Progressive Left Ventricular Remodeling for Predicting Mortality in Children With Dilated Cardiomyopathy: The Pediatric Cardiomyopathy Registry.

BACKGROUND: Pediatric dilated cardiomyopathy often leads to death or cardiac transplantation. We sought to determine whether changes in left ventricular (LV) end-diastolic dimension (LVEDD), LV end-diastolic posterior wall thickness, and LV fractional shortening (LVFS) over time may help predict adverse outcomes. METHODS AND RESULTS: We studied children up to 18 years old with dilated cardiomyopathy, enrolled between 1990 and 2009 in the Pediatric Cardiomyopathy Registry. Changes in LVFS, LVEDD, LV end-diastolic posterior wall thickness, and the LV end-diastolic posterior wall thickness:LVEDD ratio between baseline and follow-up echocardiograms acquired ≈1 year after diagnosis were determined for children who, at the 1-year follow-up had died, received a heart transplant, or were alive and transplant-free. Within 1 year after diagnosis, 40 (5.0%) of the 794 eligible children had died, 117 (14.7%) had undergone cardiac transplantation, and 585 (73.7%) had survived without transplantation. At diagnosis, survivors had higher median LVFS and lower median LVEDD Z scores. Median LVFS and LVEDD Z scores improved among survivors (Z score changes of +2.6 and -1.1, respectively) but remained stable or worsened in the other 2 groups. The LV end-diastolic posterior wall thickness:LVEDD ratio increased in survivors only, suggesting beneficial reverse LV remodeling. The risk for death or cardiac transplantation up to 7 years later was lower when LVFS was improved at 1 year (hazard ratio [HR], 0.83; P=0.004) but was higher in those with progressive LV dilation (HR, 1.45; P<0.001). CONCLUSIONS: Progressive deterioration in LV contractile function and increasing LV dilation are associated with both early and continuing mortality in children with dilated cardiomyopathy. Serial echocardiographic monitoring of these children is therefore indicated. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT00005391.

Cardiac imaging and biomarkers for assessing myocardial fibrosis in children with hypertrophic cardiomyopathy.

BACKGROUND: Myocardial fibrosis, as diagnosed on cardiac magnetic resonance imaging (cMRI) by late gadolinium enhancement (LGE), is associated with adverse outcomes in adults with hypertrophic cardiomyopathy (HCM), but its prevalence and magnitude in children with HCM have not been established. We investigated: (1) the prevalence and extent of myocardial fibrosis as detected by LGE cMRI; (2) the agreement between echocardiographic and cMRI measurements of cardiac structure; and (3) whether serum concentrations of N-terminal pro hormone B-type natriuretic peptide (NT-proBNP) and cardiac troponin-T are associated with cMRI measurements. METHODS: A cross-section of children with HCM from 9 tertiary-care pediatric heart centers in the U.S. and Canada were enrolled in this prospective NHLBI study of cardiac biomarkers in pediatric cardiomyopathy (ClinicalTrials.gov Identifier: NCT01873976). The median age of the 67 participants was 13.8 years (range 1-18 years). Core laboratories analyzed echocardiographic and cMRI measurements, and serum biomarker concentrations. RESULTS: In 52 children with non-obstructive HCM undergoing cMRI, overall low levels of myocardial fibrosis with LGE >2% of left ventricular (LV) mass were detected in 37 (71%) (median %LGE, 9.0%; IQR: 6.0%, 13.0%; range, 0% to 57%). Echocardiographic and cMRI measurements of LV dimensions, LV mass, and interventricular septal thickness showed good agreement using the Bland-Altman method. NT-proBNP concentrations were strongly and positively associated with LV mass and interventricular septal thickness (P < .001), but not LGE. CONCLUSIONS: Low levels of myocardial fibrosis are common in pediatric patients with HCM seen at referral centers. Longitudinal studies of myocardial fibrosis and serum biomarkers are warranted to determine their predictive value for adverse outcomes in pediatric patients with HCM.

Association between homograft tissue exposure and allosensitization prior to heart transplant in patients with congenital heart disease.

