High-density mapping of atrial fibrillation in a chronic substrate: evidence for distinct modes of repetitive wavefront propagation

Background Temporal dynamics of electrical wave propagation during AF is unknown. There are reports of transient linking of atrial activation. We aim to characterize temporal dynamics of wave propagation patterns during AF in an established chronically remodeled substrate. Methods Bi-atrial epicardial mapping of AF (mean duration 62 ± 61 s) was performed in 13 sheep with induced hypertension using custom-designed plaques. Wave propagation patterns were classified into periods of repetitive activity termed modes. Results In total, we identified 9241 distinct depolarization events which were classified as: passing wave (69% occurrence, 68.6% of total time), point source (20.4%, 13.1%), wave collision (4%, 2.8%), re-entrant wave (0.7%, 6.3%), half-rotation (2.9%, 4.4%), wave splitting (2.7%, 4.3%), conduction block (0.05%, 0.03%) and figure of eight reentry (0.05%, 0.05%). Episodes of re-entrant activity had mean length 701 ± 1012 ms. A total of 435 modes of distinct periods of repetitive activity were detected (121 in LA and 314 in RA). Looking at temporal changes between modes, we found a preferential transition: change between train of waves propagating from direction of coronary sinus and reentrant activity. High density mapping of the hypertensive fibrillating atria observed 20% point sources and 0.7% of reentrant activation which may have served as drivers of AF. Remaining activations were peripheral waves. Majority of the activation was organized into events of transient linking with existence of preferential types of transitions. Conclusions These findings support the importance of substrate based regions of anatomically or functionally determined preferential conduction in the maintenance of AF.