Heart-block is a serious condition in which the conducting mechanism between the atrium and ventricle is impaired (incomplete heart-block), or destroyed (complete heart-block) so that the atrium and ventricle beat at different rates independently of one another. During the incomplete state the pulse is irregular, but when the heart-block becomes complete and the ventricles contract independently of the atria, the pulse becomes regular and very slow, and the individual is liable to fainting or convulsive attacks.