Non-invasive diagnosis of an intramyocardial dissecting haematoma of the left ventricular free wall by cardiac magnetic resonance.
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Adult↗
Biomedical subjects
M Schmoeckel
Publications and source records attributed to M Schmoeckel.
Fluorescent microspheres reveal different regional blood flow in hyperacutely rejected nontransgenic and hDAF pig hearts.
Classic features of hyperacute rejection show differential severity in the inner compared to the outer myocardium. In the present study, regional blood flow (RBF) measured by fluorescent microspheres served as a marker of the extent of hyperacute rejection. Using a working heart model, hearts of nontransgenic and hDAF transgenic pigs were perfused with human blood. Additionally, hDAF transgenic pig hearts were perfused with human blood containing GAS914 or the GPIIb/IIIa inhibitor tirofiban. Injections of fluorescent microspheres into the donor heart were performed in situ and during perfusion. Reference arterial blood samples were collected from the inferior aorta and the afterload line. Perfusion was terminated before hyperacutely rejected hearts failed to pump against the afterload column. RBF was determined in tissue samples of standardized areas of the left atrium and ventricle. Each specimen was divided into subepicardial and subendocardial tissue samples. Fluorescence intensity was measured using an automated luminescence spectrometer. At the end of perfusion with human blood, hyperacutely rejected nontransgenic pig hearts showed a higher RBF in the subendocardium. In hDAF-transgenic pig hearts perfused with unmodified human blood the subendocardial/subepicardial blood flow ratio changed in favor of the subepicardium. This ratio was not further improved by GAS914. In contrast, tirofiban was able to assimilate subepicardial and subendocardial blood flow. In conclusion, RBF of hyperacutely rejected pig hearts was inhomogeneous. Inhibition of complement activation improved the reduced subepicardial RBF, but depletion of antibodies had no positive effect. The ability of tirofiban to further increase subepicardial RBF affirms thrombosis of subepicardial veins as the defining characteristic of hyperacute rejection.
Acute Disease↗
Assessing fluid responsiveness during open chest conditions.
BACKGROUND: Measurement of ventilation-induced left ventricular stroke volume variations (SVV) or pulse pressure variations (PPV) is useful to optimize preload in patients after cardiac surgery. The aim of this study was to investigate the ability of SVV and PPV measured by arterial pulse contour analysis to assess fluid responsiveness in patients undergoing coronary artery bypass surgery during open-chest conditions. METHODS: We studied 22 patients immediately after midline sternotomy. We determined SVV, PPV, left ventricular end-diastolic area index by transoesophageal echocardiography, global end-diastolic volume index and cardiac index by thermodilution before and after removal of blood 500 ml and after volume substitution with hydroxyethyl starch 6%, 500 ml. RESULTS: Blood removal resulted in a significant increase in SVV from 6.7 (2.2) to 12.7 (3.8)%. PPV increased from 5.2 (2.5) to 11.9 (4.6)% (both P<0.001). Cardiac index decreased from 2.9 (0.6) to 2.3 (0.5) litres min(-1) m(-2) and global end-diastolic volume index decreased from 650 (98) to 565 (98) ml m(-2) (both P<0.025). Left ventricular end-diastolic area index did not change significantly. After fluid loading SVV decreased significantly to 6.8 (2.2)% and PPV decreased to 5.4 (2.1)% (both P<0.001). Concomitantly, cardiac index increased significantly to 3.3 (0.5) litres min(-1) m(-2) (P<0.001) and global end-diastolic volume index increased significantly to 663 (104) ml m(-2) (P<0.005). Left ventricular end-diastolic area index did not change significantly. We found a significant correlation between the increase in cardiac index caused by fluid loading and SVV as well as PPV before fluid loading (SVV, R=0.74, P<0.001; PPV, R=0.61, P<0.005). No correlations were found between values of global end-diastolic volume index or left ventricular end-diastolic area index before fluid loading and the increase in cardiac index. CONCLUSION: Measurement of SVV or PPV allows assessment of fluid responsiveness in hypovolaemic patients under open-chest and open-pericardium conditions. Thus, measuring heart-lung interactions may improve haemodynamic management during surgical procedures requiring mid-line sternotomy.
