BACKGROUND:The coexistence of severe mitral regurgitation (MR) and mild-to-moderate aortic stenosis (AS) presents diagnostic and therapeutic challenges. Limited data exists on outcomes following mitral transcatheter edge-to-edge repair (M-TEER) therapy in this patient population. AIMS:This study is aimed to evaluate clinical outcomes following M-TEER in patients with mild-to-modearte AS compared with those without aortic stenosis. METHODS:A single-center retrospective study was conducted on 238 patients who underwent M-TEER therapy between January 2014 and December 2024. Patients with severe AS, cardiogenic shock, and failed or aborted cases were excluded. We compared patients with mild-to-moderate AS (n = 30) to those without AS (n = 208). PRIMARY OUTCOME:Acute hypoxemic respiratory failure (AHRF) within 24 h (SpO2 ≤ 90% ≥ 30 min or need for O2/NIV/IMV, adjudicated as cardiogenic). SECONDARY OUTCOMES:Post-procedural in-hospital mortality, acute kidney injury, hospital length of stay (LOS), 30-day rate of heart failure hospitalization (HFH), and 30-day rate of all-cause readmission. Multivariable logistic regression was used to identify independent predictors of AHRF, hospital LOS, and 30-day HFH. RESULTS:Following M-TEER, the mild-to-moderate AS group experienced significantly higher rates of AHRF (16.7% vs. 3.8%, p = 0.0142; adjusted OR 4.38, 95% CI 1.36-14.61, p = 0.014). Within the parsimonious adjusted model, AS remained independently associated with AHRF, whereas the other included covariates were not. There was no significant difference in the 30-day rate of all-cause readmission, 30-day rate of HFH, AKI, LOS, or in-hospital mortality between groups. CONCLUSION:In patients undergoing M-TEER, the presence of mild-to-moderate AS is independently associated with an increased risk of early post-procedural AHRF, without differences in other short-term clinical outcomes. Given the single-center retrospective design and the limited number of clinical events, these findings should be considered hypothesis-generating and warrant validation in larger, prospective, multicenter studies.

Following our previous experience with cardiac xenotransplantation of a genetically modified porcine heart into a live human, we sought to achieve improved results by selecting a healthier recipient and through more sensitive donor screening for potential zoonotic pathogens. Here we transplanted a 10-gene-edited pig heart into a 58-year-old man with progressive, debilitating inotrope-dependent heart failure due to ischemic cardiomyopathy who was not a candidate for standard advanced heart failure therapies. He was maintained on a costimulation (anti-CD40L, Tegoprubart) blockade-based immunomodulatory regimen. The xenograft initially functioned well, with excellent systolic and diastolic function during the first several weeks posttransplantation. Subsequently, the xenograft developed rapidly progressing diastolic heart failure, biventricular wall thickening and, ultimately, near-complete loss of systolic function necessitating initiation of extracorporeal membranous oxygenation on day 31. Given these setbacks, the patient chose to transition to comfort care after 40 days. As with our first patient, histology did not reveal substantial immune cell infiltration but suggested capillary endothelial injury with interstitial edema and early fibrosis. No evidence of porcine cytomegalovirus replication in the xenograft was observed. Strategies to overcome the obstacle of antibody-mediated rejection are needed to advance the field of xenotransplantation. In the second case in which a genetically modified pig heart was transplanted into a living person, the xenografted heart functioned well initially, but antibody-mediated rejection occurred thereafter, pointing to the need for improved strategies to avoid this complication.

Improvement in gene modifications of donor pigs has led to the prevention of early cardiac xenograft rejection and significantly prolonged cardiac xenograft survival in both heterotopic and orthotopic preclinical non-human primate (NHP) models. This progress formed the basis for FDA approval for compassionate use transplants in two patients. Based on our earlier report of 9-month survival of seven gene-edited (7-GE) hearts transplanted (life-supporting orthotopic) in baboons, we transplanted 10 gene-edited pig hearts into baboons (n = 4) using non-ischemic continuous perfusion preservation (NICP) and immunosuppression regimen based on co-stimulation blockade by anti-CD40 monoclonal antibody. This pivotal study expands on the 7-GE backbone, with 3 additional gene edits, using 10-GE pigs as donors to baboon recipients. 10 GE cardiac xenografts provide life-supporting function up to 225 days (mean 128 ± 36 days) in a non-human primate model. Undetectable or latent porcine cytomegalovirus (PCMV) does not influence cardiac xenograft survival in this study but still needs more exploration with a larger cohort. Xenograft histology demonstrates adipose (Fat) deposition (n = 1), chronic vasculopathy (n = 1), micro and macro thrombosis, and acute cellular rejection (n = 1). These data demonstrate that 10 GE cardiac xenografts have variable cardiac xenograft survival in NHP due to perhaps presence of 4th antigen and require further study. However, these 10GE organs may be suitable for clinical cardiac xenotransplantation and have already been utilized in two human cases. There is a shortage of organs donated for use in transplantation. Instead, animal organs could potentially be used for people with end-stage organ failure. We modified pig hearts to make them more like human organs and transplanted them into non-human primates. The pig hearts functioned in the non-human primates for up to 225 days. These hearts could also potentially be used in people with heart failure. Singh, Goerlich et al. transplant 10 gene modified pig hearts into non-human primates. Life-supporting function occurred for up to 225 days but there was evidence of adipose deposition, chronic vasculopathy, micro and macro thrombosis, and acute cellular rejection.

