Search

Background: To share the results of a web-based expert panel discussion focusing on the management of acute and chronic aortic disease during the coronavirus (COVID-19) pandemic. Methods: A web-based expert panel discussion on April 18, 2020, where eight experts were invited to share their experience with COVID-19 disease touching several aspects of aortic medicine. After each talk, specific questions were asked by the online audience, and results were immediately evaluated and shared with faculty and participants. Results: As of April 18, 73.3% answered that more than 200 patients have been treated at their respective settings. Sixty-four percent were reported that their hospital was well prepared for the pandemic. In 57.7%, the percentage of infected healthcare professionals was below 5% whereas 19.2% reported the percentage to be between 10% and 20%. Sixty-seven percent reported the application of extracorporeal membrane oxygenationin less than 2% of COVID-19 patients whereas 11.8% reported application in 5%–10% of COVID-19 patients. Thirty percent of participants reported the occurrence of pulmonary embolism in COVID-19 patients. Three percent reported to have seen aortic ruptures in primarily elective patients having been postponed because of the anticipated need to provide sufficient ICU capacity because of the pandemic. Nearly70% reported a decrease in acute aortic syndrome referrals since the start of the pandemic. Conclusion: The current COVID-19 pandemic has—besides the stoppage of elective referrals—also led to a decrease of referrals of acute aortic syndromes in many settings. The reluctance of patients seeking medical help seems to be a major driver. The number of patients, who have been postponed due to the provisioning of ICU resources but having experienced aortic rupture in the waiting period, is still low. Further, studies are needed to learn more about the influence that the COVID-19 pandemic has on the treatment of patients with acute and chronic aortic disease.

BACKGROUND Veno-arterial extracorporeal membrane oxygenation therapy is a growing treatment modality for acute cardiorespiratory failure. Cardiac output monitoring during veno-arterial extracorporeal membrane oxygenation therapy remains challenging. This study aims to validate a new thermodilution technique during veno-arterial extracorporeal membrane oxygenation therapy using a pig model. METHODS Sixteen healthy pigs were centrally cannulated for veno-arterial extracorporeal membrane oxygenation, and precision flow probes for blood flow assessment were placed on the pulmonary artery. After chest closure, cold boluses of 0.9% saline solution were injected into the extracorporeal membrane oxygenation circuit, right atrium, and right ventricle at different extracorporeal membrane oxygenation flows (4, 3, 2, 1 l/min). Rapid response thermistors in the extracorporeal membrane oxygenation circuit and pulmonary artery recorded the temperature change. After calculating catheter constants, the distributions of injection volumes passing each circuit were assessed and enabled calculation of pulmonary blood flow. Analysis of the exponential temperature decay allowed assessment of right ventricular function. RESULTS Calculated blood flow correlated well with measured blood flow (r = 0.74, P < 0.001). Bias was -6 ml/min [95% CI ± 48 ml/min] with clinically acceptable limits of agreement (668 ml/min [95% CI ± 166 ml/min]). Percentage error varied with extracorporeal membrane oxygenation blood flow reductions, yielding an overall percentage error of 32.1% and a percentage error of 24.3% at low extracorporeal membrane oxygenation blood flows. Right ventricular ejection fraction was 17 [14 to 20.0]%. Extracorporeal membrane oxygenation flow reductions increased end-diastolic and end-systolic volumes with reductions in pulmonary vascular resistance. Central venous pressure and right ventricular ejection fractions remained unchanged. End-diastolic and end-systolic volumes correlated highly (r = 0.98, P < 0.001). CONCLUSIONS Adapted thermodilution allows reliable assessment of cardiac output and right ventricular behavior. During veno-arterial extracorporeal membrane oxygenation weaning, the right ventricle dilates even with stable function, possibly because of increased venous return. : WHAT WE ALREADY KNOW ABOUT THIS TOPIC: Veno-arterial extracorporeal membrane oxygenation is an accepted rescue therapy for patients experiencing severe cardiac or pulmonary failure.Weaning from veno-arterial extracorporeal membrane oxygenation is important for determining next steps in patients' cardiopulmonary care. Assessment of right ventricular function during veno-arterial extracorporeal membrane oxygenation support and weaning is often done using echocardiography, but echocardiographic guidance provides challenges because right ventricular dimensions change with ventricular loading and may not be related to intrinsic right ventricular function. WHAT THIS ARTICLE TELLS US THAT IS NEW In 16 healthy pigs that received veno-arterial extracorporeal membrane oxygenation support via central cannulation, a novel adaptation of thermodilution cardiac output assessment provided reliable estimation of right ventricular cardiac output and right ventricular function.Future studies appear warranted to determine whether this method of modified thermodilution can be used to accurately assess right ventricular output and function during veno-arterial extracorporeal membrane oxygenation support.

