OBJECTIVES We hypothesized that specific ECG findings might herald multiple episodes of ventricular fibrillation (VF) in patients with Brugada syndrome (BS). BACKGROUND The electrocardiographic predictors of an electrical storm (ES, defined as ��� 4 VF episodes in a day) in patients with BS have not yet been reported. METHODS All patients with BS who visited the emergency department for evaluation of syncope or repeat shocks were prospectively analyzed. ECGs were recorded twice a day and whenever a dynamic repolarization change was noted on the ECG monitoring. The mode of the onset and the coupling intervals of the PVCs initiating VF episodes were analyzed in 82 (storm group, 5 patients) and 26 (control group, 7 patients) VF episodes recorded during continuous ECG monitoring or ICD interrogations. RESULTS The ECGs recorded within 30 minutes before the occurrence of an ES exhibited a widespread appearance of J waves not only in the right precordial leads but also in the left precordial and limb leads. VF episodes were commonly initiated by PVCs with a short-long-short (SLS) sequence in the ES group (42/82, 51%) while SLS sequences were rarely recorded in the control group (3/26, 12%, p<0.001). Coupling intervals were significantly shorter in the ES group as compared with those of the control group (315짹46 ms vs. 398짹31 ms, p<0.001). CONCLUSIONS A widespread appearance of electrocardiographic J waves across the precordial and limb leads may identify a subgroup of Brugada syndrome patients with high arrhythmogenic activity.