CONGRESS ABSTRACT

Background: Ventricular arrhythmias (VAs) are frequently observed in pediatric patients with structurally normal hearts and typically have a benign course. While the associations between VAs, left ventricular (LV) dysfunction, symptoms, and outcomes are extensively documented in adults, these relationships are less clearly understood in the pediatric context. Aim: This study aims to assess the clinical characteristics, natural history, and outcomes of idiopathic VAs in children and adolescents with structurally normal hearts. Methods: We retrospectively evaluated pediatric pts (< 18 y.o.) diagnosed with idiopathic VAs at our Institution. Exclusion criteria included congenital heart disease, primary electrical disorders, and cardiomyopathies. Collected data encompassed demographics, medical history, 12-lead ECG, 24-hour ECG Holter monitoring, exercise testing (ET), echocardiography, and cardiac magnetic resonance, both at initial evaluation and during the follow-up (FUP). Results: The study included 101 pts (mean age at presentation 10.5 ± 4.6). 46 patients exhibited VAs originating from the outflow tracts, while 55 had VAs from other sites. Patients with outflow tract VAs were older (11.7 years ± 3.7 vs 9.9 years ± 4.4, p=0.03), had longer QRS duration (135 msec ± 18.7 vs 122 msec ± 24, p=0.0084) and a higher arrhythmic burden at initial evaluation (14% ± 12.9 vs 8.5% ± 8.3, p=0.043). No differences in LV function were found. Moreover, within the cohort, 93 patients exhibited preserved LV function and 8 showed LV dysfunction (EF< 53%). Patients with LV dysfunction had a higher prevalence of sustained and non-sustained ventricular tachycardias (sVT, ns-VT) compared to those with preserved LV function (62.5%, vs 21.3%, p=0.03). Notably, after starting antiarrhythmic therapies, at FUP no more significant difference was found between the two groups. Additionally, the arrhythmic burden observed at 24-hour ECG Holter was higher in patients with LV dysfunction, although this difference did not reach statistical significance (22.6% ± 17.6% vs 9.4% ± 10.2%, p=0.09). Conclusions: In pediatric patients with idiopathic VAs, development of LV dysfunction is associated with the presence of s- and ns-VTs, whilst no other clinical and ECG features seem to predict LV dysfunction. Furthermore, patients with VAs originating from outflow tracts exhibit higher age, longer QRS, and greater arrhythmic burdens on 24-ECG Holter, but no increased risk of developing LV dysfunction.