Multifocal atrial tachycardia is defined by an irregularly irregular supraventricular tachycardia at a rate greater than 100 beats per minute with more than 2 different P wave morphologies. A P wave precedes each QRS. This arrhythmia is due to multiple premature automatic foci and typically occurs in the setting of severe respiratory failure. This must be differentiated from atrial fibrillation. As with atrial fibrillation, aberrant conduction is common. The following animation illustrates what we have just described.