Background: While clinical overlap between Kawasaki disease (KD) and multisystem inflammatory syndrome in children (MIS-C) has been evident, information regarding those presenting with shock has been limited. We sought to determine associations with shock within and between diagnosis groups. Methods: The International KD Registry enrolled contemporaneous patients with either KD or MIS-C from 39 sites in 7 countries from January 1, 2020, to January 1, 2023. Demographics, clinical features and presentation, management, laboratory values, and outcomes were compared between the diagnosis and shock groups. Results: Shock at presentation was noted for 19 of 672 KD patients (2.8%) and 653 of 1472 MIS-C patients (44%; P < 0.001). Within both groups, patients with shock were significantly more likely to be admitted to the intensive care unit, to receive inotropes, and to have greater laboratory abnormalities indicative of hyperinflammation and organ dysfunction, including abnormal cardiac biomarkers. Patients with KD and shock had a greater maximum coronary artery z score (median +2.62) vs KD patients without shock (+1.36; P < 0.001) and MIS-C patients with shock (+1.45 [vs +1.32 for MIS-C patients without shock]; P < 0.001). They were also more likely to have large coronary artery aneurysms. In contrast, MIS-C patients with shock had lower left ventricular ejection fraction (mean 51.6%) vs MIS-C patients without shock (56.6%; P < 0.001) and KD patients with shock (56.7% [vs 62.8% for KD patients without shock]; P = 0.04). Conclusions: Although patients with KD presenting with shock are clinically similar to patients with MIS-C, especially those with shock, they have more severe coronary artery involvement, whereas MIS-C patients with shock have lower left ventricular ejection fraction.

Introduction: Thrombocytosis, sometimes extreme, after acute Kawasaki disease (KD) is common and felt to be pathognomonic of this diagnosis, although has also been reported after multisystem inflammatory syndrome in children (MIS-C), a clinically similar condition. We sought to determine differences in factors associated with thrombocytosis for each condition. Methods: From 01/2020 to 10/2023 across 41 sites in 8 countries from the International KD Registry, 1674 MIS-C and 1290 contemporaneous KD patients with adequate laboratory data were included in the analysis. Age-related cutpoints (derived from the CALIPER Study of normal children/adolescents; AJCP 2020; 154:342) were applied to peak platelet counts to define thrombocytosis (age <1 year, >647 x10 9 /L; age 1 to <12 years, >434; age 12 to <21 years, >371). Associations of demographic, clinical, laboratory and outcome factors with thrombocytosis were determined for each diagnosis group. Results: Thrombocytosis was more prevalent after KD (57%) than MIS-C (49%; p<0.001), with higher median peak platelet count (492 vs. 413 x10 9 /L; p<0.001). The difference remained significant after adjustment for age. Thrombocytosis was significantly associated with greater total days of fever for both KD (median 8 vs. 7 days; p=0.005) and MIS-C (median 7 vs. 6 days; p<0.001), but not with any symptoms/signs or presentation with shock in either group. For both groups, thrombocytosis was associated with significantly greater laboratory abnormalities, specifically higher markers of inflammation, lower hemoglobin and lower albumin. Cardiac biomarkers (peak NTproBNP, peak troponin I) were significantly lower for KD patients with thrombocytosis. While there was no significant association of thrombocytosis with ventricular function in either group (FIGURE A), coronary artery involvement was worse for both groups if thrombocytosis occurred (FIGURE B), with an overall lower prevalence and severity for patients with MIS-C, despite more severe clinical presentation and greater laboratory abnormalities. Conclusions: Thrombocytosis has a high prevalence for both KD and MIS-C, and is associated with both more severe inflammation and greater coronary artery involvement for both diagnoses.