Adult↗
Long-term survival of nonhuman primates receiving life-supporting transgenic porcine kidney xenografts.
BACKGROUND: Recently, there has been a resumed interest in clinical xenotransplantation using pig organs. However, no data are available yet regarding the capacity of porcine organs to sustain the life of a primate beyond the first month. We have attempted to obtain long-term survival of nonhuman primates using human decay-accelerating factor (hDAF) transgenic pig organs and an immunosuppressive strategy particularly aimed at neutralizing the humoral component of the immune response. METHODS: hDAF transgenic or control kidneys were transplanted into 14 bilaterally nephrectomized cynomolgus monkeys (Macaca fascicularis) that underwent splenectomy and were immunosuppressed with cyclosporine A, cyclophosphamide, and steroids. All animals also received recombinant erythropoietin. Postoperatively, the primates were monitored daily. Laboratory evaluations included serum biochemistry, hematology, and measurements of hemolytic antipig antibodies. To assess the role of splenectomy in the control of humoral response, historical data were also used from a group of monkeys (n=7) that received the same immunosuppressive regimen and an hDAF transgenic porcine kidney but did not have splenectomy or receive recombinant erythropoietin. RESULTS: This immunosuppressive approach obtained the longest survival time (78 days) described to date of a primate receiving a life-supporting porcine renal xenograft. Furthermore, four of nine animals in this series survived for 50 days or more. Most biochemical measurements in this study (including plasma urea, creatinine, sodium, and potassium concentrations) remained within normal ranges for several weeks in all of the longest-surviving animals. CONCLUSIONS: Normalization of renal function (urea and creatinine) in primate recipients of porcine renal xenografts suggests that pig kidneys may be suitable for future clinical xenotransplantation. Additional immunosuppressive approaches, specifically designed to prevent humorally mediated immunological damage, should be explored to further prolong survival of primates that have received porcine xenografts.
Animals↗
IG-therasorb immunoapheresis in orthotopic xenotransplantation of baboons with landrace pig hearts.
BACKGROUND: The major problem of xenotransplantation is, that hyperacute xenograft rejection (HXR) causes graft failure within minutes or a few hours because of natural antibodies and activation of the complement system. As a preclinical model we transplanted pig hearts orthotopically into baboons. To prevent HXR after orthotopic xenotransplantation (oXHTx), the immunoglobulins (Ig) and natural antibodies were adsorbed to reusable Ig-Therasorb immunoadsorption (IA) columns. METHODS: We performed three oXHTx of landrace pig hearts into baboons (19+/-6.8 kg), using extracorporeal circulation (ECC) connected to the IA unit. After separating the recipient's blood into plasma and cellular fraction by a plasma filter, plasma flow was directed to the Ig-Therasorb column coated with polyclonal sheep-antibodies against human IgG, IgM, and IgA. Intraoperative treatment consisted of 4 cycles of IA. For a control, we transplanted one pig heart into a baboon (16.9 kg) without applying IA. Perioperatively, serum concentrations of Ig, anti-pig-antibodies, complement and cardiac enzymes were determined. Tissue samples of myocardium were collected at the end of the study for immunohistochemical examinations, light microscopic examination (LM) and electron microscopic examination (EM). For cardiac monitoring after oXHTx, we used ECG, echocardiography, and invasive measurement of cardiac output. To prevent a mismatch of donor and recipient heart size, the donor pig had a 30-40% lower body weight than the recipient baboon. RESULTS: Four cycles of IA removed >80% of IgG, IgM, and IgA from plasma. The graft of the control animal failed after 29 min. The first oXHTx with IA was intentionally terminated after 100 min, the second oXHTx after 11 hr and the third oXHTx after 21 hr. All xenografts showed no histological signs of HXR. After weaning off ECC, these donor hearts worked in sinus rhythm without electrocardiographic ST-segment elevation. An excellent cardiac output was measured by echocardiography and thermodilution (2 L/min). Serological parameters indicating cardiac damage were significantly lower after IA if compared with the control experiment. Macroscopically, the xenograft of the control animal showed massive hemorrhage in comparison with the almost inconspicuous grafts after IA. The myocardium of the IA group demonstrated fewer deposits of Ig and complement components compared with the control animal. CONCLUSION: Baboons do not hyperacutely reject a porcine xenograft after antibody depletion by the Ig-Therasorb column. In our experiment only 4 cycles of immunoapheresis effectively prevented HXR after oXHTx of baboons. The Ig-Therasorb column is a reusable device, which can be handled easily in combination with the ECC. IA must be tested in oXHTx longterm survival experiments, especially in combination with transgenic pig organs, which could be a reliable preclinical approach for future clinical xenotransplantation.
