Identifying low-grade cellular rejection after heart transplantation in children by using gene expression profiling.

Endomyocardial biopsy (EMB) remains the gold standard for detecting rejection after heart transplantation but is costly and invasive. This study aims to distinguish no rejection (0R) from low-grade rejection (1R/2R) after heart transplantation in children by using global gene expression profiling in blood. A total of 106 blood samples with corresponding EMB from 18 children who underwent heart transplantation from 2011 to 2014 were analyzed (18 baseline/pretransplantation samples, 88 EMB samples). Corresponding rejection grades for each blood sample were 0R in 39% (34/88), 1R in 51% (45/88), and 2R in 10% (9/88). mRNA from each sample was sequenced. Differential expression analysis was performed at the gene level. A k-nearest neighbor (kNN) analysis was applied to the most differentially expressed (DE) genes to identify rejection after transplantation. Mean age at transplantation was 10.0 ± 5.4 yr. Expression of B cell and T cell receptor sequences was used to measure the effect of posttransplantation immunosuppression. Follow-up samples had lower levels of immunoglobulin gene families compared with pretransplantation ( P < 3E-5) (lower numbers of activated B cells). T cell receptor alpha and beta gene families had decreased expression in 0R samples compared with pretransplantation ( P < 4E-5) but recovered to near baseline levels in 1R/2R samples. kNN using the most DE gene (MKS1) and k = 9 nearest neighbors correctly identified 83% (73/88) of 1R/2R compared with 0R by leave-one-out cross validation. Using a genomic approach we can distinguish low-grade cellular allograft rejection (1R/2R) from no rejection (0R) after heart transplantation in children despite a wide age range.

Predictors of outcomes in children awaiting heart transplantation: an experience from a National Paediatric Heart Transplantation Programme.

OBJECTIVES: The risk of mortality while awaiting heart transplantation (HT) may be greater in the setting of a smaller population and lower donor organ rates. Optimizing allocation policy and identifying the most vulnerable patients will help reduce mortality. As such, we aimed to evaluate the predictors of outcomes in patients awaiting HT as part of a National Paediatric HT Programme. METHODS: Between 1988 and 2015, 200 children were listed for HT as part of a National Paediatric HT Programme. We categorized patients as experiencing one of four competing events: (i) transplant, (ii) death, (iii) delisting for clinical deterioration and (iv) delisting for clinical improvement. Comparison was made across three study eras: Era 1: 1988-95; Era 2: 1996-2005; Era 3: 2006-15. A multivariable competing risk regression analysis was performed to determine the independent predictors of transplantation and the composite event of death or delisting for clinical deterioration. RESULTS: Among the 200 patients listed, 60% (119/200) underwent transplantation, 22% (44/200) died on the waiting list, 7% (13/200) were delisted for clinical deterioration and 11% (21/200) were delisted due to clinical improvement, with 2% (3/200) being still active on the waiting list. The mortality-rate for patients who remained on the waiting list decreased from 27% in Era 1 to 18% in Era 3. The survival from wait-listing was 57, 47 and 39% at 5, 10 and 15 years, respectively. On multivariable competing risk regression, older age (HR 1.09, 95% CI 1.01-1.18, P = 0.029) and the absence of inotropic support (HR 2.22, 1.23-4.00, P = 0.0073) were predictors of reaching transplantation. Higher creatinine (per 20 µmol/l, HR 1.42, 1.03-1.95, P = 0.03) was a predictor of the composite endpoint of death or delisting for deterioration. CONCLUSIONS: In this analysis of a National Paediatric HT Programme, waiting-list mortality has decreased over time though it remains higher than countries with higher donor rates. The requirement for inotropic support and worsening renal function were predictors of failure to reach transplantation. These patients are likely to benefit the most from ventricular-assist device therapy and higher priority listing.

Increasing Complexity of Heart Transplantation in Patients With Congenital Heart Disease.

