Incessant Focal Atrial Tachycardia Originating From the Right Inferior Pulmonary Vein With Extremely Short Cycle Length and Variable Exit Block.

The underlying mechanism of focal atrial tachycardia (AT) is usually considered to be abnormal automaticity, typically with a cycle length (CL) exceeding 120 ms. We present a case of a 29-year-old female with recurrent symptomatic palpitations. She was referred for electrophysiologic study and catheter ablation. Twelve-lead ECG showed a sinus rhythm with incessant atrial ectopic beats and occasional aberrant conduction. P-wave morphology during ectopic revealed positive deflections in Leads I, II, aVL, aVF, and V1-V6, suggesting a left-sided origin. Intracardiac recordings obtained using a circular multipolar mapping catheter demonstrated incessant, repetitive, regular spike potentials with an extremely short CL at the posterior aspect of the right inferior pulmonary vein (RIPV). The tachycardia CL within the RIPV was approximately 70 ms and was conducted to the left atrium (LA) with variable exit block ranging from 2:1 to 4:1 conduction. Successful ablation was performed at the earliest activation and shortest CL site outside the RIPV with exit block from the RIPV to LA. The mechanism for this tachycardia is uncertain, but the very short CL suggests that a localized spiral wave re-entry may be involved.