This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Steinman, R. T. Articles by Lehmann, M. H. Search for Related Content PubMed PubMed Citation Articles by Steinman, R. T. Articles by Lehmann, M. H.

Circulation, Vol 76, 759-767, Copyright © 1987 by American Heart Association

ARTICLES

Beat-to-beat changes in atrioventricular nodal excitability and its modulation by concealed conduction during functional 2:1 block in man

RT Steinman and MH Lehmann
Electrophysiology Laboratory, Wayne State University, Detroit, MI.

An atrial pacing model of functional 2:1 block was used in 10 patients to investigate for the first time the electrophysiologic properties of the human atrioventricular node during intermittent conduction. By varying the terminal portion of the 2:1 atrial train and using the extrastimulus technique, we characterized atrioventricular nodal (AVN) conduction and refractoriness after five different methods of AVN activation: a conducted beat (method I), a conducted beat with omission of the prior blocked beat (method II), a blocked beat (method III), a blocked beat "converted" to one that conducts by omission of the prior conducted beat (method IV), and finally, 1:1 conduction at twice the cycle length of the 2:1 train (control method V). Observed AVN conduction times obeyed the following relationship: method I greater than method II greater than method V, indicating a cumulative effect of concealed penetration by the blocked beats. During 2:1 block, the AVN effective refractory period (ERP) alternated with a mean beat-to-beat difference of at least 100 msec, due mostly to marked ERP abbreviation during AVN activation by method III (vs both 2:1 train cycle length and activation by method V). Concealed penetration by the blocked beat prolonged AVN ERP for the propagated beat (vs that with methods II and V), but to a lesser extent than conduction time was increased. Moreover, the AVN recovery curve with method I was displaced upward and to the right compared with that with methods II to V.(ABSTRACT TRUNCATED AT 250 WORDS)