Use of implantable cardioverter defibrillators after out-of-hospital cardiac arrest: a prospective follow-up study

Background

Survivors of out-of-hospital cardiac arrest are at high risk of recurrent arrests, many of which could be prevented with implantable cardioverter defibrillators (ICDs). We sought to determine the ICD insertion rate among survivors of out-of-hospital cardiac arrest and to determine factors associated with ICD implantation.

Methods

The Ontario Prehospital Advanced Life Support (OPALS) study is a prospective, multiphase, before–after study assessing the effectiveness of prehospital interventions for people experiencing cardiac arrest, trauma or respiratory arrest in 19 Ontario communities. We linked OPALS data describing survivors of cardiac arrest with data from all defibrillator implantation centres in Ontario.

Results

From January 1997 to April 2002, 454 patients in the OPALS study survived to hospital discharge after experiencing an out-of-hospital cardiac arrest. The mean age was 65 (standard deviation 14) years, 122 (26.9%) were women, 398 (87.7%) had a witnessed arrest, 372 (81.9%) had an initial rhythm of ventricular tachycardia or ventricular fibrillation (VT/VF), and 76 (16.7%) had asystole or another arrhythmia. The median cerebral performance category at discharge (range 1–5, 1 = normal) was 1. Only 58 (12.8%) of the 454 patients received an ICD. Patients with an initial rhythm of VT/VF were more likely than those with an initial rhythm of asystole or another rhythm to undergo device insertion (adjusted odds ratio OR] 9.63, 95% confidence interval CI] 1.31–71.50). Similarly, patients with a normal cerebral performance score were more likely than those with abnormal scores to undergo ICD insertion (adjusted OR 12.52, 95% CI 1.74–92.12).

Interpretation

A minority of patients who survived cardiac arrest underwent ICD insertion. It is unclear whether this low usage rate reflects referral bias, selection bias by electrophysiologists, supply constraint or patient preference.People who survive out-of-hospital cardiac arrest have an increased risk of recurrent arrest of 18%–20% in the first year.^1,2 Three large randomized studies evaluated the use of implantable cardioverter defibrillators (ICDs) versus antiarrhythmic drugs in survivors of out-of-hospital cardiac arrest.^3,4,5 The largest of the 3 studies involved 1016 patients and found a 39% relative risk reduction in mortality in the ICD group.³ The 2 smaller studies both reported nonsignificant reductions in mortality in the ICD group.^4,5 Two recent meta-analyses showed that the use of ICDs was associated with significant and important increases in survival among cardiac arrest survivors: all-cause mortality was reduced by 23%–28% with their use for secondary prevention, and the rate of sudden cardiac death was reduced by 50% in both meta-analyses.^6,7Guidelines from several national and international societies recommend insertion of ICDs in all survivors of cardiac arrest without a reversible cause.^8,9 Despite advances in ICD insertion and technology, studies to date suggest that the utilization rate is low, at least in some settings.^10,11 Several factors, including patient preference, physician referral, availability and cost, may contribute to the underutilization of ICDs.The Ontario Prehospital Advanced Life Support Study (OPALS)^12,13 is a multiphase before–after study designed to systematically evaluate the effectiveness of various prehospital interventions for people experiencing cardiac arrest, trauma or respiratory arrest. As an extension of the OPALS study, we sought to determine the rate of ICD insertion among survivors of cardiac arrest, as well as the factors associated with ICD implantation.