Myocardial infarction induces a decrease in [Ca²⁺]_i transients. (A) Ejection fraction measured by echocardiography in control (white bar; n = 12) and coronary artery occlusion (PMI; red bar; n = 12)–operated mice. (B) Cardiomyocyte area expressed in square micrometers for sham (white bar; n = 14 cells from three animals) and PMI (red bar; n = 11 cells from three animals). (C) Line-scan images during field stimulation at 2 Hz of one ventricular myocyte from sham (top) or PMI (bottom) mice. (D–F) Intracellular [Ca²⁺]_i transient peak (D), decay time (E), and cell shortening (F; 34 cells from eight sham mice and 30 cells from eight PMI mice) in ventricular myocytes. Peak expressed as maximum F/F₀, where F is the fluorescence trace and F₀ is the fluorescence during the diastolic period. *, P < 0.05; **, P < 0.01; ***, P < 0.001 versus myocytes from sham mice. Error bars represent the SEM.