Abstract 16196: 3 Shocks and You're Out: Impact of Shocks on Mortality in Patients with Implantable Cardioverter Defibrillators
Background Studies have questioned the safety of ICDs by observing an association between ICD shocks and mortality, but there is conflicting data on whether shocks are a primary or secondary marker of mortality risk. We sought to determine the relationship between ICD shocks and mortality.
Methods In a prospective observational study, consecutive patients with ICDs were surveyed assessing demographics and medical history. ICD shock history was assessed and all-cause mortality determined from the Social Security Death Index.
Results Among 690 patients enrolled, 88% had ICDs placed for primary prevention, 34.2% received at least 1 shock, and 14.9% received at least 1 inappropriate shock. Over a mean follow-up of 2.8 years, total number of shocks (p=0.006) and appropriate shocks (p=0.001), but not inappropriate shocks (p=0.928) were associated with worse mortality. Patients who died received an average of 5.37 shocks, compared to 2.33 shocks in patients who did not die. Patients with 3 or more shocks had a mortality rate of 15.1%, whereas less than 3 shocks had a mortality of 6.7%.
Conclusions Similar to SCDHeFT findings, appropriate shocks are predictors of mortality, but inappropriate shocks are not, suggesting that shocks may be a secondary marker rather than a primary cause of mortality risk. However, mortality rates increase significantly in patients who receive 3 or more shocks. Whether suppression of shocks would reduce mortality warrants future study.
- © 2012 by American Heart Association, Inc.