BACKGROUND: Surgical repair for patients with congenital heart disease (CHD) often incorporates homograft tissue or other foreign material that can lead to allosensitization. We sought to identify the relationship between pre-sensitization prior to heart transplant and exposure to homograft tissue in CHD patients. METHODS: Retrospective chart review of all CHD patients who underwent heart transplant at a major pediatric transplant center between 1/1/2011-3/31/18. Operative records determined use of homograft tissue or foreign material. Panel reactive antibody (PRA) and LuminexTM single-antigen bead (SAB) testing results were reviewed. Statistical analysis determined odds of pre-sensitization in patients exposed to homograft tissue. RESULTS: Fifty-six CHD patients underwent transplant during the review period. Thirteen patients (23%) were pre-sensitized by PRA>10%. By SAB testing, 33 patients (59%) developed any anti-HLA antibody >0 MFI, 30 patients (54%) >2000 MFI, and 19 patients (34%) >6000 MFI. Patients with homografts were more likely to be pre-sensitized by PRA (OR = 7.31, p = .007), and to have developed any anti-HLA antibody at various levels, >0 (OR = 4.52, p = .034), >2000 (OR = 8.59, p = .003), and >6000 (OR = 8.50, p = .004). Of patients with homografts, those pre-sensitized by PRA had longer exposure times (9.80 vs 4.96 years, p = .025). There was no difference in exposure time with relation to pre-sensitization by SAB testing. CONCLUSIONS: Previous exposure to homograft tissue appears to increase the odds of pre-sensitization by either the PRA or SAB testing. Longer exposure time to homograft tissue prior to transplant is associated with increased pre-sensitization at transplant as determined by PRA, though not by SAB testing.

Transcriptomic heterogeneity of antibody mediated rejection after heart transplant with or without donor specific antibodies.

BACKGROUND: Antibody mediated rejection (AMR) is an increasingly studied cause of graft failure after heart transplantation. AMR diagnosis previously required the detection of circulating donor specific antibodies (DSA); however, the most recent criteria only require pathological findings. This classification defined a subset of patients with AMR, yet without known antibodies. Here, we sought to evaluate differences in the transcriptome profile associated with different types of AMR. METHODS: RNA sequencing was used on endomyocardial biopsies to analyze and compare transcriptomic profiles associated with different subtypes of AMR defined by immunopathological and histopathological findings, as well as the presence or absence of DSA. Gene expression profiles were characterized for each diagnostic group. RESULTS: The most divergent gene expression profiles were observed between patients with or without DSA. AMR subtypes associated with DSA showed expression of signature genes involved in monocyte activation and response to interferon. There was also substantial difference between the transcriptomic profiles of AMR defined by histopathological and immunopathological findings, the latter being associated with expression of mucin genes. In contrast, there was no differential RNA expression between patients with pAMR1i without DSA and those without AMR. Likewise, no differential expression was observed between patients with pAMR1h with DSA and pAMR2. CONCLUSIONS: Overall, our studies reveal different expression profiles in endomyocardial biopsies in relation to some key criteria used to diagnose AMR. These findings support the view that the diagnosis of AMR encompasses several phenotypes that may rely on distinct mechanisms of injury.

Impact of Genetic Testing for Cardiomyopathy on Emotional Well-Being and Family Dynamics: A Study of Parents and Adolescents.

BACKGROUND: Genetic testing is indicated for children with a personal or family history of hereditary cardiomyopathy to determine appropriate management and inform risk stratification for family members. The implications of a positive genetic result for children can potentially impact emotional well-being. Given the nuances of cardiomyopathy genetic testing for minors, this study aimed to understand how parents involve their children in the testing process and investigate the impact of genetic results on family dynamics. METHODS: A survey was distributed to participants recruited from the Children's Cardiomyopathy Foundation and 7 North American sites in the Pediatric Cardiomyopathy Registry. The survey explored adolescent and parent participants' emotions upon receiving their/their child's genetic results, parent-child result communication and its impact on family functionality, using the McMaster Family Assessment Device. RESULTS: One hundred sixty-two parents of minors and 48 adolescents who were offered genetic testing for a personal or family history of cardiomyopathy completed the survey. Parents whose child had cardiomyopathy were more likely to disclose positive diagnostic genetic results to their child (P=0.014). Parents with unaffected children and positive predictive testing results were more likely to experience negative emotions about the result (P≤0.001) but also had better family functioning scores than those with negative predictive results (P=0.019). Most adolescents preferred results communicated directly to the child, but parents were divided about whether their child's result should first be released to them or their child. CONCLUSIONS: These findings have important considerations for how providers structure genetic services for adolescents and facilitate discussion between parents and their children about results.

