Ventricular Tachyarrythmias Following Cardiac Arrest in Public Settings versus Home (ML Weisfeldt et al)

Published - Written by John Staples

Your pulse begins to race and your breath quickens. You saw the elderly man in the blue coat collapse seconds ago, and it was immediately apparent that something was very wrong.  You call for help and rush over, beginning compression-only CPR after finding him unresponsive and pulseless on your primary survey.  As you connect him to the AED, you think:  Hang on a second … where am I?

Although it has the makings of a bad dream, thousands of scenarios exactly like this were examined in a thought-provoking study published in this week’s NEJM.  Dr. Myron Weisfeldt (Johns Hopkins University, Baltimore, MD) and the Resuscitation Outcomes Consortium Investigators sought to explain why AED placement in public settings has been demonstrated to improve outcomes, while AED placement in residential settings has not.

Their prospective cohort study evaluated adult out-of-hospital cardiac arrests (OHCA) taking place between 2005 and 2007 in ten North American communities. Of the 12,930 OHCA in which the initial rhythm was known or deemed shockable by an AED, 2042 occurred in public and 10,888 at home or another non-public location.  Compared to those occurring at home, a patient with bystander-witnessed OHCA occurring in public was more likely to have initial VF/VT (60% vs 35%; adjusted odds ratio 2.28, 95%CI 1.96-2.66), and more likely to survive to hospital discharge when AEDs were applied by bystanders (34% vs 12%; adjusted odds ratio 2.49, 95%CI 1.03-5.99).  After hypothesizing that location of OHCA might be a surrogate for co-morbidity and the severity of underlying cardiac disease (i.e. less healthy individuals might be housebound), the authors suggest that a prudent public health strategy might concentrate on putting AEDs in public locations and address the OHCAs occurring at home by improving CPR training and delivery.

In an accompanying editorial Dr. Gust Bardy of the Seattle Institute for Cardiac Research roundly disagrees with this interpretation of the study data.   He argues that the collapse-to-911-call and 911-call-to-ambulance-arrival intervals are both likely to be longer when OHCA occurs at home.  These delays make deterioration into asystole more likely and might explain the trial results.  Moreover, AEDs at home can provide definitive therapy for VF/VT.  Why discourage residential AED availability in favor of improvements in CPR, when the latter hasn’t been conclusively demonstrated to improve survival?  He comes to the “heretical, [but] … not unethical” conclusion that the value of CPR itself warrants close examination – perhaps even a randomized trial comparing CPR-plus-defibrillation to defibrillation alone.

Considering all of this, does it matter where you are?  From the perspective of the man in the blue coat, the presence of bystanders, their ability to act quickly, and the availability of an AED might be vitally important and dependent on where he’s collapsed.  Nevertheless, the optimal public health strategy to address the dismal survival of OHCA is uncertain, and where that leaves us is clear: In the middle of an academic debate that doesn’t look like it’ll collapse any time soon.