What are the two shockable rhythms in cardiac arrest?

• A. Asystole and PEA
• B. VF and pulseless VT
• C. NSR and VT
• D. AF and VT

Answer: (B)

In cardiac arrest, defibrillation is effective only for the rhythms that can be "reset" with a high-energy shock: ventricular fibrillation and pulseless ventricular tachycardia.

Ventricular fibrillation is chaotic, uncoordinated electrical activity with no organized contractions, so there’s no pulse or blood flow. Pulseless ventricular tachycardia is a rapid, abnormal rhythm that fails to produce a palpable pulse and adequate perfusion. A shock aims to reset the electrical activity so the heart can regain an organized, perfusing rhythm.

Non-shockable rhythms, like asystole (no electrical activity) and pulseless electrical activity (electrical activity without effective mechanical heart pumping), do not respond to defibrillation and require continued CPR and treatment of reversible causes.