Assessment of native cardiac output during extracorporeal circulation is challenging. We assessed a modified Fick principle under conditions such as dead space and shunt in 13 anesthetized swine undergoing centrally cannulated veno-arterial extracorporeal membrane oxygenation (V-A ECMO, 308 measurement periods) therapy. We assumed that the ratio of carbon dioxide elimination (V̇co2) or oxygen uptake (V̇o2) between the membrane and native lung corresponds to the ratio of respective blood flows. Unequal ventilation/perfusion (V̇/Q̇) ratios were corrected towards unity. Pulmonary blood flow was calculated and compared to an ultrasonic flow probe on the pulmonary artery with a bias of 99 mL/min (limits of agreement −542 to 741 mL/min) with blood content V̇o2 and no-shunt, no-dead space conditions, which showed good trending ability (least significant change from 82 to 129 mL). Shunt conditions led to underestimation of native pulmonary blood flow (bias −395, limits of agreement −1,290 to 500 mL/min). Bias and trending further depended on the gas (O2, CO2) and measurement approach (blood content vs. gas phase). Measurements in the gas phase increased the bias (253 [LoA −1,357 to 1,863 mL/min] for expired V̇o2 bias 482 [LoA −760 to 1,724 mL/min] for expired V̇co2) and could be improved by correction of V̇/Q̇ inequalities. Our results show that common assumptions of the Fick principle in two competing circulations give results with adequate accuracy and may offer a clinically applicable tool. Precision depends on specific conditions. This highlights the complexity of gas exchange in membrane lungs and may further deepen the understanding of V-A ECMO.

A hypothermic avalanche victim underwent, during extracorporeal warming from asystolic arrest, 3-dimensional transesophageal echocardiography. At 33°C core temperature, left ventricular ejection fraction had recovered, whereas myocardial strain still demonstrated significant dysfunction until 36°C. Deformation analysis seems more sensitive than global assessment during myocardial recovery from hypothermic cardiac arrest. (Level of Difficulty: Intermediate.), Graphical abstract

INTRODUCTION Infective endocarditis (IE) and other severe infections induce significant changes in the immune response in a considerable number of affected patients. Numerous IE patients develop a persistent functional immunological phenotype that can best be characterized by a profound anti-inflammation and/ or functional "anergy." This is pronounced in patients with unresolved infectious foci and was previously referred to as "injury-associated immunosuppression" (IAI). IAI can be assessed by measurement of the monocytic human leukocyte antigen-DR (mHLA-DR) expression, a global functional marker of immune competence. Persistence of IAI is associated with prolonged intensive care unit length of stay, increased secondary infection rates, and death. Immunomodulation to reverse IAI was shown beneficial in early immunostimulatory (randomized controlled) clinical trials. METHODS Prospective 1:1 randomized controlled clinical study to compare the course of mHLA-DR in patients scheduled for cardiac surgery for IE. Patients will receive either best standard of care plus cytokine adsorption during surgery while on cardiopulmonary bypass (protocol A) versus best standard of care alone, that is, surgery without cytokine adsorption (protocol B). A total of 54 patients will be recruited and randomized. The primary endpoint is a change in quantitative expression of mHLA-DR (antibodies per cell on CD14+ monocytes/ macrophages, assessed using a quantitative standardized assay) from baseline (preoperation [pre-OP], visit 1) to day 1 post-OP (visit 4). DISCUSSION This randomized controlled clinical trial (RECReATE) will compare 2 clinical treatment protocols and will investigate whether cytokine adsorption restores monocytic immune competence (reflected by increased mHLA-DR expression) in patients with IE undergoing cardiac surgery. TRIAL REGISTRATION This protocol was registered in ClinicalTrials.gov, under number NCT03892174, first listed on March 27, 2019.

