Hansjörg Jenni

Mortality and neurologic injury after surgical repair with hypothermic circulatory arrest in acute and chronic proximal thoracic aortic pathology: effect of age on outcome.

Background— The goal of this study was to determine whether advanced age affects mortality and incidence of neurological injury in patients undergoing surgical repair with hypothermic circulatory arrest in acute and chronic thoracic aortic pathology. Methods and Results— A university center audit was done of 523 consecutive patients (median age, 64 years; interquartile range, 56–71 years) between 2005 and 2010. Mortality in acute type A aortic dissection (207 patients) was 9.7%, and in chronic ascending aortic aneurysms (316 patients) was 2.2% (P<0.001). Neurological injury was observed in 16.9% of patients with acute type A aortic dissection (chronic ascending aortic aneurysms, 7.9%; P=0.002). Multivariable regression analysis revealed hypothermic circulatory arrest >40 minutes (odds ratio [OR], 4.21; 95% confidence interval [CI], 1.60–11.06; P=0.004) and redo surgery (OR, 3.44; 95% CI, 1.11–10.64; P=0.03) but not age (OR, 1.98; 95% CI, 0.73–5.38; P=0.18) as independent predictor of mortality. Emergency surgery (OR, 3.27; 95% CI, 1.31–8.15; P=0.01) and extracardiac arteriopathy (OR, 2.38; 95% CI, 1.26–4.50; P=0.008) but not age (OR, 1.80; 95% CI, 0.93–3.48; P=0.08) were independent predictors of neurological injury. Conclusions— Age is not associated with increased risk for mortality and neurological injury in patients undergoing surgical repair for acute and chronic thoracic aortic pathology with hypothermic circulatory arrest. Extended hypothermic circulatory arrest times, reflecting the extent of disease, and redo surgery predict mortality, whereas emergency surgery and extracardiac arteriopathy predict neurological injury.

Preservation of Amputated Extremities by Extracorporeal Blood Perfusion; a Feasibility Study in a Porcine Model

BACKGROUND Successful extremity transplantations and replantations have to be performed within 6 h of amputation to avoid irreversible tissue loss. This study investigates ex vivo the technical feasibility and the limb preservation potential of extracorporeal whole blood perfusion in a porcine model. METHODS Forelimbs of eight large white pigs were divided into paired groups: I perfusion group, II contralateral cold ischemia controls. In group I axillary arteries and veins were cannulated and perfusion with anticoagulated autologous blood was performed for 12 h; O(2), CO(2), Hb, lactate, potassium, pH, and muscle contractility were monitored. Tissue biopsies were examined by histology and immunofluorescence. Group II was stored at 4°C. RESULTS Continuous limb perfusion could be performed in all extremities of group I for 12 h. pH was maintained normal and potassium controlled with insulin and glucose. Lactate levels increased initially during perfusion due to the lack of a metabolizing liver. Muscle stimulation was possible throughout the entire perfusion, whereas a complete loss of response was noted in cold ischemia controls. Minor tissue damage was observed histologically and by immunofluorescence in group I, whereas the samples of group II were apparently preserved with the exception of a loss of endothelial heparan sulfate. CONCLUSIONS The tissue preserving potential and the feasibility of extremity perfusion using common extracorporeal blood circulation techniques was demonstrated in this ex vivo study. The results encourage further investigations in prolonged perfusion followed by limb replantation. This approach harbors promising clinical potential for extremity preservation in extremity transplantation and replantation.

Experimental Acute Type B Aortic Dissection: Different Sites of Primary Entry Tears Cause Different Ways of Propagation

BACKGROUND Many dissections seem to also have a retrograde component. The aim of the study was to evaluate different sites of primary entry tears and the propagation of the dissecting membrane, antegrade and retrograde, in an experimental model of acute type B aortic dissection. METHODS The entire thoracic aortic aorta including the supraaortic branches was harvested from 26 adult pigs. An intimal tear of 15 mm was created by contralateral incisions sites 20 mm downstream the origin of the left subclavian artery. In 13 cases the dissection was created at the concavity and in 13 cases at the convexity. The aortic annulus was then sewn into a silicon ring of a driving chamber. The distal aorta was connected to a tubing with adjustable resistance elements. The circulation was driven by the pneumatically driven Vienna heart to mimic aortic flow and pressure. RESULTS Mean circulation time was 64 ± 45 minutes. A mean pressure of 152 ± 43 mm Hg and a mean flow of 4.5 ± 1.0 L/minute were reached. The median antegrade propagation length of the dissecting membrane was 65 mm. The median retrograde propagation length in primary entry tears at the convexity was 20 mm and was stopped by the left subclavian artery. In aortas with the primary entry tear at the concavity, median retrograde propagation length was 21 mm extending up to the ascending aorta in 16%. CONCLUSIONS In this experimental model of acute type B aortic dissection, we confirmed that many type B dissections do also have a retrograde component. At the convexity, this component is stopped by the left subclavian artery as an anatomic barrier. At the concavity, the propagation of the dissecting membrane may extend up to the ascending aorta and may therefore cause retrograde type A dissection. These findings may substantiate clinical need for treatment of type B dissections with a primary entry tear at the concavity.

