Automatic external defibrillators-friend or foe?

Automatic external defibrillators (AEDs) in public places are invaluable in resuscitation from sudden cardiac arrest. We report a case of inappropriate AED shock from inadequate sensing of intrinsic rhythm and review the available data on detection criteria in AEDs. The case exemplifies the potential for an inappropriately advised AED shock to set off a cascade of events leading to potentially unnecessary cardiac interventions based on the presumption that a dangerous ventricular arrhythmia had occurred. It highlights the importance of careful review of all electrocardiographic data during resuscitation efforts during syncope and presumed cardiac arrest. We believe that this case has an important message that is relevant to a wide audience of health care workers who manage patients during and after cardiac arrest.