Introduction Three-dimensional left (LV) and right-ventricular (RV) assessment by transesophageal echocardiography (TEE) overcomes problems of 2D TEE such as incomplete coverage and mathematical assumptions of chamber geometry. Myocardial deformation parameters (strain) are reported to allow earlier detection of subclinical abnormalities and to improve prognostic accuracy compared to global assessment. Strain data describing functional recovery of the myocardium from severe hypothermic arrest are scarce. Methods A 55 year-old male victim of an avalanche accident arrived at the emergency department in asystole at 28°C core temperature under ongoing CPR (hypothermia stage IV). Reperfusion and rewarming was performed by percutaneous cannulation and minimized extracorporeal circulation (MiECC). Ventricular fibrillation ensued at 32°C and converted to sinus rhythm after defibrillation. At 33°C a full-volume loop (6 beats) was acquired for each ventricle, and tissue doppler interrogation was performed for assessment of diastolic function. Exams were repeated at 36°C. Images were analyzed for ventricular function and strain for all AHA segments. Results In hypothermia, LV ejection fraction (LVEF, 54%) and global circumferential strain (-35.9%) appeared normal but longitudinal strain was impaired (-13.5%). Basal myocardial segments showed hypo- and dyskinesia, while peak strain in more apical segments was preserved. This resulted in marked heterogeneity of strain curves. Diastology revealed restrictive LV dysfunction (III°). RV ejection fraction (RVEF, 45%) and global longitudinal strain were impaired (-15.2%). After normothermia had been reestablished, LVEF (68%) and strain had improved further (circumferential: -37.7%, longitudinal: -14.5%). Contractile function of LV segments had regained homogeneity among all segments. Time to peak systolic strain was shortened. Diastolic dysfunction had improved to pseudonormal (II°). RVEF (74%) and strain (-44.1%) also showed marked recovery. The figure shows numerical function changes for both ventricles and LV strain curves at 33°C and 36°C core temperature. Discussion In post-arrest core hypothermia at 33°C, LVEF may appear normal and RVEF only mildly impaired, whereas segmental LV and global RV strain analysis may reveal a still severely ab-nor¬mal myocardial systolic function. Such a discordant pattern in a hypothermic post-ischemic heart may show marked improvement when core temperature normalizes. Three-dimensional TEE in combination with myocardial strain analysis may be a useful adjunct for evaluating post-arrest recovery of cardiac function in victims of accidental hypothermic cardiac arrest.

Background Recent evidence suggests that acetate-buffered infusions result in better hemodynamic stabilization than 0.9% saline in patients undergoing major surgery. The choice of buffer in balanced crystalloid solutions may modify their hemodynamic effects. We therefore compared the inopressor requirements of Ringer’s acetate and lactate for perioperative fluid management in patients undergoing cardiac surgery. Methods Using a randomized controlled double-blind design, we compared Ringer’s acetate (RA) to Ringer’s lactate (RL) with respect to the average rate of inopressor administered until postoperative hemodynamic stabilization was achieved. Secondary outcomes were the cumulative dose of inopressors, the duration of inopressor administration, the total fluid volume administered, and the changes in acid-base homeostasis. Patients undergoing elective valvular cardiac surgery were included. Patients with severe cardiac, renal, or liver disease were excluded from the study. Results Seventy-five patients were randomly allocated to the RA arm, 73 to the RL. The hemodynamic profiles were comparable between the groups. The groups did not differ with respect to the average rate of inopressors (RA 2.1 mcg/kg/h, IQR 0.5–8.1 vs. RL 1.7 mcg/kg/h, IQR 0.7–8.2, p = 0.989). Cumulative doses of inopressors and time on individual and combined inopressors did not differ between the groups. No differences were found in acid-base parameters and their evolution over time. Conclusion In this study, hemodynamic profiles of patients receiving Ringer’s lactate and Ringer’s acetate were comparable, and the evolution of acid-base parameters was similar. These study findings should be evaluated in larger, multi-center studies. Trial registration Clinicaltrials.gov NCT02895659. Registered 16 September 2016. Electronic supplementary material The online version of this article (10.1186/s13054-019-2423-8) contains supplementary material, which is available to authorized users.

