The present invention relates to piperidinesulfonylureas and piperidinesulfonylthioureas of formula I, in which A, X, R(1), R(2) and R(3) have the meanings indicated in the claims. The compounds of formula I are valuable active pharmaceutical ingredients which show in particular an inhibiting effect on ATP-sensitive potassium channels of the cardiac muscle and are suitable, for example, for the treatment of disorders of the cardiovascular system such as coronary heart disease, arrhythmias, cardiac insufficiency, cardiomyopathies or reduced contractility of the heart or for the prevention of sudden cardiac death. The invention further relates to processes for preparing the compounds of formula I, their use and pharmaceutical compositions comprising them.