Atrial tachycardia is a type of heart rhythm problem in which the heart's electrical impulse comes from an ectopic 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, 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. 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.