Ex Vivo Working Porcine Heart Model.

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.

Pharmacological and mechanical properties of isolated pig coronary veins.

Recent successful cardiac transplantation from pig to non-human primates and the first pig-to-human transplantation has put the focus on the properties of the pig heart. In contrast to the coronary arteries, the coronary veins are less well characterized and the aim was to examine the mechanical and pharmacological properties of coronary veins in comparison to the arteries. Vessel segments from the left anterior descending coronary artery (LAD) and the concomitant vein were isolated from pig hearts in cardioplegia and examined in vitro. The wall thickness, active tension and active stress at optimal circumference were lower in coronary veins, reflecting the lower intravascular pressure in vivo. Reverse transcription polymerase chain reaction (RT-PCR) analysis of myosin isoforms showed that the vein could be characterized as having a slower smooth muscle phenotype compared to the artery. Both vessel types contracted in response to the thromboxane agonist U46619 with EC50 values of about 20 nM. The artery contracted in response to acetylcholine. Precontracted arteries relaxed in noradrenaline and substance P. In contrast, the veins relaxed in acetylcholine, contracted in noradrenaline and were unresponsive to substance P. In conclusion, these results demonstrate significant differences between the coronary artery and vein in the smooth muscle properties and in the responses to sympathetic and parasympathetic stimuli.

Xenografts Show Signs of Concentric Hypertrophy and Dynamic Left Ventricular Outflow Tract Obstruction After Orthotopic Pig-to-baboon Heart Transplantation.

BACKGROUND: Orthotopic cardiac xenotransplantation has seen substantial advancement in the last years and the initiation of a clinical pilot study is close. However, donor organ overgrowth has been a major hurdle for preclinical experiments, resulting in loss of function and the decease of the recipient. A better understanding of the pathogenesis of organ overgrowth after xenotransplantation is necessary before clinical application. METHODS: Hearts from genetically modified ( GGTA1-KO , hCD46/hTBM transgenic) juvenile pigs were orthotopically transplanted into male baboons. Group I (control, n = 3) received immunosuppression based on costimulation blockade, group II (growth inhibition, n = 9) was additionally treated with mechanistic target of rapamycin inhibitor, antihypertensive medication, and fast corticoid tapering. Thyroid hormones and insulin-like growth factor 1 were measured before transplantation and before euthanasia, left ventricular (LV) growth was assessed by echocardiography, and hemodynamic data were recorded via a wireless implant. RESULTS: Insulin-like growth factor 1 was higher in baboons than in donor piglets but dropped to porcine levels at the end of the experiments in group I. LV mass increase was 10-fold faster in group I than in group II. This increase was caused by nonphysiological LV wall enlargement. Additionally, pressure gradients between LV and the ascending aorta developed, and signs of dynamic left ventricular outflow tract (LVOT) obstruction appeared. CONCLUSIONS: After orthotopic xenotransplantation in baboon recipients, untreated porcine hearts showed rapidly progressing concentric hypertrophy with dynamic LVOT obstruction, mimicking hypertrophic obstructive cardiomyopathy in humans. Antihypertensive and antiproliferative drugs reduced growth rate and inhibited LVOT obstruction, thereby preventing loss of function.

Impact of an Okinawa/Nordic based diet on endocrinological and periodontal conditions in individuals with type 2 diabetes. A randomized case-control study.

OBJECTIVES: To assess if the results following intake of a diet using an Okinawan-based Nordic diet (OBND) over one month differs in endocrinological, periodontal clinical outcome, and serum cytokine levels compared to a standard hospital care diet in individuals with diabetes type 2 (T2D) (control group). BACKGROUND: Scientific evidence suggests that the use of diet for individuals with T2D may be beneficial. METHODS: Participating individuals with T2D were randomly assigned to a test (OBND) (n = 14), or control group (n = 16). Anthropometric data, blood glucose levels, HbA1c levels, lipids, serum inflammation markers (CRP, and a routine panel of 24 cytokines), blood pressure, gingival bleeding on probing (BOP), probing pocket depths (PPD), and clinical attachment levels (CAL) were studied. RESULTS: Statistical analyses of baseline study data failed to demonstrate study group differences. The mean weight reduction was greater in the OBND group (4.1 kg) versus the control group (1.3 kg) (p < 0.01). The reduction in BMI was 1.4 kg/m2 in OBND (p < 0.001) and 0.5 kg/m2 in the control group, respectively (p < 0.01). Diastolic and systolic blood pressure reductions were greater in the OBND group than in the control group (p < 0.01). Periodontal study parameters (BOP % scores) and (PPD values) decreased (p < 0.001) overall with no between group differences. The OBND resulted in reduction of serum levels of IFNγ, Eotaxin IL-9, IP10,IL17a, MCP-1,m and PDFBB compared to the control diet. CONCLUSIONS: A strict T2D- diet provides an association between reduction in serum HbA1c and BOP scores. Serum levels decreases in IFNγ, Eotaxin IL-9, IP-10, IL17a. MCP-1, and PDFBB were only found in the test group.

