Preventive Effects of the Angiotensin-II Receptor Blocker on Atrial Remodeling in an Ischemic Heart Failure Model of Rats

Background and Objectives: It is widely known that angiotensin-II receptor blockers (ARBs) have reverse remodeling effects in atrium. Although atrial fibrillation is frequent in ischemic heart failure clinically, experiments to demonstrate ARB's effects on atrial remodeling in a heart failure model are rare. Materials and Methods: A heart failure model and a sham-operated group were formed in 25 Sprague-Dawley male rats of roughly 260 g in weight. Ischemic heart failure models were obtained via ligation of the left anterior descending coronary artery. In the ARB group, 30 mg/kg of losartan was administrated over a day for 4 weeks. Echocardiography was performed to measure left ventricle ejection fraction and left atrial diameter (LAD) at the baseline and 4 weeks after the operation. 4 weeks later, histologic and immunohistochemical evaluation were performed. Results: Groups were divided into the sham group, heart failure group, and heart failure-ARB group. We maintained 5 rats in each group for 4 weeks after operation. The decrease of left ventricular ejection fraction in the heart failure-ARB group was less than that in the heart failure group (p=0.023). The increase of LAD in the heart failure-ARB group was less than that in the heart failure group (p=0.025). Masson's trichrome stain revealed less fibrosis in the heart failure-ARB group. Immunohistochemical stain and western blot for connexin 43 showed less expression in the heart failure-ARB group. Conclusion: In the ischemic heart failure model of rats, structurally and histologically, the ARB, losartan, has atrial reverse-remodeling effects. However, electrically, its role as an electrical stabilizer should be studied further.