Changes in circumferential strain can differentiate pediatric heart transplant recipients with and without graft rejection.

BACKGROUND: Routine surveillance protocols rely heavily on endomyocardial biopsy (EMB) for detection of rejection in pediatric heart transplant recipients. More sensitive echocardiographic tools to assess rejection may help limit the number of EMBs. This study compared changes in left ventricular (LV) strain in patients who had rejection versus those who did not. METHODS: A single center retrospective review was conducted between 2013 and 2020. Patients were categorized based on rejection history. Echocardiograms were evaluated at the time of 2 consecutive EMBs; in the rejection group, the second echocardiogram was collected at the time of a rejection episode. Conventional measures of LV function and speckle-tracking echocardiography-derived longitudinal (LS) and circumferential strain (CS) were measured. RESULTS: 17 patients were in the non-rejection group and 17 were in the rejection group (30 total rejection episodes). The rejection group was older at the time of transplant (12.5 vs. 1.3 years, p = .01). A decline in CS was seen in the rejection group at the second echocardiogram [-18.5 (IQR -21.5, -14.6) to -15.7 (IQR -19.8, -13.2)] while CS improved in the non-rejection group [-20.8 (IQR -23.9, -17.8) to -23.9 (IQR -24.9, -20.1)]. This difference in change reached significance (p = .02). A similar pattern was seen in LS that neared significance (p = .06). There was no significant difference in ejection fraction change (p = .24). CONCLUSIONS: Patients in the non-rejection group displayed improvement in CS between echocardiograms while patients in the rejection group showed subsequent decline. Worsening of LV CS may help identify acute rejection in the early post-transplant period.

Longer Ischemic Time is Associated with Increased Ventricular Stiffness as Measured by Pressure-Volume Loop Analysis in Pediatric Heart Transplant Recipients.

BACKGROUND: The purpose of this study was to investigate the associations between clinical factors and cardiac function as measured by pressure-volume loops (PVLs) in a pediatric heart transplant cohort. METHODS: Patients (age < 20 years) who underwent heart transplantation presenting for a clinically indicated catheterization were enrolled. PVLs were recorded using microconductance catheters (CD Leycom®, Zoetermeer, Netherlands). Demographic data, serum B-type natriuretic peptide (BNP), time from transplant, ischemic time, presence of transplant coronary artery disease, donor-specific antibodies, and history of rejection were recorded at the time of catheterization. PVL data included contractility indices: end-systolic elastance and preload recruitable stroke work; ventricular-arterial coupling index; ventricular stiffness constant, Beta; and isovolumic relaxation time constant, tau. Associations between PVL measures and clinical data were investigated using non-parametric statistical tests. RESULTS: A total of 18 patients were enrolled. Median age was 8.7 years (IQR 5-14 years). There were ten males and eight females. Six patients had a history of rejection and ten had positive donor-specific antibodies. There was no transplant coronary artery disease. Median BNP was 100 pg/mL (IQR 46-140). Time from transplant to PVL obtained during catheterization procedure was 4.1 years (IQR 1.7-7.8 year). No single clinical characteristic was statistically significant when correlated with PVL data. However, longer ischemic time was associated with worse Beta (r = 0.49, p = 0.05). CONCLUSIONS: Our study found that longer ischemic times are associated with increased left ventricular stiffness. No other single clinical variable is associated with cardiac dysfunction as determined by PVL analysis.

Autoimmune enteropathy and hepatitis in pediatric heart transplant recipient.

AIE is a rare disorder in children that presents with severe diarrhea and malabsorption, caused by immune-mediated damage to intestinal mucosa. AIE is often associated with various syndromes of immunodeficiency including IPEX syndrome (immune dysregulation, polyendocrinopathy and enteropathy, X-linked). Dysfunctional T regulatory cells are the source of pathology in both IPEX syndrome and AIE as they are essential in maintaining tolerance to self-antigens and eliminating autoreactive B cells. This case report describes a 10-year-old cardiac transplant and total thymectomy patient on chronic immunosuppression with tacrolimus that presented with AIE and extraintestinal manifestations of cyclical hepatitis. Transition from tacrolimus to sirolimus successfully increased T regulatory cells and resolved enteritis and hepatitis symptoms. Data support that thymectomy at <1 year of age increases risk of autoimmune disease due to abnormal immune maturation. Studies suggest that the sirolimus promotes the upregulation of the FoxP3 protein that is classically associated with Tregs. In turn, Tregs prevent the maturation of autoreactive B cells that lead to autoimmune reactions.