Animals↗
Influence of ischemic time on hyperacute xenograft rejection of pig hearts in a working heart perfusion model with human blood.
In xenotransplantation long ischemic time of grafts is supposed to have a marked influence on hyperacute rejection (HXR). We investigated the influence of different cold ischemic times on HXR of ex vivo "working pig hearts" perfused with human blood. Xenoreactive natural antibodies (XNAb) as a trigger of HXR were eliminated by Ig-Therasorb immunoadsorption (IA). Explanted Landrace pig hearts of group G1 and group G3 (with additional IA) underwent 4 h of cold ischemia prior to xenoperfusion. Control groups G2 and G4 (with IA) were kept ischemic for only 46.6 +/- 15.8 and 51.2 +/- 4.2 min, respectively. Ischemic time prolonged the perfusion time in our working heart model (G1: 356 +/- 46.1 min; G2: 125 +/- 31 min; P < 0.05). IA had no additional impact on perfusion time but was effective by itself. The heart weight increased fourfold more in G2 as compared to the other groups. IA without ischemia significantly improved cardiac output in G4 (G3: 198.8 +/- 15.4 mL/min; G4: 338.5 +/- 16.0 mL/min). Coronary flow in G2 was significantly lower than in G1 (G1: 157.9 +/- 9.15 mL/min; G2: 59.4 +/- 20.1 mL/min). Histological signs of HXR (light and electron microscopy) could be found in G2 in contrast to the other groups. Parameters of serological damage showed a minimum in G4 and the maximum in G2. In G1 XNAb were nearly equally eliminated immediately after the start of xenoperfusion as in IA groups G4 and G3. Four hours of ischemic time showed beneficial effects in preventing HXR, possibly caused by changes of the endothelial cell surface (for example, glycosylation or loss of alpha1-3Gal epitopes with a hapten effect).
Acute Disease↗
Prevention of hyperacute xenograft rejection in orthotopic xenotransplantation of pig hearts into baboons using immunoadsorption of antibodies and complement factors.
To prevent hyperacute xenograft rejection (HXR) caused by preformed natural antibodies (XNAb) after orthotopic heart xenotransplantation (oXHTx) of landrace pig hearts into baboons, we used immunoadsorption of immunoglobulins IgG, IgM and IgA and complement with the reusable Ig-Therasorb column. In addition to functional data, tissue was sampled for histological, immunohistochemical and electron microscopical analysis. We performed three oXHTx of landrace pig hearts to baboons using extracorporeal circulation (ECC) connected to the immunoadsorption unit. Intraoperative treatment consisted of four cycles of immunoabsorption (IA). One oXHTx of a baboon without IA served as a control. A mismatch of donor and recipient heart size was prevented by selecting a 30-40% lower body weight of donor pigs than recipients. Four cycles of IA removed more than 80% of IgG, IgM and IgA, 86% of antipig antibodies and 66% of complement factors C3 and C4 from plasma. The graft of the control animal failed after 29 min. Orthotopic xenotransplantation with IA was selectively terminated after 100 min, 11 h and 21 h, respectively without any histological signs of HXR in light and electron microscopy. After weaning off from ECC these donor xenografts showed sufficient function with normal ECG and excellent cardiac output in echocardiography and invasive measurement (1.93 +/- 0.035 l/min). The myocardium of the control xenograft demonstrated more deposits of Ig and complement components (C3, C4) than in the IA group. Baboons survive HXR after orthotopic pig heart xenotransplantation due to antibody depletion by reusable Ig-Therasorb column treatment. Long-term survival in an orthotopic baboon xenotransplantation model after IA, especially in combination with transgenic pig organs, could be a reliable preclinical trial for future clinical xenotransplantation programs.
