With the advent of the new methods of cardiac examination, many disturbances of rhythm, previously unsuspected, have been discovered in the heart during infancy and childhood. It has been shown, however, that, on the whole, the occurrence of cardiac irregularities, with the exception of sinus arrhythmia, is much more commonly found in adult life than in childhood. Of the various arrhythmias, one of the least commonly encountered in childhood is heart block.
Heart block may be defined as "an abnormal heart mechanism in which there is a delay in, or absence of, response of the ventricle to auricular impulses."1 The cardiac impulse normally arises in the sinus node and passes thence to the auriculoventricular node, and then down the bundle of His and its two branches to the Purkinje fibers and the muscle cells. By means of the electrocardiograph, the time taken for the impulse to travel over this
BASS MH. HEART BLOCK AND CONGENITAL HEART DISEASE IN CHILDHOOD. JAMA. 1918;70(5):287-288. doi:10.1001/jama.1918.02600050009004