Atrial tachycardia (AT) is a regular atrial rhythm at a constant rate of >100 beats per min originating outside of the sinus node (waveform 1) . Focal ATs arise from a single site within the left or right atrium, in contrast to macroreentrant atrial arrhythmias (eg, atrial flutter) and atrial fibrillation, which involve multiple sites or larger circuits.
In the past, focal ATs were considered to be due predominantly to enhanced automaticity. Thus, they were often referred to as automatic ATs. However, the more inclusive term focal AT is preferred, as this encompasses automatic, triggered, and microreentrant etiologies that cannot be distinguished easily on the surface electrocardiogram.
Focal ATs are usually paroxysmal and self-limited, although in some patients, focal AT may be present nearly continuously (ie, incessant AT). Incessant AT is important as it may be associated with left ventricular dysfunction . (See "Tachycardia-mediated cardiomyopathy", section on 'Atrial tachycardia'.)
The characteristics and management of the common, repetitive forms of focal AT are discussed here. Macroreentrant atrial arrhythmias (eg, atrial flutter), atrial fibrillation, and other forms of supraventricular tachycardia are discussed in detail separately. (See "Overview of atrial flutter" and "Overview of atrial fibrillation" and "Clinical manifestations, diagnosis, and evaluation of narrow QRS complex tachycardias".)
Definition — In 2001, the Joint Expert Group from the Working Group of Arrhythmias of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology (now called the Heart Rhythm Society) classified regular ATs according to electrophysiologic mechanisms and anatomy . The Joint Expert Group defined focal AT as "being characterized by atrial activation starting rhythmically at a small area (focus) from where it spreads centrifugally." This definition indicates that the arrhythmia arises from an area that is smaller than would be required for classical macroreentry, which conventionally is considered to be a circuit greater than 2 cm in diameter.