Development and prevention of ischemic contracture ("stone heart") in the pig heart.

Stone heart (ischemic contracture) is a rare and serious condition observed in the heart after periods of warm ischemia. The underlying mechanisms are largely unknown and treatment options are lacking. In view of the possibilities for cardiac donation after circulatory death (DCD), introducing risks for ischemic damage, we have investigated stone heart in pigs. Following cessation of ventilation, circulatory death (systolic pressure <8 mmHg) occurred within 13.1 ± 1.2 min; and a stone heart, manifested with asystole, increased left ventricular wall thickness and stiffness, established after a further 17 ± 6 min. Adenosine triphosphate and phosphocreatine levels decreased by about 50% in the stone heart. Electron microscopy showed deteriorated structure with contraction bands, Z-line streaming and swollen mitochondria. Synchrotron based small angle X-ray scattering of trabecular samples from stone hearts revealed attachment of myosin to actin, without volume changes in the sarcomeres. Ca2+ sensitivity, determined in permeabilized muscle, was increased in stone heart samples. An in vitro model for stone heart, using isolated trabecular muscle exposed to hypoxia/zero glucose, exhibited the main characteristics of stone heart in whole animals, with a fall in high-energy phosphates and development of muscle contracture. The stone heart condition in vitro was significantly attenuated by the myosin inhibitor MYK-461 (Mavacamten). In conclusion, the stone heart is a hypercontracted state associated with myosin binding to actin and increased Ca2+ sensitivity. The hypercontractile state, once developed, is poorly reversible. The myosin inhibitor MYK-461, which is clinically approved for other indications, could be a promising venue for prevention.

Excitation and contraction of cardiac muscle and coronary arteries of brain-dead pigs.

Excitability and contraction of cardiac muscle from brain-dead donors critically influence the success of heart transplantation. Membrane physiology, Ca2+-handling, and force production of cardiac muscle and the contractile properties of coronary arteries were studied in hearts of brain-dead pigs. Cardiac muscle and vascular function after 12 h brain death (decapitation between C2 and C3) were compared with properties of fresh tissue. In both isolated cardiomyocytes (whole-cell patch clamp) and trabecular muscle (conventional microelectrodes), action potential duration was shorter in brain dead, compared to controls. Cellular shortening and Ca2+ transients were attenuated in the brain dead, and linked to lower mRNA expression of L-type calcium channels and a slightly lower ICa,L, current, as well as to a lower expression of phospholamban. The current-voltage relationship and the current above the equilibrium potential of the inward K+ (IK1) channel were altered in the brain-dead group, associated with lower mRNA expression of the Kir2.2 channel. Delayed K+ currents were detected (IKr, IKs) and were not different between groups. The transient outward K+ current (Ito) was not observed in the pig heart. Coronary arteries exhibited increased contractility and sensitivity to the thromboxane analogue (U46619), and unaltered endothelial relaxation. In conclusion, brain death involves changes in cardiac cellular excitation which might lower contractility after transplantation. Changes in the inward rectifier K+ channel can be associated with an increased risk for arrhythmia. Increased reactivity of coronary arteries may lead to increased risk of vascular spasm, although endothelial relaxant function was well preserved.

A novel nonlinear afterload for ex vivo heart evaluation: Porcine experimental results.

