Cardiac magnetic resonance assessment of acute rejection and cardiac allograft vasculopathy in pediatric heart transplant.

BACKGROUND: In pediatric heart transplant (PHT), cardiac catheterization with endomyocardial biopsy (EMB) is standard for diagnosing acute rejection (AR) and cardiac allograft vasculopathy (CAV) but is costly and invasive. OBJECTIVES: To evaluate the ability of cardiac magnetic resonance (CMR) to noninvasively identify differences in PHT patients with AR and CAV. METHODS: Patients were enrolled at three children's hospitals. Data were collected from surveillance EMB or EMB for-cause AR. Patients were excluded if they had concurrent diagnoses of AR and CAV, CMR obtained >7days from AR diagnosis, they had EMB negative AR, or could not undergo contrasted, unsedated CMR. Kruskal-Wallis test was used to compare groups: (1) No AR or CAV (Healthy), (2) AR, (3) CAV. Wilcoxon rank-sum test was used for pairwise comparisons. RESULTS: Fifty-nine patients met inclusion criteria (median age 17years [IQR 15-19]) 10 (17%) with AR, and 11 (19%) with CAV. AR subjects had worse left ventricular ejection fraction compared to Healthy patients (p = 0.001). Global circumferential strain (GCS) was worse in AR (p = 0.054) and CAV (p = 0.019), compared to Healthy patients. ECV, native T1, and T2 z-scores were elevated in patients with AR. CONCLUSIONS: CMR was able to identify differences between CAV and AR. CAV subjects had normal global function but abnormal GCS which may suggest subclinical dysfunction. AR patients have abnormal function and tissue characteristics consistent with edema (elevated ECV, native T1 and T2 z-scores). Characterization of CMR patterns is critical for the development of noninvasive biomarkers for PHT and may decrease dependence on EMB.

The Fontan immunophenotype and post-transplant outcomes in children: A multi-institutional study.

BACKGROUND: Patients after Fontan palliation represent a growing pediatric population requiring heart transplant (HTx) and often have lymphopenia (L) and/or hypogammaglobinemia that may be exacerbated by protein-losing enteropathy (PLE, P). The post-HTx effects of this altered immune phenotype are not well studied. METHODS: In this study of the Pediatric Heart Transplant Society Registry, 106 Fontan patients who underwent HTx between 2005 and 2018 were analyzed. The impact of lymphopenia and PLE on graft survival, infection, rejection, and malignancy was analyzed at 1 and 5 years post-HTx. RESULTS: The following combinations of lymphopenia and PLE were noted: +L+P, n = 37; +L-P, n = 23; -L+P, n = 10; and -L-P, n = 36. Graft survival between the groups was similar within the first year after transplant (+L+P: 86%, +L-P: 86%, -L+P: 87%, -L-P: 89%, p = .9). Freedom from first infection post-HTx was greatest among -L-P patients compared to patients with either PLE, lymphopenia, or both; with a 22.1% infection incidence in the -L-P group and 41.4% in all others. These patients had a significantly lower infection rate in the first year after HTx (+L+P: 1.03, +L-P: 1, -L+P: 1.3, -L-P: 0.3 infections/year, p < .001) and were similar to a non-single ventricle CHD control group (0.4 infections/year). Neither freedom from rejection nor freedom from malignancy 1 and 5 years post-HTx, differed among the groups. CONCLUSIONS: Fontan patients with altered immunophenotype, with lymphopenia and/or PLE, are at increased risk of infection post-HTx, although have similar early survival and freedom from rejection and malignancy. These data may encourage alternative immunosuppression strategies and enhanced monitoring for this growing subset of patients.

Cardiac magnetic resonance diastolic indices correlate with ventricular filling pressures in pediatric heart transplant recipients.