BACKGROUND:Patients with multisystem inflammatory syndrome in children (MIS-C) and Kawasaki disease (KD) have overlapping clinical features. We compared demographics, clinical presentation, management, and outcomes of patients according to evidence of previous SARS-CoV-2 infection. METHODS:The International Kawasaki Disease Registry (IKDR) enrolled KD and MIS-C patients from sites in North, Central, and South America, Europe, Asia, and the Middle East. Evidence of previous infection was defined as: Positive (household contact or positive polymerase chain reaction [PCR]/serology), Possible (suggestive clinical features of MIS-C and/or KD with negative PCR or serology but not both), Negative (negative PCR and serology and no known exposure), and Unknown (incomplete testing and no known exposure). RESULTS:Of 2345 enrolled patients SARS-CoV-2 status was Positive for 1541 (66%) patients, Possible for 89 (4%), Negative for 404 (17%) and Unknown for 311 (13%). Clinical outcomes varied significantly among the groups, with more patients in the Positive/Possible groups presenting with shock, having admission to intensive care, receiving inotropic support, and having longer hospital stays. Regarding cardiac abnormalities, patients in the Positive/Possible groups had a higher prevalence of left ventricular dysfunction, and patients in the Negative and Unknown groups had more severe coronary artery abnormalities. CONCLUSIONS:There appears to be a spectrum of clinical features from MIS-C to KD with a great deal of heterogeneity, and one primary differentiating factor is evidence for previous acute SARS-CoV-2 infection/exposure. SARS-CoV-2 Positive/Possible patients had more severe presentations and required more intensive management, with a greater likelihood of ventricular dysfunction but less severe coronary artery adverse outcomes, in keeping with MIS-C.

Cardiovascular magnetic resonance (CMR) has become the reference standard for quantitative and qualitative assessment of ventricular function, blood flow, and myocardial tissue characterization. There is a preponderance of large CMR studies and registries in adults; However, similarly powered studies are lacking for the pediatric and congenital heart disease (PCHD) population. To date, most CMR studies in children are limited to small single or multicenter studies, thereby limiting the conclusions that can be drawn. Within the PCHD CMR community, a collaborative effort has been successfully employed to recognize knowledge gaps with the aim to embolden the development and initiation of high-quality, large-scale multicenter research. In this publication, we highlight the underlying challenges and provide a practical guide toward the development of larger, multicenter initiatives focusing on PCHD populations, which can serve as a model for future multicenter efforts.

Background We aimed to study the clinical characteristics, myocardial injury, and longitudinal outcomes of COVID-19 vaccine-associated myocarditis (C-VAM). Methods In this longitudinal retrospective observational cohort multicenter study across 38 hospitals in the United States, 333 patients with C-VAM were compared with 100 patients with multisystem inflammatory syndrome in children (MIS-C). We included patients <= 30 years of age with a clinical diagnosis of acute myocarditis after COVID-19 vaccination based on clinical presentation, abnormal biomarkers and/or cardiovascular imaging findings. Demographics, past medical history, hospital course, biochemistry results, cardiovascular imaging, and follow-up information from April 2021 to November 2022 were collected. The primary outcome was presence of myocardial injury as evidenced by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging. Findings Patients with C-VAM were predominantly white (67%) adolescent males (91%, 15.7 +/- 2.8 years). Their initial clinical course was more likely to be mild (80% vs. 23%, p < 0.001) and cardiac dysfunction was less common (17% vs. 68%, p < 0.0001), compared to MIS-C. In contrast, LGE on CMR was more prevalent in C-VAM (82% vs. 16%, p < 0.001). The probability of LGE was higher in males (OR 3.28 [95% CI: 0.99, 10.6, p = 0.052]), in older patients (>15 years, OR 2.74 [95% CI: 1.28, 5.83, p = 0.009]) and when C-VAM occurred after the first or second dose as compared to the third dose of mRNA vaccine. Mid-term clinical outcomes of C-VAM at a median follow-up of 178 days (IQR 114-285 days) were reassuring. No cardiac deaths or heart transplantations were reported until the time of submission of this report. LGE persisted in 60% of the patients at follow up. Interpretation Myocardial injury at initial presentation and its persistence at follow up, despite a mild initial course and favorable mid-term clinical outcome, warrants continued clinical surveillance and long-term studies in affected patients with C-VAM.

Evidence from medicine and other fields has shown that gender diversity results in better decision making and outcomes. The incoming workforce of congenital heart specialists (especially in pediatric cardiology) appears to be more gender balanced, but past studies have shown many inequities. Gender‐associated differences in leadership positions, opportunities presented for academic advancement, and recognition for academic contributions to the field persist. In addition, compensation packages remain disparate if evaluated based on gender with equivalent experience and expertise. This review explores these inequities and has suggested individual and institutional changes that could be made to recruit and retain women, monitor the climate of the institution, and identify and eliminate bias in areas like salary and promotions.

