atrial tachycardia [L, atrium, hall; Gk, tachys, quick, kardia, heart] , rapid beating of the atria caused by abnormal automaticity, triggered activity, or intraatrial reentry. The atrial rate is usually less than 200/min; however, in cases of digitalis excess, the rate increases gradually to 130/min to 250/min as the digitalis is continued. When there is 2:1 conduction, the atrial rhythm is irregular in 50% of cases. The contour of the P waves is different from that of the sinus P wave except in cases of digitalis-induced atrial tachycardia, when the P wave is almost identical to the sinus P wave. Vagal maneuvers have no effect on atrial tachycardia, although they do cause atrioventricular block. Atrial tachycardia may be either nonparoxysmal (common) or paroxysmal (uncommon). Also called auricular tachycardia.