BACKGROUND: Existing working heart models for ex vivo functional evaluation of donor hearts often use cardiac afterloads made up of discrete resistive and compliant elements. This approach limits the practicality of independently controlling systolic and diastolic aortic pressure to safely test the heart under multiple loading conditions. We present and investigate a novel afterload concept designed to enable such control. METHODS: Six ∼70 kg pig hearts were evaluated in vivo, then ex vivo in left-ventricular working mode using the presented afterload. Both in vivo and ex vivo, the hearts were evaluated at two exertion levels: at rest and following a 20 µg adrenaline bolus, while measuring aortic pressure and flow, left ventricular pressure and volume, and left atrial pressure. RESULTS: The afterload gave aortic pressure waveforms that matched the general shape of the in vivo measurements. A wide range of physiological systolic pressures (93 to 160 mm Hg) and diastolic pressures (73 to 113 mm Hg) were generated by the afterload. CONCLUSIONS: With the presented afterload concept, multiple physiological loading conditions could be tested ex vivo, and compared with the corresponding in vivo data. An additional control loop from the set pressure limits to the measured systolic and diastolic aortic pressure is proposed to address discrepancies observed between the set limits and the measured pressures.

Machine Perfusion for Human Heart Preservation: A Systematic Review.

Currently, static cold storage (SCS) of hearts from donations after brainstem death remains the standard clinically. However, machine perfusion (MP) is considered an approach for donor organ management to extend the donor pool and/or increase the utilization rate. This review summarizes and critically assesses the available clinical data on MP in heart transplantation. We searched Medline (PubMed), Cochrane, Embase, and clinicaltrials.gov, along with reference lists of the included publications and identified 40 publications, including 18 articles, 17 conference abstracts, and five ongoing clinical trials. Two types of MP were used: hypothermic MP (HMP) and normothermic MP (NMP). Three studies evaluated HMP, and 32 evaluated NMP. Independent of the system, MP resulted in clinical outcomes comparable to traditional SCS. However, NMP seemed especially beneficial for high-risk cases and donation after circulatory death (DCD) hearts. Based on currently available data, MP is non-inferior to standard SCS. Additionally, single-centre studies suggest that NMP could preserve the hearts from donors outside standard acceptability criteria and DCD hearts with comparable results to SCS. Finally, HMP is theoretically safer and simpler to use than NMP. If a machine malfunction or user error occurs, NMP, which perfuses a beating heart, would have a narrower margin of safety. However, further well-designed studies need to be conducted to draw clear conclusions.

Prevention of Ischemic Myocardial Contracture Through Hemodynamically Controlled DCD.

PURPOSE: Ischemic myocardial contracture (IMC) or "stone heart" is a condition with rapid onset following circulatory death. It inhibits transplantability of hearts donated upon circulatory death (DCD). We investigate the effectiveness of hemodynamic normalization upon withdrawal of life-sustaining therapy (WLST) in a large-animal controlled DCD model, with the hypothesis that reduction in cardiac work delays the onset of IMC. METHODS: A large-animal study was conducted comprising of a control group ([Formula: see text]) receiving no therapy upon WLST, and a test group ([Formula: see text]) subjected to a protocol for fully automated computer-controlled hemodynamic drug administration. Onset of IMC within 1 h following circulatory death defined the primary end-point. Cardiac work estimates based on pressure-volume loop concepts were developed and used to provide insight into the effectiveness of the proposed computer-controlled therapy. RESULTS: No test group individual developed IMC within [Formula: see text], whereas all control group individuals did (4/6 within [Formula: see text]). CONCLUSION: Automatic dosing of hemodynamic drugs in the controlled DCD context has the potential to prevent onset of IMC up to [Formula: see text], enabling ethical and medically safe organ procurement. This has the potential to increase the use of DCD heart transplantation, which has been widely recognized as a means of meeting the growing demand for donor hearts.

Pro-IL-1ß Is an Early Prognostic Indicator of Severe Donor Lung Injury During Ex Vivo Lung Perfusion.

