Inadvertent electrical isolation of the left atrial appendage during catheter ablation of persistent atrial fibrillation

Background: Left atrial appendage (LAA) isolation is rare and may be associated with impaired transport function and thromboembolism. Objective: The purpose of this study was to determine the mechanisms of inadvertent isolation of the LAA during atrial fibrillation (AF) ablation. Methods: This study consisted of 11 patients (ejection fraction 0.43 ± 0.18, left atrial diameter 51 ± 8 mm) with persistent AF who had LAA conduction block during a procedure for AF (n = 8) or atrial tachycardia (AT) (n = 3). Results: LAA conduction block occurred during ablation at the Bachmann bundle region in 6 patients, mitral isthmus in 3, LAA base in 2, and coronary sinus in 1. The mean distance from the ablation site to the LAA base was 5.0 ± 1.9 cm. LAA isolation was transient in all 6 patients in whom LAA conduction was monitored and was permanent in the 4 patients in whom conduction was not monitored during energy delivery. The remaining patient was noted to have LAA isolation during a redo procedure before any ablation. Nine of (82%) the 11 patients have remained arrhythmia-free without antiarrhythmic drugs at mean follow-up of 6 ± 7 months, and all have continued taking warfarin. Conclusion: Electrical isolation of the LAA may occur during ablation of persistent AF and AT even when the ablation site is remote from the LAA. This likely is due to disruption of the Bachmann bundle and its leftward extension, which courses along the anterior left atrium and bifurcates to surround the LAA. Monitoring of LAA conduction during ablation of persistent AF or AT is important in avoiding permanent LAA isolation.