Introduction
Atrial tachycardia (AT) is a regular supraventricular tachycardia originating in the atria and away from the sinus node.[1] Focal ATs arise from a single site within the left or right atrium, in contrast to macro reentrant atrial arrhythmias such as atrial flutter and atrial fibrillation, which involve multiple sites or larger circuits. AT is relatively uncommon, accounting for between 5 and 15 percent of arrhythmias in adults undergoing an electrophysiology study for paroxysmal supraventricular tachycardia.[2] The incidence of AT is similar among men and women.
Warm-up and cool-down phenomena refer to an observable acceleration when transition from normal sinus rhythm to tachycardia and deceleration, when transitioning from tachycardia to a normal sinus rhythm. The presence of this suggests that enhanced automaticity is the underlying mechanism of the tachyarrhythmia.[1] We observed the cool down phenomenon and report the application of this to diagnose a case of narrow complex tachycardia.