R. Morton Bolman

Risk factors for the development of bronchiolitis obliterans syndrome after lung transplantation

OBJECTIVE This study identifies specific clinical and immunologic factors in lung transplant recipients that influence the subsequent development of chronic allograft dysfunction. METHODS The study group consisted of 132 consecutive patients who received lung allografts (76 single, 25 bilateral single, and 31 heart-lung) and survived at least 90 days. One hundred twenty-one patients were used in the analysis that modeled time to development of histologic obliterative bronchiolitis or bronchiolitis obliterans syndrome. RESULTS Variables noted to have an effect on the time to development of bronchiolitis obliterans syndrome included cytomegalovirus pneumonitis (RR = 3.2, p = 0.001), late acute rejection (RR = 1.3, p = 0.02), human leukocyte antigen mismatches at the A loci (RR = 1.8, p = 0.02), total human leukocyte antigen mismatches (RR = 1.4, p = 0.04), and absence of donor antigen-specific hyporeactivity (52% vs 100% survival free from bronchiolitis obliterans syndrome at 2 years; p = 0.005). Cytomegalovirus pneumonitis had a significant effect on time to obliterative bronchiolitis (RR = 3.6, p = 0.0005), as did donor antigen-specific hyporeactivity (52% vs 100% survival free from obliterative bronchiolitis at 2 years; p = 0.01). In multivariate analysis, cytomegalovirus pneumonitis (RR = 3.2, p = 0.02), human leukocyte antigen mismatches at the A loci (RR = 2.4, p = 0.006), and late acute rejection (RR = 1.3, p = 0.02) were identified as predictors of bronchiolitis obliterans syndrome. Cytomegalovirus pneumonitis was associated with time to development of histologic obliterative bronchiolitis (RR = 2.3, p = 0.02). CONCLUSIONS Several risk factors were associated with the development of chronic allograft dysfunction, which, in turn, had a significant impact on long-term survival. Early identification of lung allograft recipients with risk factors for the development of bronchiolitis obliterans syndrome may allow modification in immunosuppression and antiviral therapy to potentially decrease the prevalence of this disorder.

The immunopathology of cardiac xenograft rejection in the guinea pig-to-rat model.

The mechanisms underlying rejection by rats of vascularized guinea pig xenografts have been controversial. The aim of this study was to define, using sequential immunopathologic analysis, the contributions of xenoreactive antibody, complement, and effector cells to the rejection of guinea pig cardiac xenografts by Lewis rats. In untreated recipients, hyperacute rejection of guinea pig cardiac xenografts occurred in 20±10.2 min and was characterized by focal endothelial deposition of IgM and by diffuse deposition of C3. IgG was not localized to endothelial surfaces, but was present in the same locations as albumin, suggesting that the accumulation of IgG might reflect nonspecific leakage of plasma proteins from blood vessels. No polymorphonuclear or monocytic infiltrate was observed. Depletion from rats of xeno-reactive antibody to undetectable levels prolonged the survival of guinea pig cardiac xenografts, but did not prevent hyperacute rejection; the rejected xenografts contained deposits of C3 along the microvasculature but no deposits of IgM or IgG. No cellular infiltrate was observed. Depletion of complement with cobra venom factor prolonged the survival of xenografts up to 96 hr. Xenograft tissues from complement-depleted animals had diffuse deposits of IgM along the microvasculature, but no detectable deposits of C3 or IgG were noted. Graft tissues obtained at various times after transplantation into complement-depleted animals revealed cellular infiltrates consisting of granulocytes, monocytes, and lymphocytes, but few cells bearing an NK cell phenotype. Our findings are consistent with the concept that complement activation is essential for the hyperacute rejection of discordant xenografts, and that in this particular model complement activation can proceed without the involvement of antibody. However, our findings also suggest that xenoreactive antibody contributes to hyperacute rejection and, along with effector cells, contributes to the later rejection of a xenograft when hyperacute rejection has been averted. Finally, we show that when hyperacute rejection is avoided, a form of vascular rejection occurs in which certain of the pathologic features—i.e., interstitial hemorrhage, interstitial edema, and thrombosis—are very similar to those observed in hyperacute rejection. Whether this form of rejection is a delayed form of the process that leads to hyperacute rejection or a novel pathologic process of graft rejection has yet to be determined.

