SLC8A1 and heart failure: During relaxation, Ca2+ is immediately transported into the SR via Serca2a and extruded by the sarcolemmal Ncx1. 50 Heart failure is associated with reduced Serca2a expression51–53 and increased Ncx1 expression,54–56 which has been shown to contribute to both contractile dysfunction and arrhythmogenesis.54 Our data suggests a beneficial effect of miR‐1 gene transfer in Ca2+ homeostasis by directly modulating Ncx1 expression levels.