Which of the following is a cardiac arrest rhythm?

• A. Ventricular fibrillation
• B. Atrial fibrillation with a pulse
• C. Sinus tachycardia
• D. Sinus bradycardia

Answer: (A)

The question tests the ability to tell which rhythms indicate cardiac arrest versus those with a pulse. A cardiac arrest rhythm is one where there is no effective heartbeat or circulation, and the rhythm is typically based on chaotic, uncoordinated electrical activity that fails to produce a pulse.

Ventricular fibrillation is the classic arrest rhythm because the ventricles quiver in a chaotic, disorganized way and there is no coordinated contraction to pump blood. This is why it’s treated as a medical emergency with immediate defibrillation when a shock is appropriate.

The other options describe rhythms that either have organized electrical activity or slower rates with a pulse (atrial fibrillation with a pulse, sinus tachycardia, sinus bradycardia). These are not cardiac arrest rhythms because a pulse is usually present, unless the situation decompensates into arrest, which is not indicated by these patterns alone.