Clinical Research
Heart Rhythm Disorder
Inappropriate Implantable Cardioverter-Defibrillator Shocks: Incidence, Predictors, and Impact on Mortality

https://doi.org/10.1016/j.jacc.2010.06.059Get rights and content
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Objectives

The purpose of this study was to assess the incidence, predictors, and outcome of inappropriate shocks in implantable cardioverter-defibrillator (ICD) patients.

Background

Despite the benefits of ICD therapy, inappropriate defibrillator shocks continue to be a significant drawback. The prognostic importance of inappropriate shocks outside the setting of a clinical trial remains unclear.

Methods

From 1996 to 2006, all recipients of defibrillator devices equipped with intracardiac electrogram storage were included in the current analysis and clinically assessed at implantation. During follow-up, the occurrence of inappropriate ICD shocks and all-cause mortality was noted.

Results

A total of 1,544 ICD patients (79% male, age 61 ± 13 years) were included in the analysis. During the follow-up period of 41 ± 18 months, 13% experienced ≥1 inappropriate shocks. The cumulative incidence steadily increased to 18% at 5-year follow-up. Independent predictors of the occurrence of inappropriate shocks included a history of atrial fibrillation (hazard ratio [HR]: 2.0, p < 0.01) and age younger than 70 years (HR: 1.8, p = 0.01). Experiencing a single inappropriate shock resulted in an increased risk of all-cause mortality (HR: 1.6, p = 0.01). Mortality risk increased with every subsequent shock, up to an HR of 3.7 after 5 inappropriate shocks.

Conclusions

In a large cohort of ICD patients, inappropriate shocks were common. The most important finding is the association between inappropriate shocks and mortality, independent of interim appropriate shocks.

Key Words

implantable cardioverter-defibrillator
inappropriate shock
mortality
sudden death

Abbreviations and Acronyms

AF
atrial fibrillation
CI
confidence interval
HR
hazard ratio
ICD
implantable cardioverter-defibrillator
NYHA
New York Heart Association
VF
ventricular fibrillation
VT
ventricular tachycardia

Cited by (0)

Prof. Bax has received research grants from GE Healthcare, Bristol-Myers Squibb Medical Imaging, St. Jude, Medtronic, Boston Scientific, Biotronik, and Edwards Lifesciences. Prof. Schalij has received research grants from Biotronik, Medtronic, and Boston Scientific. All other authors have reported that they have no relationships to disclose.