Bardy GH et al. for the HAT investigators (2008) Home use of automated external defibrillators for sudden cardiac arrest. N Engl J Med 358: 1793–1804

When sudden cardiac arrest occurs at home, timely medical attention from emergency services can be difficult to achieve. A multicenter clinical trial has been performed to determine whether home use of an automated external defibrillator (AED), before the arrival of emergency medical services, can improve survival in such circumstances.

The patients enrolled in this trial had previously had anterior-wall myocardial infarction but were not eligible to receive an implantable cardioverter-defibrillator. Of the 7,001 patients included, 3,495 were randomly assigned an AED to be used by their companions if a sudden cardiac arrest occurred at home, before calling emergency medical services.

The companions of 167 patients assigned an AED were unable or unwilling to use the device during follow-up (median 37.3 months). The number of patients who died (222 [6.4%] patients provided with an AED and 228 [6.5%] controls) and the mechanism of death (e.g. cardiac tachyarrhythmia, heart failure) did not differ between the two patient groups. Home defibrillators were used on 32 patients in the AED group and shock was advised for 13 of these individuals. No inappropriate shock was recorded. Eight patients each in the AED and control groups were successfully resuscitated at home following sudden cardiac arrest.

Access to a home AED did not improve survival in this group of patients with previous anterior-wall myocardial infarction, but the authors of this study attribute this result to a very low event rate, a high proportion of unwitnessed events, and underuse of the AEDs in emergencies, rather than problems with device efficacy.