Oct 1, 1987

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

Circulation
R T Steinman, M H Lehmann

Abstract

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 bea...Continue Reading

Mentioned in this Paper

Heart Block
Refractory Period, Electrophysiological
Cardiac Conduction System
Structure of Atrioventricular Node
Cardiac Pacing, Artificial
Electrocardiographic Recorders
NODAL

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