BACKGROUND: Ex vivo lung perfusion (EVLP) is used to evaluate and recondition extended criteria donor lungs for transplantation. Interleukin-1ß (IL-1ß) has been identified as a prognostic indicator of nonrecovery during EVLP. This may be an effect of inflammasome activation or cellular necrosis following donation and graft preservation. Delineating the mechanism of IL-1ß release is required. METHODS: The inactive intracellular precursor molecule, pro-IL-1ß, was characterized along with the pro-IL-1ß processing enzyme, caspase-1, in the perfusate of n = 20 human lungs that had undergone EVLP (n = 10 lungs that failed to recover and were discarded versus n = 10 lungs that reconditioned and were transplanted). In an experimental porcine model, n = 8 lungs underwent EVLP and were randomized to receive either a specific NLRP3 inflammasome inhibitor or control. RESULTS: Significant increases in pro-IL-1ß and caspase-1 were observed in the perfusate from human lungs that did not recondition during EVLP compared with those that successfully reconditioned and were used for transplantation. Within the porcine EVLP, NLRP3 inflammasome inhibition reduced IL-1ß within the perfusate compared with controls, but this had no impact on lung function, hemodynamics, or inflammation. CONCLUSIONS: Our data suggest that pro-IL-1ß is passively released following cellular necrosis of the donor lung.

Cold non-ischemic heart preservation with continuous perfusion prevents early graft failure in orthotopic pig-to-baboon xenotransplantation.

BACKGROUND: Successful preclinical transplantations of porcine hearts into baboon recipients are required before commencing clinical trials. Despite years of research, over half of the orthotopic cardiac xenografts were lost during the first 48 hours after transplantation, primarily caused by perioperative cardiac xenograft dysfunction (PCXD). To decrease the rate of PCXD, we adopted a preservation technique of cold non-ischemic perfusion for our ongoing pig-to-baboon cardiac xenotransplantation project. METHODS: Fourteen orthotopic cardiac xenotransplantation experiments were carried out with genetically modified juvenile pigs (GGTA1- KO/hCD46/hTBM) as donors and captive-bred baboons as recipients. Organ preservation was compared according to the two techniques applied: cold static ischemic cardioplegia (IC; n = 5) and cold non-ischemic continuous perfusion (CP; n = 9) with an oxygenated albumin-containing hyperoncotic cardioplegic solution containing nutrients, erythrocytes and hormones. Prior to surgery, we measured serum levels of preformed anti-non-Gal-antibodies. During surgery, hemodynamic parameters were monitored with transpulmonary thermodilution. Central venous blood gas analyses were taken at regular intervals to estimate oxygen extraction, as well as lactate production. After surgery, we measured troponine T and serum parameters of the recipient's kidney, liver and coagulation functions. RESULTS: In porcine grafts preserved with IC, we found significantly depressed systolic cardiac function after transplantation which did not recover despite increasing inotropic support. Postoperative oxygen extraction and lactate production were significantly increased. Troponin T, creatinine, aspartate aminotransferase levels were pathologically high, whereas prothrombin ratios were abnormally low. In three of five IC experiments, PCXD developed within 24 hours. By contrast, all nine hearts preserved with CP retained fully preserved systolic function, none showed any signs of PCXD. Oxygen extraction was within normal ranges; serum lactate as well as parameters of organ functions were only mildly elevated. Preformed anti-non-Gal-antibodies were similar in recipients receiving grafts from either IC or CP preservation. CONCLUSIONS: While standard ischemic cardioplegia solutions have been used with great success in human allotransplantation over many years, our data indicate that they are insufficient for preservation of porcine hearts transplanted into baboons: Ischemic storage caused severe impairment of cardiac function and decreased tissue oxygen supply, leading to multi-organ failure in more than half of the xenotransplantation experiments. In contrast, cold non-ischemic heart preservation with continuous perfusion reliably prevented early graft failure. Consistent survival in the perioperative phase is a prerequisite for preclinical long-term results after cardiac xenotransplantation.

Non-ischemic Heart Preservation via Hypothermic Cardioplegic Perfusion Induces Immunodepletion of Donor Hearts Resulting in Diminished Graft Infiltration Following Transplantation.

