AIM To test of the implantable-cardioverter-defibrillator is done at the time of implantation. We investigate if any testing should be performed.METHODS All consecutive patients between January 2006 and December 2008 undergoing implantable cardioverterdefibrillator(ICD) implantation/replacement(a total of 634 patients) were included in the retrospective study.RESULTS Sixteen patients(2.5%) were not tested(9 with LA/LVthrombus, 7 due to operator’s decision). Analyzed were 618 patients [76% men, 66.4 + 11 years, 24% secondary prevention(SP), 46% with left ventricular ejection fraction(LVEF) < 20%, 56% had coronary artery disease(CAD)] undergoing defibrillation safety testing(SMT) with an energy of 21 + 2.3 J. In 22/618 patients(3.6%) induced ventricular fibrillation(VF) could not be terminated with maximum energy of the ICD. Six of those(27%) had successful SMT after system modification or shock lead repositioning, 14 patients(64%) received a subcutaneous electrode array. Younger age(P = 0.0003), non-CAD(P = 0.007) and VF as index event for SP(P = 0.05) were associated with a higher incidence of ineffective SMT. LVEF < 20% and incomplete revascularisation in patients with CAD had no impact on SMT.CONCLUSION Defibrillation testing is well-tolerated. An ineffective SMT occurred in 4% and two third of those needed implantation of a subcutaneous electrode array to passa SMT > 10 J. AIM To test of the implantable-cardioverter-defibrillator is done at the time of implantation. We investigate if any testing should be performed. METHODS All consecutive patients between January 2006 and December 2008 undergoing implantable cardioverter-defibrillator (ICD) implantation / replacement (a total of 634 patients were included in the retrospective study .RESULTS Sixteen patients (2.5%) were not tested (9 with LA / LVthrombus, 7 due to operator’s decision). Analyzed were 618 patients [76% men, 66.4 + 11 years, 24% secondary prevention (SP) with 46% with left ventricular ejection fraction (LVEF) <20%, 56% had coronary artery disease (CAD)] undergoing defibrillation safety testing (SMT) with an energy of 21 + 2.3 J. In 22/618 Six of those (27%) had successful SMT after system modification or shock lead repositioning, 14 patients (64%) received a subcutaneous electrode (3.6%) induced ventricular fibrillation (VF) could not be terminated with maximum energy of the ICD. Younger age (P = 0.0003), non-CAD (P = 0.007) and VF as index event for SP (P = 0.05) were associated with a higher incidence of ineffective SMT. LVEF <20% and incomplete revascularisation in patients with CAD had no impact on SMT. CONCLUSION Defibrillation testing is well-tolerated. An ineffective SMT occurred in 4% and two third of those needed needed implantation of a subcutaneous electrode array to passa SMT> 10 J.