Atrial fibrillation has which characteristic?

• A. Presence of discernible P waves
• B. Regular rhythm
• C. Narrow QRS complexes only
• D. Absence of discernible P waves

Answer: (D)

Atrial fibrillation disrupts organized atrial depolarization, so there are no distinct P waves before each heartbeat on the ECG. The atria twitch chaotically, producing irregular, often erratic baselines called fibrillatory waves, and the overall rhythm is irregularly irregular. The QRS complexes are usually normal in width unless there’s another conduction issue, so the defining feature is the absence of discernible P waves. That’s why the statement describing no identifiable P waves best matches atrial fibrillation. The other ideas—clear P waves, a regular rhythm, or a statement that only narrow QRS complexes occur—don’t capture the hallmark irregular atrial activity and lack of organized atrial depolarization.