A, Representative traces of Ca2+-spark (Fluo-4) recordings in WT and S2814D myocytes in absence and presence of KN-93 (10-μmol/L). B, Mean±SEM Ca2+-spark frequency (CaSF). Numbers indicate myocytes from at least 3 mice in each group. *P<0.05 and **P<0.01 vs. WT. C, Surface L1-ECG and intracardiac atrial electrogram showing P-wave absence and irregular RR-intervals in S2814D mice following atrial-burst pacing (right), suggestive of AF. WT-mice typically reverted to sinus rhythm immediately following atrial pacing (left). D,E Bar graphs summarizing the incidence of reproducible AF in WT, S2814D-control mice and S2814D-mice treated with KN-93 (10-μmol/kg, i.p.). Numbers indicate mice.