Mechanisms responsible for the initiation and maintenance of atrial fibrillation assessed by non-contact mapping system

Background: This study is aimed to assess the initiation and maintenance mechanisms of atrial fibrillation (AF) and their relationships with the anatomical structures of the left atrium (LA) and pulmonary veins (PVs). Methods: Thirty-seven patients (pts; 33 men, mean age 50 ± 12, range 25-68 years) with paroxysmal AF (n = 29) and persistent AF (n = 8) who underwent mapping of the LA and PV using 3D non-contact endocardial mapping system (EnSite 3000) were included. Atrial premature complexes (APCs) which triggered the initiation of AF lasted longer than 1 min were mapped and the activation sequence on isopotential color maps was analyzed. Results: Wave front dynamics and the relationship with the underlying anatomical structures were assessed. APCs from PV were related to the initiation of AF, but not to the maintenance of AF in 59.5% of the pts (focally triggered type) whereas APCs from PV not only initiated AF but also maintained AF without continuous triggering in 27% (focally driven type). Mixed type and indeterminate type of AF was in 4.5% and 13.5%, respectively. During AF, the mean number of wavelet was 1.45 (maximum 3 in 76.5%). Anatomical structures showing frequent wave break and slow conduction were mostly located at the septopulmonary bundle (86.5%) and the posterior LA roof between left superior PV and right superior PV (54.1%). Conclusion: Focal repetitive activity from PV played an important role in both initiation and maintenance of AF using NCM study. Specific anatomical structures such as septopulmonary bundle or posterior LA roof were associated with the spontaneous wave break and heterogeneous conduction delay, which was also appears to be important in the maintenance of AF.