Defibrillation is indicated if the patient is in which rhythm?

• A. Sinus rhythm
• B. Atrial fibrillation
• C. V-tach or V-fib
• D. Asystole

Answer: (C)

Defibrillation is used for shockable rhythms, specifically when the heart is in ventricular fibrillation or pulseless ventricular tachycardia. In these rhythms, the electrical activity is chaotic or too rapid to produce effective cardiac output, so a high-energy shock is given to depolarize the myocardium and allow the heart’s natural pacemakers to reestablish a coordinated rhythm.

Sinus rhythm is normal and does not require shock. Atrial fibrillation is not a shockable rhythm in most emergent settings and is managed with rate or rhythm control and anticoagulation, or synchronized cardioversion if the patient is unstable with a pulse. Asystole and pulseless electrical activity are non-shockable: they’re treated with CPR and appropriate medications rather than defibrillation.