BACKGROUND: Atrial and ventricular filling pressures are routinely used in pediatric heart transplant (PHTx) recipients to assess graft function. We hypothesized that cardiac magnetic resonance (CMR) diastolic indices correlate with filling pressures, providing a noninvasive method of hemodynamic assessment. METHODS: Pediatric heart transplant recipients were prospectively enrolled at the time of cardiac catheterization. Pulmonary capillary wedge pressure (PCWP) and right atrial pressure (RAP) were measured. CMR included standard volumetric analysis. Filling curves were calculated by contouring every phase in the short-axis stack. Global longitudinal and circumferential strain (GLS, GCS) were calculated using feature tracking. Atrial volumes and ejection fraction were calculated from 4-chamber and 2-chamber cine images. Correlations were analyzed using Spearman's Rho; modeling was performed with multivariable logistic regression. RESULTS: A total of 35 patients with a mean age of 15.5 years were included, 12 with acute rejection. The median time post-transplant was 6.2 years. Peak filling rate (PFR) and peak LV ejection rate/end-diastolic volume (PER/EDV) correlated with PCWP (rho = 0.48 p = .005, and rho = -0.35 p = .046, respectively) as did GLS and GCS (rho = 0.52 p = .002, and 0.40 p = .01). Indexed maximum and minimum left atrial (LA) volume correlated with PCWP (rho = 0.41, p = .01, rho = 0.41 p = .01), and LA ejection fraction inversely correlated with PCWP (rho = -0.40, p = .02). GLS and GCS correlated with RAP (rho = 0.55, p = .001 and rho = 0.43, p = .01). A model including LV GLS and PFR estimated PCWP ≥12 mmHg with an area under the curve of 0.84. CONCLUSIONS: Cardiac magnetic resonance can be a useful noninvasive modality to assess for signs of diastolic dysfunction after PHTx.

Clinically Suspected Myocarditis Temporally Related to COVID-19 Vaccination in Adolescents and Young Adults: Suspected Myocarditis After COVID-19 Vaccination.

BACKGROUND: Understanding the clinical course and short-term outcomes of suspected myocarditis after the coronavirus disease 2019 (COVID-19) vaccination has important public health implications in the decision to vaccinate youth. METHODS: We retrospectively collected data on patients <21 years old presenting before July 4, 2021, with suspected myocarditis within 30 days of COVID-19 vaccination. Lake Louise criteria were used for cardiac MRI findings. Myocarditis cases were classified as confirmed or probable on the basis of the Centers for Disease Control and Prevention definitions. RESULTS: We report on 139 adolescents and young adults with 140 episodes of suspected myocarditis (49 confirmed, 91 probable) at 26 centers. Most patients were male (n=126, 90.6%) and White (n=92, 66.2%); 29 (20.9%) were Hispanic; and the median age was 15.8 years (range, 12.1-20.3; interquartile range [IQR], 14.5-17.0). Suspected myocarditis occurred in 136 patients (97.8%) after the mRNA vaccine, with 131 (94.2%) after the Pfizer-BioNTech vaccine; 128 (91.4%) occurred after the second dose. Symptoms started at a median of 2 days (range, 0-22; IQR, 1-3) after vaccination. The most common symptom was chest pain (99.3%). Patients were treated with nonsteroidal anti-inflammatory drugs (81.3%), intravenous immunoglobulin (21.6%), glucocorticoids (21.6%), colchicine (7.9%), or no anti-inflammatory therapies (8.6%). Twenty-six patients (18.7%) were in the intensive care unit, 2 were treated with inotropic/vasoactive support, and none required extracorporeal membrane oxygenation or died. Median hospital stay was 2 days (range, 0-10; IQR, 2-3). All patients had elevated troponin I (n=111, 8.12 ng/mL; IQR, 3.50-15.90) or T (n=28, 0.61 ng/mL; IQR, 0.25-1.30); 69.8% had abnormal ECGs and arrhythmias (7 with nonsustained ventricular tachycardia); and 18.7% had left ventricular ejection fraction <55% on echocardiogram. Of 97 patients who underwent cardiac MRI at a median 5 days (range, 0-88; IQR, 3-17) from symptom onset, 75 (77.3%) had abnormal findings: 74 (76.3%) had late gadolinium enhancement, 54 (55.7%) had myocardial edema, and 49 (50.5%) met Lake Louise criteria. Among 26 patients with left ventricular ejection fraction <55% on echocardiogram, all with follow-up had normalized function (n=25). CONCLUSIONS: Most cases of suspected COVID-19 vaccine myocarditis occurring in persons <21 years have a mild clinical course with rapid resolution of symptoms. Abnormal findings on cardiac MRI were frequent. Future studies should evaluate risk factors, mechanisms, and long-term outcomes.

