Abstract 17189: Superior Vena Cava as the Substrate of Various Forms of Atrial Tachycarrhythmias: Consideration into the Mechanism and Tachycardia Circuit

Abstract

Background: The superior vena cava (SVC) is known to possess the myocardial sleeves extending from the right atrium which has been shown to be a substrate for various atrial tachyarrhythmias. However, the precise mechanisms and electrophysiologic feature of these atrial tachyarrhythmias, originating from the SVC has not been elucidated well. Objective: The purpose of this study was to define the mechanisms and electrophysiologic characteristics of atrial tachyarrhythmias originating from the SVC. Methods: In 21 patients with atrail tachycarrhythmias originating from the SVC, the mechanism and tachycardia circuit were examined by the contact or non-contact mapping system (EnSite NavX or 3000). Results: There were 5 reentrant atrial tachycardia (AT), 4 focal ATs and 12 atrial fibrillation (AF). Three reentrant ATs showed a macro-reentrant activation around the SVC sleeve with critical slow conduction zone (SCZ) in the SVC and the remaining 2 showed a localized reentry within the SVC. Four focal AT showed a focal discharge source in the SVC. In 8 of 9 ATs, SCZ or focal discharge source was observed at the area extending from the anterior to lateral portions of the SVC. All 12 AF were initiated by the repetitive discharge from SVC and was maintained by the meandering reentrant activation within the SVC involving the junction between the SVC and right atrium during AF. All 9 ATs were terminated by the radiofrequency energy delivery to the SCZ (n=4) and the focal discharge source (n=3) or isolation of SVC (n=2). All 12 AF were terminated by the circular application of radiofrequency energy delivery around the junction between SVC and right atrium, resulting in the SVC isolation in 9 patients. Conclusions: SVC provides the focal discharge source and the substrate of SCZ of AT. These critical area for maintaining AT mostly located at the antero-lateral portions of the SVC. Focal discharge source and substrate for meandering reentry within the SVC also maintained the SVC origin AF. These unique electrophysiologic characteristics of SVC provide the substrate of various forms of atrial tachycarrhythmias.