Electrophysiological identification of superior vena cava: Novel insight into slow conduction or conduction block

Introduction: It has not been clarified how to identify the electrophysiological junction between right atrium (RA) and superior vena cava (SVC). The aim of this study was to identify the electrophysiological RA–SVC junction according to slow conduction or conduction bock and to examine the electrophysiological SVC isolation procedure. Methods: Seventy-three consecutive atrial fibrillation patients who underwent SVC mapping using a CARTO 3 system were enrolled in this study. Slow conduction or conduction block between the RA and SVC was identified by adjusting the lower threshold criteria of the early meets late function and was described as a white line. The SVC isolation was performed along the white line and with pacing maneuvers to confirm direct SVC capture. Results: Activation mapping (1296 ± 631 points) was obtained in 66 patients (90%) in 4.6 ± 1.8 min. Slow conduction or conduction block was observed in all patients. The threshold for detecting slow conduction or conduction block was 24 ± 8 ms. The location of the electrophysiological RA–SVC junction was higher in the anterior portion (anterior-septal, anterior, and anterior-lateral) than in the posterior portion (posterior-septal, posterior, and posterior-lateral) (−2.3 ± 6.2 mm vs. 7.1 ± 6.3 mm, p <.001). The SVC isolation at the electrophysiological RA–SVC junction was successful in all patients without any injury to the sinus node function. Asymptomatic phrenic nerve injury was observed in three patients (4.5%). Conclusion: In all patients, the electrophysiological RA–SVC junction determined by slow conduction or conduction block was identified and the electrophysiological SVC isolation was performed successfully and safely.