A new study published today in the NEJM (Ventricular Tachyarrhythmias after Cardiac Arrest in Public versus at Home) confirms what we have known for years, that lives would be saved if more AEDs were available in more public places. The real interesting aspect of the study, however, was its finding that patients who suffer cardiac arrest at home are much less likely to have a shockable rhythm than patients who arrest in a public place. Quoting from the study:

"For cardiac arrests at home, the incidence of ventricular fibrillation or pulseless ventricular tachycardia was 25% when the arrest was witnessed by emergency-medical-services (EMS) personnel, 35% when it was witnessed by a bystander, and 36% when a bystander applied an AED. For cardiac arrests in public, the corresponding rates were 38%, 60%, and 79%."

The lack of a shockable rhythm translates, as expected, to a lower survival rate: 6% for in-home cardiac arrest versus 17% for cardiac arrest in public. Overall survival was 7%. The study's authors suggest that the reason why patients at home are much less likely to have a shockable rhythm is that they are generally older and suffer from more chronic diseases than patients encountered in a public setting.

Although nothing in this study suggests we need to consider changes in cardiac arrest management, it may help EMS providers establish reasonable expectations for the success of their efforts.