Acute Disease↗
Technique of immunoapheresis in heterotopic and orthotopic xenotransplantation of pig hearts into cynomolgus and rhesus monkeys.
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Animals↗
Report of the Xenotransplantation Advisory Committee of the International Society for Heart and Lung Transplantation: the present status of xenotransplantation and its potential role in the treatment of end-stage cardiac and pulmonary diseases.
An urgent and steadily increasing need exists world-wide for a greater supply of donor thoracic organs. Xenotransplantation offers the possibility of an unlimited supply of hearts and lungs that could be available electively when required. However, anti-body- mediated mechanisms cause the rejection of pig organs transplanted into non-human primates, and these mechanisms provide major immunologic barriers that have not yet been overcome. Having reviewed the literature on xenotransplantation, we present a number of conclusions on its present status with regard to thoracic organs, and we make a number of recommendations relating to eventual clinical trials. Although pig hearts have functioned in heterotopic sites in non-human primates for periods of several weeks, median survival of orthotopically transplanted hearts is currently ,1 month. No transplanted pig lung has functioned for even 24 hours. Current experimental results indicate that a clinical trial would be premature. A potential risk exists, hitherto undetermined, of transferring infectious organisms along with the donor pig organ to the recipient, and possibly to other members of the community. A clinical trial of xeno-transplantation should not be undertaken until experts in microbiology and the relevant regulatory authorities consider this risk to be minimal. A clinical trial should be considered when approximately 60% survival of life-supporting pig organs in non-human primates has been achieved for a minimum of 3 months, with at least 10 animals surviving for this minimum period. Furthermore, evidence should suggest that longer survival (.6 months) can be achieved. These results should be achieved in the absence of life-threatening complications caused by the immunosuppressive regimen used. The relationship between the presence of anti-HLA antibody and anti-pig antibody and their cross-reactivity, and the outcome of pig-organ xenotransplantation in recipients previously sensitized to HLA antigens require further investigation. We recommend that the patients who initially enter into a clinical trial of cardiac xenotransplantation be unacceptable for allotransplantation, or acceptable for allotransplantation but unlikely to survive until a human cadaveric organ becomes available, and in whom mechanical assist-device bridging is not possible. National bodies that have wide-reaching government-backed control over all aspects of the trials should regulate the initial clinical trial and all subsequent clinical xenotransplantation procedures for the foreseeable future. We recommend coordination and monitoring of these trials through an international body, such as the International Society for Heart and Lung Transplantation, and setting up a registry to record and widely disperse the results of these trials. Xenotransplantation has the potential to solve the problem of donor-organ supply, and therefore research in this field should be actively encouraged and supported.
Adult↗
The influence of antibody and complement removal with a Ig-Therasorb column in a xenogeneic working heart model.
