It is well known that Ca2+ is mainly released from the sarcoplasmic reticulum (SR) by the ryanodine receptor 2 (RyR2) channel, but the number of RyR2 channels in patients with chronic AF is significantly reduced or unchanged (Tang et al., 2007; Greiser and Schotten, 2013), and it is difficult to explain why SCaEs increase in AF. The gene discussed is RYR2; the disease is atrial fibrillation.