationsmedizin Kardiologie Abstract: OBJECTIVES: – Oxygenation of blood and other physiological solutions are routinely required in fundamental research for both in vitro and in vivo experimentation. However, very few oxygenators with suitable priming volumes (

El aumento de la esperanza y calidad de vida, junto con la mayor rapidez y comodidad de los distintos medios de transporte, ha posibilitado que viajeros con enfermedades cronicas, embarazadas o ninos emprendan viajes turisticos a zonas tropicales o subtropicales. Por otra parte, el aumento de la cooperacion internacional ha propiciado la aparicion de viajeros de larga estancia que viven en condiciones similares a las de la poblacion local. Estos viajeros presentan una serie de caracteristicas especiales, debidas a sus condiciones fisicas, tratamientos habituales o tipo de condiciones de vida durante el viaje, que les hacen mas susceptibles de presentar algun tipo de problema de salud durante el viaje. Por este motivo, las recomendaciones habituales para viajeros son insuficientes en estos grupos y es preciso realizar un consejo al viajero individualizado que tenga en cuenta estos factores. En esta revision se presentan de forma resumida las principales advertencias que deben realizarse en estos grupos de viajeros especiales.