Owing to improved surgical results, there is a growing population of patients with repaired congenital heart disease (CHD) requiring heart transplantation. The objective of the study was to review our experience in these patients. A retrospective review of the outcomes of heart transplantation in patients with CHD (n = 77) between 1988 and 2014 was performed. Outcomes of early (1988-1999) and late (2000-2014) eras were compared. In results, the mean age was 18 ± 14 years (range: 16 days-58 years). Seventy (91%) patients underwent a mean of 2.6 ± 1.3 (range: 1-6) cardiac operations before transplantation, whereas 7 were primary transplants. Univentricular palliation had been performed in 44 (57%) patients. Patients with CHD in the later era had longer mean cardiopulmonary bypass time (early: 190 ± 70 minute vs late: 271 ± 115 minute; P < 0.001), ischemic times (early: 222 ± 98 minute vs late: 275 ± 102 minute; P = 0.039), and more often required reconstruction of the great arteries at the time of transplantation (8% vs 28%; P = 0.036). In those with prior univentricular palliations, the ratio of ischemic to cardiopulmonary bypass time decreased in the later era (early: 1.41 ± 0.60 vs late: 0.99 ± 0.37; P = 0.016), reflecting increased intraoperative complexity. Following transplantation, hospital mortality was 13% (10/77; 7 due to primary graft failure). There was no difference in inhospital mortality between the 2 eras (P = 0.52); however, patients in the later era more often required postoperative extracorporeal membrane oxygenation (early: 8%, 3/38 vs late: 28%, 11/39; P = 0.036). In patients with prior univentricular palliations, those in the late era were more likely to experience postoperative renal impairment (early: 1/21, 5% vs late: 9/23, 39%; P = 0.01). Patients with CHD had higher 30-day mortality (CHD: n = 8, 10% vs non-CHD: n = 17, 3.8%; P = 0.021), but similar survival at 10 years (67% ± 12% vs 70% ± 4.7%; P = 0.87) compared to those without CHD. In conclusion, patients with CHD undergoing cardiac transplantation in the recent era were more complex. They had a greater number of prior cardiac operations, and more often underwent complex vascular reconstructions and required more prolonged intraoperative preparation.

Surgical strategies to facilitate heart transplantation in children after failed univentricular palliations: the role of advanced intraoperative surgical preparation.

OBJECTIVES: Heart transplantation in children after univentricular palliation is a technical challenge. As the national referral centre for heart transplantation in children, we review national trends in transplantation and describe technical innovations used in the current era. METHODS: Children undergoing heart transplantation were separated into patients with (i) structural congenital heart disease (sCHD; subdivided into univentricular and biventricular) and (ii) cardiomyopathy (CM). The operation notes and surgeons' diagrams were reviewed with particular attention to surgical innovations introduced after 2000. RESULTS: Between January 1988 and December 2012, 111 primary transplantations were performed: 50 for sCHD (30 univentricular and 20 biventricular) and 61 for CM. Thirty-day mortality for univentricular patients compared to those with CM was significantly higher before 2000 (21 vs 0%, 3/14 vs 0/20, P = 0.023) and not different after 2000 (8 vs 6%, 3/38 vs 1/16, P = 0.852). At the same time, the percentage of patients with univentricular physiology increased from 47% (14 of 30 patients) to 80% (16 of 20 patients) versus those with biventricular physiology. After 2000, 12 of 16 patients (75%) with univentricular sCHD required reconstruction of the great vessels. Of these, 8 (50%) patients had reached the stage of Fontan, 5 had reached bidirectional cavopulmonary shunt, 2 had reached Kawashima procedure and 1 had only a Blalock-Taussig shunt. The following techniques were employed in 12 transplantations: aortic arch replacement (n = 3), hilum-to-hilum pulmonary artery (PA) reconstruction (n = 5), PA patch reconstruction (n = 5), reconstruction of the PA bifurcation using donor bifurcation (n = 2) and left superior vena cava (SVC) to donor SVC reconstruction (n = 3). CONCLUSIONS: In the current era, the majority of children undergoing heart transplantation for sCHD have had univentricular palliation. These patients pose challenges because of prior surgeries and complex anatomy, but the techniques described here in may enable improved outcome.

