There are described new condensed diazepinones of general formula ##STR1## wherein .circle.B represents one of the divalent groups ##STR2## and D represents the groups ##STR3## and X.sup.1, X.sup.2 represents a .dbd.CH-- group or, if .circle.B assumes the meaning of the divalent group S, U or W, they may also represent an N atom, A.sup.1 and A.sup.2 in general represent lower alkylene groups, Z represents a C--C bond or the groups, --O--, --S--, --CH.sub.2 --, or --(CH.sub.2).sub.2 --; R represents hydrogen or methyl, R.sup.1 and R.sup.2 generally represent alkyl groups which, together with the nitrogen atom between them, may also form a saturated monocylic, heterocyclic group, R.sub.3 represents alkyl, chlorine or hydrogen, R.sub.4 represents hydrogen or methyl, R.sup.5 and R.sup.6 represent hydrogen, halogen or alkyl, R.sub.7 represents hydrogen, chlorine or methyl, R.sup.8 represents hydrogen or lower alkyl, R.sup.9 represents hydrogen, halogen, lower alkyl and R.sup.10 represents hydrogen or methyl and R.sup.12 represents branched or unbranched alkyl. The compounds of general formula I and the acid addition salts thereof may be resolved into their isomers. The compounds of formula I and their salts may be used as vagal pacemakers for the treatment of bradycardia and bradyarrhythmia.