Myocyte growth, repair, and oxidative stress following pediatric heart transplantation.

Cardiac remodeling is associated with plasma biomarkers of fibrinogenesis, inflammation, and oxidative stress, and upregulation of mitogenic, pro-fibrotic, and apoptotic signaling pathways. Our primary objective was to evaluate biomarker and subcellular myocardial changes in pediatric heart transplant recipients. Fifty-two-week prospective, randomized (tacrolimus, Tac, vs. cyclosporine, CsA), open-label, parallel group study. Serial myocardial biopsies were probed for mitogenic and pro-inflammatory proteins. Plasma biomarkers of oxidative stress (F2α isoprostanes, nitrotyrosine), and inflammation and oxidation (hsCRP and cystatin-C) were measured. Nine of 11 randomized patients completed the study (four Tac, five CsA). Mean levels of F2α isoprostanes, hsCRP, and cystatin-C were maximal at Week 2. Peak activation of all MAP kinases in myocardial tissue was maximal at Week 10; no association was seen with rejection. Cardiac Bax/Bcl-2 levels (index of apoptosis) correlated negatively with F2α isoprostanes at Week 2 (r = -0.88) and with hsCRP at Week 52 (r = -0.67). At Week 52, hsCRP levels correlated positively with molecular indices of cardiac cell growth. We found evidence of systemic and myocardial oxidative damage and inflammation early posttransplant, which may be related to the remodeling process. Further study is needed to better understand the cardiac and systemic repair processes following pediatric heart transplantation.

Donors' characteristics and impact on outcomes in pediatric heart transplant recipients.

Organ availability and acceptability limit pediatric HTx. What characteristics define an unacceptable or high-risk pediatric donor remains unclear. The purpose of this study was to characterize a large cohort of pediatric donors and determine the donor risk factors, including cumulative risk, that affect recipient survival. Data from the PHTS, a prospective multicenter study, were used to examine the impact of donor factors on the outcomes of patients listed <18 yr of age who received a HTx between 1993 and 2009. Donor data were available for 3149 of 3156 HTx (99.8%). Donor cause of death, need for inotropes, or CPR did not affect survival outcomes (p = 0.05). Ischemic time also did not have an impact on overall recipient survival; however, longer ischemic times negatively impacted one-yr post-transplant survival (p < 0.0001). There was no impact of cumulative risk factors on survival (p = 0.8). Although used in a minority of cases, hormonal therapy in the donor positively impacted survival (p = 0.03). In multivariate analysis, the only donor factor associated with decreased survival was smaller donor BSA, the other factors being related to the recipient characteristics. When analyzed by recipient age, there were no donor-related factors that affected survival for those who received a transplant at <6 months of age. Longer ischemic time (p < 0.0001) and greater age difference between the recipient and donor (p = 0.0098) were donor-related factors impacting early-phase survival for recipients who received a graft at ≥10 yr of age. Factors perceived to define a marginal or high-risk pediatric heart donor including inotrope use, CPR and donor cause of death may have less impact on outcomes than previously thought. Longer ischemic times did impact one yr, but not overall survival, and this impact was much greater with older donors. Parameters for accepting a donor heart can potentially be expanded, especially in the infant age group, but strong consideration should always be given to the interaction between ischemic time and donor age.

The evolution of pediatric heart retransplantation over three decades: An analysis from the PHTS.

BACKGROUND: Retransplantation is rare and associated with worse survival and more morbidity. The study aim is to describe an updated cohort of pediatric retransplants, determine if there has been an era effect on outcomes, and understand if identified trends are explained by changes in patient selection. METHODS: Pediatric Heart Transplant Society database analysis of retransplantation patients <18 years of age (Era 1: 1993-2001, Era 2: 2002-2010, Era 3: 2011-2018). Multivariate analysis identified risk factors for graft loss. Multiphase parametric hazard modeling was used to depict era and risk factor effect. RESULTS: Survival was lower (p < .0001) for retransplant (n = 222) compared to primary transplant (n = 6548) (median 9.3 vs 20.2 years). Median survival increased from Era 1 to 2 (4.8 vs 9.3 years; p < .0001) with no incremental change in Era 3. Era 2 and 3 retransplants had a longer inter-transplant interval (p < .0001), were less frequently for early graft failure (p = .0004) or acute rejection (p = .007), more frequently from a ventricular assist device (p = .0014), and less frequently from extracorporeal membrane oxygenation (p = .0024). Predictors of graft loss included Era 1 (HR 10.55, p = .001), congenital heart disease (HR 4.42, p = .01), inter-transplant interval <1 year (HR 5.34, p = .002), and mechanical support (ventricular assist device HR 7.47, p = .0042; extracorporeal membrane oxygenation HR 10.09, p < .0001). For each 1-year increase in inter-transplant interval, graft loss risk decreased by 1.15 (p = .0002). Retransplantation was associated with more rejection, infection, and allograft vasculopathy. CONCLUSIONS: Graft survival has improved in pediatric retransplants making it a viable option in select patients. Retransplantation should be avoided in the setting of early graft failure especially requiring mechanical support.

