Reverse-Remodeling Effects of Angiotensin II Type 1 Receptor Blocker in a Canine Atrial Fibrillation Model

BACKGROUND: The reverse-remodeling effect of angiotensin II type 1 receptor blocker (ARB) on atrial fibrillation (AF) is unclear. METHODS AND RESULTS: Sustained AF was induced in 20 dogs by 4-week rapid atrial pacing. The AF duration, atrial effective refractory period (AERP) and intra-atrial conduction time (CT) were measured every 2 weeks. After 4-week pacing, dogs were randomly assigned to control (n=10) and ARB (olmesartan; n=10) groups. Olmesartan was administered orally (3 mg.kg(-1).day(-1)) after pacing was terminated, and continued for the 4-week recovery period. After 4-week pacing, AERP shortening, CT prolongation and AF maintenance were not significantly different between the 2 groups. During the recovery, AERP recovered to baseline in both groups. CT remained prolonged in the control group during the recovery, but recovered to baseline in the olmesartan group. The mean AF duration in the olmesartan group after 4-week-recovery was significantly shorter than that in the control group (58+/-20 vs 1,337+/-226 s, p<0.001). Olmesartan significantly decreased interstitial fibrosis compared with the control group (9+/-1% vs 15+/-1 at the right atrial appendage, p<0.001). CONCLUSION: Olmesartan has a reverse-remodeling effect on AF-induced structural changes, indicating that it may be useful for preventing AF recurrence after the termination of sustained AF.