A pharmaceutical composition comprising (S)-methyl-3-[4-(2-hydroxy-3-isopropylamino)propoxy]phenylpropionate in a concentration between about 75 mM and about 150 mM, which is substantially free of the R-isomer or pharmaceutically acceptable salt thereof, is provided. A method of treating a cardiac disorder is also provided and includes administering to a subject in need thereof a therapeutically effective amount of a pharmaceutical composition comprising (S)-methyl-3-[4-(2-hydroxy-3-isopropylamino)propoxy]phenylpropionate hydrochloride, wherein the (S)-methyl-3-[4-(2-hydroxy-3-isopropylamino)propoxy]phenylpropionate hydrochloride is present at a concentration between about 75 mM and about 150 mM and wherein the pharmaceutical composition is substantially free of (R)-methyl-3-[4-(2-hydroxy-3-isopropylamino)propoxy]phenylpropionate or pharmaceutically acceptable salt thereof.