Focal atrial fibrillation presenting in the origin of atrial tachycardia

Introduction The preferential origin of atrial tachycardia (AT) is generally associated with specific anatomical atrial structures such as crista terminalis, tricuspid annulus, mitral annulus, and pulmonary veins. There are 3 major mechanisms of focal AT: enhanced automaticity, triggered activity, and microreentry. Focal AT can be eliminated via radiofrequency ablation with fairly good long-term outcomes. In previous reports, atrial fibrillation (AF) with pseudo–atrial flutter had been presented; in those cases, the organized flutter rhythms were mostly confined far from AF origins. In our cases, we successfully entrained the narrow complex tachycardia. Fractionated potentials were present in the electrogram at the earliest tachycardia activation localized to a small area (0.25 cm), which suggested a mechanism of focal AF. Radiofrequency ablation at the earliest activation sites with fractionated potentials terminated the focal AF and AT. The objective of this case report was to demonstrate the underlying mechanisms of AT as a manifestation of focal AF.