To compare intraoperative cerebral microembolic load between minimally invasive extracorporeal circulation (MiECC) and conventional extracorporeal circulation (CECC) during isolated surgical aortic valve replacement (SAVR), we conducted a randomized trial in patients undergoing primary elective SAVR at a tertiary referral hospital. The primary outcome was the procedural phase-related rate of high-intensity transient signals (HITS) on transcranial Doppler ultrasound. HITS rate was used as a surrogate of cerebral microembolism in pre-defined procedural phases in SAVR using MiECC or CECC with (+F) or without (-F) an oxygenator with integrated arterial filter. Forty-eight patients were randomized in a 1:1 ratio to MiECC or CECC. Due to intraprocedural Doppler signal loss (n = 3), 45 patients were included in final analysis. MiECC perfusion regimen showed a significantly increased HITS rate compared to CECC (by a factor of 1.75; 95% confidence interval, 1.19-2.56). This was due to different HITS rates in procedural phases from aortic cross-clamping until declamping [phase 4] (P = 0.01), and from aortic declamping until stop of extracorporeal perfusion [phase 5] (P = 0.05). Post hoc analysis revealed that MiECC-F generated a higher HITS rate than CECC+F (P = 0.005), CECC-F (P = 0.05) in phase 4, and CECC-F (P = 0.03) in phase 5, respectively. In open-heart surgery, MiECC is not superior to CECC with regard to gaseous cerebral microembolism. When using MiECC for SAVR, the use of oxygenators with integrated arterial line filter appears highly advisable. Only with this precaution, MiECC confers a cerebral microembolic load comparable to CECC during this type of open heart surgery.

Background: In pig-to-human xenotransplantation, interactions between human natural killer (NK) cells and porcine endothelial cells (pEC) are characterized by recruitment and cytotoxicity. Protection from xenogeneic NK cytotoxicity can be achieved in vitro by the expression of the non-classical human leukocyte antigen-E (HLA-E) on pEC. Thus, the aim of this study was to analyze NK cell responses to vascularized xenografts using an ex vivo perfusion system of pig limbs with human blood. Methods: Six pig forelimbs per group, respectively, stemming from either wild-type (wt) or HLA-E/hCD46 double-transgenic (tg) animals, were perfused ex vivo with heparinized human blood for 12hours. Blood samples were collected at defined time intervals, cell numbers counted, and peripheral blood mononuclear cells analyzed for phenotype by flow cytometry. Muscle biopsies were analyzed for NK cell infiltration. In vitro NK cytotoxicity assays were performed using pEC derived from wt and tg animals as target cells. Results: Ex vivo, a strong reduction in circulating human CD45 leukocytes was observed after 60minutes of xenoperfusion in both wt and tg limb groups. NK cell numbers dropped significantly. Within the first 10minutes, the decrease in NK cells was more significant in the wt limb perfusions as compared to tg limbs. Immunohistology of biopsies taken after 12hours showed less NK cell tissue infiltration in the tg limbs. In vitro, NK cytotoxicity against hCD46 single tg pEC and wt pEC was similar, while lysis of double tg HLA-E/hCD46 pEC was significantly reduced. Finally, circulating cells of pig origin were observed during the ex vivo xenoperfusions. These cells expressed phenotypes mainly of monocytes, B and T lymphocytes, NK cells, as well as some activated endothelial cells. Conclusion: sEx vivo perfusion of pig forelimbs using whole human blood represents a powerful tool to study humoral and early cell-mediated rejection mechanisms of vascularized pig-to-human xenotransplantation, although there are several limitations of the model. Here, we show that (i) transgenic expression of HLA-E/hCD46 in pig limbs provides partial protection from human NK cell-mediated xeno responses and (ii) the emergence of a pig cell population during xenoperfusions with implications for the immunogenicity of xenografts.

Introduction Hypothermic circulatory arrest (HCA) in conjunction with selective antegrade cerebral perfusion (sACP) is frequently used for neuroprotection.(1) Nonetheless optimal sACP has only been investigated in animal studies.(2) The objective of this study was to determine sACP during HCA necessary to reach baseline tissue oxygenation as measured by near infrared spectroscopy (NIRS). Methods With local ethics committee approval, consecutive patients scheduled for elective aortic arch surgery in HCA were included in this prospective observational single center study. Bilateral sACP was institued by introducing perfusion catheters in the innominate and left carotid artery. The quality of sACP was monitored by bifrontal NIRS. Baseline NIRS were measured before anesthesia induction in the awake patient. NIRS values were recorded after initiation of HCA at sACP of 6, 8 and 10 milliliters (ml) per ideal body weight (kg) per minute (min). For comparison the mean of bifrontal NIRS in each patient was calculated for this interim analysis. Differences in NIRS between sACP flow rates were assessed by one-way ANOVA and Bonferroni t-test. A p Results Fifteen patients had complete datasets (4 female). NIRS was 62 (8) at baseline; 56 (11) at 6; 62 (11) at 8 and 63 (9) at 10 ml/kg/min sACP, respectively. ANOVA showed no significant differences between baseline and the three distinct sACP (p = 0.223). Bonferroni t-test indicated no differences between the different sACP and the baseline (all p>0.05). Duration of HCA was 12 (15) minutes. All patients were discharged after a length of hospital stay of 10 +/- 4 days. Three patients had new onset focal neurological deficits before discharge and three patients had postoperative delirium. Discussion SACP of 6-10ml is the range often used in centers of aortic arch surgery. (1) In an animal-model, the lower threshold of 6ml/kg/min was confirmed recently, since venous saturation decreased markedly when sACP was lowered below this sACP.(2) Our data support this finding in humans as sACP f of 6 ml/kg/min is sufficient to reach baseline NIRS values. A further increase, e.g., to 8 or 10 ml/kg/min, is not associated with an even better NIRS. The data suggest that sufficient frontal brain oxygenation can be achieved with a relatively low sACP flow rate in HCA.