We read with great interest the study by Seifert et al,1Seifert S.M. Lumbreras-Marquez M.I. Goobie S.M. et al.Tranexamic acid administered during cesarean delivery in high-risk patients: maternal pharmacokinetics, pharmacodynamics, and coagulation status.Am J Obstet Gynecol. 2022; 227: 763.e1-763.e10Abstract Full Text Full Text PDF Scopus (4) Google Scholar who assessed the pharmacokinetics (PK) and pharmacodynamics (PD) of tranexamic acid (TXA) administered to women at risk for postpartum hemorrhage (PPH) undergoing cesarean delivery. A combined assessment of PK and PD is meaningful in elucidating a clinically effective level of TXA, as multiple modifiers of bleeding and fibrinolysis interact during PPH. The authors empirically selected a target TXA plasma concentration (>10 mg/L). All patients had a TXA level >10 mg/L at 1 hour, which was maintained in more than half of the patients at 3 hours. Although these data seem to suggest that the studied TXA dosing should cover a postpartum surge of tPA, it is difficult to assess the overall hemostatic function at the patient level. The TXA concentration per se does not prove antifibrinolytic efficacy or clinical hemostasis. To assess the PD, the authors used a serially measured tissue factor-activated test (EXTEM) of rotational thromboelastometry (ROTEM; Instrumentation Laboratory, Bedford, MA). There are several potential issues with using EXTEM in the assessment of localized or systemic fibrinolysis. First, the EXTEM maximum clot firmness (MCF) or maximum lysis (ML) parameters are rather insensitive to the in vivo plasmin generation reflected on D-dimer or plasmin-antiplasmin complex levels.2Raza I. Davenport R. Rourke C. et al.The incidence and magnitude of fibrinolytic activation in trauma patients.J Thromb Haemost. 2013; 11: 307-314Abstract Full Text Full Text PDF PubMed Scopus (369) Google Scholar A half-life of tissue plasminogen activator is rather short (5 minutes),3Chandler W.L. Alessi M.C. Aillaud M.F. Henderson P. Vague P. Juhan-Vague I. Clearance of tissue plasminogen activator (TPA) and TPA/plasminogen activator inhibitor type 1 (PAI-1) complex: relationship to elevated TPA antigen in patients with high PAI-1 activity levels.Circulation. 1997; 96: 761-768Crossref PubMed Scopus (202) Google Scholar and an EXTEM test performed with peripheral venous blood is unlikely to capture localized fibrinolysis in the postpartum uterus. The low incidence of hyperfibrinolysis may simply represent the insensitivity of an EXTEM test. Second, even if higher ML values were present, it is important to consider the possibility of platelet-mediated clot retraction. Arnolds and Scavone previously observed increased clot lysis (≥3%) at 30 minutes on kaolin-activated thromboelastography in 12.7% (15 of 118) PPH cases.4Arnolds D.E. Scavone B.M. Thromboelastographic assessment of fibrinolytic activity in postpartum hemorrhage: a retrospective single-center observational study.Anesth Analg. 2020; 131: 1373-1379Crossref PubMed Scopus (18) Google Scholar However, a simultaneously performed functional fibrinogen test using abciximab failed to demonstrate any clot lysis in 13 of the 15 cases (86.7%). Clot retraction is driven by platelets, and thus, a platelet inhibitor allows differentiation from clot lysis. Seifert et al also performed an assay (FIBTEM [ROTEM for assessing fibrinogen levels and fibrin polymerization]) with platelet inhibitor cytochalasin D, but the results were not reported. Third, the authors’ comment that “TXA concentration was associated with enhanced clot strength” was based on a weak positive correlation between TXA concentration and EXTEM-MCF (r=0.32). For cases with substantial bleeding, it is plausible that the accompanying hemodilution lowered both TXA and MCF and caused this correlation. Tranexamic acid for cesarean delivery: evidence of fibrinolysis?American Journal of Obstetrics & GynecologyVol. 228Issue 1PreviewWe read the letter “Tranexamic acid for cesarean delivery: induction of a regimen for postpartum hemorrhage?” in response to our publication “Tranexamic acid administered during cesarean delivery in high-risk patients: maternal pharmacokinetics, pharmacodynamics, and coagulation status.” We agree that using systemic whole blood to detect postpartum hyperfibrinolysis with rotational thromboelastometry (ROTEM; Instrumentation Laboratory, Bedford, MA) may have limitations.1 Consistent with this, we saw no evidence of hyperfibrinolysis in peripheral samples by comparing EXTEM (ROTEM without aprotinin) vs APTEM (ROTEM with aprotinin) clotting time and maximum clot firmness (MCF). Full-Text PDF

HomeCirculation: Cardiovascular InterventionsVol. 16, No. 10First-in-Human Endovascular Aortic Root Repair (Endo-Bentall) for Acute Type A Dissection No AccessCase ReportRequest AccessFull TextAboutView Full TextView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissionsDownload Articles + Supplements ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toSupplemental MaterialNo AccessCase ReportRequest AccessFull TextFirst-in-Human Endovascular Aortic Root Repair (Endo-Bentall) for Acute Type A Dissection Mehrdad Ghoreishi, Diljon Chahal, Aakash Shah, Jeanwan Kang, Jeffrey Hirsch, Douglas Tran, Dana McCloskey, Melsjan Shkullaku, Anuj Gupta, Erik R. Strauss, Siamak Dahi, Bradley S. Taylor and Shahab Toursavadkohi Mehrdad GhoreishiMehrdad Ghoreishi Correspondence to: Mehrdad Ghoreishi, MD, Division of Cardiac Surgery, Department of Surgery, University of Maryland School of Medicine, 7th Floor, S. Paca St, Baltimore, MD, 21224, Email E-mail Address: [email protected] https://orcid.org/0009-0002-1370-398X Division of Cardiac Surgery, Department of Surgery (M.G., A.S., D.T., D.M., S.D., B.S.T.), University of Maryland School of Medicine, Baltimore. , Diljon ChahalDiljon Chahal https://orcid.org/0000-0003-2717-1486 Division of Interventional Cardiology, Department of Medicine (D.C., M.S., A.G.), University of Maryland School of Medicine, Baltimore. , Aakash ShahAakash Shah https://orcid.org/0000-0003-2302-733X Division of Cardiac Surgery, Department of Surgery (M.G., A.S., D.T., D.M., S.D., B.S.T.), University of Maryland School of Medicine, Baltimore. , Jeanwan KangJeanwan Kang Division of Vascular Surgery, Department of Surgery (J.K., S.T.), University of Maryland School of Medicine, Baltimore. , Jeffrey HirschJeffrey Hirsch Department of Diagnostic Radiology and Nuclear Medicine (J.H.), University of Maryland School of Medicine, Baltimore. , Douglas TranDouglas Tran https://orcid.org/0000-0001-9231-440X Division of Cardiac Surgery, Department of Surgery (M.G., A.S., D.T., D.M., S.D., B.S.T.), University of Maryland School of Medicine, Baltimore. , Dana McCloskeyDana McCloskey Division of Cardiac Surgery, Department of Surgery (M.G., A.S., D.T., D.M., S.D., B.S.T.), University of Maryland School of Medicine, Baltimore. , Melsjan ShkullakuMelsjan Shkullaku Division of Interventional Cardiology, Department of Medicine (D.C., M.S., A.G.), University of Maryland School of Medicine, Baltimore. , Anuj GuptaAnuj Gupta Division of Interventional Cardiology, Department of Medicine (D.C., M.S., A.G.), University of Maryland School of Medicine, Baltimore. , Erik R. StraussErik R. Strauss https://orcid.org/0000-0002-6424-9441 Division of Cardiac Anesthesiology, Department of Anesthesiology (E.R.S.), University of Maryland School of Medicine, Baltimore. , Siamak DahiSiamak Dahi https://orcid.org/0000-0002-0015-8989 Division of Cardiac Surgery, Department of Surgery (M.G., A.S., D.T., D.M., S.D., B.S.T.), University of Maryland School of Medicine, Baltimore. , Bradley S. TaylorBradley S. Taylor https://orcid.org/0000-0002-4153-9892 Division of Cardiac Surgery, Department of Surgery (M.G., A.S., D.T., D.M., S.D., B.S.T.), University of Maryland School of Medicine, Baltimore. and Shahab ToursavadkohiShahab Toursavadkohi Shahab Toursavadkohi, MD, Division of Vascular Surgery, Department of Surgery, 7th Floor, S. Paca St, Baltimore, MD, 21224, Email E-mail Address: [email protected] Division of Vascular Surgery, Department of Surgery (J.K., S.T.), University of Maryland School of Medicine, Baltimore. Originally published22 Sep 2023https://doi.org/10.1161/CIRCINTERVENTIONS.123.013348Circulation: Cardiovascular Interventions. 2023;16FootnotesFor Sources of Funding and Disclosures, see page 685.Supplemental Material is available at https://www.ahajournals.org/doi/suppl/10.1161/CIRCINTERVENTIONS.123.013348.Correspondence to: Mehrdad Ghoreishi, MD, Division of Cardiac Surgery, Department of Surgery, University of Maryland School of Medicine, 7th Floor, S. Paca St, Baltimore, MD, 21224, Email mghoreishi@som.umaryland.eduShahab Toursavadkohi, MD, Division of Vascular Surgery, Department of Surgery, 7th Floor, S. Paca St, Baltimore, MD, 21224, Email stoursavadkohi@som.umaryland.eduREFERENCES1. Gaia DF, Bernal O, Castilho E, Ferreira CBND, Dvir D, Simonato M, Palma JH. First-in-human Endo-Bentall procedure for simultaneous treatment of the ascending aorta and aortic valve.JACC Case Rep. 2020; 2:480–485. doi: 10.1016/j.jaccas.2019.11.071CrossrefMedlineGoogle Scholar2. Gandet T, Westermann D, Conradi L, Panuccio G, Heidemann F, Rohlffs F, Kolbel T. Modular Endo-Bentall procedure using a "Rendez-Vous Access.".J Endovasc Ther. 2022; 29:711–716. doi: 10.1177/15266028211065959CrossrefMedlineGoogle Scholar3. Leshnower BG, Duwayri YM, Nicholson WJ, Ueyama H, Gleason P, Shekiladze N, Greenbaum AB, Babaliaros V. Endo-Bentall procedure using off-the-shelf catheter devices to repair an aorto-atrial fistula.Circ Cardiovasc Interv. 2023; 16:e012848. doi: 10.1161/CIRCINTERVENTIONS.122.012848LinkGoogle Scholar4. Zaid S, Attizzani GF, Krishnamoorthy P, Yoon SH, Dallan LM, Chetcuti S, Fukuhara S, Grossman PM, Goel SS, Atkins MD, et al. First-in-human multicenter experience of the newest generation supra-annular self-expanding Evolut FX TAVR system.JACC Cardiovasc Interv. 2023; 16:1626–1635. doi: 10.1016/j.jcin.2023.05.004CrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetailsCited By Menges A, Zimmermann A, Stoklasa K, Reitnauer D, Meuli L and Reutersberg B (2024) Hospital Incidence, Sex Disparities, and Perioperative Mortality in Open Surgically Treated Patients with Aneurysms of the Ascending Aorta and Aortic Arch in Switzerland, Healthcare, 10.3390/healthcare12030388, 12:3, (388) October 2023Vol 16, Issue 10 Advertisement Article InformationMetrics © 2023 American Heart Association, Inc.https://doi.org/10.1161/CIRCINTERVENTIONS.123.013348PMID: 37737022 Originally publishedSeptember 22, 2023 Keywordsaortic valvedissectionpatientsriskstentsPDF download Advertisement SubjectsAcute Coronary SyndromesAortic Valve Replacement/Transcatheter Aortic Valve ImplantationCardiovascular Surgery

