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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: Despitecardiac involvement includingdecreased left ventricularejectionfraction(LVEF) (medianLVEF=47%, IQR43%-53%) and increased troponin I (median 101 ng/mL, IQR 50-661 ng/mL) during hospitalization, there were no persistent cardiac changes observed in cardiacMR 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, mildpericardial effusion(8-9 mm)wasfoundin 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. [ABSTRACT FROM AUTHOR]

Background: Native myocardial T1 and T2 relaxation times are diagnostic tools used in clinical practice for adult and pediatric populations. Use of a mapping technique requires accurate knowledge of normal ranges in healthy patients, which is lacking in pediatric populations.Purpose: To establish normal values for native T1 and T2 mapping in healthy pediatric subjects of different ages and sex.Study Type: Prospective.Population: Thirty-eight healthy children (9-18 years; mean age 14.0 ± 2.7).Field Strength: Cardiac MR with a 3T scanner. T1 and T2 mapping using MyoMaps software.Assessment: T1 and T2 relaxation times were calculated from a 0.7-1.0 cm2 region of interest placed at the mid-ventricular short-axis slice in the interventricular septum by two observers. Inter- and intraobserver variability was assessed.Statistical Tests: The Student's t-test or the Mann-Whitney test for unpaired samples was applied to compare one continuous variable between two category groups. One-way analysis of variance (ANOVA) or a Kruskal-Wallis test was applied to compare one continuous variable between three category groups. Correlation between two continuous variables was assessed with a Pearson or Spearman test.Results: The mean native T1 relaxation time was 1223 ± 29 msec and T2 relaxation time was 43 ± 4.5 msec. There was no correlation between T1 /T2 values and age or body surface area (for T1 P = 0.94 and 0.90 and for T2 P = 0.19 and 0.64, respectively). There was weak correlation between T1 values and body mass index (BMI) (r = 0.448, P = 0.005). T2 values were significantly higher in females compared with males (44.6 ± 4.2 vs. 40.4 ± 3.8 msec, P = 0.002). We found a significant rise of T2 relaxation time in the pubertal period (age 13-15 years) comparing to prepubertal (age 9-12 years). Inter- and intraobserver agreement of T1 (r = 0.93; r = 0.99) and T2 (r = 0.96; r = 0.95) were high.Data Conclusion: We report normal values of native T1 and T2 relaxation times obtained with Myomaps software for 3T cardiac MR in a healthy pediatric population.Level Of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:912-918. [ABSTRACT FROM AUTHOR]