Background: Initiation and perpetuation of atrial fibrillation (AF) are poorly understood despite recent advantages which have been made in interventional treatment procedures for patients suffering from symptomatic atrial arrhythmias. Important triggers of AF initiation are found inside the pulmonary veins (PVs), adjunctive cardiac structures like the vein of marshall or the coronary sinus as well as the left atrial (LA) posterior wall or the left atrial appendage (LAA). Additionally, consistent rotational activity which might play a role in maintenance of AF waves has been investigated in earlier studies. The exact role of the LAA as origin of focal sources and as a localization of consistent rotational activity is not known until today.

Panoramic mapping via multielectrode catheters and the use of advanced mapping systems allow for the detection of such localized sources and drivers for the initiation and perpetuation of AF. Recently, a new algorithm for the analysis of repetitive AF propagation has been introduced.

In this study, we investigated the use of a novel mapping software for the detection of focal sources and rotational activity (as a surrogate of AF drivers) during AF to identify electrical phenomena inside the LAA in patients undergoing AF ablation.

Methods: Consecutive patients who underwent first-time radiofrequency-based catheter ablation for symptomatic persistent AF were analysed. Patients underwent AF ablation aiming for PVI as well as substrate modification based on the individual distribution of left atrial bipolar low voltage areas (<0.5mV). Electroanatomic mapping of the LA and LAA was conducted prior and after PVI aiming for identification of localized sources and rotational activity (regions of interest, ROI) inside the LAA. Mapping was performed using a multielectrode catheter enabling high-density electroanatomic reconstruction. AF propagation maps were acquired during AF.

Results: A total of 58 patients (mean age 67.0±10.0 years, 33 male (56%), mean duration of AF prior ablation 29±24 months, mean left ventricular ejection fraction 52±6%, mean body mass index 29.4±5.2, anti-arrhythmics (class I or III) or digoxin prescription in 22.4%) were analysed. Mean procedure time (skin-to-skin) was 13:06±27:38 minutes with a mean fluoroscopy duration of 8:07±4:20 minutes and a mean of 11:26±04:25 minutes for LA mapping. During LA mapping a mean of 2192±1117 bipolar mapping points and a mean of 173±76 AF propagation points were acquired. Bipolar voltage mapping revealed low voltage areas with a mean of 7.8±14.9% from the total LAA area. AF propagation mapping prior to PVI identified ROI inside the LAA in 48 of 58 patients (82.9%): Focal sources were found in 48 patients (82.9%) and rotational activity in 7 cases (12.1%). AF propagation mapping after PVI identified focal sources in 36 cases (62.1%) and rotational activity in 3 cases (5.2%) inside the LAA. Stability over time of these mapping findings, irrespective of PVI, was found in 36 patients (36 focal sources and 3 rotational activities in 36 patients, 62.1%).

Conclusion: Focal sources and repetitive drivers are commonly revealed inside the LAA in patients undergoing catheter ablation for persistent AF using a novel algorithm for the analysis of AF propagation maps. These ROI might represent a potential arrhythmogenic substrate and should be considered as a potential target for catheter ablation in selected AF patients.