Introduction: Many donor organs contain significant leukocyte reservoirs which upon transplantation activate recipient leukocytes to initiate acute rejection. We aimed to assess whether non-ischemic heart preservation via ex vivo perfusion promotes immunodepletion and alters the inflammatory status of the donor organ prior to transplantation. Methods: Isolated porcine hearts underwent ex vivo hypothermic, cardioplegic perfusion for 8 h. Leukocyte populations were quantified in left ventricle samples by flow cytometry. Cell-free DNA, cytokines, and chemokines were quantified in the perfusate. Tissue integrity was profiled by targeted proteomics and a histological assessment was performed. Heterotopic transplants comparing ex vivo hypothermic preservation and static cold storage were utilized to assess graft infiltration as a solid clinical endpoint. Results:Ex vivo perfusion significantly immunodepleted myocardial tissue. The perfusate displayed a selective, pro-inflammatory cytokine/chemokine pattern dominated by IFN-γ. The tissue molecular profile was improved following perfusion by diminished expression of nine pro-apoptotic and six ischemia-associated proteins. Histologically, no evidence of tissue damage was observed and cardiac troponin I was low throughout perfusion. Cell-free DNA was detected, the source of which may be necrotic/apoptotic leukocytes. Post-transplant graft infiltration was markedly reduced in terms of both leucocyte distribution and intensity of foci. Conclusions: These findings demonstrate that ex vivo perfusion significantly reduced donor heart immunogenicity via loss of resident leukocytes. Despite the pro-inflammatory cytokine pattern observed, a pro-survival and reduced ischemia-related profile was observed, indicating an improvement in graft viability by perfusion. Diminished graft infiltration was observed in perfused hearts compared with those preserved by static cold storage following 48 h of transplantation.

Pig-to-non-human primate heart transplantation: The final step toward clinical xenotransplantation?

BACKGROUND: The demand for donated human hearts far exceeds the number available. Xenotransplantation of genetically modified porcine organs provides an alternative. In 2000, an Advisory Board of the International Society for Heart and Lung Transplantation set the benchmark for commencing clinical cardiac xenotransplantation as consistent 60% survival of non-human primates after life-supporting porcine heart transplantations. Recently, we reported the stepwise optimization of pig-to-baboon orthotopic cardiac xenotransplantation finally resulting in consistent success, with 4 recipients surviving 90 (n = 2), 182, and 195 days. Here, we report on 4 additional recipients, supporting the efficacy of our procedure. RESULTS: The first 2 additional recipients succumbed to porcine cytomegalovirus (PCMV) infections on Days 15 and 27, respectively. In 2 further experiments, PCMV infections were successfully avoided, and 3-months survival was achieved. Throughout all the long-term experiments, heart, liver, and renal functions remained within normal ranges. Post-mortem cardiac diameters were slightly increased when compared with that at the time of transplantation but with no detrimental effect. There were no signs of thrombotic microangiopathy. The current regimen enabled the prolonged survival and function of orthotopic cardiac xenografts in altogether 6 of 8 baboons, of which 4 were now added. These results exceed the threshold set by the Advisory Board of the International Society for Heart and Lung Transplantation. CONCLUSIONS: The results of our current and previous experimental cardiac xenotransplantations together fulfill for the first time the pre-clinical efficacy suggestions. PCMV-positive donor animals must be avoided.

Ex Vivo Lung Perfusion Improves the Inflammatory Signaling Profile of the Porcine Donor Lung Following Transplantation.

BACKGROUND: Primary graft dysfunction and allograft rejection represent major caveats to successful lung transplantation. Reducing inflammation in donor lungs before transplantation may improve outcomes. Evidence exists that ex vivo lung perfusion (EVLP) can alter the donor lung environment, although the mechanisms remain unclear. This study aimed to characterize the inflammatory signaling profile of the lung following standard and EVLP transplant and delineate the immediate impact on the recipient circulation. METHODS: Female recipient pigs (n = 12) were randomized to undergo left lung transplantation from male donors either using the gold standard protocol (static cold storage) or following 3 hours of EVLP. The relative phosphorylation of 44 phosphokinases and the relative expression of 35 apoptosis-related molecules were profiled within the donor lung 24 hours posttransplantation. RESULTS: A global profile of mitochondrial salvage and cell survival was observed in the EVLP lung tissue compared with lungs undergoing standard transplantation. This included increased phosphorylation of downstream prosignaling kinases, including ERK1/2 and FAK. In addition, there was upregulated expression of the antiapoptotic proteins Bcl-2, HSP-70, LIVIN, and PON2 with downregulation of apoptosis inducing mitochondrial associated molecules, including clusterin, cytochrome C, and HTRA2/OMI. In the early postoperative period, there were significantly lower levels of circulating mitochondrial DNA in recipients receiving EVLP lungs compared with a standard transplant (P = 0.016). Genomic DNA did not differ between groups, with donor DNA undetectable at all time points. CONCLUSIONS: EVLP alters the inflammatory signaling profile of the donor lung before transplantation, with a global cell survival and antiapoptotic signature.

