These findings have important implications for clinical practice and may help guide medical management for adolescents with ICDs and their families.

Background-Prolongation of the QT interval after exercise can be used to help diagnose long-QT syndrome, especially when the resting QT interval is borderline. The aim of this study was to determine the normal ranges for QT and corrected QT in the recovery phase after exercise in children. Methods and Results-Ninety-four volunteer boys and girls aged 8 to Ͻ17 years without any history of heart disease underwent exercise testing and had a 12-lead ECG performed in the supine position for 10 minutes of recovery. The QT was measured using a standardized tangent method, with the baseline defined as the Q-Q line. The recovery QT was maximally short at 1 minute of recovery in 93 of 94 children then lengthened and stabilized at 4 to 5 minutes recovery. The recovery QT lengthens as heart rate decreases in an approximately linear fashion with a mean increase of 15 ms per 10-beat decrease in heart rate. The 98th percentiles for the corrected QT using the Bazett formula during minutes 4 to 6 in recovery were from 482 to 491 ms. There was excellent intraobserver and interobserver reliability, with intraclass correlation coefficients of 0.95 and 0.88, respectively. Conclusions-There is substantial individual variability of the normal repolarization process in the postexercise recovery period in children. The study provides a reference for normal responses for similar populations using a specific measurement protocol that can be easily applied. (Circ Arrhythm Electrophysiol. 2011;4:448-455.)

Electrical storm (ES) presents a difficult management problem that has predominantly been described in adults and there are limited published data relating to children. We set out to characterize ES in children to assist management based on published literature and own institutional experience. We retrospectively analyzed the records of children presenting with ES to our institution between July 2001 and July 2011 and conducted a systematic literature review. Four children were identified (median age: 5.7 years, range: 3.3-9.6 years, one male). Each ES was of different character and different management strategies were used. All patients were alive at a median follow-up of 5.7 years and all had received implantable cardioverter-defibrillators. Two patients were felt to have catecholaminergic polymorphic ventricular tachycardia, one possible long QT syndrome and one the "short-coupled" variant of torsades de pointes. At least three of our four patients had possible iatrogenic contribution to their ES. Forty-seven cases of ES in children with variable management strategies were identified from the published literature. ES is a rare medical emergency in children with multiple etiologies requiring individualized management.

Submammary ICD implantation in young females is feasible and safe. Long-term follow-up data reveal stable sensing and HV lead performance.