Atrial tachycardia is an umbrella term for an abnormal heart rhythm, specifically a subtype of Supraventricular tachycardia, in which the heart's electrical impulse begins in the upper chambers (atria), rather than from the sinoatrial node, which is the normal origin of the heart's electrical activity. As with any other form of tachycardia, the underlying mechanism can be from various triggers such as 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, i.e. digoxin toxicity or Adverse drug reaction.