Dilated cardiomyopathy in infants and children.

The outcome of medical treatment of dilated cardiomyopathy in infants and children was reviewed to develop a predictive index for selection of patients likely to benefit from cardiac transplantation. The clinical findings, laboratory investigations, treatment and outcome of 20 patients (Group 1) less than 2 years of age at presentation and 12 patients (Group 2) greater than 2 years of age at onset were compared. Of 20 Group 1 patients, 5 (25%) died. Available autopsies (four patients) showed endocardial fibroelastosis. Of 15 survivors, 10 showed improvement in cardiac status and 5 remained unchanged. Ninety-three percent of survivors had dilated cardiomyopathy consistent with endocardial fibroelastosis by angiocardiography. All 12 Group 2 patients died. In addition to age at presentation and poor outcome, Group 2 differed from Group 1 in having a higher incidence of other family members with cardiomyopathy, more significant rhythm disturbances at presentation and a more rapid course to death. Risk factors of poor outcome in both groups included persistent cardiomegaly and the development of significant arrhythmias by Holter electrocardiographic monitoring. Cardiac transplantation is recommended for children with dilated cardiomyopathy presenting after age 2 years who survive 1 month. Those patients less than 2 years old at presentation whose condition has not improved after 1 year and who have persistent cardiomegaly or complex ventricular arrhythmias may also benefit from transplantation.

Early and Late Airway Complications After Lung Transplantation: Incidence and Management

BACKGROUND Airway anastomosis complications continue to be a source of morbidity for lung transplant recipients. METHODS This study analyzes incidence, treatment, and follow-up of airway anastomotic complications occurring in 127 consecutive lung transplant airway anastomoses (77 single lung and 25 bilateral sequential lung). Complications were categorized as stenosis (11), granulation tissue (8), infection (7), bronchomalacia (5), or dehiscence (3). Follow-up after treatment ranged from 6 months to 4 years. RESULTS Nineteen airway anastomosis complications (15.0%) occurred in 18 patients. Telescoping the airway anastomosis reduced the complication rate to 12 of 97 (12.4%), compared with 7 of 30 (23.3%) for omental wrapping, (p = 0.15). Complications developed in 13 of 77 single-lung airway anastomoses (16.9%) versus 6 of 50 bilateral sequential lung recipients (12.0%). Treatment consisted of stenting (9 airway anastomoses), bronchodilation (8), laser debridement (4), rigid bronchoscopic debridement (2), operative revision (2), and growth factor application (2). There was no difference in actuarial survival between patients with or without airway anastomosis complications (p = 1.0). CONCLUSIONS Airway anastomosis complications can be successfully managed in the immediate or late postoperative period with good outcome up to 4 years after intervention.

Prevalence and variability of internal mammary artery graft use in contemporary multivessel coronary artery bypass graft surgery: analysis of the Society of Thoracic Surgeons National Cardiac Database.

