Which ECG finding is characteristic of ventricular fibrillation?

• A. Regular rhythm with wide QRS complexes
• B. Normal sinus rhythm
• C. Atrial flutter
• D. Chaotic, irregular rhythm without identifiable P waves or QRS complexes

Answer: (D)

Ventricular fibrillation is a life-threatening rhythm where the ventricles depolarize in a highly disorganized, quivering pattern, so there is no effective contraction. On ECG this appears as a chaotic, irregular baseline with no recognizable P waves or QRS complexes—the waveform is erratic and lacks a repeating, organized pattern. Because there is no coordinated ventricular activity, cardiac output stops and immediate defibrillation is required.

Regular rhythm with wide QRS complexes would point to a ventricular tachycardia pattern, not fibrillation. Normal sinus rhythm shows identifiable P waves followed by QRS complexes in a regular sequence. Atrial flutter presents with sawtooth flutter waves from the atria. The absence of identifiable P waves or QRS complexes, with a chaotic rhythm, is the hallmark of ventricular fibrillation.