Abstract 2644: High Prevalence of a Novel Conduction Pattern Around the Coronary Sinus in Cavotricuspid Isthmus Dependent Right Atrial Flutter

Objective : We tested our hypothesis that, in atrial flutter (AFL) dependent on the cavotricuspid isthmus (CTI), lower loop reentry (LLR) is the common pathway route at the coronary sinus (CS) posterior site, and thus, dual loop reentry (DLR) is a common circular pattern. Methods and result s: We studied 25 patients with CTI-dependent AFL, 16 with chronic counterclockwise atrial flutter (CCW-AFL) and 9 with clockwise atrial flutter (CW-AFL) and determined the precise reentry circuitry, especially for conduction patterns around the CS orifice, using electroanatomical mapping. We measured post pacing interval and tachycardia cycle length during entrainment from sites within the flutter circuit. In 16 of the 25 CCW-AFL patients, the CS anterior pacing site was within the AFL circuit in 13. The CS anterior pacing site was within the AFL circuit in 6 of the 9 CW-AFL patients. In 8 each of 16 CCW-AFL and 9 CW-AFL patients, both the CS anterior and posterior sites were within the AFL circuit. Results of 3-Dimensional (3D) activation mapping suggest that all of these patients had a DLR circuit, and that CS posterior conduction broke through the eustachian valve/ridge. Conclusion : CS posterior conduction consisted of the flutter circuit and appeared to be critical for maintaining AFL. Almost all AFL patients had DLR formed within the LLR or the superior RA circuit constituted from CS posterior conduction and in the anterior loop around the tricuspid annulus.