OBJECTIVE: Organ transplantation is limited by the number of brain-dead human donors. Xenotransplantation could be an alternative to guarantee a constant supply of organs. A major problem of xenotransplantation are xenogeneic natural antibodies (XNAb) directed against species-specific antigens of a discordant donor species (e.g. pig). They trigger the hyperacute xenograft rejection (HXR). Re-usable immunoapheresis (LA)-columns Ig-Therasorb (Therasorb, Baxter) were used to adsorb these XNAb. The effect of immunoapheresis of the perfusing human blood was investigated in ex vivo working pig hearts. METHODS: Hearts of 12 landrace pigs (body weight 14-31 kg) were explanted after inducing cardiac arrest with 4 degrees C Celsior solution. Human blood (500 ml, heparinized) was obtained from healthy volunteers. In group 1 (G1, n = 6), blood as perfusate remained untreated. In group 2 (G2, n = 6), native blood was separated by plasmapheresis into cellular components and plasma. The latter passed through the Ig-Therasorb column for removal of immunoglobulins (so-called immunoadsorption or immunoapheresis). After back-table preparation the hearts were mounted to the working heart model. After 20 min of reperfusion in Langendorff mode, the working heart mode was established. Blood samples were taken isochronously for measurement of: CK(-MB), LDH, ASAT, troponin, immunoglobulins, complement activity, anti-pig antibodies and others. After cessation of the heart, atrial and ventricular tissue samples were taken for histological examinations (light/electron microscopy and immunohistochemistry). RESULTS: Two cycles of immunoapheresis reduced the levels of IgG by 84%, IgM by 83.3% and IgA by 76%. In G2, the antibody immunoadsorption of blood prolonged the duration of the working heart mode significantly to 335+/-37.5 min. In contrast, hearts of group 1 (control) failed after 125+/-31.3 min. Heart rate was significantly different between both groups (G1, 77.3+/-6.1 beats/min; G2, 86.5+/-5.5 beats/min). In G2 cardiac output was 118% and mean coronary flow was 154.6% higher than in G1. CK, LDH and ASAT showed no differences in the two groups. Heart weight increased significantly more in group 1 than in G2. Histological examination indicated specific signs of HXR in G1 after 1.5 h, whereas in G2 only slight unspecific damages were found after 6 h. CONCLUSION: Antibody removal by means of immunoapheresis results in a significantly improved xenogeneic cardiac function. Immunoapheresis may, therefore, become an important adjunct in future pig-to-man clinical xenotransplantation.
Animals↗
Effects of prolonged cold storage time in xenotransplantation.
BACKGROUND: Ischemia and reperfusion injury after prolonged ischemic time (IT) has a marked influence on hyperacute xenograft rejection (HXR). The aim of the study was to investigate the impact of different cold ischemic times on the HXR of ex vivo "working pig hearts" perfused with human blood. Xenoreactive natural antibodies (XNAb) as the trigger of HXR were reduced by immunoadsorption (IA) using an Ig-Therasorb column. METHODS: Hearts of 24 Landrace pigs (13-31 kg) were harvested after cardioplegia with Celsior-solution and split into 4 groups. In Group C1 (n = 6) the short ischemic time (IT) lasted 48.9+/-10 minutes on the average prior to start of xenoperfusion, in Group I1 IT lasted 4 hours instead. Groups C2 and 12 experienced the same IT as C1 and I1, respectively, but underwent 2 cycles of IA in addition. IA removed immunoglobulins IgG, IgM and IgA from the perfusate. In the working heart mode hemodynamic parameters were measured in defined intervals. Blood samples were collected at the same time to determine myocardial enzymes, immunoglobulins, complement and anti-pig-antibodies. At the end of the study (cardiac arrest) tissue was sampled for histologic examination (light/electron microscopy (LM/EM) and immunohistochemistry). RESULTS: Survival time of the control Group C1 was 125 minutes. IA resulted in an extension of perfusion time to 6.5 hours in C2. Four hours of IT (I1) prolonged the working time of hearts when compared with C1. IA had no additional impact (I2). Heart weight increased significantly in C1 without IA. Cardiac output and coronary flow in C1 were significantly lower when compared with the other 3 groups. IA improved cardiac output (CO) in C2 (vs C1, p < 0.001). Histologic signs of HXR (LM/EM) could be found in C1 in contrast to the other groups. Serologic parameters for myocardial damage were higher in groups with prolonged IT than in groups with short IT. CONCLUSION: Prolonged ischemia and reperfusion injury showed controversial effects in this specific xenogeneic heart transplant model. In contrast to observations in allogeneic transplantation 4 hours of IT showed a beneficial behaviour of the xenografts. Reasons could be either a protective effect of the Celsior solution or changes of the endothelial cell surface (in terms of glycosylation or loss of alpha1-3Gal-epitopes). Tolerance of prolonged IT would allow transportation of xenografts over long distances.
Animals↗
[Xenotransplantation of hDAF-transgenic swine hearts].