Continuous infusion of thymoglobulin for induction therapy in pediatric heart transplant recipients; experience and outcomes with a novel strategy for administration.

Minimal data exist on the perioperative use of TG for induction in pediatric HTx recipients. We report our experience using continuous infusion of TG on (i) perioperative adverse events, (ii) rejection, (iii) CAV, and (iv) PTLD. TG was infused via peripheral intravenous intra- and perioperatively as a continuous infusion (24 h/day). Starting dose was 1.5 mg/kg/day titrated to achieve target lymphocyte count of 0.1-0.3 x 10(9)/L. Fifty-five patients received TG; mean age at HTx was 4.4 yr (1 day-17.8 yr). The mean duration of TG was three and a half days (2-7 days). Median platelet count during TG infusion was 95 x 10(9)/L (28-228). Five patients had TG stopped for low platelets (at 4-6 days post-HTx) - all started maintenance immunosuppression. There was no perioperative mortality due to infection. Mean follow-up of 46 survivors was 2.3 yr (0.6-5.8 yr). Fifty-one percent had > or = ISHLT 2R rejection at a median time of 33 days post-HTx (7 days-2 yr). One patient developed PTLD 1.4 yr post-HTx; three patients developed mild-moderate CAV. TG as a continuous infusion appears to have a good safety profile. Though mild thrombocytopenia was prevalent, there was no bleeding attributable solely to TG. Whether early depletion of T-cell function will translate into long-term benefits remains to be determined.

Outcomes of children with cardiomyopathy listed for transplant: a multi-institutional study.

BACKGROUND: Dilated (DCM), restrictive (RCM), and hypertrophic (HCM) cardiomyopathies (CM) in children have varying clinical courses and therapeutic options. Heart transplantation (HTx) offers a chance for long-term survival; but outcomes after listing have not been well defined. METHODS: A multi-institutional registry of 3,147 patients listed for HTx (January 1993-December 2006) was used to compare outcomes of 1,320 children with CM (42%) and 1,827 with non-CM (58%) etiologies. Comparisons were made between sub-groups: 1,098 DCM (83%), 145 RCM (11%), and 77 HCM (6%). RESULTS: CM patients had a waitlist mortality of 17% vs 32% for non-CM patients (p < 0.0001), with no difference between the CM sub-groups. Risk factors were younger age, black race (relative risk [RR], 1.65; p = 0.009), mechanical ventilation (RR, 3.17; p < 0.001), and extracorporeal membrane oxygenation (RR, 2.16; p < 0.001). Ten-year survival after listing was 66% for CM vs 53% for non-CM (p < 0.0001). HCM and RCM patients aged < 1 year at the time of listing had the highest waitlist mortality and the lowest overall survival. CM patients had a better 10-year survival after HTx (68% vs 61%, p < 0.0001). Risk factors for death early after HTx included mechanical ventilation at HTx (RR, 3.07; p < 0.001), longer ischemic time (RR, 1.27; p = 0.01), and earlier era (RR, 1.77; p = 0.002). Late risk factors included black race (RR, 3.01; p < 0.001), HCM or RCM (RR, 1.93; p = 0.007), and older age (RR, 1.9; p < 0.001). CONCLUSION: Children with CM have a lower waitlist mortality and better survival post-HTx than children with a non-CM diagnosis. DCM patients have the best and HCM or RCM patients aged younger than 1 year have the worst overall outcomes.