BACKGROUND:Asialoglycoprotein receptor 1 (ASGR1) mediates capture and phagocytosis of platelets in pig to primate liver xenotransplantation. However thrombocytopenia is also observed in xenotransplantation or xenoperfusion of other porcine organs than liver. We therefore assessed ASGR1 expression as well as ASGR1 mediated xenogeneic platelet phagocytosis in vitro and ex vivo on porcine aortic femoral arterial and liver sinusoidal endothelial cells (PAEC/PFAEC/PLSEC). METHODS:Porcine forelimbs were perfused with whole heparinized human or autologous pig blood. Platelets were counted at regular intervals. Pig limb muscle and liver as well as PAEC/PFAEC/PLSEC were characterized for ASGR1 expression. In vitro PAEC cultured on microcarrier beads and incubated with non anticoagulated human blood were used to study binding of human platelets and platelet white blood cell aggregation. Carboxyfluorescein diacetate succinimidyl ester labeled human platelets were exposed to PAEC/PFAEC/PLSEC and analyzed for ASGR1 mediated phagocytosis. RESULTS:Human platelet numbers decreased from 102 {\textpm} 33 at beginning to 13 {\textpm} 6 {\texttimes} 10/µL (P < 0.0001) after 10 minutes of perfusion whereas no significant decrease of platelets was seen during autologous perfusions (171 {\textpm} 26 to 122 {\textpm} 95 {\texttimes} 10/µL). The PAEC PFAEC and PLSEC all showed similar ASGR1 expression. In vitro no correlation was found between reduction in platelet count and platelet white blood cell aggregation. Phagocytosis of human carboxyfluorescein diacetate succinimidyl ester labeled platelets by PAEC/PFAEC/PLSEC peaked at 15 minutes and was inhibited (P < 0.05 to P < 0.0001) by rabbit anti ASGR1 antibody and asialofetuin. CONCLUSIONS:The ASGR1 expressed on aortic and limb arterial pig vascular endothelium plays a role in binding and phagocytosis of human platelets. Therefore ASGR1 may represent a novel therapeutic target to overcome thrombocytopenia associated with vascularized pig to primate xenotransplantation.

Revascularization of an amputated limb within 4-6h is essential to avoid extensive ischemia/reperfusion (I/R) injury leading to vascular leakage, edema and tissue necrosis. I/R injury is a pathological inflammatory condition that occurs during reperfusion of an organ or tissue after prolonged ischemia. It is characterized by a complex crosstalk between endothelial cell activation and the activation of plasma cascades. Vasculoprotective pharmacological intervention to prevent I/R injury might be an option to prolong the time window between limb amputation and successful replantation. We used C1-easterase inhibitor (C1-INH) in this study because of its known inhibitory effects on the activation of the complement, coagulation and kinin cascades. Forelimbs of 8 large white pigs were amputated, subjected to ischemia, and then reperfused with autologous whole blood. All limbs were exposed to 9h of cold ischemia at 4°C. After 2h of cold ischemia the limbs were either perfused with of C1-INH (1U/ml in hydroxyethyl starch, n=8) or hydroxyethyl starch alone (n=7). After completion of the 9-h ischemia period, all limbs were ex vivo perfused with heparinized autologous whole blood for 12h using a pediatric heart lung machine to simulate in vivo revascularization. Our results show that I/R injury in the control group led to a significant elevation of tissue deposition of IgG and IgM, complement C3b/c, C5b-9 and MBL. Also, activation of the kinin system was significantly increased, namely bradykinin in plasma, and expression of bradykinin receptors 1 and 2 in tissue. In addition, markers for endothelial integrity like expression of CD31, VE-cadherin and heparan sulfate proteoglycans were decreased in reperfused tissue. Limb I/R injury also led to activation of the coagulation cascade with a significant elevation of fibrin and thrombin deposition and increased fibrinogen-like protein-2 expression. C1-INH treated limbs showed much less activation of plasma cascades and better protection of endothelial integrity compared to the reperfused control limbs. In conclusion, the use of the cytoprotective drug C1-INH significantly reduced I/R injury by protecting the vascular endothelium as well as the muscle tissue from deposition of immunoglobulins, complement and fibrin.