Clinical and hemodynamic characteristics of the pediatric failing Fontan.

AIM: To describe the clinical and hemodynamic characteristics of Fontan failure in children listed for heart transplant. METHODS: In a nested study of the Pediatric Heart Transplant Society, 16 centers contributed information on Fontan patients listed for heart transplant between 2005and 2013. Patients were classified into four mutually exclusive phenotypes: Fontan with abnormal lymphatics (FAL), Fontan with reduced systolic function (FRF), Fontan with preserved systolic function (FPF), and Fontan with "normal" hearts (FNH). Primary outcome was waitlist and post-transplant mortality. RESULTS: 177 children listed for transplant were followed over a median 13 (IQR 4-31) months, 84 (47%) were FAL, 57 (32%) FRF, 22 (12%) FNH, and 14 (8%) FPF. Hemodynamic characteristics differed between the 4 groups: Fontan pressure (FP) was most elevated with FPF (median 22, IQR 18-23, mmHg) and lowest with FAL (16, 14-20, mmHg); cardiac index (CI) was lowest with FRF (2.8, 2.3-3.4, L/min/m2). In the entire cohort, 66% had FP >15 mmHg, 21% had FP >20 mmHg, and 10% had CI <2.2 L/min/m2. FRF had the highest risk of waitlist mortality (21%) and FNH had the highest risk of post-transplant mortality (36%). CONCLUSIONS: Elevated Fontan pressure is more common than low cardiac output in pediatric failing Fontan patients listed for transplant. Subtle hemodynamic differences exist between the various phenotypes of pediatric Fontan failure. Waitlist and post-transplant mortality risks differ by phenotype.

Review of the impact of donor characteristics on pediatric heart transplant outcomes.

Heart transplantation (HTx) is a treatment option for end-stage heart failure in children. HTx is limited by the availability and acceptability of donor hearts. Refusal of donor hearts has been reported to be common with reasons for refusal including preexisting donor characteristics. This review will focus on the impact of donor characteristics and comorbidities on outcomes following pediatric HTx. A literature review was performed to identify articles on donor characteristics and comorbidities and pediatric HTx outcomes. There are many donor characteristics to consider when accepting a donor heart. Weight-based matching is the most common form of matching in pediatric HTx with a donor-recipient weight ratio between 0.7 and 3 having limited impact on outcomes. From an age perspective, donors <50 years can be carefully considered, but the impact of ischemic time needs to be understood. To increase the donor pool, with minimal impact on outcomes, ABO-incompatible donors should be considered in patients that are eligible. Other factors to be considered when accepting an organ is donor comorbidities. Little is known about donor comorbidities in pediatric HTx, with most of the data available focusing on infections. Being aware of the potential infections in the donor, understanding the testing available and risks of transmission, and treatment options for the recipient is essential. There are a number of donor characteristics that potentially impact outcomes following pediatric HTx, but these need to be taken into consideration along with their interactions with recipient factors when interpreting the outcomes following HTx.

ISHLT consensus statement on donor organ acceptability and management in pediatric heart transplantation.

The number of potential pediatric heart transplant recipients continues to exceed the number of donors, and consequently the waitlist mortality remains significant. Despite this, around 40% of all donated organs are not used and are discarded. This document (62 authors from 53 institutions in 17 countries) evaluates factors responsible for discarding donor hearts and makes recommendations regarding donor heart acceptance. The aim of this statement is to ensure that no usable donor heart is discarded, waitlist mortality is reduced, and post-transplant survival is not adversely impacted.

Renal injury and recovery in pediatric patients after ventricular assist device implantation and cardiac transplant.