Hearts of transgenic pigs expressing a human regulator of complement activation, decay accelerating factor (hDAF), were transplanted either heterotopically into the abdomen of cynomolgus monkeys or orthotopically into baboons. None of these transgenic hearts was hyperacutely rejected. Immunosuppression with a combination of cyclosporine A, cyclophosphamide and steroids produced a maximum survival of 62 days (median 40 days) in the heterotopic model. Transgenic hearts transplanted into the orthotopic position allowed a maximum survival of 9 days (median 2.5 days). A more effective and less toxic immunosuppressive protocol for the prevention of accelerated xenograft rejection is the subject of ongoing research. The use of organs from transgenic pigs may help to solve the problem of donor shortage in clinical allotransplantation.
Animals↗
Orthotopic heart transplantation in a transgenic pig-to-primate model.
BACKGROUND: Previous studies demonstrated that hearts from transgenic pigs expressing human decay-accelerating factor (hDAF) were not hyperacutely rejected when transplanted heterotopically into the abdomen of cynomolgus monkeys. This study examines orthotopic transplantation of hDAF transgenic pig hearts into baboon recipients. METHODS: Orthotopic xenogeneic heart transplantation was performed using piglets, transgenic for hDAF, as donors. Ten baboons were used as recipients and were immunosuppressed with a combination of cyclophosphamide, cyclosporine, and steroids. RESULTS: Five grafts failed within 18 hr without any histological signs of hyperacute rejection. Pulmonary artery thrombosis induced by a size mismatch was observed in two of these animals. The other three recipients died because of failure to produce even a low cardiac output and/or dysrhythmia. The remaining five animals survived between four and nine days. One animal died of bronchopneumonia on day 4. Three xenografts stopped beating on day 5 due to acute vascular rejection. The longest survivor was killed on day 9 with a beating, histologically normal xenograft, because of pancytopenia. CONCLUSIONS: The results reported here demonstrate that hDAF transgenic pig hearts are not hyperacutely rejected when transplanted into baboon recipients. Orthotopically transplanted transgenic pig hearts are capable of maintaining cardiac output in baboons. An optimum immunosuppressive regimen is the subject of ongoing research.
Animals↗
Life-supporting pig-to-primate renal xenotransplantation using genetically modified donors.
BACKGROUND: In order to circumvent the complement-mediated hyperacute rejection of discordant xenografts, a colony of pigs transgenic for the human regulator of complement activity, human decay-accelerating factor (hDAF), has been produced. METHODS: Seven kidneys from hDAF transgenic pigs and six kidneys from nontransgenic control pigs were transplanted into cynomolgus monkeys; both native kidneys were removed during the same operation. The recipient animals were immunosuppressed with cyclosporine, steroids, and cyclophosphamide. RESULTS: In the transgenic group, the median survival time was 13 days (range, 6-35 days); the median survival time in the control group was 6.5 days (range, 0.3-30 days). There were no cases of hyperacute rejection in the transgenic group, and the two longest-surviving kidneys in this group showed no evidence of rejection on histological examination. In contrast, all control kidneys underwent antibody-mediated rejection, one demonstrating hyperacute rejection and the others acute vascular rejection. CONCLUSION: This study demonstrates that (i) a kidney from an hDAF transgenic pig can support the life of a primate for up to 35 days (and also shows the basic physiological compatibility between the pig and nonhuman primate); (ii) nontransgenic kidneys are not routinely hyperacutely rejected; and (iii) the presence of hDAF on the kidney confers some protection against acute vascular rejection. Improved immunosuppression and immunological monitoring may enable extended survival.
Animals↗
Kidneys from HDAF transgenic pigs are physiologically compatible with primates.
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Anemia↗
Survival of life-supporting HDAF transgenic kidneys in primates is enhanced by splenectomy.
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Animals↗
[Effect of antibody reduction with immune apheresis Ig-Therasorb on hyperacute rejection in a xeroperfusion model].
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Animals↗
Xenotransplantation of pig organs transgenic for human DAF: an update.
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Animals↗