We report the intraoperative management of an orthotopic cardiac xenotransplant in a 57-year-old man with nonischemic cardiomyopathy requiring venoarterial extracorporeal membrane oxygenation. Transesophageal echocardiography was used for preharvest assessment. Continuous ex vivo perfusion of the heart was performed. Steps were taken to avoid potential xenozoonosis transmission to other patients and staff. Preclinical experience guided our intraoperative management in controlling hemodynamics and using prophylactic antiarrhythmic medications. Echocardiography aided in the diagnosis of aortic dissection in the patient after transplant. Intraoperative cardiac function was excellent. The patient was weaned from all mechanical support 4 days after transplant.

ON JANUARY SEVENTH, 2022, the first genetically modified porcine cardiac xenograft was transplanted into a patient at the University of Maryland Medical Center. As members of the xenotransplant team and division of cardiac anesthesiology at the University of Maryland School of Medicine, the authors here had a role in this historic event. Cardiac xenotransplantation could become a common occurrence if it proves to be a viable answer for the limited supply of donor hearts to treat end-stage heart failure.1Martin AK Ripoll JG Wilkey BJ et al.Analysis of outcomes in heart transplantation.J Cardiothorac Vasc Anesth. 2020; 34: 551-561Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar Early attempts at cardiac xenotransplantation and allotransplantation are well-known.2Bailey LL Nehlsen-Cannarella SL Concepcion W et al.Baboon-to-human cardiac xenotransplantation in a neonate.JAMA. 1985; 254: 3321-3329Crossref PubMed Scopus (294) Google Scholar, 3Hardy JD Kurrus FD Chavez CM et al.Heart transplantation in man. Developmental studies and report of a case.JAMA. 1964; 188: 1132-1140Crossref PubMed Scopus (141) Google Scholar, 4Barnard CN. The operation. A human cardiac transplant: An interim report of a successful operation performed at Groote Schuur Hospital, Cape Town.S Afr Med J. 1967; 41: 1271-1274PubMed Google Scholar The case report5Ozinsky J. Cardiac transplantation–the anaesthetist's view: a case report.S Afr Med J. 1967; 41: 1268-1270PubMed Google Scholar written by Dr Ozinsky, the anesthesiologist for the first human allogeneic heart transplant in 1967 at the Groote Schuur Hospital of the University of Cape Town in South Africa, was cited and celebrated in the Journal of Cardiac and Vascular Anesthesia 50 years later.6Swanevelder JLC Gordon PC Brink JG et al.Fifty years: Reflections since the first successful heart transplant.J Cardiothorac Vasc Anesth. 2018; 32: 14-18Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar Despite the novelty of the surgery in humans, the team back in 1967 had the prior experience of completing 48 heart transplants in a large animal model. Likewise, the authors’ cardiac anesthesiology team had considerable clinical experience not only in human heart transplantation but specifically in orthotopic xenotransplantation of genetically modified pig hearts into baboons well before January 2022. The authors’ experience started late in 2017 when an accomplished researcher, Dr Mohiuddin, brought his xenotransplant research to the University of Maryland. Xenotransplantation has numerous obstacles, including immunologic and physiological barriers related to natural antibodies to carbohydrates present on pig endothelium, uncontrolled complement activation, and incompatible procoagulant and anticoagulant proteins or receptors.7Pierson 3rd, RN Fishman JA Lewis GD et al.Progress toward cardiac xenotransplantation.Circulation. 2020; 142: 1389-1398Crossref PubMed Scopus (33) Google Scholar In addition, porcine xenotransplants have a potential infectious risk of transmitting porcine endogenous retrovirus to humans.8Patience C Takeuchi Y Weiss RA. Infection of human cells by an endogenous retrovirus of pigs.Nat Med. 1997; 3: 282-286Crossref PubMed Scopus (1014) Google Scholar These issues add further levels of complexity to an already complex procedure in cardiac transplantation. Anesthesiologists can play a major role in facilitating success in this endeavor by striving to usher cardiac xenotransplantation surgeries through the perioperative period with a consistent and vigilant approach. Collaborative efforts between surgeons and anesthesiologists are vital to the future success of xenotransplantation. The perioperative management of the first genetically modified pig-to-human cardiac transplant surgery will be presented in a follow-up case report. The overall significance of this transplant is that the cardiac function of the transplanted porcine heart was reliable throughout the perioperative period and allowed the patient to be weaned from and stay off all mechanical support for almost 2 months. The intraoperative course of the xenotransplant surgery was complicated by the development of type A aortic dissection. The need to re-arrest a newly transplanted heart was a significant event, and given the specter of perioperative cardiac xenograft dysfunction (PCXD), such a test for a xenotransplant is uncharted territory. Re-arresting the transplanted xenograft tested the cardiac preservation technique, physiological compatibility, and reserve. The entire procedure was a test of the immunogenic suitability and endurance of the porcine xenograft. An amazing amount of talented physician-researchers have made contributions to the science underlying xenotransplantation.9Eyestone W, Adams K, Ball S, et al. Gene-edited pigs for xenotransplantation. In: Cooper DKC, Byrne GW (eds): Clinical xenotransplantation: Pathways and progress in the transplantation of organs and tissues between species. New York, NY: Springer; 2020. p. 121-40.Google Scholar,10Cooper DKC Hara H Iwase H et al.Justification of specific genetic modifications in pigs for clinical organ xenotransplantation.Xenotransplantation. 2019; 26: e12516Crossref PubMed Scopus (81) Google Scholar In 2014, 1-year cardiac xenograft survival was achieved in a heterotopic pig-heart-to-baboon model with 3 genetic modifications.11Mohiuddin MM Singh AK Corcoran PC et al.One-year heterotopic cardiac xenograft survival in a pig to baboon model.Am J Transplant. 2014; 14: 488-489Crossref PubMed Scopus (94) Google Scholar Acute host antibody-mediated rejection was addressed by knocking out the alpha galactosyltransferase gene (GTKO) combined with transgenic expression of human complement regulatory protein (hCD46) and human thrombomodulin (hTBM), which was added to prevent complications related to microvascular thrombosis.12Mohiuddin MM Singh AK Corcoran PC et al.Genetically engineered pigs and target-specific immunomodulation provide significant graft survival and hope for clinical cardiac xenotransplantation.J Thorac Cardiovasc Surg. 2014; 148 (discussion 1113-4): 1106-1113Abstract Full Text Full Text PDF PubMed Scopus (92) Google Scholar An immunomodulatory treatment regimen, which included an anti-CD40 antibody, also was added.13Mohiuddin MM Singh AK Corcoran PC et al.Role of anti-CD40 antibody-mediated costimulation blockade on non-Gal antibody production and heterotopic cardiac xenograft survival in a GTKO.hCD46Tg pig-to-baboon model.Xenotransplantation. 