Background: Understanding the clinical course and short-term outcomes of suspected myocarditis following 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 7/4/2021 with suspected myocarditis within 30 days of COVID-19 vaccination. Lake Louise criteria were used for cardiac magnetic resonance imaging (cMRI) findings. Myocarditis cases were classified as confirmed or probable based on 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 median age was 15.8 years (range 12.1-20.3, IQR 14.5-17.0). Suspected myocarditis occurred in 136 patients (97.8%) following mRNA vaccine, with 131 (94.2%) following the Pfizer-BioNTech vaccine; 128 (91.4%) occurred after the 2nd dose. Symptoms started 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 ICU, two were treated with inotropic/vasoactive support, and none required ECMO 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 electrocardiograms and/or arrythmias (7 with non-sustained ventricular tachycardia); and 18.7% had left ventricular ejection fraction (LVEF) <55% on echocardiogram. Of 97 patients who underwent cMRI at 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 LVEF <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 cMRI were frequent. Future studies should evaluate risk factors, mechanisms, and long-term outcomes.

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Purpose of review To provide an international perspective and current review of pediatric heart transplantation (PHTx). Recent findings Waitlist survival and long-term outcomes in PHTx continue to improve. Strategies to maximize donor pool utilization include ABO incompatible listing for infants and expanded donor-to-recipient weight ranges. However, there is a high degree of practice variation internationally, from listing strategies and donor acceptance practices to chronic immunosuppression regimens, long-term graft surveillance, and consideration for retransplantation. Summary Common indications for PHTx include end-stage congenital heart disease and cardiomyopathy. Current median graft survival among PHTx recipients ranges from 13 to 22 years. Common morbidities include infection, rejection, renal dysfunction, coronary allograft vasculopathy, and posttransplant lymphoproliferative disease. International registry data, collaborative initiatives to standardize management, and multicenter studies continue to improve knowledge and advancement of the field.

ImportanceData are limited regarding adverse reactions after COVID-19 vaccination in patients with a history of multisystem inflammatory syndrome in children (MIS-C). The lack of vaccine safety data in this unique population may cause hesitancy and concern for many families and health care professionals.ObjectiveTo describe adverse reactions following COVID-19 vaccination in patients with a history of MIS-C.Design, Setting, and ParticipantsIn this multicenter cross-sectional study including 22 North American centers participating in a National Heart, Lung, and Blood Institute, National Institutes of Health–sponsored study, Long-Term Outcomes After the Multisystem Inflammatory Syndrome in Children (MUSIC), patients with a prior diagnosis of MIS-C who were eligible for COVID-19 vaccination (age ≥5 years; ≥90 days after MIS-C diagnosis) were surveyed between December 13, 2021, and February 18, 2022, regarding COVID-19 vaccination status and adverse reactions.ExposuresCOVID-19 vaccination after MIS-C diagnosis.Main Outcomes and MeasuresThe main outcome was adverse reactions following COVID-19 vaccination. Comparisons were made using the Wilcoxon rank sum test for continuous variables and the χ2 or Fisher exact test for categorical variables.ResultsOf 385 vaccine-eligible patients who were surveyed, 185 (48.1%) received at least 1 vaccine dose; 136 of the vaccinated patients (73.5%) were male, and the median age was 12.2 years (IQR, 9.5-14.7 years). Among vaccinated patients, 1 (0.5%) identified as American Indian/Alaska Native, non-Hispanic; 9 (4.9%) as Asian, non-Hispanic; 45 (24.3%) as Black, non-Hispanic; 59 (31.9%) as Hispanic or Latino; 53 (28.6%) as White, non-Hispanic; 2 (1.1%) as multiracial, non-Hispanic; and 2 (1.1%) as other, non-Hispanic; 14 (7.6%) had unknown or undeclared race and ethnicity. The median time from MIS-C diagnosis to first vaccine dose was 9.0 months (IQR, 5.1-11.9 months); 31 patients (16.8%) received 1 dose, 142 (76.8%) received 2 doses, and 12 (6.5%) received 3 doses. Almost all patients received the BNT162b2 vaccine (347 of 351 vaccine doses [98.9%]). Minor adverse reactions were observed in 90 patients (48.6%) and were most often arm soreness (62 patients [33.5%]) and/or fatigue (32 [17.3%]). In 32 patients (17.3%), adverse reactions were treated with medications, most commonly acetaminophen (21 patients [11.4%]) or ibuprofen (11 [5.9%]). Four patients (2.2%) sought medical evaluation, but none required testing or hospitalization. There were no patients with any serious adverse events, including myocarditis or recurrence of MIS-C.Conclusions and RelevanceIn this cross-sectional study of patients with a history of MIS-C, no serious adverse events were reported after COVID-19 vaccination. These findings suggest that the safety profile of COVID-19 vaccination administered at least 90 days following MIS-C diagnosis appears to be similar to that in the general population.

Aortic dissection causes significant morbidity and mortality in adults and treatment guidelines are based on well-documented risk factors. Conversely, dissection after orthotopic heart transplantation is very rare, especially in the absence of infection, hypertension, or donor–recipient aortic size mismatch. Several forms of CHD are associated with aortic dilatation, but the incidence of aortic dissection and aneurysm in children is also low, which makes use of adult guidelines in children challenging. We present a 17-year-old Amish female with a homozygous gene mutation in the MYBPC3 gene known to cause lethal, infantile hypertrophic cardiomyopathy. She underwent orthotopic heart transplantation and then developed an asymptomatic aortic dissection despite no known risk factors.

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interquartile range).Results: Epitope and dnDSA data were available in 109 transplants (age 5.8 years [1][2][3][4][5][6][7][8][9][10][11][12], 66% male, 32% non-Hispanic White, follow-up 2.5 years [1.3 -4.7]). There was significant diversity in the number of epitope mismatches within each HLA locus (Fig 1A), and the number of mismatches were: A 20 (13-28), B 17 (12-22), C 10 (6-15), DR 16 (8-30), DQ 12 (8-16), and DP 8 (3-13). The number of epitope mismatches did not differ among any donor-recipient race combination (not shown). The development of dnDSA was not associated with a higher number of epitope mismatches at any HLA-loci (Fig 1B). However, patients with antibody mediated rejection (AMR) had more DQ mismatches (15 vs 11; p=0.04) than those without AMR, and there were more anti-DQB1 DSA than any other DSA in the cohort (Figure 1C). Conclusion:There is significant variability in the number of HLA epitope mismatches within each HLA locus. These data suggest that it may not be the total number of epitope mismatches but rather epitope mismatches at specific loci that vary in location and function that are of immunogenic importance. Further investigation of epitope-matching in PHTx may permit a more personalized immunosuppressive approach based on individualized alloimmune risk assessment in the future.

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