Extra Implanted Defibrillator Shocks Raise Mortality

Inappropriate shocks more common with atrial fibrillation and patients younger than 70 years

TUESDAY, Jan. 25 (HealthDay News) -- Inappropriate shocks by implantable cardioverter-defibrillators (ICDs) are associated with a higher mortality risk, according to a study published in the Feb. 1 issue of the Journal of the American College of Cardiology.

Johannes B. van Rees, M.D., of the Leiden University Medical Center in the Netherlands, and colleagues investigated the incidence, predictors, and outcomes of inappropriate shocks in ICD patients. A total of 1,544 ICD patients with intracardiac electrogram storage were followed for a period of 41 months ± 18 months between 1996 and 2006. During follow-up, the occurrence of inappropriate ICD shocks and all-cause mortality were noted.

The researchers found that a single inappropriate shock significantly increased all-cause mortality, and this risk increased with every subsequent shock, up to a hazard ratio of 3.7 after five inappropriate shocks. During the follow-up period, 13 percent of patients experienced one or more inappropriate shocks. The cumulative incidence increased steadily to 18 percent at the five-year follow-up. Predictors of inappropriate shocks included a history of atrial fibrillation and age younger than 70 years.

"Inappropriate shocks were associated with a higher risk of all-cause mortality, which increased per delivered inappropriate shock and was independent of interim appropriate shocks," the authors write.

Several authors disclosed financial relationships with the pharmaceutical industry.

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