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April 1973

Simultaneous Block Proximal and Distal to His BundleAn Example of Concealed "Concealed Conduction"

Author Affiliations


From the Department of Adult Cardiology, Division of Medicine, and the Hektoen Institute for Medical Research of the Cook County Hospital, and the Department of Medicine, Abraham Lincoln School of Medicine, University of Illinois College of Medicine, Chicago.

Arch Intern Med. 1973;131(4):588-590. doi:10.1001/archinte.1973.00320100116016

The term concealed conduction describes the effects of a cardiac impulse partially penetrating the atrioventricular (AV) junction and disturbing the conduction or formation of subsequent impulses.1,2 Examples of this phenomenon include the PR prolongation following either a blocked atrial or interpolated ventricular premature contraction, the compensatory pause following a premature ventricular beat in atrial fibrillation, and the resetting of a junctional pacemaker following retrograde penetration of a ventricular premature beat in a patient with AV dissociation.

Catheter recording of His bundle electrographs has furthered understanding of concealed conduction by permitting the precise localization of sites of conduction delay following premature beats.3 This technique also allowed the documentation of a rare form of concealed conduction, the occurrence of second-degree AV block due to the retrograde penetration of concealed junctional premature depolarizations.4,5 These depolarizations, electrocardiographically silent because of antegrade and retrograde block, were easily recorded with an electrode catheter.

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