Background— Use of an internal mammary artery (IMA) is a well-recognized, nationally endorsed quality indicator for evaluating the process of operative care for coronary artery bypass graft surgery. An objective assessment of the current status of IMA use has not been systematically performed. Methods and Results— This cross-sectional observational study analyzed data on 541 368 coronary artery bypass graft surgery procedures reported by 745 hospitals in the Society of Thoracic Surgeons National Cardiac Database from 2002 through 2005. We assessed the current status of IMA use, the association of hospital volume and IMA use, and disparities in IMA use by patient gender and race and by region of hospital location. Rates of using at least 1 IMA and bilateral IMA were 92.4% and 4.0%, with increasing trends over the years. Hospital volume was not significantly associated with IMA use. IMAs were used less frequently in women than men (for at least 1 IMA: odds ratio, 0.62; 95% confidence interval, 0.61 to 0.63; for bilateral IMA: odds ratio, 0.65; 95% confidence interval, 0.63 to 0.68) and less frequently in nonwhite patients than white patients (for at least 1 IMA: odds ratio, 0.84; 95% confidence interval, 0.81 to 0.87; for bilateral IMA: odds ratio, 0.79; 95% confidence interval, 0.75 to 0.83). There were significant differences in frequency of IMA use by hospital region. Conclusions— Frequency of IMA use in coronary artery bypass graft surgery is increasing; however, many patients still do not receive the benefits of IMA grafts, and some hospitals have a very low IMA use rate. Hospital volume is not associated with IMA use in coronary artery bypass graft surgery. Analysis of this critical performance measure reveals significant gender and race disparities.

Removal of baboon and human antiporcine IgG and IgM natural antibodies by immunoadsorption : results of in vitro and in vivo studies

The safe and effective removal of xenoreactive antibodies in the peritransplant period is likely to be critical for the clinical application of xenotransplantation involving disparate donor species, such as the pig. In an effort to develop an improved method for antibody removal in xenotransplantation, we have studied reusable antihuman antibody (Ig) columns in vitro and in vivo. Two types of columns were tested: (1) an antihuman Ig column containing polyclonal sheep antihuman IgG (heavy- and light-chain-specific) conjugated to sepharose CL-4B (Ig-Therasorb), and (2) an antihuman Ig column using polyclonal antihuman IgM (mu-chain-specific) conjugated to sepharose. Passage of human or baboon plasma through the Ig-Therasorb column resulted in 97.5% and 78.4% mean reductions in total IgG and IgM, respectively. Reductions in total IgG and IgM correlated with lowering of antipig IgG (54-486 fold) and IgM (9-54 fold) antibody titers as assessed by pig endothelial cell ELISA. The ability of the Ig-Therasorb to significantly reduce IgM may be attributed to the light chain specificity of this column. With the anti-IgM column, marked reductions in total (82.6-83.9%) and antipig (27-54 fold) IgM in human and baboon plasma occurred, while levels of total and xenoreactive IgG were slightly affected. Other than a dilutional effect, neither column resulted in significant reduction in albumin, fibrinogen, factor 5, and factor 8. Repeated in vivo use of either column in baboons achieved reductions in IgG and IgM that closely followed the results of our in vitro studies. No subject morbidity or mortality occurred. Use of the Ig-Therasorb column with immunosuppression in two baboons receiving pig renal xenografts achieved sustained reductions in antipig antibodies and prevented hyperacute rejection. Subjects were sacrificed at 11 and 13 days posttransplant with functioning xenografts and were found to have no evidence of vascular xenograft rejection. We conclude that anti-Ig columns represent a safe and effective method for antibody removal, without several of the limitations of other antibody removal techniques. Also, columns appear to be safe for repeated antibody removal in the posttransplant period.

Complement inhibition with an anti-C5 monoclonal antibody prevents acute cardiac tissue injury in an ex vivo model of pig-to-human xenotransplantation.

