Multifocal atrial tachycardia — or MAT — is a rhythm that frequently occurs in the setting of severe lung disease. MAT is characterized by three different P-wave morphologies within one 10-second 12-lead ECG at a heart rate > 100 beats per minute. This indicates multiple irritable foci generating atrial electrical activity.
This rhythm is benign, and once the underlying lung disease is treated it should resolve. If rate control is needed, the historical treatment (without much evidence to support it) has been verapamil. There is no thromboembolism risk in MAT such is seen in atrial fibrillation/flutter, since the atrium are contractile in MAT. If the heart rate is < 100 beats per minute, then the rhythm is called wandering atrial pacemaker (WAP).
The differential diagnosis of an irregularly irregular rhythm includes atrial fibrillation, atrial flutter with variable conduction and multifocal atrial tachycardia or wandering atrial pacemaker.
Irregularly Irregular Rhythms