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Background Pediatric inflammatory multisystem syndrome temporally associated with SARS‐CoV‐2 (PIMS‐TS) is an inflammatory disease occurring in a small minority of children a few weeks after acute infection. Cardiac manifestations are common, but little is known about the potentially persistent heart changes after PIMS‐TS. Purpose To analyze the frequency and type of myocardial complications of PIMS‐TS with initial cardiac involvement assessed with cardiac magnetic resonance imaging (MRI), including parametric imaging, performed 3 months after hospitalization. Study Type Retrospective. Population Nineteen consecutive children (median age 10 years, interquartile range (IQR) 10–15 years, 74% male). Field Strength/Sequence Balanced steady state free precession (bSSFP, cine imaging), modified Look‐Locker (T1 mapping), T2‐prepared bSSFP (T2‐mapping), dark‐blood T2‐weighted turbo spin echo with fat suppression and phase sensitive inversion recovery (late gadolinium enhancement (LGE)) sequences at 1.5 T. Assessment Patients were scanned after a median of 99 days (IQR 89–104 days) from the diagnosis. MR data were reviewed by three independent observers, with 13, 2, and 5 years' experience in cardiac MRI. Pre‐ and post‐contrast T1, T2, extra‐cellular volume, and T2 signal intensity (T2 SI) ratio were calculated. Diagnosis of acute myocarditis was based on modified Lake Louise criteria. Cardiac MRI parameters were compared, where possible, to previously published pediatric normal values. Statistical Tests Interclass correlation coefficient and Bland–Altman repeatability analysis. A P ‐value <0.05 was considered statistically significant. Results Despite cardiac involvement including decreased left ventricular ejection fraction (LVEF) (median LVEF = 47%, IQR 43%–53%) and increased troponin I (median 101 ng/mL, IQR 50–661 ng/mL) during hospitalization, there were no persistent cardiac changes observed in cardiac MR at follow‐up. All patients had normal size and function of the left ventricle and normal precontrast T1 and T2 relaxation times. There were no signs of LGE. Persistent, mild pericardial effusion (8–9 mm) was found in three (16%) patients. Data Conclusion There were no persistent changes on cardiac MRI in a group of children approximately 3 months post hospitalization due to PIMS‐TS with cardiac involvement. This supports the hypothesis that cardiac involvement during PIMS‐TS is a form of transient inflammatory response rather than direct and potentially persistent injury from the virus. Level of Evidence 4 Technical Efficacy Stage 3

Background. Many children presenting with myocarditis may not fully recover and have long-term complications, including dilated cardiomyopathy. Magnetic resonance imaging (MRI) has a potential for early detection of persistent changes with long-term implications, but is not performed routinely in the monitoring of myocarditis.Purpose. To monitor adolescents who present with acute myocarditis using MRI and routine diagnostic tests over the short to mid-term. Study type. Prospective.Population. 18 consecutive adolescents (median age 15.5, interquartile range 14.8-16.9 years, 78% male) with acute myocarditis.Field strength.3T scanner including cine steady-state free precession (SSFP), dark-blood T2W images and late gadolinium enhancement (LGE).Assessment. The diagnosis of acute myocarditis was based on clinical symptoms and signs, and MRI criteria (cine, T2-weighted images, late gadolinium enhancement). Follow-up MRI was performed after median 7 months (range 6-9 months). Other routine diagnostic tests included ECG, high-sensitivity troponin levels, transthoracic echocardiography and Holter monitoring. Statistical tests.Fisher's exact test, Wilcoxon test for paired samples, Mann-Whitney test for independent samples, Kruskal-Wallis test. Results. At baseline 17 patients (94%) had elevated troponin levels and/or ST-T changes on resting electrocardiogram, echocardiogram showed depressed left ventricular ejection fraction (LVEF<50%) in 4 patients (22%). At follow-up there was a complete recovery in 16 patients (89%) observed with routinely performed tests, with 2 cases of persistent ventricular arrhythmia. Despite normal left ventricular volume and LVEF, MRI disclosed ongoing active inflammation in 5 patients (28%), healed myocarditis with persistent scars in 8 patients (44%) and complete resolution of initially observed changes in 5 patients (28%). Data conclusion. In children with acute myocarditis, despite normalization of other routinely assessed parameters (including LVEF), there is a high prevalence of persistent MRI changes showing ongoing disease or remnant scars at follow-up. MRI may allow early detection and prevention of long-term complications of myocarditis in the follow-up care of children with acute myocarditis.

Physical training is associated with changes in cardiac morphology called the “athlete’s heart”, which has not been sufficiently studied in children. The aim of the study was to analyze cardiac adaptation to exercise in pre-adolescent soccer players. Thirty-six soccer players (mean age 10.1 ± 1.4 years) and 24 non-athlete male controls (10.4 ± 1.7 years) underwent cardiac magnetic resonance. Measurements of myocardial mass, end-diastolic and end-systolic volume, stroke volume and ejection fraction for left and right ventricle (LV, RV) were performed. Additionally, left and right atrial (LA, RA) areas and volumes were analysed. Relative wall thickness (RWT) was calculated to describe the pattern of cardiac remodeling. Interventricular wall thickness and LV mass were significantly higher in athletes, but remained within the reference (6.9 ± 0.8 vs. 6.2 ± 0.9 mm/√m2, p = 0.003 and 57.1 ± 7.4 vs. 50.0 ± 7.1 g/m2, p = 0.0006, respectively) with no changes in LV size and function between groups. The RWT tended to be higher among athletes (p = 0.09) indicating LV concentric remodeling geometry. Soccer players had significantly larger RV size (p < 0.04) with similar function and mass. Also, the LA volume (p = 0.01), LA area (p = 0.03) and LA diameter (p = 0.009) were significantly greater in players than in controls. Cardiac adaptations in pre-adolescent soccer players are characterized by an increased LV mass without any changes in LV size and systolic function, which is typical of resistance training with tendency to concentric remodeling. This is accompanied by increase of LA and RV size. It should be taken into account during annual pre-participation evaluation.

Epicardial adipose tissue (EAT) volume is associated with cardiovascular disease (CVD). Data regarding the influence of extremely intensive training on CVD are scarce. We compared EAT volume among ultra-marathon runners and in the sedentary control group, and assessed the correlations between EAT and risk factors of coronary artery disease (CAD). EAT volume around three main coronary vessels and right ventricle (RV) was measured in 30 healthy amateur ultrarunners and 9 sex- and age-matched sedentary controls using cardiac magnetic resonance. In addition, body composition, lipid profile, interleukin-6 (IL-6) plasma concentration, and intima-media thickness (IMT) were measured as well. The EAT volume was lower in all measured locations in the ultrarunners’ group compared to control group (p < 0.001 for all). Ultrarunners had lower BMI and fat percentage (FAT%) and more favorable lipid profile compared to the control group (p < 0.05 for all). Ultrarunners had lower rate of pathologically high levels of plasma IL-6 (>1 pg/mL) compared to the control group (17% vs. 56%, p < 0.05). IMT was similar in both groups. In the ultrarunners’ group, there was a positive correlation between EAT surrounding left anterior descending artery, circumflex artery, and RV and FAT%, and between EAT around circumflex artery and LDL and non-HDL cholesterol (p < 0.05 for all). In summary, extremely intensive training may decrease the risk of cardiovascular events in adult population of amateur athletes by reducing the amount and pro-inflammatory activity of EAT. However, more research is needed to draw firm conclusions regarding the anti- and pro-inflammatory effects of intensive training.