Cavo-tricuspid Isthmus-Dependent Atrial Flutter

Abstract

Cavo-tricuspid isthmus (CTI)-dependent atrial flutter (AFL) is the most frequently encountered right atrial (RA) macroreentrant tachycardia. The electrophysiologic substrate underlying AFL has been shown to be a combination of a slow conduction velocity in the CTI between the tricuspid annulus (TA) and inferior vena cava (IVC) [1], and anatomic or functional conduction block along the crista terminalis and Eustachian ridge. These electrophysiologic characteristics enable sustainable macrooreentrant tachycardias around the tricuspid valve. The triggers of AFL might be premature atrial contractions and/or atrial fibrillation (AF). Both clockwise (reverse typical or uncommon) and counterclockwise (typical or common) CTI-dependent AFL can occur, and counterclockwise AFL is the most commonly encountered in clinical practice presumably because the majority of triggers come from the left atrium (LA) and pulmonary veins (PVs). AFL is refractory to medical therapy and has now become routinely amenable to curative treatment by catheter ablation [2, 3]. Radiofrequency (RF) catheter ablation of the CTI is considered a first-line therapy for treating CTI-dependent AFL. This chapter focuses on the practical points for catheter ablation of CTI-dependent AFL.