2014; 21: 35-45Crossref PubMed Scopus (64) Google Scholar This model initially was used for orthotopic heart transplants starting in late 2017.14DiChiacchio L Singh AK Lewis B et al.Early experience with preclinical perioperative cardiac xenograft dysfunction in a single program.Ann Thorac Surg. 2020; 109: 1357-1361Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar In the authors’ experience, pig-to-baboon xenotransplantation from 2017 to 2019 was associated with instances of PCXD, which manifested as a decrease in cardiac function despite the titration of intravenous (IV) inotropes. The addition of non-ischemic cardiac preservation with continuous ex vivo perfusion of the heart helped to improve PCXD and advance the baboon recipients through the perioperative phase.15Längin M Mayr T Reichart B et al.Consistent success in life-supporting porcine cardiac xenotransplantation.Nature. 2018; 564: 430-433Crossref PubMed Scopus (239) Google Scholar,16Goerlich CE Griffith B Singh AK et al.Blood cardioplegia induction, perfusion storage and graft dysfunction in cardiac xenotransplantation.Front Immunol. 2021; 12667093Crossref PubMed Scopus (11) Google Scholar Further genetic knockouts of β1,4-N-acetylgalactosyltransferase and cytidine monophosphate-N-acetylneuraminic acid hydroxylase inhibited the production of the carbohydrate antigens SDa blood group antigen (SDa) and N-glycolylneuraminic acid, respectively, and xenotransplant survival extended to 2 to 3 months.17Goerlich CE, Griffith B, Hanna P, et al. The growth of xenotransplanted hearts can be reduced with growth hormone receptor knockout pig donors. J Thorac Cardiovasc Surg. https://doi.org/10.1016/j.jtcvs.2021.07.051.Google Scholar Nevertheless, the heart appeared to develop overgrowth and thickening of the myocardium, with diastolic dysfunction resulting in ascites and heart failure.18Mohiuddin M, Goerlich C, Singh A, et al. Progressive genetic modifications with growth hormone receptor knockout extends cardiac xenograft survival to 9 months. Xenotransplantation. https://doi.org/10.1111/xen.12744. [e-pub ahead of print].Google Scholar The addition of growth hormone receptor knockout appeared to decrease this myocardial thickening, with diastolic dysfunction and extended survival past 9 months when added to genetic modifications of GTKO, β1,4-N-acetylgalactosyltransferase, hTBM, hCD46, hCD47, humanized heme oxygenase-1, decay-accelerating factor, and endothelial protein C receptor.18Mohiuddin M, Goerlich C, Singh A, et al. Progressive genetic modifications with growth hormone receptor knockout extends cardiac xenograft survival to 9 months. Xenotransplantation. https://doi.org/10.1111/xen.12744. [e-pub ahead of print].Google Scholar The authors’ group (ES, PO, and BW) was involved in the anesthetic care for 41 pig-to-baboon orthotopic cardiac xenotransplants, and the experience gained from these surgeries educated their approach to the first human transplant. Although many of the details of the authors’ anesthetic care for these surgeries are not directly translatable or pertinent to human cardiac surgery, these experiences should be reported because they explain their approach to the first human xenotransplant and are useful for future reference. The baboons weighed 15 to 30 kg, and after premedication with intramuscular ketamine 10 mg/kg, the baboon was shaved and scrubbed with chlorhexidine. Inhalation induction with sevoflurane 2.0% to 2.5% was performed prior to orotracheal tube placement, which varied in size from 6.5 to 8.0. Sevoflurane provided a predictable and easily titratable maintenance anesthetic, which facilitated emergence at the end of surgery. Rocuronium (20-30 mg) was administered in most cases after intubation. Baboons have suitable veins for 18-gauge catheters, which typically were placed in each forearm. All baboons had a tunneled 10F triple-lumen catheter surgically inserted into the jugular vein prior to the day of surgery, and this catheter was transduced to monitor central venous pressure but not typically used for intraoperative medication or fluid administration since it would be excluded from circulation with the heart explanted. A 12 cm 20-gauge catheter was inserted into the femoral artery and transduced for systemic pressure. A human adult-sized transesophageal echocardiography (TEE) probe X7-2t (Philips Medical Systems, Andover, MA) was inserted without difficulty in all baboons, and an iE33 machine (Philips Medical Systems) was used for imaging. Useful TEE images were obtained with difficulty as the sizes of the hearts, and the left atria (LA) were comparatively smaller and narrower than in humans, which provides a small imaging window. Post-xenotransplant TEE images, including the images of the orifice created by the LA suture-line, which joins the native and xenotransplant LA, are shown in video 1. A point-of-care blood gas and activated clotting time analyzer were used for all cases. Intraoperative immunosuppression medications were administered at various time points and consisted of infusions of rituximab (300 mL), ganciclovir (50 mL), tocilizumab (50 mL), and antiCD40 (150 mL), in addition to bolus dosing of solumedrol and etanercept. The total volume of these infusions (550 mL) was noteworthy, especially for smaller baboons (15 kg). Additional fluid administration was minimized whilst hemoconcentration was maximized on cardiopulmonary bypass (CPB). Ceftriaxone (50 mg/kg) was given for antimicrobial prophylaxis. Heparin was administered for CPB anticoagulation, with a goal activated clotting time above 480 seconds. Intraoperative pain control was addressed with IV fentanyl boluses (total 50-100 µg) early in the xenotransplant experience, but post-CPB boluses resulted in episodes of hypotension and delayed extubation. Buprenorphine IV (0.3-0.6 mg total) was used for pain control in more recent procedures, with a buprenorphine patch (10 µg/h) applied post-extubation. After separation from CPB, the heparin anticoagulation was reversed with a small bolus of protamine (20-40 mg). Minimal postoperative bleeding or coagulopathy was encountered throughout the experience, perhaps because the baboon sternum appeared to be less vascularized with less bleeding from needle holes and bone marrow compared to humans. An article detailing the transplant surgery procedure and management of CPB is available in preprint.19Goerlich C, Griffith B, Treffalls J, et al. A standardized approach to orthotopic (life-supporting) porcine cardiac xenotransplantation in a non-human primate model. Res Sq https://doi.org/10.21203/rs.3.rs-1138842/v1. [e-pub ahead of print]Google Scholar Anecdotally, the porcine heart was exquisitely sensitive to inotropes immediately after separation from CPB. Epinephrine (0.01-0.04 µg/kg/min) and dobutamine (1.0-2.5 µg/kg/min) administration usually caused an initial overshoot in heart rate (>110) and systemic blood pressure (mean arterial pressure >70) with hyperdynamic function seen on TEE (Video 2). If the systolic function and systemic pressure decreased in the late intraoperative or early postoperative phase, inotropes could be started without such overshoot, but the need for inotropic support was usually a potential sign of pending PCXD. Overall, inotropes were avoided unless the right or left ventricular function was seen to be significantly depressed on TEE (Video 3). The authors encountered episodes of ventricular arrhythmias resistant to cardioversion, which could be related to the phenomenon of PCXD; however, anatomic and physiological factors could have played a role. With the potential of using transgenic pigs for human cardiac transplants, Crick et al (Journal of Anatomy, 1999) studied the autonomic innervation of the pig heart with immunohistochemical and histochemical techniques, which showed important differences from human hearts. Pig hearts were shown to have an extensive innervation and an intrinsic supply of neural ganglia, which would be capable of functioning without efferent control.20Crick SJ Sheppard MN Ho SY et al.Localisation and quantitation of autonomic innervation in the porcine heart I: Conduction system.J Anat. 1999; 