Aldosterone Robustly Promotes Atrial Fibrillation in the Presence of Chronic Volume Overload in Rats

We investigated the modulatory effects of aldosterone on atrial remodeling induced by an abdominal aorto-venocaval shunt (AVS) in rats, as patients with primary hyperaldosteronism are suggested to have a higher risk of developing atrial fibrillation (AF). The rats were divided into four groups based on the basis of whether they underwent AVS surgery, received aldosterone using an intraperitoneally implanted osmotic minipump, or both. Aldosterone was started at 0.5 µg/h during the AVS surgery, and morphological and electrophysiological assessments were performed four weeks after AVS creation. The atrial structural changes induced by AVS, including atrial cell hypertrophy and fibrosis, were not modulated by aldosterone, whereas P-wave duration was longer in aldosterone-treated AVS rats than in non-treated rats. Although the average AF duration induced by burst pacing was 10-25 s in the untreated, aldosterone-treated, and AVS rats, the AF duration was approximately 100 s in the aldosterone-treated AVS rats. Meanwhile, there was no significant difference in the atrial effective refractory period among the four experimental groups. Notably, premature atrial contractions (PAC) were frequently observed in aldosterone-treated sham rats, while paroxysmal AF, in addition to PAC, was detected in aldosterone-treated AVS rats, which was not induced in non-treated AVS rats. These findings suggest that aldosterone robustly promotes AF, particularly in the presence of chronic volume overload.