An automated external defibrillator (AED) will shock which of the following rhythms?

An automated external defibrillator (AED) is designed specifically to identify and deliver a shock to certain life-threatening heart rhythms to restore normal electrical activity and increase the chances of successful resuscitation. Ventricular fibrillation is one of these critical rhythms. In ventricular fibrillation, the heart's electrical activity becomes chaotic, preventing it from effectively pumping blood. The shock delivered by an AED helps to restore a normal heartbeat by allowing the heart to reset its electrical rhythm.

The other rhythms, such as sinus rhythm, asystole, and pulseless electrical activity (PEA), do not respond to defibrillation in the same way. Sinus rhythm is a normal rhythm that does not require defibrillation. Asystole represents a flatline on the monitor, indicating no electrical activity in the heart, and therefore, defibrillation would not be effective as there is no chaotic rhythm to reset. Similarly, PEA shows organized electrical activity without a pulse, and while it indicates that the heart is not functioning normally, defibrillation is not indicated because it does not involve the chaotic electrical activity that AEDs are designed to correct. Thus, the correct answer highlights the specific rhythm that AEDs target effectively—ventricular fibrillation.