Role of a novel conduction pattern around the coronary sinus in cavotricuspid isthmus dependent right atrial flutter.

Objectives: We tested our hypothesis that, in atrial flutter (AFL) dependent on the cavotricuspid isthmus (CTI), lower loop reentry is the common pathway route at the coronary sinus posterior site, and thus, dual loop reentry is a common circular pattern.

Methods And Results: 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 coronary sinus orifice, using electroanatomical mapping. We measured post pacing interval and tachycardia cycle length during entrainment from sites within the flutter circuit. The coronary sinus anterior pacing site was within the AFL circuit in 16 of the 25 CCW-AFL patients, and in 6 of the 9 CW-AFL patients. Both the coronary sinus anterior and posterior sites were within the AFL circuit in 8 of 16 CCW-AFL and 8 of the 9 CW-AFL patients. Results of 3-dimensional activation mapping suggest that all of these patients have a dual loop reentry circuit, and that coronary sinus posterior conduction broke through the eustachian valve/ridge.

Conclusions: Coronary sinus posterior conduction consisted of the flutter circuit and appeared to be critical for maintaining AFL.