Atrial fibroblast-derived exosomal miR-21 upregulate myocardial KCa3.1 via the PI3K-Akt pathway during rapid pacing oleh Fu Yuntao, Liang Jinjun, Liu Hua Fen, Chen Huiyu, Liu Dishiwen, Cao Zhen, Youcheng Wang, Xuewen Wang, Yuanjia Ke, Cheng Yanni, Guo Kexin, Peng Zhibin, Yang Mei, Qingyan Zhao