Ventricular fibrillation is an uncoordinated contraction of the cardiac muscle of the ventricles, making them quiver rather than contract properly.

• A. Ventricular fibrillation
• B. Ventricular tachycardia
• C. Sinus tachycardia
• D. Atrial fibrillation

Answer: (A)

The situation describes the heart’s ventricles losing coordinated electrical activity and simply quivering instead of contracting in a synchronized way. This is ventricular fibrillation, where chaotic ventricular activity produces no effective pumping and thus no meaningful cardiac output. On an ECG, you’d see a jagged, irregular baseline without recognizable P waves or distinct QRS complexes, reflecting the disorganized rhythm.

Why this is the best fit: the defining feature is uncoordinated, chaotic ventricular activity leading to quivering, not a rapid, organized heartbeat or activity originating from the atria or SA node.

Other rhythms differ in origin and pattern. Ventricular tachycardia is a very fast but generally more organized ventricular rhythm with wide QRS complexes and can still produce some cardiac output. Sinus tachycardia is a fast heart rate that maintains a coordinated rhythm originating from the SA node. Atrial fibrillation involves disorganized activity in the atria, with irregularly irregular ventricular response, but the ventricles themselves aren’t quivering due to disorganized ventricular impulses.

Clinically, this is an emergency requiring immediate attention, typically defibrillation if the patient is pulseless, along with CPR as indicated.