Genetic Causes of Cardiomyopathy in Children: First Results From the Pediatric Cardiomyopathy Genes Study.

Background Pediatric cardiomyopathy is a genetically heterogeneous disease with substantial morbidity and mortality. Current guidelines recommend genetic testing in children with hypertrophic, dilated, or restrictive cardiomyopathy, but practice variations exist. Robust data on clinical testing practices and diagnostic yield in children are lacking. This study aimed to identify the genetic causes of cardiomyopathy in children and to investigate clinical genetic testing practices. Methods and Results Children with familial or idiopathic cardiomyopathy were enrolled from 14 institutions in North America. Probands underwent exome sequencing. Rare sequence variants in 37 known cardiomyopathy genes were assessed for pathogenicity using consensus clinical interpretation guidelines. Of the 152 enrolled probands, 41% had a family history of cardiomyopathy. Of 81 (53%) who had undergone clinical genetic testing for cardiomyopathy before enrollment, 39 (48%) had a positive result. Genetic testing rates varied from 0% to 97% between sites. A positive family history and hypertrophic cardiomyopathy subtype were associated with increased likelihood of genetic testing (P=0.005 and P=0.03, respectively). A molecular cause was identified in an additional 21% of the 63 children who did not undergo clinical testing, with positive results identified in both familial and idiopathic cases and across all phenotypic subtypes. Conclusions A definitive molecular genetic diagnosis can be made in a substantial proportion of children for whom the cause and heritable nature of their cardiomyopathy was previously unknown. Practice variations in genetic testing are great and should be reduced. Improvements can be made in comprehensive cardiac screening and predictive genetic testing in first-degree relatives. Overall, our results support use of routine genetic testing in cases of both familial and idiopathic cardiomyopathy. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT01873963.

T cell repertoire analysis suggests a prominent bystander response in human cardiac allograft vasculopathy.

T cells are implicated in the pathogenesis of cardiac allograft vasculopathy (CAV), yet their clonality, specificity, and function are incompletely defined. Here we used T cell receptor ß chain (TCRB) sequencing to study the T cell repertoire in the coronary artery, endomyocardium, and peripheral blood at the time of retransplant in four cases of CAV and compared it to the immunoglobulin heavy chain variable region (IGHV) repertoire from the same samples. High-dimensional flow cytometry coupled with single-cell PCR was also used to define the T cell phenotype. Extensive overlap was observed between intragraft and blood TCRBs in all cases, a finding supported by robust quantitative diversity metrics. In contrast, blood and graft IGHV repertoires from the same samples showed minimal overlap. Coronary infiltrates included CD4+ and CD8+ memory T cells expressing inflammatory (IFNγ, TNFα) and profibrotic (TGFß) cytokines. These were distinguishable from the peripheral blood based on memory, activation, and tissue residency markers (CD45RO, CTLA-4, and CD69). Importantly, high-frequency rearrangements were traced back to endomyocardial biopsies (2-6 years prior). Comparison with four HLA-mismatched blood donors revealed a repertoire of shared TCRBs, including a subset of recently described cross-reactive sequences. These findings provide supportive evidence for an active local intragraft bystander T cell response in late-stage CAV.

Anti-hypertensive treatment in the immediate post-operative period and 1 year after pediatric heart transplantation.

