23-30: Multifocal Atrial Tachycardia

ECG Findings

• Irregularly irregular narrow-complex tachycardia at a rate > 100 bpm

• Multiple P-wave morphologies, with at least three distinct P-wave morphologies in the same lead

• Varying PP, PR, and RR intervals

Pearls

1. Multiple atrial foci are capable of acting as pacemakers. When irritated by stretching, medications, or certain acute medical conditions, these foci compete in pacing the atria.

2. The different atrial foci produce P waves of different morphologies.

3. Since the atrial foci vary in distance to the AV node, PR intervals vary.

4. Multifocal atrial tachycardia (MAT) usually results from exacerbation of another condition that produces distention or irritation of the atria. The most common cause of MAT is chronic obstructive pulmonary disease (COPD) exacerbation. Treatment of the underlying condition should correct the arrhythmia.

5. Even though MAT itself is not usually fatal, it is a poor prognostic sign.