Which rhythm is considered shockable for immediate defibrillation?

Which rhythm is considered shockable for immediate defibrillation?

• A. Asystole
• B. Pulseless electrical activity
• C. Sinus bradycardia with pulse
• D. Ventricular fibrillation

Answer: (D)

Shockable rhythms are those where the heart’s electrical activity is chaotic enough that a rapid energy input can reset the rhythm. Ventricular fibrillation fits this: the ventricles quiver with no organized contraction, so there’s no effective pumping and no pulse. A defibrillation shock briefly depolarizes a critical mass of heart muscle, allowing the heart’s natural pacemaker to reestablish a perfusing rhythm. The other options aren’t treated with immediate defibrillation. Asystole is a flatline with no electrical activity, and pulseless electrical activity shows electrical activity but no effective heartbeat—both require CPR and other interventions, not shock. Sinus bradycardia with a pulse isn’t in cardiac arrest and isn’t treated with shocks; it’s managed by rhythm control and addressing underlying causes.

Shockable rhythms are those where the heart’s electrical activity is chaotic enough that a rapid energy input can reset the rhythm. Ventricular fibrillation fits this: the ventricles quiver with no organized contraction, so there’s no effective pumping and no pulse. A defibrillation shock briefly depolarizes a critical mass of heart muscle, allowing the heart’s natural pacemaker to reestablish a perfusing rhythm.

The other options aren’t treated with immediate defibrillation. Asystole is a flatline with no electrical activity, and pulseless electrical activity shows electrical activity but no effective heartbeat—both require CPR and other interventions, not shock. Sinus bradycardia with a pulse isn’t in cardiac arrest and isn’t treated with shocks; it’s managed by rhythm control and addressing underlying causes.