195: 341-357Crossref PubMed Google Scholar,21Crick SJ Anderson RH Ho SY et al.Localisation and quantitation of autonomic innervation in the porcine heart II: Endocardium, myocardium and epicardium.J Anat. 1999; 195: 359-373Crossref PubMed Google Scholar The pig heart is known to develop ventricular arrhythmia, particularly in the setting of cardiac surgery with cardioplegia.22Pasrija C Quinn RW Alkhatib H et al.Development of a reproducible swine model of chronic ischemic mitral regurgitation: Lessons learned.Ann Thorac Surg. 2021; 111: 117-125Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar To mitigate perioperative arrhythmias, a combination of amiodarone (0.25-0.5 mg/min) and lidocaine (1-2 mg/kg/h) were started prior to porcine heart implantation. In addition, an infusion of dexmedetomidine (0.5-1.0 µg/kg/h) was administered to decrease surges of endogenous catecholamines and possibly decrease arrhythmia. A secondary cause of refractory arrhythmia could be intracardiac thrombus formation, which was common in xenografts without the hTBM gene modification.23Goerlich CE Kaczorowski D Singh A et al.Human thrombomodulin transgene expression prevents intracardiac thrombus in life supporting pig-to-baboon cardiac xenotransplantation.J Heart Lung Transpl. 2020; 39: S145Abstract Full Text PDF PubMed Scopus (0) Google Scholar Although instances of intracardiac thrombi were not recorded with TEE, clots were seen on gross examination immediately after cardiac arrest. As the experience progressed with more genetic modifications and ex-vivo perfusion of the heart, the occurrence of ventricular arrhythmias diminished. Epicardial pacing was occasionally required before weaning from CPB, but the intrinsic rhythm was sufficient and preferred in most cases. Early in the authors’ experience, they observed that the porcine heart function and hemodynamics were overly sensitive to calcium chloride boluses (50-100 µg). Serum ionized calcium would predictably decrease below 1.00 mmol/L in the absence of regular calcium supplementation after CPB. This hypocalcemia may be related to immunosuppression medications, particularly anti-CD40. T-cell expression of CD40 ligand sensitizes bone marrow stroma cells to the parathyroid hormone for the induction of osteoclast formation, which would break down cortical bone and release calcium.24Gao Y Wu X Terauchi M et al.T cells potentiate PTH-induced cortical bone loss through CD40L signaling.Cell Metab. 2008; 8: 132-145Abstract Full Text Full Text PDF PubMed Scopus (113) Google Scholar The anti-CD40 medication may produce a functional state of hypoparathyroidism, thereby causing this observed calcium-seeking physiology. Calcium chloride infusions (100-200 mg/h) provided stable hemodynamics and helped avoid unexpected declines in cardiac function after transplantation. The authors avoided calcium chloride bolus administration. Early postoperative extubation became a common goal as their experience progressed. Low rates of bleeding and improved cardiac function with the ex-vivo perfusion and improved genetic modifications facilitated this goal. Immediately after closure, a chest x-ray was taken to assess the lung fields for consolidation, effusion, and pneumothorax. Buprenorphine IV was administered close to the end of surgery, and a buprenorphine patch was applied as fentanyl was difficult to titrate and typically caused systemic hypotension and unpredictable respiratory depression. Dexmedetomidine was stopped while infusions of amiodarone, calcium chloride, lidocaine, and occasionally inotropic medications were continued. Sugammadex (2 mg/kg) was administered in some cases if rocuronium had been redosed. Once the baboons spontaneously began ventilating, they were transported to their cage while still intubated. With the door closed, the oxygen level in the cage could be increased. Each baboon was fitted into a restraining jacket, which held the mediastinal drains on bulb suction and protected the infusion tubing connected to their 10F tunneled central venous catheter. The external portion of the infusion tubing had metal armor, which was connected to infusion pumps outside of the cage. Intramuscular injections of ketamine (10-20 mg) facilitated this transition if the baboon emerged from anesthesia before the process could be complete. Vital signs were monitored by direct observation and with a surgically implanted hemodynamic telemetric monitoring device.25Längin M Panelli A Reichart B et al.Perioperative telemetric monitoring in pig-to-baboon heterotopic thoracic cardiac xenotransplantation.Ann Transplant. 2018; 23: 491-499Crossref PubMed Scopus (6) Google Scholar Multiple years of experience with orthotopic cardiac xenotransplantation guided the authors’ decision-making and prepared them for the clinical challenge of a porcine cardiac transplant into a human patient. Prior knowledge and experience in allograft transplantation, along with medication regimens and exposure to PCXD in the pig-to-baboon model, were brought to the operating room on January 7. The decision to administer amiodarone, dexmedetomidine, lidocaine, and calcium chloride infusions stemmed from this previous experience. Additionally, inotropes and other vasoactive agents, which commonly are used for allogeneic heart transplants, were avoided because of the observation of increased sensitivity of the porcine heart. Other potential issues related to size mismatch and small LA orifice area were anticipated well in advance by the surgeon, Dr Bartley Griffith, because of his previous experience in the pig-to-baboon model. Issues related to fluid management, CPB, and cardioplegia for the xenograft were well understood and anticipated by the perfusion staff because they also were involved in the pig-to-baboon surgeries. Team cohesion was facilitated by prior experiences and played a role in the management of the unexpected intraoperative aortic dissection. Early formation of a collaborative multidisciplinary cardiac surgery team made this translational research effort possible. None. eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiI5OTdlMDdmMjk4MzJlZDgyM2MxZDViNDZlNDc4M2FlZCIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNjc2NDg4MDg4fQ.oAlWHgKS5adW780iujxTeI0ZftlQoI3SrN1ldyV7DzGvAHZQVniENQB9eqcssBzQNtNCelIElte5K-P38SBuQ-N3IIB87TU8YT6WWaIWNHtgTuyEjFGsf1rq9GkefV95sCMCD7H2y3tKUJj-8dRh2_jovZXp7uaiU7GKALtGzx4Zjt8WVQOwxC8jco5G-fL_ZaNDlzAIkn78-E9ltiixvsqJaTPTNmttNYkTUUiGvQ3mGYKh6O9WgePqjNcqMY5JVC9bVRFwyj80HXgd7DYYaNEkrhhpUixA5U-o_oIxc2wQdAfgwwH31CxnS7eN_-1DYtQdm9IOi4Sv3phQe1Ewew Download .mp4 (5.54 MB) Help with .mp4 files eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiIwZjY0ZGZiZDNkNThmOTI5NGQ4ZjY3YzZmNzU3ZGI3MiIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNjc2NDg4MDg4fQ.ABLClwJtrRtJBAbtxkeP3zQxkFrsqxi_otiWuagOypqBIZp6UDXa5j-TQ4fR-GYtkXBwz7P8GhKE0C1iVBf7ECftOXcdP8XTI_G4XG2yJsefK9c31vYPK39r5BEpOZDxTIqNKO8pIcYW0_EIBQ9jtVYp-Nj_OBzDeirQhv1k3ft1Kf3yBqpnY2lKupbGu4PDd56LIkbGVOS4smRmR0cq2zgm0qSNuP5TH-SVWyC56oKraa7gIS1n4qBmQEAqXvuP6csDNY1QiPNteuVW0FCwUlawX1pxuOBs7B0sSlrUJydsbHkNkgMNKRoPZWnue83DWbyOE0FxEx44Q1O6wVsh-Q Download .mp4 (5.68 MB) Help with .mp4 files eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiIwMWI5MzBjNTQzZmFjNWQzY2RiYjk0NDI4OTQxODlmNCIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNjc2NDg4MDg4fQ.U3HyEb8bLjkeiSgnwuI4fVvFI1Q1yYFzbEzE6G92JJGBzIvsdZCNeAyw0pQPlDJOs6qWWAEsNrw1LqFYKpZRs4__YPPNQY0ymGv6Q-Wkyt2OBasBjC7KKaSUS4EM04NlY0Xs54Dc4yidJvOO0r4nTEGNNjrMbWUaRIYEJwvggxEaFlRs4RoW16TJ2Ec82sY4MeUOoZ5uxrtp4sjbm8SiPvsJb4Z_PFGtBvJvUd_Rai_r-OBL9K0_JREbm94S_FMrS3OhrCI6gKjv6yYfK_ylSUGBvAx0KSlUKmD5znxR-l5dgQlg573OzJPVOkW7qL_Kuwe2Lme0ZffzwwTs0ZurAg Download .mp4 (6.3 MB) Help with .mp4 files

