Predictors of an inadequate defibrillation safety margin at ICD implantation: insights from the National Cardiovascular Data Registry

J Am Coll Cardiol. 2014 Jul 22;64(3):256-64. doi: 10.1016/j.jacc.2014.01.085.


Background: Defibrillation testing is often performed to establish effective arrhythmia termination, but predictors and consequences of an inadequate defibrillation safety margin (DSM) remain largely unknown.

Objectives: The aims of this study were to develop a simple risk score predictive of an inadequate DSM at implantable cardioverter-defibrillator (ICD) implantation and to examine the association of an inadequate DSM with adverse events.

Methods: A total of 132,477 ICD Registry implantations between 2010 and 2012 were analyzed. Using logistic regression models, factors most predictive of an inadequate DSM (defined as the lowest successful energy tested <10 J from maximal device output) were identified, and the association of an inadequate DSM with adverse events was evaluated.

Results: Inadequate DSMs occurred in 12,397 patients (9.4%). A simple risk score composed of 8 easily identifiable variables characterized patients at high and low risk for an inadequate DSM, including (with assigned points) age <70 years (1 point); male sex (1 point); race: black (4 points), Hispanic (2 points), or other (1 point); New York Heart Association functional class III (1 point) or IV (3 points); no ischemic heart disease (2 points); renal dialysis (3 points); secondary prevention indication (1 point); and ICD type: single-chamber (2 points) or biventricular (1 point) device. An inadequate DSM was associated with greater odds of complications (odds ratio: 1.22; 95% confidence interval: 1.09 to 1.37; p = 0.0006), hospital stay >3 days (odds ratio: 1.24; 95% confidence interval: 1.19 to 1.30; p < 0.0001), and in-hospital mortality (odds ratio: 1.96; 95% confidence interval: 1.63 to 2.36; p < 0.0001).

Conclusions: A simple risk score identified ICD recipients at risk for an inadequate DSM. An inadequate DSM was associated with an increased risk for in-hospital adverse events.

Keywords: adverse events; complications; defibrillation safety margin; defibrillation threshold; implantable cardioverter-defibrillator; mortality; national registries; risk score.

Publication types

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

MeSH terms

  • Adult
  • Aged
  • Cardiovascular Diseases / diagnosis
  • Cardiovascular Diseases / therapy*
  • Cohort Studies
  • Databases, Factual / trends*
  • Defibrillators, Implantable / adverse effects
  • Defibrillators, Implantable / trends*
  • Electric Countershock / adverse effects
  • Electric Countershock / trends*
  • Female
  • Humans
  • Length of Stay / trends*
  • Male
  • Middle Aged
  • Predictive Value of Tests
  • Registries*
  • Risk Factors