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Background/Aim: We previously reported that late gadolinium enhancement (LGE) on cardiac MRI (CMR) was as high as 82% in pediatric patients with COVID-19 vaccine-associated myocarditis (C-VAM) despite mild clinical symptoms and normal left ventricular function. As LGE can be a harbinger for future adverse events including arrhythmias, heart failure or sudden cardiac death, we sought to identify predictors for LGE in C-VAM, specifically assessing troponin as a screening marker for C-VAM patients at risk for myocardial scarring who could then be referred for a confirmatory CMR with LGE. Methods: In this longitudinal multicenter retrospective observational study across 38 U.S. member institutions of the M yocarditis A fter C OVID V accination (MACiV) study network, 333 patients with C-VAM based on CDC criteria were included from April 2021 to November 2022. Data collected included demographics, laboratory values, clinical and cardiac imaging characteristics and outcomes. Using logistic regression, troponin levels at presentation were assessed as a log transformed continuous variable and categorized into tertiles. Results: The C-VAM patients were predominantly white (67%) adolescent males (91%, 15.7± 2.8 years). There were 216/333 (65%) patients who had both a reported troponin value and had a CMR. On univariate analysis, elevated troponin increased the probability of having LGE (OR=1.29, 95% CI: 1.06, 1.58, p=0.012). Even after controlling for age, race, sex, number of vaccine doses and left ventricular ejection fraction (OR=1.32, 95% CI: 1.06, 1.65, p=0.013). Patients >15 years compared to those ≤15 years of age were 2.94 (95% CI: 1.28, 6.75, p=0.011) times more likely to have LGE at presentation. Patients with troponin levels in the highest tertile compared to lowest tertile were 2.66 times (95% CI: 1.04, 6.83, p=0.042) more likely to have LGE along with a greater involvement > 4 AHA myocardial segments with LGE (p=0.004) Conclusions: Higher troponin values are associated with presence of late gadolinium enhancement on cardiac MRI in patients with COVID-19 vaccine-associated myocarditis. Troponin levels at presentation may facilitate risk stratification and function as a screening tool to identify those C-VAM patients with the greatest likelihood of myocardial scarring, who may benefit from undergoing CMR for tissue characterization.

The incidence of Kawasaki Disease has a peak in the winter months with a trough in late summer/early fall. Environmental/exposure factors have been associated with a time-varying incidence. These factors were altered during the COVID-19 pandemic. The study was performed through the International Kawasaki Disease Registry. Data from patients diagnosed with acute Kawasaki Disease and Multiple Inflammatory Syndrome-Children were obtained. Guideline case definitions were used to confirm site diagnosis. Enrollment was from 1/2020 to 7/2023. The number of patients was plotted over time. The patients/month were tabulated for the anticipated peak Kawasaki Disease season (December-April) and non-peak season (May-November). Data were available for 1975 patients from 11 large North American sites with verified complete data and uninterrupted site reporting. The diagnosis criteria were met for 531 Kawasaki Disease and 907 Multiple Inflammatory Syndrome-Children patients. For Multiple Inflammatory Syndrome-Children there were peaks in January of 2021 and 2022. For Kawasaki Disease, 2020 began (January-March) with a seasonal peak (peak 26, mean 21) with a subsequent fall in the number of cases/month (mean 11). After the onset of the pandemic (April 2020), there was no clear seasonal Kawasaki Disease variation (December-April mean 12 cases/month and May-November mean 10 cases/month). During the pandemic, the prevalence of Kawasaki Disease decreased and the usual seasonality was abolished. This may represent the impact of pandemic public health measures in altering environmental/exposure aetiologic factors contributing to the incidence of Kawasaki Disease.

SARS-CoV-2 Variants and MIS-C Multisystem inflammatory syndrome in children has been less severe with each subsequent SARS-CoV-2 variant. However, critical illness in hospitalized patients with MIS-C remains prevalent.

