Multifocal atrial tachycardia

Multifocal (or multiform) atrial tachycardia (MAT) is an abnormal heart rhythm, specifically a type of supraventricular tachycardia, that is particularly common in older people and is associated with exacerbations of chronic obstructive pulmonary disease (COPD). Normally, the heart rate is controlled by a cluster of pacemaker cells called the sinoatrial node (SA node). When different clusters of cells known as ectopic pacemakers, that are outside the SA node take over control of the heart rate, and the rate exceeds 100 beats per minute, this is called multifocal atrial tachycardia. A fast heart rate below 100, is technically not a tachycardia and is then termed multifocal atrial rhythm, also known as wandering atrial tachycardia.

"Multiform" refers to the observation of variable P wave shapes, while "multifocal" refers to the underlying cause. Although these terms are used interchangeably, some sources prefer "multiform" since it does not presume any underlying mechanism.