Clinical characteristics of electrical storm in patients with early repolarization syndrome

Background Early repolarization syndrome (ERS) is an idiopathic ventricular fibrillation (VF) associated with inferolateral J waves. While electrical storms (ES) in ERS is not rare, their characteristics and risk factors are not fully understood. Objective This study aimed to clarify the significance of ES in ERS. Methods We evaluated 44 patients with ERS who experienced VF/sudden cardiac death or arrhythmic syncope. We assessed clinical characteristics to identify the risk factors for ES. Results In total, 13 patients (30%) experienced ES (ES group). Of these, 11 patients experienced ES during the acute phase of initial VF episodes, and 2 patients experienced ES during follow-up. VF associated with ES occurred during therapeutic hypothermia in 6 of 13 patients. The J wave voltage during therapeutic hypothermia was higher in the ES group than that in the non-ES group. Isoproterenol was used in 5 patients, which decreased J wave voltage and relieved ES. Among the clinical markers, shorter QT and QTp intervals (the interval from QRS onset to the peak of T wave), pilsicainide-induced ST-elevation, and high points on the Shanghai Score System (SSS) were associated with ES. Although pilsicainide induced ST elevation in 6 patients, spontaneous Brugada electrocardiographic patterns did not appear to be associated with VF. Therapeutic hypothermia was also a risk factor for acute-phase ES. Conclusions Patients with ERS in the ES group frequently had short QT and QTp intervals, pilsicainide-induced ST elevations, and high SSS scores. Therapeutic hypothermia was also associated with acute phase ES.