Triple immunosuppression reduces mononuclear cell infiltration and prolongs graft life in pig–to–newborn baboon cardiac xenotransplantation

AbstractObjective: Pig hearts transplanted into unmedicated newborn baboons do not undergo hyperacute rejection by preformed xenoantibody and complement. These grafts are rejected at days 3 to 4 in association with the infiltration of macrophages and natural killer cells. We investigated whether an immunosuppressive regimen used widely in cardiac allotransplantation could reduce this cellular response and prolong xenograft life. Methods: Ten newborn baboons underwent heterotopic pig cardiac xenotransplantation. Five baboons were immunosuppressed with mycophenolate mofetil (100 mg/kg), methylprednisolone acetate (0.8 mg/kg), and cyclosporine A (INN: ciclosporin; 10 mg/kg). Xenograft rejection was studied by light microscopy and immunofluorescence. The induced humoral response to porcine xenoantigens was documented by enzyme-linked immunosorbent assay using synthetic α-1,3-galactosyl epitopes coupled to bovine serum albumin. Results: Graft life was extended from a mean of 3.6 ± 0.5 days (n = 5) to a mean of 6.2  ± 1.1 days (n = 5, p = 0.01). In comparison with controls, explanted grafts from medicated baboons demonstrated reduced infiltration with natural killer cells and macrophages, but increased evidence of complement-mediated rejection substantiated by increased deposition of immunoglobulin M, complement, and fibrin. In all baboons receiving transplants, levels of both immunoglobulin M and immunoglobulin G anti-galactose were significantly increased after transplantation, with immunoglobulin G levels remaining persistently elevated. Conclusions: These results indicate that cyclosporine-based triple immunosuppression marginally prolonged xenograft survival and appears to have reduced the natural killer cell and macrophage infiltrates. The immunosuppressive protocol, however, was not adequate to prevent the induced immunoglobulin M humoral response and prevent complement-mediated graft injury. (J Thorac Cardiovasc Surg 1998;115:998-1006

Birth weight and complexity are significant factors for the management of hypoplastic left heart syndrome

Classic options for treatment of hypoplastic left heart syndrome include the Norwood procedure (NW) and heart transplantation (HT). Recently off-pump palliative procedures were introduced in the management of these patients. Risk factors influencing the decision between the NW with staged reconstruction or off-pump palliation and HT were assessed. Between January 2002 and January 2006, 69 patients with hypoplastic left heart syndrome were referred for either a NW (n = 33) or HT (n = 36). Patients referred for HT underwent off-pump palliation (catheter-based, n = 20, or surgical hybrid procedures, n = 7) until a donor organ became available: including patent ductus arteriosus stenting (80.6%), atrial septostomy (41.7%), and branch pulmonary artery banding (55.6%). Heart transplantation patients were more complex, based on a higher Aristotle Comprehensive Complexity score calculated at birth (HT 18.8 +/- 2.4 versus NW 17.7 +/- 1.7; p 20) correlated with surgical death with NW (p < 0.01). Noticeably, surgical survival was 85.7% for infants with birth weight of 2.5 kg or greater undergoing NW. Overall survival is similar for hypoplastic left heart syndrome patients referred for the NW or HT. Lower birth weight and higher complexity are risk factors for patients undergoing NW. Off-pump palliation followed by HT or further staged palliation should be considered for these high-risk hypoplastic left heart syndrome patients