A method for treating severe heart failure, comprising administering to a patient an effective amount of a benzazepine compound (1): wherein R1 is H or halogen, R2 is OH, or —NR5R6 (R5 and R6 are H or lower alkyl, R3 is H, halogen, lower alkyl, or lower alkoxy, R4 is halogen, lower alkyl or lower alkoxy, or a salt thereof, and a pharmaceutical composition containing the benzazepine compound (1) or a salt thereof and use of the compound (1) or a salt thereof for preparing a medicament for treatment of severe heart failure.