Early defibrillation is most beneficial during cardiac arrest when the patient is in which rhythm?

• A. Asystole
• B. Pulseless electrical activity
• C. Ventricular fibrillation or pulseless ventricular tachycardia
• D. Normal sinus rhythm

Answer: (C)

Early defibrillation is most beneficial when the heart is in a shockable rhythm—ventricular fibrillation or pulseless ventricular tachycardia. In these patterns the chaotic or rapid electrical activity prevents effective circulation, so delivering a shock can reset the electrical system and permit a perfusing rhythm to resume, which improves the chances of survival if done promptly. When the rhythm is asystole or pulseless electrical activity, there is little to no organized electrical activity or no pulse, so defibrillation is unlikely to help; the focus shifts to high-quality CPR and addressing reversible causes. A normal sinus rhythm is not an arrest rhythm, so defibrillation would not be applicable there.