The present invention provides medicines for treating cardiac insufficiency which contain as an active ingredient indane derivatives of formula (I) wherein R1 represents hydrogen atom, nitro group, cyano group, C1-6 alkylcarbonylamino, R2 and R3 each independently represent C1-6 alkyl group, R4 represents hydroxyl group or C1-6 alkylcarbonyloxy group or represents a bond or oxygen atom together with R5, R5 represents hydrogen atom or represents a bond or oxygen atom together with R4, R6 represents hydrogen atom, hydroxyl group or NR7R8, n means 0 or an integer of 1 to 4, X represents C═O, CH2, SO2 or NR16, Y represents NR17 when X is C═O, CH2 or SO2 and represents C═O when X is NR16, Z is absent when Y represents NR17 or represents NR18 when Y is C═O, W represents aromatic groups or lactam rings, or pharmaceutically acceptable salt thereof.