Epicardial Ca²⁺ waves at the onset of reperfusion are fragmented into non-propagated events in SDKO hearts. (A and B) Protocol and typical examples of line scan recordings of epicardial Ca²⁺ waves obtained at the beginning of reperfusion in intact WT and SDKO hearts. (C) Frequency of Ca²⁺ waves and mini-waves during pre-ischaemia and at the beginning of reperfusion in WT and SDKO hearts. (D) Protocol and typical recordings of line scan before and after the addition of the SERCA2a inhibitor CPA in SDKO hearts. Red arrows in B and D indicate fragmented SR Ca² waves. One-way ANOVA followed by Tukey’s post hoc test, was used to compare different groups. A P-value <0.05 was considered significant. *P < 0.05 vs. WT mice, ^#P < 0.05 vs. pre-ischaemia. Data are obtained from five WT and five SDKO hearts.