In atrial tachycardia, absence of P waves is a hallmark of which rhythm?

• A. Atrial tachycardia
• B. Atrial fibrillation
• C. Junctional rhythm
• D. Sinus rhythm

Answer: (A)

P waves represent atrial depolarization. When you don’t see discrete P waves before each QRS, it means the atria aren’t firing in an organized way. That pattern is classic for atrial fibrillation, where the atria quiver chaotically and there are no distinct P waves, producing an irregularly irregular ventricular rhythm with fibrillatory activity instead of normal atrial beats.

In contrast, atrial tachycardia has an atrial origin but still generates P waves for each beat, though their shape may be abnormal. Sinus rhythm shows normal, clearly identifiable P waves before every QRS, and a junctional rhythm often lacks visible P waves or has retrograde/inverted P waves that can be hidden in the QRS. So the absence of P waves points to atrial fibrillation rather than atrial tachycardia.