Characteristics of Localized Re-Entrant Atrial Tachycardia Involving the Coronary Sinus in the Tachycardia Circuit.

Background: Localized-re-entrant atrial tachycardias (ATs) involving the coronary sinus (CS) as a critical part of the circuit (CS-ATs) remain poorly characterized.

Objectives: The goal of this study was to determine the prevalence, clinical characteristics, and electrophysiological properties of CS-ATs.

Methods: CS-ATs were identified in a cohort of 545 consecutive patients with 775 ATs mapped by using a high-density mapping system.

Results: Eight CS-ATs (1.0% of all ATs; 95% CI: 0.5%-2.0%) were identified in 8 patients (1.5% of all patients; 95% CI: 0.7%-2.9%). All had prior ablation in the inferior septum, bottom wall of the left atrium (LA), or CS, resulting in scar formation in either the inferior septum or bottom wall in 6 patients (75%). The mean tachycardia cycle length was 299 ± 70 milliseconds. The CS segment involved in the tachycardia circuit measured 28 ± 11 mm in length, with a conduction time of 58 ± 31 milliseconds (21% ± 13% of tachycardia cycle length). All CS-ATs exhibited a centrifugal activation pattern originating from the inferior part of the LA. CS-ATs were correctly diagnosed in only 2 patients. Ablation targeting the LA-CS connection successfully terminated CS-AT in 4 patients, and ethanol infusion into the vein of Marshall was required in 3 patients. CS-AT could not be terminated in 1 patient because of an inappropriate ablation strategy.

Conclusions: CS-ATs are a rare cause of AT, typically occurring after ablation in the inferior part of the LA or CS. Diagnosing CS-ATs can be challenging. Ablation targeting the LA-CS connection is effective, and ethanol infusion into the vein of Marshall is a viable therapeutic option.