Atrial tachycardia is a type of heart rhythm problem in which the heart's electrical impulse comes from an ectopic pacemaker (that is, an abnormally located cardiac pacemaker) in the upper chambers (atria) of the heart, rather than from the sinoatrial node, the normal origin of the heart's electrical activity. Atrial tachycardias can exhibit very regular (consistent) heart rates ranging typically from 140 to 220 beats per minute.
As with any other form of tachycardia (rapid heart beat), the underlying mechanism can be either the rapid discharge of an abnormal focus, the presence of a ring of cardiac tissue that gives rise to a circle movement (reentry), or a triggered rapid rhythm due to other pathological circumstances (as would be the case with some drug toxicities, such as digoxin toxicity). Atrial tachycardia is a risk factor for atrial fibrillation, as the rapid rhythm can trigger or degrade into the lack of a rhythm. All atrial tachycardias are by definition supraventricular tachycardias.
Forms of atrial tachycardia (ATach) include multifocal atrial tachycardia (MAT), ectopic atrial tachycardia (EAT), unifocal atrial tachycardia (UAT), and paroxysmal atrial tachycardia (PAT). The taxonomy varies somewhat between users (regarding names that mean the same versus those that label subsets). The codification of the terms "first detected", "paroxysmal", "persistent", and "permanent" in the classification of atrial fibrillation should be compared for reference.