Alexandria M. Berg

Flow cytometric detection of HLA-specific antibodies as a predictor of heart allograft rejection

BACKGROUND Historically, panel reactive antibody (PRA) analysis to detect HLA antibodies has been performed using cell-based complement-dependent cytotoxicity (CDC) techniques. Recently, a flow cytometric procedure (FlowPRA) was introduced as an alternative approach to detect HLA antibodies. The flow methodology, using a solid phase matrix to which soluble HLA class I or class II antigens are attached is significantly more sensitive than CDC assays. However, the clinical relevance of antibodies detected exclusively by FlowPRAhas not been established. In this study of cardiac allograft recipients, FlowPRA was performed on pretransplant sera with no detectable PRA activity as assessed by CDC assays. FlowPRA antibody activity was then correlated with clinical outcome. METHODS PRA analysis by anti-human globulin enhanced (AHG) CDC and FlowPRA was performed on sera corresponding to final cross-match specimens from 219 cardiac allograft recipients. In addition, sera collected 3-6 months posttransplant from 91 patients were evaluated. The presence or absence of antibodies was correlated with episodes of rejection and patient survival. A rejection episode was considered to have occurred based on treatment with antirejection medication and/or histology. RESULTS By CDC, 12 patients (5.5%) had pretransplant PRA >10%. In contrast, 72 patients (32.9%) had pretransplant anti-HLA antibodies detectable by FlowPRA (34 patients with only class I antibodies; 7 patients with only class II antibodies; 31 patients with both class I and class II antibodies). A highly significant association (P<0.001) was observed between pretransplant HLA antibodies detected by FlowPRA and episodes of rejection that occurred during the first posttransplant year. Fifteen patients died within the first year posttransplant. Of nine retrospective flow cytometric cross-matches that were performed, two were in recipients who had no pretransplant antibodies detectable by FlowPRA. Both of these cross-matches were negative. In contrast, five of seven cross-matches were positive among recipients who had FlowPRA detectable pretransplant antibodies. Posttransplant serum specimens from 91 patients were also assessed for antibodies by FlowPRA. Among this group, 58 patients had FlowPRA antibodies and there was a trend (although not statistically significant) for a biopsy documented episode of rejection to have occurred among patients with these antibodies. CONCLUSIONS Collectively, our data suggest that pre- and posttransplant HLA antibodies detectable by FlowPRA and not AHG-CDC identify cardiac allograft recipients at risk for rejection. Furthermore, a positive donor reactive flow cytometric cross-match is significantly associated with graft loss. Thus, we believe that detection and identification of HLA-specific antibodies can be used to stratify patients into high and low risk categories. An important observation of this study is that in the majority of donor:recipient pairs, pretransplant HLA antibodies were not directed against donor antigens. We speculate that these non-donor-directed antibodies are surrogate markers that correspond to previous T cell activation. Thus, the rejection episodes that occur in these patients are in response to donor-derived MHC peptides that share cryptic determinants with the HLA antigens that initially sensitized the patient.

Heart Transplantation in Children With a Fontan Procedure

BACKGROUND Previous studies have reported that children with a prior Fontan procedure have decreased survival after heart transplantation. We examined 190 primary pediatric heart transplants. METHODS Since 1988, 27 (14.2%) of 190 children less than 18 years old undergoing primary heart transplantation had a Fontan procedure 3.7 ± 4.3 years before transplantation. Compared with 163 (85.8%) non-Fontan primary transplants, the Fontan patients were similar in age (8.2 ± 5.0 vs 6.5 ± 6.0 years), presensitization, and pretransplant clinical status. More Fontan patients had prior operations (100% vs 50%; p < 0.0001) and needed pulmonary artery reconstruction (100% vs 23.5%; p < 0.0001). Twelve (44%) had protein-losing enteropathy. RESULTS Donor ischemic times (211 ± 72 vs 170 ± 61 minutes; p = 0.0018) and cardiopulmonary bypass times (197 ± 91 vs 121 ± 53 minutes; p < 0.0001) were greater in the Fontan group as were durations of ventilator support (4.9 ± 6.6 vs 2.6 ± 3.9 days; p = 0.018) and hospital stay (20.2 ± 17.5 vs 14.3 ± 12.4 days; p = 0.0435). The Fontan group had one 30-day mortality. One-year actuarial survival (81.5% vs 84.6%, Fontan vs non-Fontan) and five-year actuarial survival (65.5% vs 66.2%, Fontan vs non-Fontan) were similar, as was rejection incidence at one year (2.0 ± 2.0 vs 1.7 ± 1.9 episodes per patient; p = 0.3972). Five Fontan patients (18.5%) required retransplantation 4.9 ± 3.6 years posttransplant compared with 18 non-Fontan patients (11.0%) retransplanted 5.2 ± 3.4 years posttransplant (p = 0.3346). CONCLUSIONS Contrary to prior reports, we did not identify any early or midterm disadvantage for children undergoing heart transplantation after a previous Fontan procedure despite more complex transplant operations. We contend that carefully selected children with a failing Fontan circulation can do as well as other children with heart transplantation.