Complement dependent early immunological responses during ex vivo xenoperfusion of hCD46/HLA‐E double transgenic pig forelimbs with human blood

Besides α1,3‐galactosyltransferase gene (GGTA1) knockout, several transgene combinations to prevent pig‐to‐human xenograft rejection are currently being investigated. In this study, the potential of combined overexpression of human CD46 and HLA‐E to prevent complement‐ and NK‐cell‐mediated xenograft rejection was tested in an ex vivo pig‐to‐human xenoperfusion model.

Long-Term Results after Proximal Thoracic Aortic Redo Surgery

Objective To evaluate early and mid-term results in patients undergoing proximal thoracic aortic redo surgery. Methods We analyzed 60 patients (median age 60 years, median logistic EuroSCORE 40) who underwent proximal thoracic aortic redo surgery between January 2005 and April 2012. Outcome and risk factors were analyzed. Results In hospital mortality was 13%, perioperative neurologic injury was 7%. Fifty percent of patients underwent redo surgery in an urgent or emergency setting. In 65%, partial or total arch replacement with or without conventional or frozen elephant trunk extension was performed. The preoperative logistic EuroSCORE I confirmed to be a reliable predictor of adverse outcome- (ROC 0.786, 95%CI 0.64–0.93) as did the new EuroSCORE II model: ROC 0.882 95%CI 0.78–0.98. Extensive individual logistic EuroSCORE I levels more than 67 showed an OR of 7.01, 95%CI 1.43–34.27. A EuroSCORE II larger than 28 showed an OR of 4.44 (95%CI 1.4–14.06). Multivariate logistic regression analysis identified a critical preoperative state (OR 7.96, 95%CI 1.51–38.79) but not advanced age (OR 2.46, 95%CI 0.48–12.66) as the strongest independent predictor of in-hospital mortality. Median follow-up was 23 months (1–52 months). One year and five year actuarial survival rates were 83% and 69% respectively. Freedom from reoperation during follow-up was 100%. Conclusions Despite a substantial early attrition rate in patients presenting with a critical preoperative state, proximal thoracic aortic redo surgery provides excellent early and mid-term results. Higher EuroSCORE I and II levels and a critical preoperative state but not advanced age are independent predictors of in-hospital mortality. As a consequence, age alone should no longer be regarded as a contraindication for surgical treatment in this particular group of patients.

Porcine extrahepatic vascular endothelial asialoglycoprotein receptor 1 mediates xenogeneic platelet phagocytosis in vitro and in human-to-pig ex vivo xenoperfusion

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 ± 33 at beginning to 13 ± 6 × 103/&mgr;L (P < 0.0001) after 10 minutes of perfusion, whereas no significant decrease of platelets was seen during autologous perfusions (171 ± 26 to 122 ± 95 × 103/&mgr;L). 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.

Activation of the lectin pathway of complement in pig-to-human xenotransplantation models

Background Natural IgM containing anti-Gal antibodies initiates classic pathway complement activation in xenotransplantation. However, in ischemia-reperfusion injury, IgM also induces lectin pathway activation. The present study was therefore focused on lectin pathway as well as interaction of IgM and mannose-binding lectin (MBL) in pig-to-human xenotransplantation models. Methods Activation of the different complement pathways was assessed by cell enzyme-linked immunosorbent assay using human serum on wild-type (WT) and &agr;-galactosyl transferase knockout (GalTKO)/hCD46-transgenic porcine aortic endothelial cells (PAEC). Colocalization of MBL/MASP2 with IgM, C3b/c, C4b/c, and C6 was investigated by immunofluorescence in vitro on PAEC and ex vivo in pig leg xenoperfusion with human blood. Influence of IgM on MBL binding to PAEC was tested using IgM depleted/repleted and anti-Gal immunoabsorbed serum. Results Activation of all the three complement pathways was observed in vitro as indicated by IgM, C1q, MBL, and factor Bb deposition on WT PAEC. MBL deposition colocalized with MASP2 (Manders’ coefficient [3D] r2=0.93), C3b/c (r2=0.84), C4b/c (r2=0.86), and C6 (r2=0.80). IgM colocalized with MBL (r2=0.87) and MASP2 (r2=0.83). Human IgM led to dose-dependently increased deposition of MBL, C3b/c, and C6 on WT PAEC. Colocalization of MBL with IgM (Pearson’s coefficient [2D] rp2=0.88), C3b/c (rp2=0.82), C4b/c (rp2=0.63), and C6 (rp2=0.81) was also seen in ex vivo xenoperfusion. Significantly reduced MBL deposition and complement activation was observed on GalTKO/hCD46-PAEC. Conclusion Colocalization of MBL/MASP2 with IgM and complement suggests that the lectin pathway is activated by human anti-Gal IgM and may play a pathophysiologic role in pig-to-human xenotransplantation.