A nonrandomized open-label phase 2 trial of nonischemic heart preservation for human heart transplantation.

Pre-clinical heart transplantation studies have shown that ex vivo non-ischemic heart preservation (NIHP) can be safely used for 24 h. Here we perform a prospective, open-label, non-randomized phase II study comparing NIHP to static cold preservation (SCS), the current standard for adult heart transplantation. All adult recipients on waiting lists for heart transplantation were included in the study, unless they met any exclusion criteria. The same standard acceptance criteria for donor hearts were used in both study arms. NIHP was scheduled in advance based on availability of device and trained team members. The primary endpoint was a composite of survival free of severe primary graft dysfunction, free of ECMO use within 7 days, and free of acute cellular rejection ≥2R within 180 days. Secondary endpoints were I/R-tissue injury, immediate graft function, and adverse events. Of the 31 eligible patients, six were assigned to NIHP and 25 to SCS. The median preservation time was 223 min (IQR, 202-263) for NIHP and 194 min (IQR, 164-223) for SCS. Over the first six months, all of the patients assigned to NIHP achieved event-free survival, compared with 18 of those assigned to SCS (Kaplan-Meier estimate of event free survival 72.0% [95% CI 50.0-86.0%]). CK-MB assessed 6 ± 2 h after ending perfusion was 76 (IQR, 50-101) ng/mL for NIHP compared with 138 (IQR, 72-198) ng/mL for SCS. Four deaths within six months after transplantation and three cardiac-related adverse events were reported in the SCS group compared with no deaths or cardiac-related adverse events in the NIHP group. This first-in-human study shows the feasibility and safety of NIHP for clinical use in heart transplantation. ClinicalTrial.gov, number NCT03150147.

Intact coronary and myocardial functions after 24 hours of non-ischemic heart preservation.

Objectives. The aim of this study was to investigate endothelium dependent relaxation (EDR) in coronary artery and the myocardial contractility after 24 h of non-ischemic heart preservation (NIHP). Design. Explanted cardioplegic hearts from six pigs were preserved by NIHP for 24 h. The perfusion medium consisted of an albumin containing hyperoncotic cardioplegic nutrition-hormone solution with erythrocytes to a hematocrit of 10%. Coronary artery ring segments were then studied in organ baths. Thromboxane A2 was used for vasocontraction and Substance P to elicit endothelium dependent relaxation. A heart trabecula from the right ventricle was mounted in an organ bath and a special stimulation protocol was used to characterize myocardial contractility. Fresh cardioplegic hearts from 11 pigs were used as controls. The water content of the hearts was calculated. Results. There was no significant difference between NIHP and fresh controls regarding EDR (91.2 ± 1.2% vs 93.1 ± 1.8%). The contraction force, potentiation and calcium recirculation fraction did not differ between the groups. The water content of the myocardium was 79.3 ± 0.2% for NIHP and 79.5 ± 0.2% for controls. Conclusions. NIHP for 24 h keeps coronary artery EDR and myocardial contractility intact and causes no edema.

Author Correction: Consistent success in life-supporting porcine cardiac xenotransplantation.

In this Letter, Mayuko Kurome and Valeri Zakhartchenko have been added to the author list (affiliated with Institute of Molecular Animal Breeding and Biotechnology, Gene Center, LMU Munich, Munich, Germany). The author list and 'Author contributions' section have been corrected online; see accompanying Amendment.

Phase-controlled intermittent intratracheal insufflation of oxygen during chest compression-active decompression mCPR improves coronary perfusion pressure over continuous insufflation.

