Ca²⁺ and electrophysiological homeostasis disorders in RyR2^A690E+/− cardiomyocytes. (A) Representative calcium transients (CaTs) images and corresponding CaT traces from wild-type (WT) and RyR2^A690E+/− myocytes, distinct PCTs, and Ca²⁺ oscillations induced by isoproterenol (ISO) are indicated with arrows, respectively. (B) Pie charts of the incidence of PCT and Ca²⁺ oscillations. (C) Intact cardiomyocytes were incubated in normal Tyrode solution, V_m was measured using patch clamp, and action potentials (Aps) were induced by stimulator at 1 Hz. Representative traces of APs from WT and RyR2^A690E+/− myocytes, with early afterdepolarizations (EADs), delayed afterdepolarizations (DADs), and trigger activities (TAs) indicated with arrows. (D–F) Their respective percentages in total tested cells. Data are presented as means ± standard error of the mean (SEM), analysed by χ² (and Fisher's exact) test for proportions. *P < 0.05; **P < 0.01; ***P < 0.001. RyR, ryanodine receptor.