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Circulation, Vol 65, 1269-1275, Copyright © 1982 by American Heart Association

ARTICLES

Concealed reentry: a mechanism of atrioventricular nodal alternating Wenckebach periodicity

L Littmann and RH Svenson

Alternating WEnckebach periodicity is generally believed to reflect bilevel block due to horizontal electrophysiologic dissociation in the conducting tissues. We describe a case of atrial pacing-induced atrioventricular nodal alternating Wenckebach periodicity with concealed reentry in a longitudinally dissociated AV conduction system. Three observations support this unique mechanism: Concealed reentry occurred during the course of alternating Wenckebach periodicity; it could be invoked to explain the peculiar conduction patterns in this patient; and alternative mechanisms did not explain the alternating Wenckebach periods. Our findings also indicate that long conduction times during 2:1 block can be due to concealed reentry rather than concealed antegrade conduction, and participation in the echo process of a retrograde pathway with electrophysiologic characteristics of an atrioventricular nodal bypass tract does not exclude manifest and concealed reentry at a subatrial level.