Tricyclic compounds for treating heart and circulatory diseases

A compound of the formula:

• ##STR9## wherein R.sub.1 is hydrogen, C.sub.1 -C.sub.6 alkyl, C.sub.2 -C.sub.6 alkenyl or C.sub.3 -C.sub.7 cycloalkyl;
• R.sub.2 is hydrogen, cyano, C.sub.1 -C.sub.6 alkyl, C.sub.2 -C.sub.6 alkenyl, or a carbonyl group substituted by hydroxyl, C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy, amino, C.sub.1 -C.sub.6 alkylamino, C.sub.2 -C.sub.12 dialkylamino or hydrazino, or
• R.sub.2 and R.sub.1 together with the carbon to which they are attached form a C.sub.3 -C.sub.7 cycloalkyl ring, or R.sub.1 and R.sub.2 together form C.sub.3 -C.sub.7 alkylidene or C.sub.3 -C.sub.7 cycloalkylidene,
• T is oxlygen or sulphur or an NR.sub.4 group wherein R.sub.4 is hydrogen or a C.sub.1 -C.sub.6 alkyl;
• R.sub.3 is hydrogen, C.sub.1 -C.sub.6 alkyl, hydroxyl, amino or mercapto, C.sub.1 -C.sub.6 alkylthio, pyridylcarbonylamino, C.sub.1 -C.sub.6 alkylcarbonylamino, C.sub.3 -C.sub.7 cycloalkyl, C.sub.2 -C.sub.6 alkenyl, C.sub.3 -C.sub.7 cycloalkenyl, C.sub.2 -C.sub.6 alkynyl, C.sub.1 -C.sub.6 haloalkyl, C.sub.1 -C.sub.6 -alkoxy-C.sub.1 -C.sub.6 -alkyl, carboxy-C.sub.1 -C.sub.6 -alkyl or C.sub.1 -C.sub.6 -alkoxycarbonyl-C.sub.1 -C.sub.6 -alkyl and
• X is an oxygen or sulphur atom or an NR.sub.5 group, wherein R.sub.5 is hydrogen or an C.sub.1 -C.sub.6 alkyl;
• a tautomer thereof
• or a physiologically acceptable salt thereof with an inorganic or organic acid.