A, Whole-cell patch-clamp and confocal imaging were used to measure ICa density (upper), Ca2+ transients (middle) and cell shortening (lower). B, ICa density and amplitude of Ca2+ transients were compared among sham (14 cells), NC (19 cells) and antagomir (18 cells) groups. C, Gain of E-C coupling calculated as the amplitude of Ca2+ transient per unit ICa density. D, Fractional shortening of cardiomyocytes measured by cell edge-detection of Ca2+ transients at 0 mV. *P <0.05 and **P <0.01 vs. sham; #P <0.05 vs. NC.