Which tachycardia is often mistaken for atrial fibrillation?

• A. Multifocal atrial tachycardia
• B. Atrial flutter
• C. Sinus tachycardia
• D. Ventricular tachycardia

Answer: (A)

This question tests recognizing a tachycardia that can mimic atrial fibrillation because of an irregular rhythm, yet has a distinct atrial activity pattern. The tachycardia in question comes from several different atrial pacemaker foci, so the P waves change shape beat to beat. On a rhythm strip you’ll see at least three different P-wave morphologies before the QRS complexes, and the P–QRS intervals vary. Because the atria are firing from multiple sites unpredictably, the rhythm is irregular, which is what often leads clinicians to think of atrial fibrillation at a quick glance.

In contrast, true atrial fibrillation usually shows an irregularly irregular rhythm with no discrete P waves at all—instead you see fibrillatory waves or just an erratic baseline. Thus, the presence of multiple, distinct P-wave shapes with an irregular rhythm points to multifocal atrial tachycardia rather than atrial fibrillation.

MAT is often associated with conditions like COPD or other forms of hypoxemia and electrolyte disturbances; addressing the underlying cause and using rate control (such as calcium channel blockers, when appropriate) are standard parts of management.