Effect of Induction Therapy on Graft Survival in Primary Pediatric Heart Transplantation: A Propensity Score Analysis of the UNOS Database.

BACKGROUND: The use of induction therapy in pediatric heart transplantation has increased. The aim of this study was to investigate the effects of induction therapy on graft survival. METHODS: The United Network for Organ Sharing database was queried for isolated pediatric heart transplants from January 1, 1994, to December 31, 2013. Propensity scores for induction treatment were calculated by estimating probability of induction using a logistic regression model. Transplants were then matched between induction treatment groups based on the propensity score, reducing potential biases. Using only propensity score matched transplants, the effect of induction therapy on graft survival was investigated using Cox-proportional hazards. Subgroup analyses were performed based on age, race, recipient cardiac diagnosis, HLA, and recipient panel-reactive antibody (PRA). RESULTS: Of 4565 pediatric primary heart transplants from 1994 to 2013, 3741 had complete data for the propensity score calculation. There were 2792 transplants successfully matched (induction, n = 1396; no induction, n = 1396). There were no significant differences in transplant and pretransplant covariates between induction and no induction groups. In the Cox-proportional hazards model, the use of induction of was not associated with graft loss (hazard ratio [HR], 0.88; 95% confidence interval [95% CI], 0.75-1.01; P = 0.07). In subgroup analyses, induction therapy may be associated with improved survival in patients with PRA greater than 50% (HR, 0.57; 95% CI, 0.34-0.97) and congenital heart disease (HR, 0.78; 95% CI, 0.64-0.96). CONCLUSIONS: Induction therapy is not associated with improved graft survival in primary pediatric heart transplantation. However, in pediatric heart transplant recipients with PRA greater than 50% or congenital heart disease, induction therapy is associated with improved survival.

Validation of a Simple Score to Determine Risk of Early Rejection After Pediatric Heart Transplantation.

OBJECTIVES: This study aimed to develop a reliable and feasible score to assess the risk of rejection in pediatric heart transplantation recipients during the first post-transplant year. BACKGROUND: The first post-transplant year is the most likely time for rejection to occur in pediatric heart transplantation. Rejection during this period is associated with worse outcomes. METHODS: The United Network for Organ Sharing database was queried for pediatric patients (age <18 years) who underwent isolated orthotopic heart transplantation from January 1, 2000 to December 31, 2012. Transplantations were divided into a derivation cohort (n = 2,686) and a validation (n = 509) cohort. The validation cohort was randomly selected from 20% of transplantations from 2005 to 2012. Covariates found to be associated with rejection (p < 0.2) were included in the initial multivariable logistic regression model. The final model was derived by including only variables independently associated with rejection. A risk score was then developed using relative magnitudes of the covariates' odds ratio. The score was then tested in the validation cohort. RESULTS: A 9-point risk score using 3 variables (age, cardiac diagnosis, and panel reactive antibody) was developed. Mean score in the derivation and validation cohorts were 4.5 ± 2.6 and 4.8 ± 2.7, respectively. A higher score was associated with an increased rate of rejection (score = 0, 10.6% in the validation cohort vs. score = 9, 40%; p < 0.01). In weighted regression analysis, the model-predicted risk of rejection correlated closely with the actual rates of rejection in the validation cohort (R(2) = 0.86; p < 0.01). CONCLUSIONS: The rejection score is accurate in determining the risk of early rejection in pediatric heart transplantation recipients. The score has the potential to be used in clinical practice to aid in determining the immunosuppressant regimen and the frequency of rejection surveillance in the first post-transplant year.

Effect of human leukocyte antigen-C and -DQ matching on pediatric heart transplant graft survival.

