Abstract 13102: Brain Angiotensin II Type1 Receptor Blockade Ameliorates the Development of Atrial Fibrillation via Sympathoinhibition Independent of Depressor Response in Hypertensive Rats
Background: Previous studies demonstrated that the pathophysiology of atrial fibrillation (AF) with hypertension is associated with sympathoexcitation or the renin-angiotensin system. Conventional therapies, however, do not sufficiently prevent the development of AF. We reported that sympathoexcitation via brain angiotensin type1 receptors (AT1R) plays an important role in hypertension. Here we examined the hypothesis that brain AT1R-induced sympathoexcitation contributes to the development of AF in hypertension.
Methods and Results: Sixteen-week-old male stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar Kyoto rats (WKY) were divided into 4 groups and administered treatment for 2 weeks, as follows: 1) SHRSP treated with intracerebroventricular infusion (ICV) of vehicle, S-VEH; 2) SHRSP treated with ICV of the AT1R blocker, losartan (1 mg/kg/day), S-LOS; 3) SHRSP treated with oral administration of hydralazine (100 mg/L in drinking water), S-HYD; 4) WKY treated with ICV of vehicle, W-VEH. Systolic blood pressure was significantly lower in both S-LOS and S-HYD than in S-VEH (201.0±1.7 and 172.4±4.0 vs. 233.0±3.5 mmHg, n=7-8/group, respectively, P<0.05). Urinary norepinephrine excretion for 24 hours as an indicator of sympathoexcitation was significantly reduced in S-LOS, but increased in S-HYD despite the larger depressor response. The induction rates of AF by transesophageal burst pacing were higher in S-VEH and S-HYD than in S-LOS and W-VEH (96±2% and 92±4% vs. 74±6% and 71±9%, n=7-8/group, respectively, p<0.05). AF duration was markedly inhibited in S-LOS, but not in S-HYD (Figure). Interstitial atrial fibrosis and echocardiographic parameters did not differ among SHRSP groups.
Conclusions: Blockade of brain AT1R lowered the inducibility and sustainability of AF via sympathoinhibition independent of depressor response in hypertensive rats. We conclude that brain AT1R is a potential target of treatment for AF with hypertension.
Author Disclosures: T. Nagayama: None. Y. Hirooka: None. T. Kishi: None. Y. Mukai: None. S. Inoue: None. A. Chishaki: None. K. Sunagawa: None.
- © 2014 by American Heart Association, Inc.