Implantable cardioverter-defibrillator shock prevention does not reduce mortality: a systemic review

Heart Rhythm. 2012 Dec;9(12):2068-74. doi: 10.1016/j.hrthm.2012.08.032. Epub 2012 Sep 1.


Background: Mortality is increased among implantable cardioverter-defibrillator (ICD) recipients who receive shocks; however, whether shocks cause this increase or are simply a marker of risk is unknown. Antiarrhythmic medications, catheter ablation, and enhanced ICD programming all may reduce ICD shocks, but whether shock reduction decreases mortality is unknown.

Objective: The purpose of this study was to conduct a meta-analysis to estimate the impact of ICD shock reduction on survival.

Methods: Two independent reviewers searched MEDLINE, EMBASE, and and extracted data from randomized controlled trials assessing the efficacy of interventions to prevent ICD shocks.

Results: Seventeen randomized trials were included in this analysis, including 5875 patients. Mean ejection fraction of all trial participants was 32%, and 25% of the patients received ICD therapy for primary prophylaxis. Antiarrhythmic medications (odds ratio [OR] 0.59, 95% confidence interval [CI] 0.36-0.96, P = .03) and catheter ablation of ventricular tachycardia (OR 0.35, 95% CI 0.19-0.62, P = .0004) significantly reduced the proportion of patients receiving shocks. However, there was no significant reduction in mortality among trials of antiarrhythmic medications (OR 1.07, 95% CI 0.72-1.59, P = .73) or catheter ablation (OR 0.72, 95% CI 0.32-1.64, P = .44). The 5 ICD programming trials had sufficiently heterogeneous interventions that pooling of their results was not performed. However, only the PAINFREE-II (Pacing Fast Ventricular Tachycardia Reduces Shock Therapies) trial demonstrated a significant reduction in shocks (OR 0.38, 95% CI 0.22-0.65), but this was not associated with any significant reduction in mortality (OR 1.41, 95% CI 0.81-2.45).

Conclusion: There is no compelling evidence that existing interventions that reduce ICD shocks significantly improve survival.

Publication types

  • Review
  • Systematic Review

MeSH terms

  • Death, Sudden, Cardiac* / epidemiology
  • Death, Sudden, Cardiac* / etiology
  • Death, Sudden, Cardiac* / prevention & control
  • Defibrillators, Implantable*
  • Global Health
  • Humans
  • Tachycardia, Ventricular* / mortality
  • Tachycardia, Ventricular* / therapy