Cardiac xenotransplantation has been proposed to bridge the gap between supply and demand for patients with end-stage heart failure requiring transplantation. However, differences in pig anatomy compared with human anatomy require modification of the surgical approach. In addition, careful consideration should be given to size matching before transplantation. (Level of Difficulty: Advanced.).

OBJECTIVES The aim of this study was to present a rigorous method to analyse the intraoperative echocardiographic images from the novel mitral translocation procedure, which assesses the changes in mitral structure and function and compares this data to a control group of patients who have no mitral regurgitation (MR). METHODS Transoesophageal echocardiography was post-processed using dedicated 3D software. Ten patients with normal mitral valves (MV) undergoing non-mitral cardiac surgery served as controls. Mitral coaptation area, mid-leaflet coaptation length and mitral annular circumference were measured in 3D. RESULTS Twenty-three consecutive patients with severe secondary MR underwent MV translocation. All patients had none/trace MR post-translocation. The mean coaptation surface area increased from 63 to 427 mm2 (P < 0.001) and coaptation length increased from 1.0 to 10.5 mm (P < 0.001). The control group coaptation surface area (136 mm2) and length (2.5 mm) were greater than pre-translocation (P = 0.019; P < 0.001) and less than post-translocation (P < 0.001; P < 0.001). 3D mitral annular circumference in the translocation group decreased 15% (130-110 mm) (P < 0.001). Post-translocation, the mean gradient was 2(2-3) mmHg with the diastolic mitral orifice area of 3.4 ± 0.3 cm2 by planimetry and 3.5 ± 0.3 cm2 by pressure half-time. The coaptation to septum distance remained unchanged (P = 0.305) without systolic anterior leaflet motion. CONCLUSIONS This echocardiographic analysis method demonstrates that MV translocation abolishes secondary MR, increases coaptation area and length and produces acceptable diastolic function. This method of analysis should allow precise structural and quantitative assessment of the durability of the repair in future long-term follow-up.

Purpose of Review This review describes the latest information related to the administration of lysine analogues during cardiac surgery. An awareness of appropriate antifibrinolytic administration will maximize benefit for blood conservation efforts and possibly decrease morbidity and mortality. Recent Findings Recent pharmacodynamic assessments for antifibrinolytics are more sensitive. Research suggests that lower dose regimens may not provide maximal inhibition of fibrinolysis but may be equally effective in decreasing transfusion of blood products. Effective lower dose regimens may decrease the incidence of seizures and possibly morbidity and mortality. Summary The lysine analogues are a key addition to blood conservation efforts in cardiac surgery. Finding an optimized dosing regimen is complex and may include factors such as total dosage and timing of administration. Understanding of the pharmacokinetics and pharmacodynamics of these drugs will help perioperative physicians evaluate their own practice and improve their own regimens.

