Extracardiac structures are frequently present within close proximity to the left atrium: Relevance to catheter ablation.

Background: The coronary sinus (CS) including the great cardiac vein is an important anatomic structure that is considered a landmark for the mitral annulus (MA) and also a target for catheter ablation.

Objective: This study evaluated the anatomical relationship between the CS and its surrounding structures visualized by multi-detector computed tomography (MDCT).

Methods: We performed MDCT on 42 patients, and the ranges of the coronary arteries (CAs) and esophagus that ran closest (<5 mm) to the CS were examined. In addition, the distances between the CS and the MA and left ventricle and left atrium were compared with the amplitudes of the local atrial and ventricular electrograms in the CS at the most lateral point (3 o'clock) and the inferior point (6 o'clock) in the CS.

Results: The distal portion of the right CA ran near the antero-inferior side of the CS ostium in 92% of the patients. The esophagus and the left circumflex CA proximity to the CS ran from 15 to 41 mm and from 53 to 104 mm from the ostium in all patients. At the 3 o'clock and 6 o'clock position of the MA, the distance between the center of the CS and MA was 12 and 13 mm, respectively, and showed negative correlation with the ratio of atrial and ventricular electrograms.

Conclusion: The right CA, the left circumflex CA, and the esophagus were frequently located near the CS. The CS was shifted away from the MA, and the CS-MA distance could be predicted with intracardiac electrograms.