Roger Esmel-Vilomara

Background: Cardiac magnetic resonance (CMR) enables the quantitative characterization of myocardial tissue through parametric myocardial tissue mapping. It shows a strong correlation with invasive histologic techniques in assessing diffuse myocardial fibrosis using native T1 mapping and extracellular volume (ECV), as well as in assessing myocardial edema with T2 mapping. Pediatric applicability is currently limited by a lack of specific reference values for this population, with no recommendations available from the Society of Cardiac Magnetic Resonance. Objective: To determine reference values for global left ventricular native T1, T2 mapping, and extracellular volume fraction and to assess the influence of age, heart rate, body surface area, and sex on these parameters in children and adolescents. Materials and methods: Data were retrospectively collected between 2018 and 2024. A total of 194 healthy children aged up to 17 years underwent CMR. The participants had a mean age of 12.6 (3.4) CI [12.1; 13.1] years (range 0.3–17), and 41% were female. A 1.5-T Siemens MAGNETOM Avanto Fit scanner was used. Native T1 mapping was performed at the base, mid-chamber, and apex of the left ventricle in the short-axis view at end-diastole using a MOLLI sequence, before and 15 min after the administration of a gadobutrol-based contrast agent. T2 mapping was performed before contrast administration at the base, mid-chamber, and apex of the left ventricle at end-diastole using a dark blood turbo spin echo sequence featuring a T2 preparation pulse and a balanced steady-state free precession (bSSFP). Linear regression models were employed to explore the relationships between native T1, ECV, and T2 mapping values and heart rate, age, and body surface area (BSA). Results: The results showed a mean global native T1 of 1004±37 ms, ECV of 25.9±3.6%, and T2 of 48.8±4 ms. T1 and ECV values were negatively correlated with age and BSA ( P P P P =0.953 in the septum and P =0.445 in the free wall). Native T1 values were significantly higher in female patients than in males when analyzed separately for the interventricular septum and the left ventricular free wall ( P =0.014 and P =0.001). Conclusion: This study provides a median range of values in native T1, T2 mapping, and ECV in a pediatric population. The low number of participants under the age of 6 should be taken into account in the results of our study. Our findings corroborate that native T1 is influenced by both age and heart rate, while T2 is primarily affected by age alone. We observed higher native T1 values in females, highlighting the need for separate, sex-specific reference ranges. Therefore, age, heart rate, and sex should be considered in pediatric myocardial mapping.

Background and Aims: Congenital long QT syndrome (LQTS) is a heterogeneous disorder in which genotype and QTc duration modulate the risk of major arrhythmic events (MAEs), but contemporary paediatric outcome data remain limited. This study aimed to characterize clinical features, management strategies, and predictors of MAEs in a nationwide paediatric LQTS cohort. Methods: This retrospective multicentre study analysed children (<18 years) diagnosed with LQTS across 30 tertiary centres (2004–24) using 2022 European Society of Cardiology criteria. MAEs were defined as sudden cardiac death, aborted cardiac arrest, or appropriate implantable cardioverter-defibrillator (ICD) therapy. Results: The cohort included 371 children (58% male; median diagnosis age 6.0 years; interquartile range .25–11 years). Pathogenic/likely pathogenic variants were identified in 86.5%, mainly in KCNQ1, KCNH2, or SCN5A, while 5.7% harboured high-risk genotypes (Jervell–Lange-Nielsen, calmodulinopathies, CACNA1C/Timothy). Beta-blockers were prescribed in 92.4%. Over a median 6-year follow-up, 14 children (3.8%) experienced MAEs, which occurred predominantly in those with high-risk genotypes, QTc ≥550 ms or very early presentation. MAEs were rare in LQT1–3 with QTc 80% arrhythmia-free survival without major complications. Conclusions: In this nationwide paediatric LQTS cohort, MAEs were uncommon and clustered in children with malignant genotypes, markedly prolonged QTc and very early presentation, particularly foetal or neonatal bradycardia. These data support the current genotype and QTc-guided management strategy, with beta-blockers as the cornerstone therapy and selective use of left cardiac sympathetic denervation and ICDs in high-risk profiles.

Introduction: Parvovirus B19 (PVB19) myocarditis is a life-threatening condition with high morbidity and mortality in children. While electrocardiograms are commonly used in the early assessment of myocarditis, no specific electrocardiogram pattern has been consistently linked to PVB19. The objective of this study is to identify a distinctive electrocardiogram pattern associated with PVB19 myocarditis and evaluate its diagnostic accuracy. Methods: This retrospective case–control study included 77 paediatric patients diagnosed with acute myocarditis at a single centre in Barcelona over 16 years (August 2008–September 2024). Twenty patients had PVB19 myocarditis, confirmed by polymerase chain reaction in blood or endomyocardial biopsy, while 57 patients had myocarditis caused by other viruses. Electrocardiogram were assessed by three cardiologists blinded to the aetiological diagnosis. Results: A specific electrocardiogram pattern in the limb leads, characterised by peaked P waves, low QRS complex voltages, and altered repolarisation (manifesting as negative or flat T waves, with or without QTc prolongation), was observed in 14 of 20 patients (70%) with PVB19 myocarditis. Two additional patients exhibited low voltages and altered repolarisation without peaked P waves, and all demonstrated repolarisation abnormalities. In contrast, only 1 of 57 patients with myocarditis from other viruses exhibited the full electrocardiogram pattern. The pattern demonstrated a specificity of 98% and a sensitivity of 70% for PVB19 myocarditis. Conclusion: The identified electrocardiogram pattern shows strong diagnostic specificity for PVB19 myocarditis in paediatric patients and may serve as a useful early diagnostic tool. Further multicentre studies are needed to confirm these findings and explore their clinical implications.