Pyrimidinedione derivatives and antiarrhythmic agents containing same

A pyrimidinedione derivative which is represented by the formula (I) ##STR136## wherein A is --(CH.sub.2).sub.m --, --B--(CH.sub.2).sub.k --, D--(CH.sub.2).sub.l -- or ##STR137## B is an oxygen atom, sulfur atom, ##STR138## and D is ##STR139## R.sup.1 and R.sup.2 are so linked with each other as to make an alkylene chain and thus form a heterocyclic structure,

• each of R.sup.3 and R.sup.4 is independently a hydrogen atom or lower alkyl group,
• each of X.sup.1, X.sup.2 and X.sup.3 is independently a hydrogen atom, --CO--R.sup.6, halogen atom, lower alkyl group, halogen-substituted lower alkyl group, hydroxyl group, lower alkyloxy group, lower alkylthio group, lower alkyloxycarbonyl group, carboxyl group, cyano group, amino group, lower alkanoyloxy group, lower alkanoylamino group, lower alkylsulfonamido group, lower alkylsulfonyl group, ureido group, lower alkylsulfinyl group, sulfamoyl group, heterocyclic ring, mono- or di-lower alkylamino group, phenyl-substituted lower alkylamino group, trifluoroacetylamino group, trifluoromethylsulfonamido group, phenylsulfonamido group or unsaturated lower alkyloxy group,
• R.sup.5 is a hydrogen atom, lower alkylsulfonyl group or lower alkyl group,
• R.sup.6 is a lower alkyl group (which may be substituted by a halogen atom, phenyl group or lower alkyloxycarbonyl group), unsaturated lower alkyl group (which may be substituted by a phenyl group or substituted phenyl group), cycloalkyl group, phenyl group or heterocyclic ring,
• n is 2 or 3, m is 0, 1, 2, 3 or 4, k is 2, 3 or 4, and l is 0, 1, 2, 3 or 4.