Multisystem inflammatory syndrome in children (MIS-C) has emerged as a rare delayed hyperinflammatory response to SARS-CoV-2 infection and causes severe morbidity in the pediatric age group. Although MIS-C shares many clinical similarities to Kawasaki disease (KD), important differences in epidemiologic, clinical, immunologic, and potentially genetic factors exist and suggest potential differences in pathophysiology and points to be explored and explained. Epidemiologic features include male predominance, peak age of 6 to12 years, and specific racial or ethnicity predilections. MIS-C is characterized by fever, prominent gastrointestinal symptoms, mucocutaneous manifestations, respiratory symptoms, and neurologic complaints, and patients often present with shock. Cardiac complications are frequent and include ventricular dysfunction, valvular regurgitation, pericardial effusion, coronary artery dilation and aneurysms, conduction abnormalities, and arrhythmias. Emerging evidence regarding potential immunologic mechanisms suggest that an exaggerated T-cell response to a superantigen on the SARS-CoV-2 spike glycoprotein-as well as the formation of autoantibodies against cardiovascular, gastrointestinal, and endothelial antigens-are major contributors to the inflammatory milieu of MIS-C. Further studies are needed to determine both shared and distinct immunologic pathway(s) that underlie the pathogenesis of MIS-C vs both acute SARS-CoV-2 infection and KD. There is evidence to suggest that the rare risk of more benign mRNA vaccine-associated myopericarditis is outweighed by a reduced risk of more severe MIS-C. In the current review, we synthesize the published literature to describe associated factors and potential mechanisms regarding an increased risk of MIS-C and cardiac complications, provide insights into the underlying immunologic pathophysiology, and define similarities and differences with KD.

Kawasaki disease (KD) and Multisystem Inflammatory Syndrome in Children (MIS-C) associated with COVID-19 show clinical overlap and both lack definitive diagnostic testing, making differentiation challenging. We sought to determine how cardiac biomarkers might differentiate KD from MIS-C. The International Kawasaki Disease Registry enrolled contemporaneous KD and MIS-C pediatric patients from 42 sites from January 2020 through June 2022. The study population included 118 KD patients who met American Heart Association KD criteria and compared them to 946 MIS-C patients who met 2020 Centers for Disease Control and Prevention case definition. All included patients had at least one measurement of amino-terminal prohormone brain natriuretic peptide (NTproBNP) or cardiac troponin I (TnI), and echocardiography. Regression analyses were used to determine associations between cardiac biomarker levels, diagnosis, and cardiac involvement. Higher NTproBNP (≥ 1500 ng/L) and TnI (≥ 20 ng/L) at presentation were associated with MIS-C versus KD with specificity of 77 and 89

Coronavirus disease 2019 (COVID-19) is an ongoing global pandemic that has affected nearly 600 million people to date across the world. While COVID-19 is primarily a respiratory illness, cardiac injury is also known to occur. Cardiovascular magnetic resonance (CMR) imaging is uniquely capable of characterizing myocardial tissue properties in-vivo, enabling insights into the pattern and degree of cardiac injury. The reported prevalence of myocardial involvement identified by CMR in the context of COVID-19 infection among previously hospitalized patients ranges from 26 to 60%. Variations in the reported prevalence of myocardial involvement may result from differing patient populations (e.g. differences in severity of illness) and the varying intervals between acute infection and CMR evaluation. Standardized methodologies in image acquisition, analysis, interpretation, and reporting of CMR abnormalities across would likely improve concordance between studies. This consensus document by the Society for Cardiovascular Magnetic Resonance (SCMR) provides recommendations on CMR imaging and reporting metrics towards the goal of improved standardization and uniform data acquisition and analytic approaches when performing CMR in patients with COVID-19 infection.

Background: Comparisons between Kawasaki disease (KD) and Multisystem Inflammatory Syndrome in Children (MIS-C) have been critiqued, with suggestions that KD Shock Syndrome (KDSS) patients may be a more valid comparison. We compared contemporaneous KD and MIS-C patients, both with and without shock at presentation. Methods: The International KD Registry enrolled 2144 patients with either KD (site diagnosis confirmed by AHA criteria) or MIS-C (site diagnosis confirmed by CDC criteria) from 40 sites in 7 countries from 01/2020 to 01/2023. Data collected included demographics, clinical features and presentation, management, laboratory values, and outcomes, and diagnosis/shock groups were compared. Results: Shock at presentation was noted for 19 of 672 (2.8%) KD patients and 653 of 1472 (38%; p<0.001) MIS-C patients. For both groups, shock patients were significantly more likely to be admitted to ICU, receive inotropes, and have cardiac arrest or arrhythmia. Groups did not differ by sex, but MIS-C patients and shock patients were older. While MIS-C shock patients were less likely to be White, KD shock and MIS-C shock patients more likely to be Black. For inflammatory markers, while shock patients in both groups had higher CRP and ferritin compared to non-shock patients, ESR was similar in both groups to non-shock patients, and higher WBC was only noted for MIS-C shock versus MIS-C non-shock patients. KD shock patients had similar values to MIS-C shock patients, with the exception of lower ferritin. Shock patients had higher NTproBNP (both diagnoses) and Troponin I (MIS-C only). Shock patients had lower LV ejection fraction, more so for MIS-C patients ( Figure A ). KD shock patients had higher max coronary artery Z scores versus MIS-C patients ( Figure B ). Conclusions: KD shock patients are more similar to MIS-C patients, particularly those with shock. Shock was associated with worse coronary artery involvement for KD patients, and worse LV dysfunction for both MIS-C and KD.

