Relation between total shock energy and mortality in patients with implantable cardioverter-defibrillator.
BACKGROUND
Implantable Cardioverter-Defibrillator (ICD) shocks have been associated with mortality. However, no study has examined the relation between total shock energy and mortality. The aim of this study is to assess the association of total shock energy with mortality, and to determine the patients who are at risk of this association.


METHODS
Data from 316 consecutive patients who underwent initial ICD implantation in our hospital between 2000 and 2011 were retrospectively studied. We collected shock energy for 3 years from the ICD implantation, and determined the relation of shock energy on mortality after adjusting confounding factors.


RESULTS
Eighty-seven ICD recipients experienced shock(s) within 3 years from ICD implantation and 43 patients had died during the follow-up. The amount of shock energy was significantly associated with all-cause death [adjusted hazard ratio (HR) 1.26 (per 100 joule increase), p < 0.01] and tended to be associated with cardiac death (adjusted HR 1.30, p = 0.08). The survival rate of patients with high shock energy accumulation (≥182 joule) was lower (p < 0.05), as compared to low shock energy accumulation (<182 joule), likewise to no shock. Besides, the relation between high shock energy accumulation and all-cause death was remarkable in the patients with low left ventricular ejection fraction (LVEF ≤40%) or atrial fibrillation (AF).


CONCLUSIONS
Increase of shock energy was related to mortality in ICD recipients. This relation was evident in patients with low LVEF or AF.
['Tenma|Taro|T|', 'Yokoshiki|Hisashi|H|', 'Mitsuyama|Hirofumi|H|', 'Watanabe|Masaya|M|', 'Mizukami|Kazuya|K|', 'Kamada|Rui|R|', 'Takahashi|Masayuki|M|', 'Sasaki|Ryo|R|', 'Maeno|Motoki|M|', 'Okamoto|Kaori|K|', 'Chiba|Yuki|Y|', 'Anzai|Toshihisa|T|']
D000328:Adult D000368:Aged D016757:Death, Sudden, Cardiac D047548:Defibrillators D017147:Defibrillators, Implantable D005260:Female D005500:Follow-Up Studies D006333:Heart Failure D006801:Humans D008297:Male D008875:Middle Aged D012189:Retrospective Studies D015996:Survival Rate
Total shock energy Mortality Implantable cardioverter-defibrillator Low left ventricular ejection fraction Atrial fibrillation Shock accumulation