Current results with pediatric heart transplantation

BACKGROUND Cardiac transplantation is an accepted treatment for children with end-stage heart failure or complex or inoperable congenital defects. METHODS Since 1988, 95 transplants have been performed in 89 children aged 4 days to 18 years (median 6.9 years, 42 patients 0-5 years). Fifty-eight (61%) had congenital or acquired heart disease, 31 (33%) had idiopathic cardiomyopathy, and 6 (6%) were retransplants. Fifty-seven of the patients had prior cardiac surgery with a range of one to eight procedures (mean 3.4 procedures/patient). At the time of transplantation, 53 (56%) were United Network for Organ Sharing (UNOS) status I, including 23 children on mechanical ventilation and 4 with mechanical circulatory support. RESULTS Thirty-day survival in this group was 96%. Posttransplant results showed a median time of ventilation of 1 day (mean 3.0+/-5.7 days), median duration of inotropic support of 2 days (mean 2.7+/-2.3 days), median intensive care unit (ICU) stay of 4 days (mean 6.9+/-9.6 days), and median hospitalization of 9 days (mean 14.3+/-13.9 days). Follow-up from 1 month to 10.3 years (mean 3.1 years) has demonstrated a 1-year actuarial survival of 79% and a 5-year actuarial survival of 69%. Rejection, both acute and chronic, accounted for the vast majority of deaths. CONCLUSIONS Pediatric heart transplantation can be accomplished with excellent early survival despite multiple prior cardiac operations and relative severity of illness. Parameters such as postoperative ventilation, inotropic support, ICU stay, and hospitalization can be kept at reasonable levels with acceptable long-term results, although rejection remains a serious problem.

Does Cytomegalovirus Serology Impact Outcome After Pediatric Heart Transplantation

BACKGROUND Cytomegalovirus (CMV) infection has been implicated in a number of complications after heart transplantation. A recent study suggested that children with positive CMV serology (CMV(+)) before transplantation are at increased risk of developing coronary allograft vasculopathy (CAV) and death when compared with CMV(-) recipients. We analyzed data from the Pediatric Heart Transplant Study Group to determine the impact of recipient CMV status and CMV mismatching on outcome. In addition, the use and efficacy of CMV prophylaxis were studied. METHODS Subjects <18 years of age who underwent heart transplantation during the period from 1993 to 2007 were analyzed. Those transplants in which either the recipient or donor were <6 months of age were excluded due to the confounding effects of maternal antibody. The primary outcome variable was freedom from CAV (mild or greater). Secondary outcomes included freedom from death and freedom from clinical CMV infection. Risk factors were assessed using parametric hazard regression. RESULTS Of the 1,598 subjects included in the analysis, 637 (40%) were CMV(+) at the time of transplantation. Some form of CMV prophylaxis was administered to 67% of all recipients, most commonly with a CMV mismatch (donor CMV(+)/recipient CMV(-)). Freedom from clinical CMV infection at 5 years was 91%. Pre-transplant CMV serology was not associated with mortality (p = 0.40) or risk of developing CAV (p = 0.10). CMV mismatch was associated with increased risk of clinical CMV disease (p < 0.001). The use of CMV prophylaxis had no association with mortality or development of CAV. There was also no significant association between CMV prophylaxis and the development of clinical CMV infection. CONCLUSIONS CMV(+) serology at time of pediatric heart transplantation had no demonstrable association with death or development of CAV. CMV(-) recipients who receive a CMV(+) organ are at increased risk of clinical CMV disease. CMV prophylaxis was commonly used, although further studies are needed to establish an optimal approach for prevention of CMV disease in this population.

Donor–Recipient Race Mismatch and Graft Survival After Pediatric Heart Transplantation

BACKGROUND Black recipient race has been shown to predict poorer graft survival after pediatric heart transplantation. We analyzed our single-center experience comparing graft survival by race and the impact of donor-recipient race mismatch. METHODS One hundred sixty-nine consecutive primary pediatric heart transplant patients were analyzed by donor and recipient race (white recipient, 99; black recipient, 60; other, 10). The groups were similar in preoperative characteristics. There were fewer donor-recipient race matches in blacks compared with whites (10 versus 71; p < 0.0001). RESULTS Although 30-day and 6-month graft survival was similar for black and white recipients (93.9% and 85.8% versus 93.3% and 83.3%, respectively), overall actuarial graft survival was significantly lower in blacks (p < 0.019). Blacks tended to have a higher incidence of positive retrospective crossmatch (n = 26, 43%) than whites (n = 29, 29%), but this was not statistically significant (p = 0.053). The median graft survival for black recipients was 5.5 years compared with 11.6 years for whites. Donor-recipient race mismatch predicted poorer graft survival (5-year graft survival 48.9% versus 72.3%; p = 0.0032). The median graft survival for donor-recipient race-matched patients was more than twice that for mismatched patients (11.6 years versus 4.4 years). Cox proportional hazard analysis showed that donor-recipient race mismatch neutralized the effect of race on graft survival. CONCLUSIONS Graft survival after pediatric heart transplantation is inferior for black recipients compared with white recipients. These differences may be explained by a high incidence of donor-recipient race mismatch, which also predicts poorer outcome for all racial groups with pediatric heart transplantation. These data may have implications for future donor allocation schemes.

