Right free-wall accessory pathway with branched atrial insertions: Clinical, electrocardiographic, and electrophysiological characteristics

Background Right free-wall (RFW) accessory pathway (AP) with branched atrial insertions is a rare, underrecognized AP that may be associated with initial ablation failure. Objective The purpose of this study was to investigate the clinical and electrophysiological characteristics of this AP. Methods From January 2011 to March 2018, 10 patients identified with branched RFW-AP were enrolled in this study, and 30 consecutive patients with conventional RFW-APs served as control group. Right atrium (RA) was activation-mapped and 3-dimensionally reconstructed during AP-mediated orthodromic tachycardia or right ventricular pacing. Atrial insertions were defined as the earliest breakout sites, and their relationship with the tricuspid annulus (TA) were described and analyzed. Results An average of 3 separate atrial insertions on the atrial side were documented among these 10 cases (5 female and 5 male; mean age 38.0 ± 13.9 years). All atrial insertions were away from the TA. The nearest atrial insertions averaged 15.9 ± 3.4 mm away from the TA, and the farthest atrial insertions were 22.6 ± 5.7 mm away from the TA. Anterograde and retrograde AP conduction remained unaffected after ablation of the first earliest breakout site but were eliminated by ablating all insertions after an average of 2.5 (range 2–2.5) remaps, 3 sites of ablation (range 2.5–4.5), 21 (range 15.5–37.8) radiofrequency applications, and 659.5 (range 464.3–1144.3) seconds of radiofrequency ablation duration. After 12-month follow-up, no patients reported AP conduction recovery or recurrent tachycardia. Conclusion RFW-AP with branched atrial insertions is an atypical AP variant and featured by >1 distinct atrial insertions on atrial side. Stepwise ablation rather than single focal ablation is required to eliminate all retrograde conduction.