A. Normalized Ca2+ transient (left) and SR Ca2+ load (right) traces, recorded in confocal microscopy from WT and Epac-DKO mice. B. Mean Ca2+ transient amplitude (ΔF/F0, where F0 is diastolic fluorescence). WT (n=31), Epac1-KO (n=17), Epac2-KO (n=39) and Epac-DKO (n=45). C. Mean Ca2+ spark frequency (CaSpF) as number of sparks per 100 μm s-1. WT (n=25), Epac1-KO (n=14), Epac2-KO (n=39) and Epac-DKO (n=34). D. Mean SR Content assessed by 10 mM caffeine-induced fluorescence change (ΔF/F0). WT (n=25), Epac1-KO (n=15), Epac2-KO (n=29) and Epac-DKO (n=14). E. CaSpF normalized to SR Ca2+ load. Number of animals: 7 WT, 6 Epac2-KO, 4 Epac1-KO and 6 Epac DKO (p=NS).