Hypertension is a known complication of pediatric heart transplantation. We sought to identify factors associated with anti-hypertensive use in pediatric heart transplant recipients immediately post-transplant and oral anti-hypertensive use at discharge and 1-year post-transplant. Retrospective chart review was conducted of patients ≤18 years who underwent heart transplantation at two major heart transplant centers between August 1, 2009 and December 31, 2017 with ≥1-year follow-up. Exclusion criteria included re-transplant, multi-organ recipients, survival <1 year, and comorbidities associated with hypertension. Anti-hypertensive use was recorded during initial ICU stay, at discharge, and 1-year post-transplant. Univariate and multivariate analyses determined associations of demographic and diagnostic factors and need for anti-hypertensives. There were 188 patients that met inclusion criteria. Anti-hypertensive infusions were required in the ICU post-transplant in 46 patients (24.5%) for a median of 3 days (1-21 days). Oral anti-hypertensives were required in 58 patients (30.9%) at discharge and 1-year post-transplant. Anti-hypertensive infusion in the ICU post-transplant was associated with donor-to-recipient weight ratio. Oral anti-hypertensive use at discharge was associated with weight ratio and pretransplant VAD use, and at 1-year, post-transplant was associated with age at transplant, steroid use at discharge, and oral anti-hypertensive use at discharge. Hypertension is common immediately following and 1-year post-transplant. Weight ratio was the only independent predictor of anti-hypertensive use in the early post-transplant period, whereas VAD use was also associated with anti-hypertensive use at discharge. Anti-hypertensive use 1-year post-transplant was not associated with those factors, but rather with age at transplant and steroid use.

Varying presentations of COVID-19 in young heart transplant recipients: A case series.

BACKGROUND: Immunosuppression is considered a risk factor for more severe clinical presentation of COVID-19. Limited data regarding clinical outcome exist in adults, whereas very little is known about the spectrum of the disease in pediatric heart transplant recipients. METHODS: We retrospectively reviewed the charts of young heart transplant patients from our tertiary care center during the coronavirus pandemic in New York City and identified patients infected with SARS-CoV-2. RESULTS: We present four cases with COVID-19 disease and elaborate on their presentation and clinical course. CONCLUSIONS: Although far from conclusive and limited by the small sample size and selection bias, these cases demonstrate mild and self-limited disease despite immunosuppressive therapy and various comorbidities that are expected to increase the severity of the clinical picture based on extrapolation from the adult experience with this novel disease.

Impact of dipyridamole on adenosine dosing in pediatric and young adult patients after heart transplantation.

BACKGROUND: Relative contraindications to adenosine use have included heart transplant and dipyridamole. We previously demonstrated the safety and efficacy of adenosine-induced atrioventricular (AV) block in healthy young heart transplant recipients while suspending dipyridamole therapy (dual antiplatelet agent). This prospective follow-up study evaluated the safety and efficacy of adenosine use in the same cohort of heart transplant recipients while on dipyridamole. METHODS: Adenosine was incrementally dosed until AV block occurred (maximum 200 mcg/kg up to 12 mg). The primary outcome was clinically significant asystole (≥12 seconds). Secondary outcomes included maximal adenosine dose, AV block duration, dysrhythmias, and clinical symptoms. Outcomes were compared to the parent study. RESULTS: Thirty of 39 eligible patients (5-24 years) were tested. No patient (0%, CI 0%-8%) experienced clinically significant asystole. AV block occurred in 29/30 patients (97%, CI 86%-100%). The median dose causing AV block was 50mcg/kg (vs 100 mcg/kg off dipyridamole; P = .011). Seventeen patients (57%, CI 39%-72%) required less adenosine to achieve AV block on dipyridamole; six (20%) required more. AV block occurred at doses ≥25 mcg/kg in all patients. In pairwise comparison to prior testing off dipyridamole, no significant change occurred in AV block duration, frequency of cardiac ectopy, or incidence of reported symptoms. No atrial fibrillation/flutter occurred. CONCLUSIONS: AV block often occurs at twofold lower adenosine doses in healthy young heart transplant recipients taking oral dipyridamole, compared with previous testing of this cohort off dipyridamole. Results suggest that initial dosing of 25 mcg/kg (maximum 0.8 mg) with stepwise escalation poses low risk of prolonged asystole on dipyridamole.