PURPOSE: It has previously been shown that continuous intratracheal insufflation of oxygen (CIO) is superior to intermittent positive pressure ventilation (IPPV) regarding gas exchange and haemodynamics. The purpose of this study was to investigate gas exchange and haemodynamics with a new technique of phase-controlled intermittent insufflation of oxygen (PIIO) compared to CIO. METHOD: Twenty (20) pigs were used, stratified into two groups (CIO, PIIO), with 10 animals each. Upon induction of ventricular fibrillation, standard ventilator support was replaced by either of CIO or PIIO ventilation. Chest compressions were delivered by the LUCAS I mCPR device. Following 20 min of CPR in normothermia, defibrillation was attempted. RESULTS: Return of spontaneous circulation (ROSC) occurrence was not significantly higher (P < 0.16) in the PIIO (9/10) than in the CIO (6/10) group. During the decompression phase the PIIO group showed significant increases in mean (P < 0.01), maximal (P < 0.02) and end-decompression (P < 0.01) coronary perfusion pressure (CPP), compared to the CIO group. PIIO resulted in increased compression phase aortic pressure (P < 0.03). Intratracheal pressure was 5-30 cmH2O within both groups during mCPR, with a significantly lower (P < 0.02) mean for the PIIO group. Arterial and venous blood gas analysis showed comparable results between the groups, when taking base line values into account. An exception was that PIIO resulted in significantly higher (P < 0.05) oxygen partial pressure during mCPR, and lower (P < 0.05) arterial lactate following ROSC. CONCLUSION: PIIO results in significantly higher CPP and compression phase aortic pressure during mCPR in a porcine population. Further studies are needed to validate these findings in humans. Study protocol conforming with ethic approval M174-15, issued by the Malmö/Lunds regionala djurförsöksetiska nämnd (REB).

Consistent success in life-supporting porcine cardiac xenotransplantation.

Heart transplantation is the only cure for patients with terminal cardiac failure, but the supply of allogeneic donor organs falls far short of the clinical need1-3. Xenotransplantation of genetically modified pig hearts has been discussed as a potential alternative4. Genetically multi-modified pig hearts that lack galactose-α1,3-galactose epitopes (α1,3-galactosyltransferase knockout) and express a human membrane cofactor protein (CD46) and human thrombomodulin have survived for up to 945 days after heterotopic abdominal transplantation in baboons5. This model demonstrated long-term acceptance of discordant xenografts with safe immunosuppression but did not predict their life-supporting function. Despite 25 years of extensive research, the maximum survival of a baboon after heart replacement with a porcine xenograft was only 57 days and this was achieved, to our knowledge, only once6. Here we show that α1,3-galactosyltransferase-knockout pig hearts that express human CD46 and thrombomodulin require non-ischaemic preservation with continuous perfusion and control of post-transplantation growth to ensure long-term orthotopic function of the xenograft in baboons, the most stringent preclinical xenotransplantation model. Consistent life-supporting function of xenografted hearts for up to 195 days is a milestone on the way to clinical cardiac xenotransplantation7.

How to avoid severe coronary vasoconstriction in potassium induced cardioplegia.

OBJECTIVES: The aim of this study was to investigate how high K+ concentrations can be safely used in cardioplegic solutions without causing severe coronary artery vasocontraction. DESIGN: Twenty-four 50 kg pigs were used. The distal part of the left anterior descending coronary artery was cut into ring segments and transferred into organ baths with Krebs solution bubbled with 95% O2 and 5% CO2. K+ concentrations between 16 and 127 mM were used to induce vasocontractions at 37, 22, 15, and 8 °C. Mg2+ (0-20 mM) were used to attenuate K+ induced vasocontractions. RESULTS: K+-Krebs solution 127 mM at 37 °C induced a strong, sustained vasocontraction defined as 100%. The contractions induced by 16, 23, 30 and 127 mM K+ were: 7.7, 38, 72 and 100% at 37 °C; 1.7, 7.4, 21 and 65% at 22 °C; 1, 6.6, 15 and 33% at 15 °C; 0.6, 2.1, 6 and 14% at 8 °C, respectively. Mg2+ reduced the K+-induced contraction at 37 °C in a concentration-dependent way and Mg2+ at 8 mM practically eliminated the risk for severe vasocontraction. CONCLUSIONS: Hypothermia (8 °C) abolishes coronary contraction induced by K+-cardioplegic solutions. In normothermic cardioplegia 8 mM Mg2+ prevents vasoconstriction.