Role of immunosuppression regimen in post-transplant lymphoproliferative disorder in pediatric heart transplant patients.

BACKGROUND: Post-transplant lymphoproliferative disorder (PTLD) contributes to morbidity and mortality after transplantation. We examined the effect of immunosuppressive regimen on the risk of developing PTLD after pediatric heart transplantation. METHODS: The 324 pediatric heart transplant patients at 2 children's hospitals were retrospectively reviewed for the primary outcome of PTLD development. Patient demographics, rejection frequency, serum cyclosporine and tacrolimus levels, induction therapy, donor and recipient Epstein-Barr virus, and cytomegalovirus serologic status were reviewed and comparisons made between immunosuppressive regimens. Comparisons were also made between transplantation in the early (1984-1995) and late (1996-2008) eras to help account for changes in clinical protocols that occurred during the study period. RESULTS: PTLD developed in 33 (10%), of whom 109 (34%) were treated with tacrolimus. PTLD developed in 15% of those treated with tacrolimus compared with 8% of patients treated solely with cyclosporine. Tacrolimus use was a significant predictor of PTLD, with a hazard ratio [HR] of 4.04 (95% confidence interval [CI], 2.03-8.02; p = 0.0001). Neither Epstein-Barr virus, cytomegalovirus donor/recipient status, nor gender predicted PTLD development. Younger age at transplant, higher rejection frequency, and induction therapy predicted PTLD development by univariate analysis. Multivariate modeling demonstrated that tacrolimus use (HR, 7.03; 95% CI, 2.87-17.2; p < 0.001) remained an independent predictor of PTLD, when controlling for age, era of transplantation, induction therapy, and rejection frequency. CONCLUSIONS: This study suggests the use of tacrolimus after pediatric heart transplantation is independently associated with an increased risk of PTLD compared with cyclosporine alone.

Late reduction in cyclosporine dosage does not improve renal function in pediatric heart transplant recipients.

OBJECTIVE: To determine the relation between cyclosporine (CSA) dosage and late renal function in pediatric heart transplant recipients. METHODS: In this retrospective study, pediatric patients were observed for at least 3 years after transplantation, with serial measurement of renal glomerular filtration rate (GFR). Patient variables examined included pre-existing disease (cardiomyopathy or congenital heart disease), age at transplantation, duration of follow-up, and CSA dosage and trough levels at 3 months after transplantation and yearly until the latest follow-up. For each patient, the least squares regression method was used to estimate the average rate of change per year (slope value) for GFR and CSA dosage during follow-up. RESULTS: Twenty-five patients who met the study criteria underwent transplantation at a median age of 11.7 years (interquartile range [IQR], 6.8-14.5 years) and were observed for a median of 6.0 years (IQR, 4-7). The median GFR at 1 year after transplantation was 73 ml/min/1.73 m(2) (IQR, 50-89) and at latest follow-up was 75 ml/min/1.73 m(2) (IQR, 57-98). The median CSA dosage and trough level at 1 year after transplantation were 6.1 mg/kg/day and 234 ng/ml, and at latest follow-up were 3.45 mg/kg/day and 141 ng/ml, respectively. The median rate of change in GFR was +1.6 ml/year of observation (95% confidence interval, -0.9, 4.7) and was inversely related to measured GFR at 1 year after transplantation. The rate of change of GFR was unrelated to any other patient variables including CSA dosages and levels at the specified time intervals and the rate of change of CSA dosage. CONCLUSIONS: Measured GFR in pediatric cardiac transplant recipients treated with CSA is moderately depressed at 12 months after transplantation and does not change significantly during subsequent years. No evidence suggests that the usual progressive reduction in CSA dosage influences renal function beyond 1 year after transplantation.