Serum parameters and echocardiographic predictors of death or need for transplant in newborns, children, and young adults with heart failure.

For children admitted with symptomatic heart failure (HF), the risk of death/need for transplantation (D/Tx) is high. Data from adult studies suggest serum measurements, such as percent lymphocytes, are valuable predictors of outcomes. The aim of this study was to identify risk factors for D/Tx in hospitalized pediatric patients with symptomatic HF. Retrospective analysis of children admitted to an academic center from January 1994 to June 2008 with clinical HF was undertaken. The most common cause of HF was dilated cardiomyopathy (58 of 99, 59%). Echocardiographic and serum measurements were collected from admission. Factors independently associated with risk of D/Tx were evaluated by a stepwise multivariate Cox regression model. There were 99 children with 139 hospitalizations. Median age at admission was 3 years (range 0 to 22). Mean systemic ventricular ejection fraction was 23% +/- 11. Risk of D/Tx per hospitalization was 60 of 139 (43%). In multivariate analysis, lymphocytopenia, lower ejection fraction, low serum sodium, and higher serum creatinine were independent predictors of D/Tx. These variables correctly predicted those subjects at risk of D/Tx in 82.1% of cases. Subgroup analysis found that brain natruretic peptide did not improve the models accuracy markedly. In conclusion, serum measurements (percent lymphocytes, sodium, and creatinine) and echocardiographic assessment routinely obtained at admission are predictive of D/Tx in children hospitalized for HF. Significant lymphocytopenia was predictive of adverse outcomes.

Aortic Complications After Pediatric Cardiac Transplantation in Patients With a Previous Norwood Reconstruction

Despite increasing surgical success with staged palliation of hypoplastic left heart syndrome and its variants, some of these children eventually may require cardiac transplantation. Sixteen (7.8%) of 206 children ≤18 years old undergoing primary heart transplantation had a previous Norwood palliation. Two (12.5%) developed significant aortic problems after transplantation related to the initial homograft reconstruction of the aorta. Patient 1 developed acute graft failure requiring extracorporeal membrane oxygenator support post-transplant. During acute retransplantation 2 days later, the new donor aorta was sewn to a remnant of the initial donor aorta rather than to the heavily calcified reconstructed native aorta. Two months later, the patient required reoperation for acute airway compression from an aortic pseudoaneurysm caused by necrosis of the bridge of aortic tissue from the first transplant. Patient 2 had multiple balloon dilatations of recurrent coarctation after transplantation. Eighteen years post-transplant, during work-up for chronic fever and weight loss, computerized tomography showed a mycotic aneurysm of the reconstructed transverse aorta with contained rupture necessitating removal and replacement of the entire reconstructed aorta. Although uncommon, aortic complications in pediatric heart transplant patients with previous Norwood arch reconstruction can present with unusual manifestations requiring heightened vigilance.

Red blood cell transfusions in children awaiting heart transplantation.

Mahle WT, Berg AM, Kanter KR. Red blood cell transfusions in children awaiting heart transplantation.
Pediatr Transplantation 2011: 15: 728–732.

Fibrofatty changes in failed pediatric cardiac allografts.

The pathogenesis of right ventricular fibrofatty changes can be broadly divided into genetic or acquired. The genetic cause is termed arrhythmogenic right ventricular dysplasia, an inherited cardiomyopathy characterized by fibrofatty replacement of the right ventricular myocardium, and represents an underdiagnosed cardiac entity leading to syncope, recurrent ventricular tachycardias, heart failure, and sudden death. Our study demonstrates that fibrofatty changes can also be seen in pediatric cardiac allografts. Conversely, fat replacement without fibrosis may be seen secondary to infectious myocarditis, chronic inflammation, and ischemia and as part of the aging process. We examined 29 failed cardiac allografts to identify the etiology of graft failure. In this study, 4 patients (13%) had severe right ventricular fibrofatty changes, and when compared with control patients, those with fibrofatty changes had a shorter interval from transplant to graft failure, 2.75 years vs 5.45 years (P = 0.029). Neither body mass index nor other physiologic parameters found on electrocardiography, echocardiography, or cardiac catherization were different between groups. Furthermore, arrhythmias indicative of arrhythmogenic right ventricular dysplasia were not observed in the study group. This study suggests the fibrofatty infiltration in cardiac allografts is a clinically different entity from arrhythmogenic right ventricular dysplasia and has an unknown etiology. Our study findings suggest that identifying fibrofatty infiltrates in cardiac transplant patients during routine right ventricular biopsy can be a predictive factor for shortened life of the pediatric cardiac allograft.