Profiling non-HLA antibody responses in antibody-mediated rejection following heart transplantation.

Antibody-mediated rejection (AMR) driven by the development of donor-specific antibodies (DSA) directed against mismatched donor human leukocyte antigen (HLA) is a major risk factor for graft loss in cardiac transplantation. Recently, the relevance of non-HLA antibodies has become more prominent as AMR can be diagnosed in the absence of circulating DSA. Here, we assessed a single-center cohort of 64 orthotopic heart transplant recipients transplanted between 1994 and 2014. Serum collected from patients with ≥ pAMR1 (n = 43) and non-AMR (n = 21) were tested for reactivity against a panel of 44 non-HLA autoantigens. The AMR group had a significantly greater percentage of patients with elevated reactivity to autoantigens compared to non-AMR (P = .002) and healthy controls (n = 94, P < .0001). DSA-positive AMR patients exhibited greater reactivity to autoantigens compared to DSA-negative (P < .0001) and AMR patients with DSA and PRA > 10% were identified as the subgroup with significantly elevated responses. Reactivity to 4 antigens, vimentin, beta-tubulin, lamin A/C, and apolipoprotein L2, was significantly different between AMR and non-AMR patients. Moreover, increased reactivity to these antigens was associated with graft failure. These results suggest that antibodies to non-HLA are associated with DSA-positive AMR although their specific role in mediating allograft injury is not yet understood.

Biventricular Impella use in pediatric patients with severe graft dysfunction from acute rejection after heart transplantation.

Rejection with severe hemodynamic compromise is a significant source of morbidity and mortality for pediatric heart transplant patients. Traditionally, treatment for these patients includes inotropes and escalation to extracorporeal membrane oxygenation (ECMO) when necessary. There is increasing interest in using percutaneous ventricular assistive devices in the pediatric population as a less invasive alternative to ECMO. We report the largest case series to date of biventricular support using percutaneous Impella devices. Retrospective case series was performed by chart review. Hemodynamics, left ventricular ejection fraction (LVEF), and indices of end organ function were collected before and after Impella placement. A 14-year-old male, 18-year-old male, and 19-year-old female, all status post heart transplant, presented with severely decreased biventricular function due to presumed clinical rejection, requiring maximal inotropic support without improvement. In all the three cases, simultaneous Impella CP and RP devices were placed percutaneously. Prior to implantation, LVEFs were 40%, 23%, and 25%, respectively. Hemodynamics measured invasively prior to device placement showed elevated filling pressures. Adverse events while on support included bleeding, hemolysis, and right femoral arterial dissection during implantation. All patients were successfully weaned from the devices and survived to discharge. The average time of right-sided support and total support was 11 days and 13 days, respectively. After device removal, right-sided pressures and echocardiographic measurements showed improvement in all patients. Bilateral Impella configuration (BiPella) is a viable option for temporary mechanical circulatory support in pediatric patients with significant graft dysfunction.

Cardiac Biomarkers in Pediatric Cardiomyopathy: Study Design and Recruitment Results from the Pediatric Cardiomyopathy Registry.

BACKGROUND: Cardiomyopathies are a rare cause of pediatric heart disease, but they are one of the leading causes of heart failure admissions, sudden death, and need for heart transplant in childhood. Reports from the Pediatric Cardiomyopathy Registry (PCMR) have shown that almost 40% of children presenting with symptomatic cardiomyopathy either die or undergo heart transplant within 2 years of presentation. Little is known regarding circulating biomarkers as predictors of outcome in pediatric cardiomyopathy. STUDY DESIGN: The Cardiac Biomarkers in Pediatric Cardiomyopathy (PCM Biomarkers) study is a multi-center prospective study conducted by the PCMR investigators to identify serum biomarkers for predicting outcome in children with dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). Patients less than 21 years of age with either DCM or HCM were eligible. Those with DCM were enrolled into cohorts based on time from cardiomyopathy diagnosis: categorized as new onset or chronic. Clinical endpoints included sudden death and progressive heart failure. RESULTS: There were 288 children diagnosed at a mean age of 7.2±6.3 years who enrolled in the PCM Biomarkers Study at a median time from diagnosis to enrollment of 1.9 years. There were 80 children enrolled in the new onset DCM cohort, defined as diagnosis at or 12 months prior to enrollment. The median age at diagnosis for the new onset DCM was 1.7 years and median time from diagnosis to enrollment was 0.1 years. There were 141 children enrolled with either chronic DCM or chronic HCM, defined as children ≥2 years from diagnosis to enrollment. Among children with chronic cardiomyopathy, median age at diagnosis was 3.4 years and median time from diagnosis to enrollment was 4.8 years. CONCLUSION: The PCM Biomarkers study is evaluating the predictive value of serum biomarkers to aid in the prognosis and management of children with DCM and HCM. The results will provide valuable information where data are lacking in children. CLINICAL TRIAL REGISTRATION NCT01873976: https://clinicaltrials.gov/ct2/show/NCT01873976?term=PCM+Biomarker&rank=1.

