Aims: Insufficient data exists regarding predictors of electrical storms(ES) and clinical outcome in patients treated with an implantable cardioverter defibrillator(ICD). The purpose of this study was to delineate a subgroup of patients likely to experience ES and to determine the impact of ES on mortality in ICD recipients. Methods and results: Baseline characteristics of 307 ICD-treated patients were retrospectively analysed. ES was defined as two or more ventricular tachyarrhythmias within 24 h leading to an immediate electrical therapy(antitachycardia pacing and/or shock), separated by a period of sinus rhythm. Clinical characteristics and survival of 123 patients experiencing a total of 294 episodes of ES(median 2 ES/ patient, range 1-9), were compared with those of 184 ES-free patients during a median follow-up of 826 days(inter-quartile 1141 days). Median actuarial duration for the first ES occurrence after ICD implant was 1417 days [95% confidence interval(CI) 1061-2363] with a median follow-up of 816 days(7-4642 days) in ES-free patients. Univariate analysis identified older age, depressed left ventricular ejection fraction(LVEF), ventricular tachycardia(VT) as index arrhythmia, chronic renal failure and absence of lipid-lowering drugs as variables significantly associated with an increased risk of ES. Multivariable Cox analysis confirmed an independent predictive value for chronic renal failure [hazard ratio(HR) 1.54, 95% CI 0.95-2.51, P=0.052], VT(HR 2.20, 95% CI 1.44-3.37, P=0.0003), and LVEF(HR 0.98, 95% CI 0.97-0.99, P=0.027). In contrast, diabetics(HR 0.49, 95% CI 0.27-0.90, P=0.022) were less affected by ES. There was no difference in survival between both groups. Conclusion: ES is frequent but does not increase mortality in ICD s recipients. Patients with severe systolic dysfunction, chronic renal failure and VT as initial arrhythmia are likely to experience ES. Diabetics are less affected by ES. Aims: Insufficient data exists on predictors of electrical storms (ES) and clinical outcome in patients treated with an implantable cardioverter defibrillator (ICD). The purpose of this study was to delineate a subgroup of patients likely to experience ES and determine the impact of ES on mortality in ICD recipients. Methods and results: Baseline characteristics of 307 ICD-treated patients were retrospectively analyzed. ES was defined as two or more ventricular tachyarrhythmias within 24 h leading to an immediate electrical therapy (antitachycardia pacing and / or shock), separated by a period of sinus rhythm. Clinical characteristics and survival of 123 patients experiencing a total of 294 episodes of ES (median 2 ES / patient, range 1-9), were compared with those of 184 ES-free patients during a median follow -up of 826 days (inter-quartile 1141 days). Median actuarial duration for the first ES occurrence after ICD implant was 1417 days [95% confidence interval (CI) 1061-2363] with a median follow-up of 816 days (7-4642 days) in ES-free patients. Univariate analysis identified older, depressed left ventricular ejection fraction (LVEF), ventricular tachycardia (VT) as index arrhythmia, chronic renal failure and absence of lipid -lowering drugs as variables significantly associated with an increased risk of ES. Multivariable Cox analysis confirmed an independent predictive value for chronic renal failure [hazard ratio (HR) 1.54, 95% CI 0.95-2.51, P = 0.052] , 95% CI 1.44-3.37, P = 0.0003), and LVEF (HR 0.98, 95% CI 0.97-0.99, P = 0.027) .In contrast, diabetics (HR 0.49, 95% CI 0.27-0.90, were was less affected by both groups. Conclusion: ES is frequent but does not increase mortality in ICD’s recipients. Patients with severe systolic dysfunction, chronic renal failure and VT as initial arrhythmia are likely to experience ES. Diabetics are less affected by ES.