Feb 1, 1978

Electrophysiologic studies on atrioventricular nodal Wenckebach cycles

The American Journal of Cardiology
M B SimsonE N Moore

Abstract

Wenckebach cycles with a 4:3 ratio, produced by rapid atrial pacing, were studied in 27 anesthetized denervated dogs using programmed stimulation. A test stimulus (S') could be inserted after any preselected beat of the Wenckebach cycle. An on-line computer measured the atrial (A) to His bundle (H) intervals. In all dogs a progressive increase in atrioventricular (A-V) nodal refractoriness was seen in the effective refractory period for each beat and a rightward shift of the A'-H' relative to the A-A' refractory curves. Atypical Wenckebach cycles could be produced by small changes in the basic cycle length. No evidence for reentry was found from the refractory curves of Wenckebach cycles and by interruption of stimulation after the third stimulus of a 4:3 Wenckebach cycle. Analysis of the A'-H' relative to the H-A' refractory curves did not confirm a positive feedback mechanism. In order to mimic a Wenckebach cycle, a blocked premature beat was inserted during stressed 1:1 conduction. The changes in the refractory curves for successive beats after the premature beat were rate-dependent and similar to those in Wenckebach cycles but smaller in magnitude. In Wenckebach cycles there is a progressive increase in refractoriness, caus...Continue Reading

Mentioned in this Paper

Heart Block
Feedback - System Communication
Etiology
Refractory Period
Cardiac Conduction System
Electrophysiology (Science)
NODAL gene
Bundle of His
Mimic brand of tebufenozide
Cardiac Electrophysiologic Stimulation and Recording Study

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