Inappropriate implantable cardioverter-defibrillator shocks in MADIT II: frequency, mechanisms, predictors, and survival impact

J Am Coll Cardiol. 2008 Apr 8;51(14):1357-65. doi: 10.1016/j.jacc.2007.09.073.


Objectives: This study sought to identify the incidence and outcome related to inappropriate implantable cardioverter-defibrillator (ICD) shocks, that is, those for nonventricular arrhythmias.

Background: The MADIT (Multicenter Automatic Defibrillator Implantation Trial) II showed that prophylactic ICD implantation improves survival in post-myocardial infarction patients with reduced ejection fraction. Inappropriate ICD shocks are common adverse consequences that may impair quality of life.

Methods: Stored ICD electrograms from all shock episodes were adjudicated centrally. An inappropriate shock episode was defined as an episode during which 1 or more inappropriate shocks occurred; another inappropriate ICD episode occurring within 5 min was not counted. Programmed parameters for patients with and without inappropriate shocks were compared.

Results: One or more inappropriate shocks occurred in 83 (11.5%) of the 719 MADIT II ICD patients. Inappropriate shock episodes constituted 184 of the 590 total shock episodes (31.2%). Smoking, prior atrial fibrillation, diastolic hypertension, and antecedent appropriate shock predicted inappropriate shock occurrence. Atrial fibrillation was the most common trigger for inappropriate shock (44%), followed by supraventricular tachycardia (36%), and then abnormal sensing (20%). The stability detection algorithm was programmed less frequently in patients receiving inappropriate shocks (17% vs. 36%, p = 0.030), whereas other programming parameters did not differ significantly from those without inappropriate shocks. Importantly, patients with inappropriate shocks had a greater likelihood of all-cause mortality in follow-up (hazard ratio 2.29, p = 0.025).

Conclusions: Inappropriate ICD shocks occurred commonly in the MADIT II study, and were associated with increased risk of all-cause mortality.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Atrial Flutter / mortality
  • Atrial Flutter / therapy*
  • Clinical Trials as Topic
  • Defibrillators, Implantable / adverse effects*
  • Electric Countershock* / adverse effects
  • Electric Countershock* / mortality
  • Electric Countershock* / statistics & numerical data
  • Equipment Failure
  • Female
  • Humans
  • Incidence
  • Male
  • Middle Aged
  • Myocardial Infarction / complications
  • Myocardial Infarction / physiopathology
  • Odds Ratio
  • Prospective Studies
  • Retrospective Studies
  • Risk Factors
  • Stroke Volume
  • Tachycardia, Supraventricular / mortality
  • Tachycardia, Supraventricular / therapy*