Abstract 10531: Dynamic Slowing of Left Atrial Conduction Precedes Initiation of Human Atrial Fibrillation
Introduction Conduction slowing is essential for reentry, but its behavior and relationship to atrial fibrillation (AF) within the human atria are unknown. We hypothesized left atrial (LA) conduction slows with rate prior to AF onset, and mostly on the posterior wall.
Methods In 23 AF patients (62±12 years; LA size 43±5mm; persistent n=11) and 3 controls (LA size 41±8mm), we recorded from a 64-pole LA basket catheter (Constellation, Boston Scientific) while pacing at the right superior pulmonary vein at 500 ms, 450, 400, 380, …, 300, 290, … to AF onset. Contour maps of atrial activation (isochrones) were created at each rate en route to AF (figure).
Results Activation times (AT) were calculated at 5288 sites (203±147 /patient). At CL 500 ms, LA AT (= latest - earliest site) did not differ for controls and AF patients (72±26 ms vs. 50±20 ms, p=0.09). Activation maps showed isochronal crowding (slowing) in a cranial-caudal direction in 20 patients (AF n=18, controls n=2) and septal-lateral in 6 patients (AF n=5). Rate acceleration further slowed conduction in 19/23 AF patients but 1/3 controls (p<0.01), and in 3 patterns: (a) steep (abrupt slowing just prior to AF onset, fig A); (b) broad (progressive slowing with rate, fig B); (c) flat. Dynamic slowing arose in the posterior LA in 9 patients and at the mitral annulus in 21 patients.
Conclusions Atrial conduction slows dynamically prior to AF initiation in AF patients but less dramatically in controls. Dynamic slowing occurred in abrupt (steep) and progressive (broad) patterns. Unexpectedly, slowing was more common at the mitral annulus than in the posterior LA. Studies should examine the contribution of conduction dynamics to human AF initiation.
- © 2011 by American Heart Association, Inc.