[Apparently unusual causes of inhibition of demand unipolar pacemakers (author's transl)].

An unusual behaviour observed in five demand endoventricular unipolar pacemakers is reported: the pacing were inhibited by coughing, deep inspirations and Valsalva manoeuvre. The findings allowed to point following remarks: a) the inhibition is related to myopotentials caused by respiratory movements which involve a large number of thoracic skeletal muscles; b) the myopotential characteristics may be differents in different patients; c) even electronic sensing characteristics may be slightly different in the same kinds and models of the same manufacturer.