Preclinical advances in life-sustaining porcine cardiac xenotransplantation from donor pigs to baboons have paved the way for the performance of porcine cardiac xenotransplantation in a human. This procedure was performed with emergency use authorisation granted by the United States Food and Drug Administration under the umbrella of investigational new drug use on compassionate grounds. The patient was denied candidacy for durable mechanical circulatory support and heart transplantation as a result of non-adherence to medical advice.Successful porcine cardiac xenotransplantation in humans will significantly increase the availability of potential donor organs for long-term management of end-stage heart failure. Human porcine cardiac xenotransplantation is associated with ethical conflicts encompassing multiple ethical principles which are not mutually exclusive and are sometimes conflicting. This article focuses on some of the ethical conflicts encountered in relation to the use of mechanical circulatory support, pretransplant evaluation, shared decision making during informed consent, infectious disease risk, preclinical and clinical testing, and the role of regulatory bodies during performance of the first human porcine cardiac xenotransplantation.An increase in human trials of xenotransplantation procedures is imminent. Potential ethical conflicts associated with xenotransplantation should be addressed appropriately.

We report orthotopic (life-supporting) survival of genetically engineered porcine cardiac xenografts (with six gene modifications) for almost 9 months in baboon recipients. This work builds on our previously reported heterotopic cardiac xenograft (three gene modifications) survival up to 945 days with an anti-CD40 monoclonal antibody-based immunosuppression. In this current study, life-supporting xenografts containing multiple human complement regulatory, thromboregulatory, and anti-inflammatory proteins, in addition to growth hormone receptor knockout (KO) and carbohydrate antigen KOs, were transplanted in the baboons. Selective "multi-gene" xenografts demonstrate survival greater than 8 months without the requirement of adjunctive medications and without evidence of abnormal xenograft thickness or rejection. These data demonstrate that selective "multi-gene" modifications improve cardiac xenograft survival significantly and may be foundational for paving the way to bridge transplantation in humans.

OBJECTIVES:To examine the pharmacokinetics (PK) and pharmacodynamics of a tranexamic (TXA) regimen designed for cardiac surgery with cardiopulmonary bypass (CPB).DESIGN:A pilot study quantifying TXA concentrations, fibrinolysis markers, and a plasmin- generation (PG) assay. For comparison, PG assay was performed on pooled normal plasma (PNP) with varying TXA concentrations.SETTING:A single-center, tertiary, academic medical center.PARTICIPANTS:Twenty patients undergoing cardiac surgery with CPB for valve surgery and/or coronary artery bypass grafting.INTERVENTION:TXA 100 mg/h infusion for 5 hours starting before incision; 1 g TXA in CPB prime and 1 g TXA at CPB end prior to heparin reversal.MEASUREMENTS AND MAIN RESULTS:The PK fit a 2-compartment disposition model. TXA concentrations were above 15 mg/L in all patients during CPB through 2 hours post-TXA infusion. During and after CPB, the TXA regimen decreased the median peak PG by 60% (95% confidence interval [CI], 56%-62%). Lowest median peak PG occurred 15 minutes postprotamine. Peak median D-dimer level of 1.24 (0.95-1.71; 95% CI) mg/L occurred at 15 minutes postprotamine and baseline-adjusted ΔD dimer correlated with increased CPB time (p = 0.004) and lower TXA level (p = 0.001). The median 24-hour chest tube output was 447 (330-664; 95% CI) mL. PG assay on PNP revealed a plateau inhibition at 5 mM TXA (786 mg/L).CONCLUSIONS:This regimen, with total perioperative dose of 2.5 grams, provided TXA concentrations above 15 mg/L for all patients from CPB initiation through 2 hours post-TXA. PG was significantly inhibited (p < 0.0001) during and after CPB, with maximum inhibition measured at 15 minutes after protamine administration.

Current repair options for functional mitral regurgitation (FMR) are not durable and do not adequately address underlying pathophysiology including leaflet tethering and insufficient coaptation. The feasibility of mitral valve translocation as a repair strategy for FMR was examined in normal swine. Seven pigs (median 62 kg, IQR 55–65 kg) with normal cardiac function were implanted with a 1-cm frustum-shaped pericardial patch inserted between the native mitral annulus and intact mitral leaflets. Operative survival was 100

BACKGROUND:Functional (secondary) mitral regurgitation (FMR) results from altered geometry of the mitral valve apparatus. Repair with restrictive mitral annuloplasty is associated with high rates of recurrent mitral regurgitation (MR). We developed a novel operative repair for FMR that translocates the intact mitral valve towards the apex. METHODS:The mitral valve was detached circumferentially and translocated into the ventricle with a frustum-shaped glutaraldehyde-treated autologous pericardial patch. Clinical and echocardiographic follow-up was performed. RESULTS:Fifteen consecutive patients with FMR (mean age, 59 years; 67% female) had mitral valve translocation between 2018 and 2020. Preoperative mean ejection fraction, left ventricular end-diastolic dimension, and systolic pulmonary artery pressure were 40% ± 11%, 59 ± 8 mm, and 49 ± 21 mm Hg, respectively; 33% had atrial fibrillation. Cardiomyopathy was ischemic in 4 and nonischemic in 11. Concomitant procedures included tricuspid valve operation (n = 8), coronary artery bypass grafting (n = 4), and atrial fibrillation ablation (n = 5). Post bypass transesophageal echocardiogram demonstrated none/trace MR in all patients and mean gradient of 3 mm Hg (interquartile range, 2-4 mm Hg). Mean leaflet extent of coaptation was 14 ± 2 mm (range, 11-17 mm). There was no postoperative mortality, stroke, or renal failure. Predismissal echocardiography showed none/trace MR in 14 patients and mild MR in 1. One patient underwent successful late rerepair of a suture line leak. Twelve patients were alive at latest follow-up and MR at 1 and 6 months was mild or less in all patients with mean leaflet extent of coaptation of 14 ± 2 mm (range, 12-16 mm) at 6 months. CONCLUSIONS:Mitral valve translocation creates a large surface of coaptation and effectively corrects FMR. Further study is needed to demonstrate the long-term durability and clinical utility of this operation.