BACKGROUND: The use of ventricular assist devices (VADs) in children with heart failure may be of particular benefit to those with accompanying renal failure, as improved renal function is seen in some, but not all recipients. We hypothesized that persistent renal dysfunction at 7 days and/or 1 month after VAD implantation would predict chronic kidney disease (CKD) 1 year after heart transplantation (HT). METHODS: Linkage analysis of all VAD patients enrolled in both the PEDIMACS and PHTS registries between 2012 and 2016. Persistent acute kidney injury (P-AKI), defined as a serum creatinine ≥1.5× baseline, was assessed at post-implant day 7. Estimated glomerular filtration rate (eGFR) was determined at implant, 30 days thereafter, and 12 months post-HT. Pre-implant eGFR, eGFR normalization (to ≥90 mL/min/1.73 m2 ), and P-AKI were used to predict post-HT CKD (eGFR <90 mL/min/1.73 m2 ). RESULTS: The mean implant eGFR was 85.4 ± 46.5 mL/min/1.73 m2 . P-AKI was present in 19/188 (10%). Mean eGFR at 1 month post-VAD implant was 131.1 ± 62.1 mL/min/1.73 m2 , significantly increased above baseline (P < 0.001). At 1 year post-HT (n = 133), 60 (45%) had CKD. Lower pre-implant eGFR was associated with post-HT CKD (OR 0.99, CI: 0.97-0.99, P = 0.005); P-AKI was not (OR 0.96, CI: 0.3-3.0, P = 0.9). Failure to normalize renal function 30 days after implant was highly associated with CKD at 1 year post-transplant (OR 12.5, CI 2.8-55, P = 0.003). CONCLUSIONS: Renal function improves after VAD implantation. Lower pre-implant eGFR and failure to normalize renal function during the support period are risk factors for CKD development after HT.

Global Left Ventricular Relaxation: A Useful Echocardiographic Marker of Heart Transplant Rejection and Recovery in Children.

BACKGROUND: Tissue Doppler velocities are impaired after heart transplantation and further diminished in acute rejection. METHODS: Left ventricular relaxation index (LVRI) was calculated as the sum of E' of the left ventricular lateral, septal and posterior walls divided by left ventricular posterior wall (LVPW) thinning (LVRI = E' lateral + E' septal + E' posterior/[systolic LVPW - diastolic LVPW/systolic LVPW]). On the basis of a prior study, LVRI > 0.8 was considered normal after transplantation. Serial LVRI measurements (n = 941) were analyzed in a total of 35 patients who underwent transplantation. The sensitivity and specificity of LVRI < 0.8 for detecting rejection were calculated. LVRI was compared at baseline, at diagnosis of rejection, and at recovery after rejection treatment for each patient. The potential role of ischemic graft time, pretransplantation waiting period, and pretransplantation diagnosis on LVRI recovery was also assessed. RESULTS: LVRI was low early after transplantation (mean, 0.69) normalizing (mean, 0.91) at a median of 39.6 days (range, 5-115 days) after transplantation. Fifteen episodes of rejection were seen in 11 patients. LVRI was lower at diagnosis of rejection compared with baseline (P = .0013). LVRI < 0.8 had 93.3% sensitivity (95% CI, 68%-99.8%) and 89.5% specificity (95% CI, 67%-99%) for detecting all rejection. LVRI recovered at a mean of 28.3 days after onset of treatment. No correlation was found to ischemic graft time, to pretransplantation waiting period, or to pretransplantation diagnosis. CONCLUSION: After the early posttransplantation period, serial measurements of LVRI appear to be a useful echocardiographic marker of heart transplantation rejection in children and of the effectiveness of rejection treatment. As such, this method may be of value in the ongoing clinical management of these difficult patients.

Novel Loss of Function in the AGK Gene: Rare Cause of End-Stage Heart Failure.

The authors present a case of mitochondrial cardiomyopathy due to a novel mutation of AGK gene that led to progressive heart failure. The cardiac magnetic resonance image findings of diffusely elevated relaxation time and increase in extracellular volume in the myocardium without early or late gadolinium enhancement may suggest mitochondrial cardiomyopathy. The authors emphasized the multidisciplinary team approach in the care of patients with mitochondrial cardiomyopathies. (Level of Difficulty: Advanced.).

Sacubitril/Valsartan: potential treatment for paediatric heart failure.

