Background The natural history and long-term outcome in pediatric patients with idiopathic ventricular fibrillation ( IVF ) are poorly characterized. We sought to define the clinical characteristics and long-term outcomes of a pediatric cohort with an initial diagnosis of IVF . Methods and Results Patients were included from an International Registry of IVF (consisting of 496 patients). Inclusion criteria were: (1) VF with no identifiable cause following comprehensive analysis for ischemic, electrical or structural heart disease and (2) age ≤16 years. These included 54 pediatric IVF cases (age 12.7±3.7 years, 59% male) among whom 28 (52%) had a previous history of syncope (median 2 syncopal episodes [interquartile range 1]). Thirty-six (67%) had VF in situations associated with high adrenergic tone. During a median 109±12 months of follow-up, 31 patients (57%) had recurrence of ventricular arrhythmias, mainly VF . Two patients developed phenotypic expression of an inherited arrhythmia syndrome during follow-up (hypertrophic cardiomyopathy and long QT syndrome, respectively). A total of 15 patients had positive genetic testing for inherited arrhythmia syndromes. Ten patients (18%) experienced device-related complications. Three patients (6%) died, 2 due to VF storm. Conclusions In pediatric patients with IVF , a minority develop a definite clinical phenotype during long-term follow-up. Recurrent VF is common in this patient group.
Keywords: complications; defibrillator; idiopathic; syncope; ventricular fibrillation; ventricular tachycardia.