Introduction: Despite several years of gender parity entering the field of pediatric cardiology, representation of women leaders trails that of their male colleagues. We sought to better understand the variation in women in leadership roles in our field. Methods: Pediatric cardiology programs that participate in the Society of Thoracic Surgeons database with > 5 cardiologists were included. Data regarding gender of physicians in 16 leadership positions was collected. We analyzed the association of women in leadership roles with center size (based on surgical volume), geographic region, presence of fellowship, and gender of division chief and department chair. Results: Of the 99 centers in this study, a median of 13 (IQR 10-15) roles/center were identified, with 4 (IQR 3-6), 33.3% held by women. The lowest representation was in pediatric cardiology chiefs: 13% (table). Programs led by women chiefs had more women in leadership roles (48% vs 35%, p=0.01). In the US, the Northeast has more %women leaders than the West, South, or Midwest: 43% vs 33, 32, 34% respectively, p=0.035. Fellowship program or a woman department chair were not associated with %women leaders. The %women varied among the different sections: lowest in invasive subspecialties, interventional (17%) and EP (20%), and highest in fetal directors (66%). Fewer cardiac MRI leads in medium or high-volume centers are women compared to low volume centers (16 vs 39%, p=0.02), otherwise no volume-based differences were seen. Conclusions: Women hold fewer leadership positions across most subsections of pediatric cardiology programs, with more equitable distribution at centers led by women division chiefs. Future studies will define barriers to leadership equity.

To determine clinical differences for children with complete Kawasaki disease (KD) with and without evidence of preceding SARS-CoV-2 infection. From January 2020, contemporaneous patients with complete KD criteria were classified as either SARS-CoV-2 positive (KDCOVID+; confirmed household exposure, positive PCR and/or serology) or SARS-CoV-2 negative (KDCOVID-; negative testing and no exposure) and compared. Of 744 patients in the International Kawasaki Disease Registry, 52 were KDCOVID- and 61 were KDCOVID+. KDCOVID+ patients were older (median 5.5 vs. 3.7 years; p < 0.001), and all additionally met diagnostic criteria for multisystem inflammatory syndrome in children (MIS-C). They were more likely to have abdominal pain (60% vs. 35%; p = 0.008) and headache (38% vs. 10%; p < 0.001) and had significantly higher CRP, troponin, and BUN/creatinine, and lower hemoglobin, platelets, and lymphocytes. KDCOVID+ patients were more likely to have shock (41% vs. 6%; p < 0.001), ICU admission (62% vs. 10%; p < 0.001), lower left ventricular ejection fraction (mean lowest LVEF 53% vs. 60%; p < 0.001), and to have received inotropic support (60% vs. 10%; p < 0.001). Both groups received IVIG (2 doses in 22% vs. 18%; p = 0.63), but KDCOVID+ were more likely to have received steroids (85% vs. 35%; p < 0.001) and anakinra (60% vs. 10%; p = 0.002). KDCOVID- patients were more likely to have medium/large coronary artery aneurysms (CAA, 12% vs. 0%; p = 0.01). KDCOVID+ patients differ from KDCOVID-, have more severe disease, and greater evidence of myocardial involvement and cardiovascular dysfunction rather than CAA. These patients may be a distinct KD phenotype in the presence of a prevalent specific trigger.