Influenza Myocarditis Treated With Antithymocyte Globulin.

Influenza is a cause of significant morbidity and mortality worldwide. Myocarditis is a rare complication of the virus and can vary widely in severity. The published cases of influenza B myocarditis in children tend to be severe with a high mortality rate. Current standard treatment of viral myocarditis is supportive care, although immunomodulatory therapies, such as steroids and intravenous immunoglobulin, are often used. T cells have been implicated in causing significant myocyte damage in myocarditis by leading to the downstream production of antibodies against viral and myocyte antigens; this has created a theoretical basis for the use of antithymocyte globulin to target T cells in these patients. We present a case of acute fulminant influenza B myocarditis in a pediatric patient that required mechanical circulatory support and improved only after treatment with antithymocyte globulin.

No Obesity Paradox in Pediatric Patients With Dilated Cardiomyopathy.

OBJECTIVES: This study aimed to examine the role of nutrition in pediatric dilated cardiomyopathy (DCM). BACKGROUND: In adults with DCM, malnutrition is associated with mortality, whereas obesity is associated with survival. METHODS: The National Heart, Lung, and Blood Institute-funded Pediatric Cardiomyopathy Registry was used to identify patients with DCM and categorized by anthropometric measurements: malnourished (MN) (body mass index [BMI] <5% for age ≥2 years or weight-for-length <5% for <2 years), obesity (BMI >95% for age ≥2 years or weight-for-length >95% for <2 years), or normal bodyweight (NB). Of 904 patients with DCM, 23.7% (n = 214) were MN, 13.3% (n=120) were obese, and 63.1% (n=570) were NB. RESULTS: Obese patients were older (9.0 vs. 5.7 years for NB; p < 0.001) and more likely to have a family history of DCM (36.1% vs. 23.5% for NB; p = 0.023). MN patients were younger (2.7 years vs. 5.7 years for NB; p < 0.001) and more likely to have heart failure (79.9% vs. 69.7% for NB; p = 0.012), cardiac dimension z-scores >2, and higher ventricular mass compared with NB. In multivariable analysis, MN was associated with increased risk of death (hazard ratio [HR]: 2.06; 95% confidence interval [CI]: 1.66 to 3.65; p < 0.001); whereas obesity was not (HR: 1.49; 95% CI: 0.72 to 3.08). Competing outcomes analysis demonstrated increased risk of mortality for MN compared with NB (p = 0.03), but no difference in transplant rate (p = 0.159). CONCLUSIONS: Malnutrition is associated with increased mortality and other unfavorable echocardiographic and clinical outcomes compared with those of NB. The same effect of obesity on survival was not observed. Further studies are needed investigating the long-term impact of abnormal anthropometric measurements on outcomes in pediatric DCM. (Pediatric Cardiomyopathy Registry; NCT00005391).

Study rationale, design, and pretransplantation alloantibody status: A first report of Clinical Trials in Organ Transplantation in Children-04 (CTOTC-04) in pediatric heart transplantation.