The Prospective comparison of angiotensin receptor antagonist Valsartan and neprilysin inhibitor Sacubitril with angiotensin-converting enzyme inhibitor (enalapril) to determine impact on Global Mortality and Morbidity in Heart Failure trial has demonstrated that Sacubitril/Valsartan is superior to Enalapril in reducing the risks of both sudden cardiac death and death from worsening heart failure. This novel combination, Sacubitril/Valsartan, is also shown to reduce the risk of hospitalisation and progression of heart failure in adults. However, the benefit of Sacubitril/Valsartan in paediatric heart failure patients is unknown. In this review, we discuss the similarities and differences in pathophysiology of heart failure in children versus adults, and the potential role of Sacubitril/Valsartan in paediatric heart failure patients.

Outcomes of fetal listed patients awaiting heart transplantation.

HTx in neonates is mainstay therapy for those with severe cardiomyopathies and congenital heart disease. Fetal listing for HTx has been proposed as a way to increase the potential window for a donor with outcomes predicted to be similar to the neonatal population. Data from the PHTS, a prospective multicenter study, were used to examine the outcomes of fetuses listed between 1993 and 2009. Four thousand three hundred and sixty-five children were listed for HTx during this period. Fetuses comprised 1% and neonates 19.8% of listed patients. In those patients listed as fetus and transplanted, the median wait time from listing to HTx was 55 days (range 4-255), with a median of 25 days (range 0-233) after birth. By six months post-listing, a higher proportion of fetal listed patients had undergone HTx with a lower waitlist mortality when compared with neonate. There was no significant difference in survival following HTx between the two group (p = 0.4). While the results of this study may be less applicable to current practice due to changes in referrals for fetal listing, they do indicate that fetal listing can be a reasonable option. These results are of particular interest at the present time given the ongoing public discourse on the proposed elimination of fetal listing within UNOS.

Ventricular assist device-associated anti-human leukocyte antigen antibody sensitization in pediatric patients bridged to heart transplantation.

BACKGROUND: Ventricular assist devices (VAD) are associated with the formation of antibodies to anti-human leukocyte antigens (HLA) or sensitization. The incidence and effects of VAD-associated anti-HLA sensitization have not been well studied in the pediatric population. METHODS: A retrospective review of all patients undergoing VAD implant at our institution from 1998 to 2008 was performed. Panel reactive antibody (PRA) results before VAD implant, after VAD implant, and after orthotopic heart transplantation (OHT) were recorded. Patients who became sensitized (PRA for class I and/or II immunoglobulin G antibodies >or= 10%) on VAD support were compared with non-sensitized patients with regard to demographics, diagnosis, device type, and blood product exposure on VAD support. Outcomes after OHT were also compared between groups. RESULTS: VAD support was initiated in 20 patients (median age, 14.4 years), with 75% survival to OHT or recovery. PRA data before and after VAD implant were available for 17 patients. VAD-associated sensitization developed in 35% of recipients. There were no differences between those sensitized in association with VAD support and non-sensitized patients with regard to age, gender, diagnosis, device type, extracorporeal membrane oxygenation use, or blood product exposure on VAD support. Black race predicted sensitization on VAD (p = 0.02). There were no differences in survival or rejection between groups. CONCLUSIONS: VAD therapy was associated with the development of anti-HLA sensitization in 35% of recipients. Black race predicted sensitization, but there were no differences in overall survival or outcomes after OHT.

The effect of age, diagnosis, and previous surgery in children and adults undergoing heart transplantation for congenital heart disease.

