Studies of heart block with his bundle electrograms

Abstract

A total of 24 patients with heart block revealed by scalar electrocardiography was studied using the His bundle electrogram. Four groups of disturbed conduction are described which include various types of heart block, partial and complete, at different sites, single and multiple, in the specialized conducting system. These are (1) intra-atrial block with delayed or blocked internodal conduction, (2) atrioventricular nodal block due to delayed or blocked conduction in the AV node, (3) His-Purkinje-system block due to delayed or blocked conduction in the fibres of the His- Purkinje-system, (4) multiple site AV block due to disturbances of conduction in the AV node and His-Purkinje-system in combination. His-Purkinje-system block is characterized by associated intraventricular block, and its relation to bilateral bundle-branch block and trifascicular block is discussed. In some instances concealed conduction disturbance, both anterograde and retrograde, is revealed by the His bundle electrogram, including facilitation of conduction in the main bundle of His. The His bundle electrogram defines more clearly the nature and extent of disturbed conduction and it may contribute to the choice of treatment, either by drugs or by artificial pacing, temporary or permanent.