Anti-HLA donor-specific antibodies are associated with worse outcomes after organ transplantation. Among sensitized pediatric heart candidates, requirement for negative donor-specific cytotoxicity crossmatch increases wait times and mortality. However, transplantation with positive crossmatch may increase posttransplantation morbidity and mortality. We address this clinical challenge in a prospective, multicenter, observational cohort study of children listed for heart transplantation (Clinical Trials in Organ Transplantation in Children-04 [CTOTC-04]). Outcomes were compared among sensitized recipients who underwent transplantation with positive crossmatch, nonsensitized recipients, and sensitized recipients without positive crossmatch. Positive crossmatch recipients received antibody removal and augmented immunosuppression, while other recipients received standard immunosuppression with corticosteroid avoidance. This first CTOTC-04 report summarizes study rationale and design and relates pretransplantation sensitization status using solid-phase technology. Risk factors for sensitization were explored. Of 317 screened patients, 290 were enrolled and 240 underwent transplantation. Core laboratory evaluation demonstrated that more than half of patients were anti-HLA sensitized. Greater than 80% of sensitized patients had class I (with or without class II) HLA antibodies, and one-third of sensitized patients had at least 1 HLA antibody with median fluorescence intensity of ≥8000. Logistic regression models demonstrated male sex, weight, congenital heart disease history, prior allograft, and ventricular assist device are independent risk factors for sensitization.

Pediatric Cardiomyopathies.

Pediatric cardiomyopathies are rare diseases with an annual incidence of 1.1 to 1.5 per 100 000. Dilated and hypertrophic cardiomyopathies are the most common; restrictive, noncompaction, and mixed cardiomyopathies occur infrequently; and arrhythmogenic right ventricular cardiomyopathy is rare. Pediatric cardiomyopathies can result from coronary artery abnormalities, tachyarrhythmias, exposure to infection or toxins, or secondary to other underlying disorders. Increasingly, the importance of genetic mutations in the pathogenesis of isolated or syndromic pediatric cardiomyopathies is becoming apparent. Pediatric cardiomyopathies often occur in the absence of comorbidities, such as atherosclerosis, hypertension, renal dysfunction, and diabetes mellitus; as a result, they offer insights into the primary pathogenesis of myocardial dysfunction. Large international registries have characterized the epidemiology, cause, and outcomes of pediatric cardiomyopathies. Although adult and pediatric cardiomyopathies have similar morphological and clinical manifestations, their outcomes differ significantly. Within 2 years of presentation, normalization of function occurs in 20% of children with dilated cardiomyopathy, and 40% die or undergo transplantation. Infants with hypertrophic cardiomyopathy have a 2-year mortality of 30%, whereas death is rare in older children. Sudden death is rare. Molecular evidence indicates that gene expression differs between adult and pediatric cardiomyopathies, suggesting that treatment response may differ as well. Clinical trials to support evidence-based treatments and the development of disease-specific therapies for pediatric cardiomyopathies are in their infancy. This compendium summarizes current knowledge of the genetic and molecular origins, clinical course, and outcomes of the most common phenotypic presentations of pediatric cardiomyopathies and highlights key areas where additional research is required. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifiers: NCT02549664 and NCT01912534.

Prospective Study of Adenosine on Atrioventricular Nodal Conduction in Pediatric and Young Adult Patients After Heart Transplantation.

BACKGROUND: Supraventricular tachycardia is common after heart transplantation. Adenosine, the standard therapy for treating supraventricular tachycardia in children and adults without transplantation, is relatively contraindicated after transplantation because of a presumed risk of prolonged atrioventricular block in denervated hearts. This study tested whether adenosine caused prolonged asystole after transplantation and if it was effective in blocking atrioventricular nodal conduction in these patients. METHODS: This was a single-center prospective clinical study including healthy heart transplant recipients 6 months to 25 years of age presenting for routine cardiac catheterization during 2015 to 2016. After catheterization, a transvenous pacing catheter was placed and adenosine was given following a dose-escalation protocol until atrioventricular block was achieved. The incidence of clinically significant asystole (≥12 seconds after adenosine) was quantified. The effects of patient characteristics on adenosine dose required to produce atrioventricular block and duration of effect were also measured. RESULTS: Eighty patients completed adenosine testing. No patient (0%; 95% confidence interval, 0-3) required rescue ventricular pacing. Atrioventricular block was observed in 77 patients (96%; 95% confidence interval, 89-99). The median longest atrioventricular block was 1.9 seconds (interquartile range, 1.4-3.2 seconds), with a mean duration of adenosine effect of 4.3±2.0 seconds. No patient characteristic significantly predicted the adenosine dose to produce atrioventricular block or duration of effect. Results were similar across patient weight categories. CONCLUSIONS: Adenosine induces atrioventricular block in healthy pediatric and young adult heart transplant recipients with minimal risk when low initial doses are used (25 µg/kg; 1.5 mg if ≥60 kg) and therapy is gradually escalated. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02462941.

