Which rhythm is defined by multifocal atrial activity with rate >100 bpm?

• A. Multifocal Atrial Tachycardia
• B. Wandering Atrial Pacemaker
• C. Atrial Fibrillation
• D. Atrial Flutter

Answer: (A)

Recognizing a rhythm with multifocal atrial activity at a rate over 100 bpm. In this pattern, the atria are being paced by several different foci, which creates at least three distinct P-wave morphologies on the ECG. The irregular rhythm and the slowed or varied PR intervals accompany these multiple atrial origins, and when the rate exceeds 100 beats per minute, it is termed Multifocal Atrial Tachycardia.

This distinguishes it from wandering atrial pacemaker, which can show multiple P-wave shapes as well but does so at a rate that is 100 bpm or slower; the tachycardic version specifically qualifies as MAT. It also differs from atrial fibrillation, where P waves are absent and the baseline is chaotic with an irregularly irregular rhythm. Atrial flutter shows a different pattern altogether—sawtooth flutter waves with a more regular rhythm and typically a consistent conduction ratio, rather than the varied P waves from multiple atrial foci.