Multifocal atrial tachycardia is a tachycardic version of wandering atrial pacemaker in which the atrial rate is greater than 100 beats per minute. Multifocal atrial tachycardia occurs when multiple areas, or ectopic foci, within the atrium generate consecutive action potentials that are all conducted to the ventricles.
Thus, each QRS complex will be preceded by a P wave; however, each P wave will have a different morphology because they originate from different areas. By definition, multifocal atrial tachycardia must have at least three distinctly different P wave morphologies and a ventricular rate of greater than 100 beats per minute.
Multifocal atrial tachycardia frequently occurs in the setting of severe lung disease and, more specifically, during an exacerbation of lung disease. 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 as seen in atrial fibrillation or atrial flutter, as the atrium are contractile in MAT. If the heart rate is less than 100 beats per minute, then the rhythm is wandering atrial pacemaker, or WAP.
The differential diagnosis of an irregularly irregular rhythm includes atrial fibrillation, atrial flutter with variable conduction and MAT or WAP.
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