The His bundle electrogram (HBE) was first used clinically to study the conduction block in the atrioventricular conducting system. ' The exact site of the conduction block is found through the record of the His potential which was recorded between A wave (depolarization of she atrium) and V wave (depolalization of the ventricle). Various grade of block is found at every site of the conducting system by using this technique and it has become clear that the site and the grade of the block is related to the prognosis. It is also used to decide the indication of the pacemaker implantation.
The old classification and the new classification of the atrioventricular block were shown. New classification: 1) intra-atrial block.2) A-V nodal block.3) intrahisian block,4) infrahisian block.5) mixed lesions. Cases of each block were shown and the ind ication of the pacemaker implantation related to each block was described.