Prevention of hyperacute xenograft rejection in the pig-to-primate combination has been accomplished by removal of natural antibodies, complement depletion with cobra venom factor, or prevention of C3 activation with the soluble complement inhibitor sCR1. Although these strategies effectively prevent hyperacute rejection, they do not address the relative contribution of early (C3a, C3b) versus late (C5a, C5b-9) activated complement components to xenogeneic organ damage. To better understand the role of the terminal complement components (C5a, C5b-9) in hyperacute rejection, an anti-human C5 mAb was developed and tested in an ex vivo model of cardiac xenograft rejection. In vitro studies demonstrated that the anti-C5 mAb effectively blocked C5 cleavage in a dose-dependent manner that resulted in complete inhibition of both C5a and C5b-9 generation. Addition of anti-C5 mAb to human blood used to perfuse a porcine heart prolonged normal sinus cardiac rhythm from a mean time of 25.2 min in hearts perfused with unmodified blood to 79,296, or > 360 min when anti-C5 mAb was added to the blood at 50 micrograms/ml, 100 micrograms/ml, or 200 micrograms/ml, respectively. In these experiments, activation of the classical complement pathway was completely inhibited. Hearts perfused with blood containing the highest concentration of anti-C5 mAb had no histologic evidence of hyperacute rejection and no deposition of C5b-9. These experiments suggest that the activated terminal complement components C5a and C5b-9, but not C3a or C3b, play a major role in tissue damage in this porcine-to-human model of hyperacute rejection. They also suggest that targeted inhibition of terminal complement activation by anti-C5 mAbs may be useful in clinical xenotransplantation.

Early and late outcomes in minimally invasive mitral valve repair: An eleven-year experience in 707 patients

OBJECTIVE This study analyzes a single institution experience with minimally invasive mitral valve repair and evaluates long-term surgical outcomes of morbidity, mortality, and rates of reoperation. Late follow-up of mitral regurgitation and left ventricular function were also assessed. METHODS Between August 1996 and October 2007, minimally invasive mitral valve repair was performed in 713 patients (mean follow-up 5.7 years). Excluding 6 repairs with robotic assistance, an perspective analysis of the remaining 707 patients was carried forth. Mean age was 57 +/- 13 years. Mean preoperative ejection fraction was 60% +/- 10%. Surgical access was through a lower ministernotomy (74%), right parasternal incision (24%), right thoracotomy (1.4%), or upper ministernotomy (0.7%). Exposure of the mitral valve was through the left atrium in 58% of the cases and transeptal in 42%. A ring annuloplasty was incorporated into 680 (96%) of 707 repairs. The Kaplan-Meier and Student t test for paired samples were used for statistical analysis. RESULTS There were 3 (0.4%) operative deaths. Perioperative morbidity included new-onset atrial fibrillation (20%), reoperation for bleeding (2%), stroke (1.9%), permanent pacemaker implantation (1.7%), deep sternal wound infection (0.7%), and aortic dissection (0.4%). Median hospital stay was 5 days. Only 31% of patients required blood transfusion during the hospital course. There were 49 (6.9%) late deaths and 34 (4.8%) failed repairs necessitating reoperation. At 11.2 years, survival was 83% (95% confidence intervals, 76.5-88.1); freedom from reoperation was 92% (95% confidence intervals, 86.2-94.9). Nine (1.3%) patients were lost to follow-up. A total of 2369 patient-years of echocardiography time were obtained in 544 patients (mean 4.36 years, range 0.47-11.09). Mean grade of mitral regurgitation decreased from 3.80 to 1.42 (P < .0001) Mean left ventricular ejection fraction decreased from 60.7% to 56.3% (P < .0001). Combined risk of death, reoperation, and recurrence of moderately severe to severe mitral regurgitation was 7.7% (43/555). CONCLUSION Minimally invasive mitral valve repair is safe, with low perioperative morbidity, low rates of recurrent mitral regurgitation, and low rates of reoperation and death at late follow-up.