BACKGROUND: A higher degree of human leukocyte antigen (HLA) matching at the A, B, and DR loci has been associated with improved long-term survival after pediatric heart transplantation in multiple International Society for Heart and Lung Transplantation registry reports. The aim of this study was to investigate the association of HLA matching at the C and DQ loci with pediatric graft survival. METHODS: The United Network of Organ Sharing database was queried for isolated heart transplants that occurred from 1988 to 2012 with a recipient age of 17 or younger and at least 1 postoperative follow-up encounter. When HLA matching at the C or DQ loci were analyzed, only transplants with complete typing of donor and recipient at the respective loci were included. Transplants were divided into patients with at least 1 match at the C locus (C-match) vs no match (C-no), and at least 1 match at the DQ (DQ-match) locus vs no match (DQ-no). Primary outcome was graft loss. Univariate analysis was performed with the log-rank test. Cox regression analysis was performed with the following patient factors included in the model: recipient age, ischemic time; recipient on ventilator, extracorporeal membrane oxygenation, ventricular assist device, or inotropes at transplant; recipient serum bilirubin and creatinine closest to transplant, ratio of donor weight to recipient weight, underlying cardiac diagnosis, crossmatch results, transplant year, and HLA matching at the A, B, and DR loci. RESULTS: Complete typing at the C locus occurred in 2,429 of 4,731 transplants (51%), and complete typing at the DQ locus occurred in 3,498 of 4,731 transplants (74%). Patient factors were similar in C-match and C-no, except for year of transplant (median year, 2007 [interquartile range, 1997-2010] vs year 2005 [interquartile range, 1996-2009], respectively; p = 0.03) and the degree of HLA matching at the A, B, and DR loci (high level of HLA matching in 11.9% vs 3%, respectively; p < 0.01). Matching at the C locus was not associated with a decreased risk of graft loss (median graft survival: 13.1 years [95% confidence interval {CI}, 11.5-14.8] in C-no vs 15.1 years [95% CI, 13.5-16.6) in C-match, p = 0.44 log-rank; hazard ratio, 0.93; 95% CI, 0.76-1.15; p = 0.52). DQ-match did not differ from DQ-no in any of the analyzed patient factors, except DQ-match was more likely to have high degree of matching at the A, B, and DR loci vs DQ-no (9.8% vs 3.2%, p < 0.01). Matching at the DQ locus was not associated with decreased risk of graft loss (median graft survival: DQ-no, 13.1 years [95% CI, 11.7-14.6) vs DQ-match, 13.0 years [95% CI, 11.4-14.6], p = 0.80, log-rank; hazard ratio, 0.95; 95% CI, 0.81-1.1; p = 0.51. CONCLUSIONS: Complete typing at the C locus of both donor and recipient occurs less often then typing at the DQ locus. A higher degree of donor-recipient HLA matching at the C locus or the DQ locus appears not to confer any graft survival advantage.

Association of human leukocyte antigen donor-recipient matching and pediatric heart transplant graft survival.

BACKGROUND: The effect of donor-recipient human leukocyte antigen (HLA) matching on outcomes remains relatively unexplored in pediatric patients. The objective of this study was to investigate the effects of donor-recipient HLA matching on graft survival in pediatric heart transplantation. METHODS AND RESULTS: The UNOS (United Network for Organ Sharing) database was queried for heart transplants occurring between October 31, 1987, and December 31, 2012, in a recipient aged ≤17 years with ≥1 postoperative follow-up visit. Retransplants were excluded. Transplants were divided into 3 donor-recipient matching groups: no HLA matches (HLA-no), 1 or 2 HLA matches (HLA-low), and 3 to 6 HLA matches (HLA-high). Primary outcome was graft loss. Four thousand four hundred seventy-one heart transplants met the study inclusion criteria. High degree of donor-recipient HLA matching occurred infrequently: HLA-high (n=269; 6%) versus HLA-low (n=2683; 60%) versus HLA-no (n=1495; 34%). There were no differences between HLA matching groups in the frequency of coronary vasculopathy (P=0.19) or rejection in the first post-transplant year (P=0.76). Improved graft survival was associated with a greater degree of HLA donor-recipient matching: HLA-high median survival, 17.1 (95% confidence interval, 14.0-20.2) years; HLA-low median survival, 14.2 (13.1-15.4) years; and HLA-no median survival, 12.1 (10.9-13.3 years) years; P<0.01, log-rank test. In Cox-regression analysis, HLA matching was independently associated with decreased graft loss: HLA-low versus HLA-no hazard ratio, 0.86 (95% confidence interval, 0.74-0.99), P=0.04; HLA-high versus HLA-no, 0.62 (95% confidence interval, 0.43-0.90), P<0.01. CONCLUSIONS: Decreased graft loss in pediatric heart transplantation was associated with a higher degree of donor-recipient HLA matching, although a difference in the frequency of early rejection or development of coronary artery vasculopathy was not seen.