Total surgical aortic arch replacement as a safe strategy to treat complex multisegmental proximal thoracic aortic pathology

OBJECTIVE To analyse the results after elective open total aortic arch replacement. METHODS We analysed 39 patients (median age 63 years, median logistic EuroSCORE 18.4) who underwent elective open total arch replacement between 2005 and 2012. RESULTS In-hospital mortality was 5.1% (n = 2) and perioperative neurological injury was 12.8% (n = 5). The indication for surgery was degenerative aneurysmal disease in 59% (n = 23) and late aneurysmal formation following previous surgery of type A aortic dissection in 35.9% (n = 14); 5.1% (n = 2) were due to anastomotical aneurysms after prior ascending repair. Fifty-nine percent (n = 23) of the patients had already undergone previous proximal thoracic aortic surgery. In 30.8% (n = 12) of them, a conventional elephant trunk was added to total arch replacement, in 28.2% (n = 11), root replacement was additionally performed. Median hypothermic circulatory arrest time was 42 min (21-54 min). Selective antegrade cerebral perfusion was used in 95% (n = 37) of patients. Median follow-up was 11 months [interquartile range (IQR) 1-20 months]. There was no late death and no need for reoperation during this period. CONCLUSIONS Open total aortic arch replacement shows very satisfying results. The number of patients undergoing total arch replacement as a redo procedure and as a part of a complex multisegmental aortic pathology is high. Future strategies will have to emphasize neurological protection in extensive simultaneous replacement of the aortic arch and adjacent segments.

Transgenic Expression of Human CD46 on Porcine Endothelium: Effect on Coagulation and Fibrinolytic Cascades During Ex Vivo Human-to-Pig Limb Xenoperfusions.

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-&agr;1,3-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.

Autotransfusion system or integrated automatic suction device in minimized extracorporeal circulation: influence on coagulation and inflammatory response

OBJECTIVE To measure surrogate markers of coagulation activation as well as of the systemic inflammatory response in patients undergoing primary elective coronary artery bypass grafting (CABG) using either the so-called Smart suction device or a continuous autotransfusion system (C.A.T.S.®). METHODS Fifty-eight patients being operated with a miniaturized circuit (minimal extracorporeal circuit, MECC) were prospectively randomized to using a so-called Smart suction device or a routine continuous autotransfusion system (C.A.T.S.®) for collection of mediastinal shed blood. The coagulation response was measured by thrombin-antithrombin complex (TAT) and D-dimer. The inflammatory response was measured by Interleukin 6 (IL-6) and complement factor 3a (C3a) at three different time points, before surgery, 2h after surgery, as well as 18 h after surgery. RESULTS No serious adverse cardiovascular event was observed. Serum levels of TAT significantly differed between both groups 2h after surgery (Smart suction 16.12 ± 13.51 μg l⁻¹ vs C.A.T.S® 9.83 ± 7.81 μg l⁻¹, p = 0.040) and returned to baseline values after 18 h in both groups. Serum levels of D-dimer showed a corresponding pattern with a peak 2h after surgery (Smart suction 1115 ± 1231 ng ml⁻¹ vs C.A.T.S.® 507 ± 604 ng ml⁻¹, p = 0.025). IL-6 levels also significantly differed between both groups 2h after surgery (Smart suction 186 ± 306 pg ml⁻¹ vs C.A.T.S.® 82 ± 71 pg ml⁻¹, p = 0.072). No significant changes in serum levels of C3a over time could be observed. CONCLUSIONS Despite no differences in the clinical course of patients with either Smart suction or C.A.T.S.® being observed, surrogate markers of coagulation and inflammation seem to be less pronounced in patients where cardiotomy blood is not being directly reinfused. As such, C.A.T.S.® should be preferred in routine CABG, as long as no extensive volume substitution is anticipated.