We present a case of a boy with long QT syndrome type 2, who was admitted after an out of hospital cardiac arrest due to ventricular fibrillation. Subsequently, all treatments – intravenous magnesium, optimisation of electrolytes, an isoproterenol infusion – failed to terminate his electrical storm. As a last option before left-sided cardiac sympathetic denervation, mexiletine was started and the electrical storm resolved completely.