Background: A common ICD therapy-related complication is arrhythmic storm(AS). The objective of our study was to define the impact of AS on patients' prognoses in order to comparethe total mortality of AS patients with the rest of the group. Material/Methods: We studied 138 patientswho received ICDs between 1994 and 2001. Patients who experienced one or more arrhythmic storms werestatistically compared with patients who had no accumulation of malignant arrhythmia or no episodes.Results: One thousand four hundred ninety episodes of arrhythmia were analyzed. Arrhythmia recurrencewas present in 71% of the patients. The majority of episodes (78%) were ventricular tachycardias andonly 3% of episodes were ventricular fibrillation. Seventy percent of all arrhythmic episodes were asymptomatic.The ICD therapy sensitivity was 99.7%. Thirty-eight arrhythmic storms in 19 patients (14%) were observedduring follow-up. The occurrence of AS was twice as high among patients with LVEF

Keywords: Algorithms, Arrhythmias, Cardiac - therapy, Defibrillators, Implantable, Electric Countershock, Stroke Volume, Ventricular Dysfunction, Left - therapy