Percutaneous coronary artery revascularization procedures in pediatric heart transplant recipients: A large single center experience.

OBJECTIVES: To describe our experience, at a large pediatric heart transplant center, with percutaneous coronary interventions (PCI) for cardiac allograft vasculopathy (CAV). BACKGROUND: CAV is a leading cause of late graft failure, mortality, and re-transplantation in pediatric heart transplant (HTx) recipients. Studies of PCI in adult patients have shown some short-term improvements, but no significant change in long-term outcomes. There are limited data on PCI for CAV in pediatric patients. We describe the largest single-center experience to date. METHODS: We performed a retrospective chart review of all pediatric HTx recipients who underwent PCI for a diagnosis of CAV from 2005 to 2014. RESULTS: Twenty-three procedures were performed in 13 patients, at a median age of 16.4 years (range 5.6-21.2) and median time from HTx to first PCI of 8.3 years (range 2.9-20.3). Three cases consisted of angioplasty alone, two cases had bare metal stents implanted, and the remaining 18 had drug-eluting stents implanted. There was acute procedural success in all but one case, and there was only one procedure-related complication (rebleeding from access site). During the follow-up interval (median 10.4 months, range 0.2-111.8), 7/13 patients had repeat PCI performed, two patients died (at 1.8 and 5.8 months post-PCI), and five were re-transplanted (range 0.2-18 months post-PCI). Freedom from death or retransplant by Kaplan-Meier analysis was 54% at 1 year. CONCLUSIONS: PCI can be performed safely and effectively in pediatric HTx recipients with CAV. Similar to the adult experience, there remains a high rate of disease progression and graft failure. © 2016 Wiley Periodicals, Inc.

Low-Dose Donor Dopamine Is Associated With a Decreased Risk of Right Heart Failure in Pediatric Heart Transplant Recipients.

BACKGROUND: Previous studies in adults have suggested that donor dopamine treatment may improve recipient outcomes in organ transplantation; in this analysis, we aimed to determine if donor dopamine reduces the incidence of postoperative right heart failure (RHF) in pediatric heart transplant recipients. METHODS: Data for recipients aged 18 years or younger transplanted at our institution between January 1, 2000, and June 15, 2011, and their respective donors were obtained. The presence of postoperative RHF was assessed for in all subjects. Donor dopamine dose was stratified into 3 groups: none, low-dose (≤5 µg/kg per minute), and high-dose (>5 µg/kg per minute). Logistic regression was used to assess the relationship between donor dopamine dose and recipient RHF. RESULTS: Of 192 recipients, 34 (18%) experienced postoperative RHF. There was no difference in baseline demographics between recipients with and without RHF. When controlling for pulmonary vascular resistance index, graft ischemic time, and cardiopulmonary bypass time, donor low-dose dopamine was independently associated with a decreased risk of RHF (odds ratio, 0.16; 95% confidence interval, 0.04-0.70; P = 0.02); however high-dose dopamine was neither associated with, nor protective of, RHF (odds ratio, 0.31; 95% confidence interval, 0.06-1.6; P = 0.16). CONCLUSIONS: Despite advances in perioperative care of the recipient, RHF persists as a complication of pediatric heart transplantation. In this study, donor pretreatment with low-dose dopamine is associated with a decreased risk of postoperative RHF in pediatric heart recipients. Further studies into this association may be useful in determining the utility of empiric donor pretreatment with low-dose dopamine.