Pyridazinyl phenyl hydrazones useful against congestive heart failure

Compounds of formula (I):

• 5
• in which
• R1 to R4 means hydrogen, alkyl, alkenyl, aryl, arylalkyl, carboxyalkyl, hydroxyalkyl or halogenalkyl, or R2 and R3 form a ring of 5-7 carbon atoms,
• R5 to R9 means hydrogen, alkyl, alkenyl, aryl, arylalkyl, acyl, hydroxy, alkoxy, alkoxycarbonyl, amino, acylamino, alkylamino, aryloxy, halogen, cyano, nitro, carboxy, alkylsulfonyl, sulfonamido or trifluoromethyl,
• wherein each aryl residue defined above by itself or as a part of another group may be substituted,
• and pharmaceutically acceptable salts and esters thereof,
• provided that a) when R1, R2, R3, R5, R6, R8 and R9 are hydrogen and R4 is methyl, R7 is not hydrogen, methoxy, cyano or methyl and b) when R1, R2, R3, R5, R6, R7 and R8 are hydrogen and R4 is methyl, R9 is not hydroxy or chloro and c) when R1, R2, R3, R5, R6, R7 and R9 are hydrogen and R4 is methyl, R8 is not trifluoromethyl.