BackgroundThe impact of adjunctive anti-inflammatory treatment on outcomes for patients with Kawasaki disease (KD) and coronary artery aneurysms (CAAs) is unknown.MethodsUsing data from the International KD Registry in patients with ≥ medium CAA we evaluate associations of treatment with outcomes and major adverse cardiac events (MACE).ResultsMedium or large CAA was present in 527 (32%) patients. All were treated with intravenous immunoglobulin (IVIG), 70% were male, and the median age was 1.3 years (interquartile range: 0.4-4.0 years). The most common acute therapies included single IVIG alone in 243 (46%), multiple IVIG in 100 (19%), multiple IVIG + corticosteroids in 75 (14%), and multiple IVIG + infliximab + corticosteroids in 44 (8%) patients. Patients who received therapy beyond single IVIG had a larger CA z-score at baseline (P < 0.001) and a higher rate of bilateral CAA (P < 0.001). Compared with IVIG alone, early adjunctive treatments (within 3 days of initial IVIG) were not associated with time to CAA regression or MACE, whereas later adjunctive therapy was associated with MACE and longer time to CAA regression. Patients receiving IVIG plus steroids vs IVIG alone had a trend towards shorter time to CAA regression and lower risk of MACE (P = 0.07). A larger CAA z-score at baseline was the strongest predictor of an increase in the CAA z-score over follow-up, lower likelihood of CAA regression, and higher risk of MACE.ConclusionsPersistence of CAA and MACE are more strongly associated with baseline severity CAA than with acute adjuvant anti-inflammatory therapy. Patients who received late adjunctive therapy are at higher risk for worse outcomes.

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.

BACKGROUND:After diagnosis of a cardiac mass, clinicians must weigh the benefits and risks of ascertaining a tissue diagnosis. Limited data are available on the accuracy of previously developed noninvasive pediatric cardiac magnetic resonance (CMR)-based diagnostic criteria. OBJECTIVES:The goals of this study were to: 1) evaluate the CMR characteristics of pediatric cardiac masses from a large international cohort; 2) test the accuracy of previously developed CMR-based diagnostic criteria; and 3) expand diagnostic criteria using new information. METHODS:CMR studies (children 0-18 years of age) with confirmatory histological and/or genetic diagnosis were analyzed by 2 reviewers, without knowledge of prior diagnosis. Diagnostic accuracy was graded as: 1) single correct diagnosis; 2) correct diagnosis among a differential; or 3) incorrect diagnosis. RESULTS:Of 213 cases, 174 (82%) had diagnoses that were represented in the previously published diagnostic criteria. In 70% of 174 cases, both reviewers achieved a single correct diagnosis (94% of fibromas, 71% of rhabdomyomas, and 50% of myxomas). When ≤2 differential diagnoses were included, both reviewers reached a correct diagnosis in 86% of cases. Of 29 malignant tumors, both reviewers indicated malignancy as a single diagnosis in 52% of cases. Including ≤2 differential diagnoses, both reviewers indicated malignancy in 83% of cases. Of 6 CMR sequences examined, acquisition of first-pass perfusion and late gadolinium enhancement were independently associated with a higher likelihood of a single correct diagnosis. CONCLUSIONS:CMR of cardiac masses in children leads to an accurate diagnosis in most cases. A comprehensive imaging protocol is associated with higher diagnostic accuracy.

Introduction: Kawasaki disease (KD) and Multisystem Inflammatory Syndrome in Children (MIS-C) associated with COVID-19 share clinical features and are both associated with coronary artery (CA) involvement. Methods: From January 2020 through January 2022, n=2566 contemporaneous KD, MIS-C and acute COVID-19 pediatric patients from 39 sites in 8 countries were enrolled into the International KD Registry. The study population was confined to 875 MIS-C patients meeting CDC criteria with confirmed or probable COVID-19 infection, and 492 KD patients meeting AHA guideline criteria without COVID-19 infection who had sufficient echo data. CA involvement was defined by maximum Z score in any branch at any timepoint (maxCAZ). Associated factors for each diagnosis were determined with multivariable logistic regression for maxCAZ>2. Results: Median maxCAZ was higher for KD (+1.43) vs MIS-C patients (+1.33; p=0.004). The groups did not differ regarding the incidence of maxCAZ>2 (KD 26% vs MIS-C 24%; p=0.42), although MIS-C patients had less severe Z score categories of involvement (FIGURE). In univariate analyses, higher peak troponin I (p<0.05) and NTproBNP (p=0.06) were associated with maxCAZ>2 for MIS-C but not KD patients. Lower LV ejection fraction was likewise associated with maxCAZ>2 for MIS-C (p=0.009) but not KD patients. For KD patients, independent factors associated with maxCAZ>2 were male sex, age <6 months, greater total days of fever, shock presentation, and higher peak platelet count and CRP (c-statistic 0.69). In contrast, for MIS-C patients the only independent factor associated with maxCAZ>2 was male sex (c-statistic 0.56). Conclusions: Compared to KD patients, MIS-C patients have a similar incidence but lesser severity of CA involvement with few associated factors, male sex being the only one in common. CA involvement was significantly associated with higher cardiac biomarkers and lower LV ejection fraction for MIS-C patients only.