Thrombocytopenia is common during extracorporeal membrane oxygenation (ECMO), and severe thrombocytopenia occurs in up to 25% of patients.1 A recent systematic review and meta-analysis confirmed that around a quarter of adult ECMO patients develop thrombocytopenia and up to half of patients require platelet transfusion.2 The authors concluded that the mechanisms causing thrombocytopenia are multifactorial and remain poorly understood.2 Thrombocytopenia is generally classified as consumptive or hypoproliferative, and measurement of plasma thrombopoietin (TPO) concentration helps distinguish between these etiologies.3 A normal plasma TPO concentration is reported to be approximately 39 pg/mL. Patients with consumptive thrombocytopenia typically have a normal or slightly elevated plasma TPO concentration (mean 63 pg/mL), while those with hypoproliferative thrombocytopenia have a high-plasma TPO concentration (mean 706 pg/mL).3 We hypothesized that adult ECMO patients would have a TPO concentration consistent with consumptive thrombocytopenia and that soluble CD40 ligand concentration, a marker of platelet activation,4 would be increased, supporting a paradigm of platelet activation, thrombus formation, and platelet consumption during ECMO. Methods The study was approved by the University of Maryland, Baltimore, Institutional Review Board. After obtaining informed consent, veno-arterial (VA) ECMO patients had plasma TPO concentration and soluble CD40 ligand concentration measured on ECMO day 1 or 2, ECMO day 3, and ECMO day 5 using a sandwich enzyme-linked immunosorbent assay (ELISA) (Catalog no. EHTHPO and no. BMS239) (ThermoFisher, Waltham, MA), which was run in accordance with manufacturer’s instructions. A Molecular Dynamics Emax Reader (Molecular Devices LLC) was used to detect emitted light (wavelength 450 nm) from a detector antibody. Changes in mean TPO concentration and mean soluble CD40 ligand concentration over time were assessed using repeat measures analysis of variance. Mean concentration at each time point was compared against mean concentration in 10 healthy control plasma samples obtained from a commercial supplier (George King Biomedical, Overland Park, KS) using Student’s t test. Healthy control plasma samples were analyzed to define the normal range for TPO concentration. To explore the relationships between platelet count, TPO, and soluble CD40 ligand concentration, we created scatterplots with Loess curves and fitted linear regression lines. Results Twenty patients were included in the study. Mean age was 58 ± 9 years, 12 patients (60%) were men, and two patients (10%) had recent cardiac surgery. Ten patients (50%) were on VA ECMO for massive pulmonary embolism, while the remainder were on VA ECMO for other indications. Mean ECMO duration was 11 ± 7 days, and mean platelet count was 103 ± 54 × 109/L on ECMO day 1 or 2, 97 ± 37 × 109/L on ECMO day 3, and 82 ± 42 × 109/L on ECMO day 5. Platelet counts during ECMO ranged from 22 × 109/L to 380 × 109/L with a mean nadir platelet count of 67 ± 23 × 109/L. Eleven of 20 patients (55%) were transfused platelet concentrates during ECMO, with the number of units ranging from 1 to 14. Two patients (10%) had heparin-induced thrombocytopenia (HIT), which was confirmed with serotonin release assay. The 10% incidence of HIT that was observed in the study was above the typical incidence in our medical center and was thought to be related to our relatively small sample size. Table 1 shows mean TPO and soluble CD40 ligand concentrations at the three study timepoints. TPO concentration did not change significantly over the first 5 ECMO days and was not significantly different from control plasma (All p > 0.05). Soluble CD40 ligand concentration did not change significantly over time and did not differ from control plasma (All p > 0.05). TPO concentration at the three study timepoints was similar to that previously reported for consumptive thrombocytopenia (T1 = 86.8 ± 36.8 pg/mL, T2 = 82.9 ± 20.6 pg/mL, and T3 = 72.3 ± 20.9 pg/mL).3Figure 1 shows the relationships between platelet count, TPO, and soluble CD40 ligand concentration. There was no significant relationship between these variables, and the fitted linear regression lines were flat. Table 1. - Thrombopoietin and Soluble CD40 Ligand Concentrations in ECMO Patients and Control Plasma Sample Thrombopoietin Level (pg/mL)* p Value for Comparison With Control Soluble CD40 Ligand (ng/mL)† p Value for Comparison With Control ECMO T1 86.8 ± 36.8 0.57 0.43 ± 0.28 0.86 ECMO T2 82.9 ± 20.6 0.62 0.48 ± 0.27 0.75 ECMO T3 72.3 ± 20.9 0.65 0.47 ± 0.33 0.86 Control plasma 77.6 ± 31.1 – 0.44 ± 0.27 – *No difference in thrombopoietin concentration over time, p = 0.33.†No difference in soluble CD40 ligand concentration over time, p = 0.85.ECMO, extracorporeal membrane oxygenation. Figure 1.: (A) shows the relationship between PLT and TPO concentration and (B) shows the relationship between PLT and SCD40L concentration. PLT, platelet count; SCD40L, soluble CD40 ligand; TPO, thrombopoietin.Discussion Thrombocytopenia occurs frequently during ECMO and can be difficult to manage. Severe thrombocytopenia predisposes patients to major bleeding and intracranial hemorrhage.5 Although it is widely assumed that platelet activation and consumption causes thrombocytopenia during ECMO, there is sparse data to support this paradigm. Human platelets circulate for 7–10 days and the mechanisms that govern their clearance by macrophages and hepatocytes are not fully understood. It has been reported that binding of Von Willebrand Factor to GP1bα induces platelet desialylation and phosphatidylserine expression, which increases platelet clearance from the circulation.6 Patients on ECMO whose blood is exposed to supraphysiologic shear may have increased binding of circulating VWF molecules to platelet GP1bα leading to increased platelet clearance, particularly when plasma-free hemoglobin concentration is elevated.7,8 Some studies suggest that platelets are adsorbed onto the ECMO circuit, but it is unclear how many platelets are lost from adsorption compared to other causes.9 Our data suggest that thrombocytopenia during ECMO is consumptive, but this may be related to increased platelet clearance from the circulation rather than platelet activation and thrombus formation. CD40 ligand is expressed on the surface of activated platelets.10 It is cleaved from platelet surfaces by metalloproteinases and is shed into the plasma. The normal soluble CD40 ligand concentration in our study suggests that platelets are not highly activated during ECMO and constitutive platelet thrombus formation seems unlikely. An important limitation of our analysis is that platelet counts are lower during ECMO and a “normal” soluble CD40 ligand concentration in ECMO patients may actually represent a relative elevation when compared to patients with normal platelet counts. Conclusion In a cohort of 20 VA ECMO patients, we found TPO concentration was near 80 pg/mL during the first 5 ECMO days, supporting a paradigm of consumptive and not hypoproliferative thrombocytopenia. Further, soluble CD40 ligand concentration was not significantly elevated during the first 5 ECMO days, contradicting the idea that platelets are constitutively activated during ECMO. Further studies are needed to better understand the specific mechanisms that account for thrombocytopenia during ECMO.

We report orthotopic (life-supporting) survival of genetically engineered porcine cardiac xenografts (with 3-9 progressive gene modifications) for almost 9 months in baboon recipients. This work builds on our previously reported heterotopic cardiac xenograft (3 gene modifications) survival up to 945 days with an anti-CD40 monoclonal antibody-based immunosuppression. In this current study, life-supporting xenografts containing multiple human complement regulatory, thromboregulatory, and anti-inflammatory proteins, in addition to growth hormone receptor knockout (KO) and carbohydrate antigen KOs, were transplanted. Selective "multi-gene" xenografts demonstrate survival greater than 8 months without the use of adjunctive medications and without evidence of abnormal xenograft thickness or rejection. These data demonstrate that selective “multi-gene" modifications improve cardiac xenograft survival significantly and may be foundational for paving the way to bridge transplantation in humans.

Acute normovolemic hemodilution is recommended as a technique to reduce allogeneic red blood cell (RBC) transfusions in cardiac surgery, but its efficacy to reduce non‐RBC transfusion has not been consistently demonstrated. We hypothesized that intraoperative large‐volume autologous whole blood (AWB) collection and reinfusion improves viscoelastic coagulation parameters.