Abstract 13765: Repeated Paroxysmal Atrial Fibrillation Episodes Remodel Ionic Currents and Promote Atrial Fibrillation in Dogs
Introduction: AF usually starts in a paroxysmal form (pAF), then progresses to persistent and finally permanent AF. Persistent AF is known to remodel the atria, promoting AF, but whether recurrent pAF episodes cause remodeling that can lead to AF progression is unknown. This study examined remodeling due to repeated electrically induced pAF epsiodes.
Methods: We compared dogs with once-daily pAF episodes (AF maintained with 600 bpm atrial pacing 3 hours/day X 28 days, n=13) to sham dogs (n=10). In vivo EP and echocardiography, and patch clamp recording/calcium transient measurement (Indo-1) in isolated LA myocytes, were used to study structural and electrical remodeling 24 hrs after the last pAF episode. A positive remodeling-control was obtained with continuous AF (cAF, 600 bpm X 7 days) maintained up until in vivo study.
Results: After a single pAF episode, AERP shortened ~8 ms with full subsequent recovery (half-time ~40 mins). Nevertheless, repeated daily pAF significantly increased AF duration and reduced AERP at terminal study (Table). pAF caused substantial ionic remodeling, significantly decreasing ICaL and Ito, and increasing IK1 and NCX current. pAF also caused mild but significant structural remodeling, dilating LA (from 2.5±0.1 to 2.8±0.1 cm, p<0.05) without changing LVEF. Diastolic/systolic [Ca2+] levels and [Ca2+] transient amplitude were unaltered by pAF, but [Ca2+] decay time and cardiomyocyte shortening were decreased, and triggered activity was enhanced. The effects of pAF were qualitatively similar to cAF but quantitatively smaller; except for LVEF (reduced from 52±3 to 43±3%, p<0.05) and [Ca2+] transients, which were only affected by cAF.
Conclusions: Repeated pAF episodes cause persistent structural and electrical remodeling, and promote AF. These results show for the first time that nonsustained AF episodes remodel atrial structural/ion current properties and emphasize the importance of reducing AF burden in preventing AF progression.
- © 2013 by American Heart Association, Inc.