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.