OBJECTIVES: We sought to evaluate the outcomes and identify risk factors for mortality after heart transplantation (HT) for congenital heart disease (CHD) in infants, children, and adults. BACKGROUND: CHD is considered a risk factor for mortality after HT, yet this unique group of patients represents a spectrum of complexity. METHODS: There were 488 patients transplanted for CHD from the combined Pediatric Heart Transplant Study (1993 to 2002, n = 367) and the Cardiac Transplant Registry Database (1990 to 2002, n = 121) who were analyzed. RESULTS: The median age at HT was 12.4 years. Primary diagnosis included single ventricle (36%), d-transposition of the great arteries (12%), right ventricular outflow tract lesions (10%), l-transposition of the great arteries (8%), ventricular/atrial septal defects (8%), left ventricular outflow obstruction (8%), and other (18%). Ninety-three percent of patients had at least 1 operation before HT. Survival at 3 months post-HT was significantly worse in CHD patients versus children with cardiomyopathy, but not adults with cardiomyopathy (86%, 94%, and 91%, respectively). There was no difference in conditional 3-month survival among the 3 groups. Five-year survival was 80%. Risk factors for early mortality were older recipient age, older donors with longer ischemic times, and pre-HT Fontan operations. Predicted survival in Fontan patients was lower (77% and 70% at 1 and 5 years) versus non-Fontan patients (88% and 81% at 1 and 5 years). Risk factors for constant phase mortality included younger recipient age, higher transpulmonary gradient, cytomegalovirus mismatch at HT, and earlier classical Glenn operation. CONCLUSIONS: Patients undergoing transplantation for CHD have a good late survival if they survive the early post-operative period. Risk factors for reduced survival are older age at transplant and a previous Fontan operation.

Prevalence and risk factors for tricuspid valve regurgitation after pediatric heart transplantation.

BACKGROUND: Risk factors for tricuspid regurgitation (TR) after adult orthotopic heart transplantation (OHT) have been reported, although there are no pediatric data. METHODS: This study was a single-center retrospective analysis of patients

Too fat or too thin? Body habitus assessment in children listed for heart transplant and impact on outcome.

BACKGROUND: Body habitus assessment (BHA), be it wasted or obese, is a useful marker of nutritional status and overall medical condition. Wasting and obesity pre-heart transplant adversely affects outcomes in adults. The utility of BHA as a prognostic factor in children post-transplant is unknown. METHODS: Weight and height at listing and standard growth charts were used to determine the ideal body weight (%IBW) and percentiles for body mass index for age (BMI%) and weight-for-length (W:L%). Wasting was defined as <90%IBW and/or 120%IBW and/or >or=95th percentile BMI% or W:L%. Outcomes of cohorts based on these criteria were compared. RESULTS: From June 1990 to December 2006, 180 children, aged 5.81 +/- 6 years, were listed for transplant. Wasting occurred in 66 (37%) and obesity in 22 (12%) children, without differences between diagnoses of cardiomyopathy or congenital heart disease. %IBW was a prognostic factor for survival post-transplant on multivariate analysis: obese patients had a hazard ratio (HR) of 3.82 (95% confidence interval [CI] 1.81 to 8.06) compared with normal BHA (p < 0.001). Wasting had a survival advantage compared with normal BHA (HR 0.51, 95% CI 0.27 to 0.94, p = 0.032). There were no significant differences between cohorts in incidence of infections, first-year rejections or graft vasculopathy. CONCLUSIONS: Abnormal BHA at listing was a prognostic factor for survival post-transplant. Obese children had increased mortality, but wasting did not adversely affect post-transplant survival in our population. Body habitus assessment may risk-stratify children at listing, potentially providing a complex target for intervention.

Indications for heart transplantation in pediatric heart disease: a scientific statement from the American Heart Association Council on Cardiovascular Disease in the Young; the Councils on Clinical Cardiology, Cardiovascular Nursing, and Cardiovascular Surgery and Anesthesia; and the Quality of Care and Outcomes Research Interdisciplinary Working Group.

BACKGROUND: Since the initial utilization of heart transplantation as therapy for end-stage pediatric heart disease, improvements have occurred in outcomes with heart transplantation and surgical therapies for congenital heart disease along with the application of medical therapies to pediatric heart failure that have improved outcomes in adults. These events justify a reevaluation of the indications for heart transplantation in congenital heart disease and other causes of pediatric heart failure. METHODS AND RESULTS: A working group was commissioned to review accumulated experience with pediatric heart transplantation and its use in patients with unrepaired and/or previously repaired or palliated congenital heart disease (children and adults), in patients with pediatric cardiomyopathies, and in pediatric patients with prior heart transplantation. Evidence-based guidelines for the indications for heart transplantation or retransplantation for these conditions were developed. CONCLUSIONS: This evaluation has led to the development and refinement of indications for heart transplantation for patients with congenital heart disease and pediatric cardiomyopathies in addition to indications for pediatric heart retransplantation.