Treatment of invasive cytomegalovirus disease in solid organ transplant patients with ganciclovir

The occurrence of cytomegalovirus infection after solid organ transplantation has been correlated with decrease patient and allograft survival. The disease has not been conquered for two majors reasons: the length of time to establish the diagnosis of CMV has been excessive, and suitable, nontoxic antiviral agents have not been available for use. The purpose of this study was to examine the current incidence and impact of tissue-invasive cytomegalovirus (TI-CMV) disease that developed in 93 patients who underwent solid organ transplantation at University of Minnesota Hospitals (3/1/87 and 6/30/89) and who were treated with antiviral agent ganciclovir ( [9-(1,3-dihydroxy-2-2-propoxymethyl)-guanine [DHPG]). During this same period of time 323 patients received kidney transplants and 71 received kidney-pancreas transplants. Three patient groups were defined: (1) no CMV; (2) CMV infection (cultural or serologic evidence of noninvasive CMV infection); and (3) evidence of TI-CMV disease based upon initial complaints of fever, malaise, dyspnea, or abdominal pain, leukopenia (WBC less than 3000/ml), and evidence of a positive CMV rapid antigen test, CMV culture, or the presence of characteristic CMV inclusion bodies upon examination of material obtained by means of bronchoscopy, upper-gastrointestinal endoscopy, colonoscopy, or liver or renal biopsy. Patients with solely fever, leukopenia, but without a rising CMV serum titer, or positive CMV urine or blood cultures were excluded from the study. A multivariate analysis revealed that rejection therapy, age greater than 50 years, and receiving an organ from a seropositive donor were all significant variables that predisposed to TI-CMV. Analysis of patient and kidney allograft survival indicated that asymptomatic CMV infection had little current impact upon patient or allograft survival, while patients who developed TI-CMV exhibited higher rates of allograft loss and mortality, despite DHPG therapy. Comparison with historical group of patients indicated that TI-CMV DHPG-treated patients exhibited a trend toward improved allograft survival that may be relevant because the historical group of patients included patients with mild CMV infection. DHPG therapy was well tolerated and produced minimal toxicity, and excellent 30-day cure rates (89.2%), although 21.2% of patients required retreatment subsequently. We are currently conducting a trial to compare the ability of DHPG administered plus an anti-CMV immune globulin preparation with acyclovir to prevent posttransplant TI-CMV disease.

Expression of human CD59 in transgenic pig organs enhances organ survival in an ex vivo xenogeneic perfusion model

The serious shortage of available donor organs for patients with end stage organ failure who are in need of solid organ transplantation has led to a heightened interest in xenotransplantation. The major barrier to successful discordant xenotransplantation is hyperacute rejection. Hyperacute rejection results from the deposition of preformed antibodies that activate complement on the luminal surface of the vascular endothelium, leading to vessel occlusion and graft failure within minutes to hours. Endogenous membrane-associated complement inhibitors normally protect endothelial cells from autologous complement -- however, these molecules are species-restricted and therefore are ineffective at inhibiting activated xenogeneic complement. To address the pathogenesis of hyperacute rejection in the pig-to-human combination, F1 offspring were generated from a transgenic founder animal that was engineered to express the human terminal complement inhibitor hCD59. High-level cell surface expression of hCD59 was detected in the hearts and kidneys of these transgenic F1 animals, similar to expression levels in human kidney tissue. The hCD59 was expressed on both large vessel and capillary endothelium. Ex vivo perfusion experiments, using human blood as the perfusate, were performed with transgenic porcine hearts and kidneys to evaluate the ability of hCD59 to inhibit hyperacute rejection. These experiments demonstrated that transgenic organs expressing hCD69 resisted hyperacute rejection, as measured by increased organ function for both the hearts and the kidneys, as compared with control pig organs. Hearts from hCD59-expressing animals demonstrated a five-fold prolongation in function compared with controls, 109.8 +/- 20.7 min versus 21.2 +/- 2.9 min (P = 0.164). The hCD59-expressing kidneys also demonstrated significantly prolonged function at 157.8 +/- 27.0 min compared with 60.0 +/- 6.1 min for controls (P = 0.0174). Deposition of C9 neoantigen In the vasculature of porcine organs perfused with human blood was markedly reduced in organs expressing hCD59. These studies demonstrate that C5b-9 plays an important role in hyperacute rejection of a porcine organ perfused with human blood and suggest that donor pigs transgenic for hCD59 may be an integral component of successful clinical xenotransplantation.