To compare intraoperative cerebral microembolic load between minimally invasive extracorporeal circulation (MiECC) and conventional extracorporeal circulation (CECC) during isolated surgical aortic valve replacement (SAVR), we conducted a randomized trial in patients undergoing primary elective SAVR at a tertiary referral hospital. The primary outcome was the procedural phase-related rate of high-intensity transient signals (HITS) on transcranial Doppler ultrasound. HITS rate was used as a surrogate of cerebral microembolism in pre-defined procedural phases in SAVR using MiECC or CECC with (+F) or without (-F) an oxygenator with integrated arterial filter. Forty-eight patients were randomized in a 1:1 ratio to MiECC or CECC. Due to intraprocedural Doppler signal loss (n = 3), 45 patients were included in final analysis. MiECC perfusion regimen showed a significantly increased HITS rate compared to CECC (by a factor of 1.75; 95% confidence interval, 1.19-2.56). This was due to different HITS rates in procedural phases from aortic cross-clamping until declamping [phase 4] (P = 0.01), and from aortic declamping until stop of extracorporeal perfusion [phase 5] (P = 0.05). Post hoc analysis revealed that MiECC-F generated a higher HITS rate than CECC+F (P = 0.005), CECC-F (P = 0.05) in phase 4, and CECC-F (P = 0.03) in phase 5, respectively. In open-heart surgery, MiECC is not superior to CECC with regard to gaseous cerebral microembolism. When using MiECC for SAVR, the use of oxygenators with integrated arterial line filter appears highly advisable. Only with this precaution, MiECC confers a cerebral microembolic load comparable to CECC during this type of open heart surgery.

BACKGROUND Dysregulation of the coagulation system due to inflammatory responses and cross-species molecular incompatibilities represents a major obstacle to successful xenotransplantation. We hypothesized that complement inhibition mediated by transgenic expression of human CD46 in pigs might also regulate the coagulation and fibrinolysis cascades and tested this in ex vivo human-to-pig xenoperfusions. METHODS Forelimbs of wild-type and hCD46/HLA-E double transgenic pigs were ex vivo xenoperfused for 12 hours with whole heparinized human blood. Muscle biopsies were stained for galactose-α1,3-galactose, immunoglobulin M, immunoglobulin G, complement, fibrin, tissue factor, fibrinogen-like protein 2, tissue plasminogen activator (tPA), and plasminogen activator inhibitor (PAI)-1. The PAI-1/tPA complexes, D-dimers, and prothrombin fragment F1 + 2 were measured in plasma samples after ex vivo xenoperfusion. RESULTS No differences of galactose expression or deposition of immunoglobulin M and immunoglobulin G were found in xenoperfused tissues of wild type and transgenic limbs. In contrast, significantly lower deposition of C5b-9 (P < 0.0001), fibrin (P = 0.009), and diminished expression of tissue factor (P = 0.005) and fibrinogen-like protein 2 (P = 0.028) were found in xenoperfused tissues of transgenic limbs. Levels of prothrombin fragment F1 + 2 (P = 0.031) and D-dimers (P = 0.044) were significantly lower in plasma samples obtained from transgenic as compared to wild-type pig limb perfusions. The expression of the fibrinolytic marker tPA was significantly higher (P = 0.009), whereas PAI-1 expression (P = 0.022) and PAI-1/tPA complexes in plasma (P = 0.015) were lower after transgenic xenoperfusion as compared to wild-type xenoperfusions. CONCLUSIONS In this human-to-pig xenoperfusion model, complement inhibition by transgenic hCD46 expression led to a significant inhibition of procoagulant and antifibrinolytic pathways.