Dec 1, 1983

Divergence between refractoriness of His-Purkinje system and ventricular muscle with abrupt changes in cycle length

Circulation
S DenkerM Akhtar

Abstract

The concept that refractoriness of the His-Purkinje system (HPS) and ventricular muscle both vary directly with cycle length is based on observations during the use of constant cycle length. During abrupt changes in ventricular cycle length, refractoriness of the ventricular muscle is known to reflect the cumulative durations of preceding cycle lengths. The effect of such changes on retrograde refractoriness of the HPS is not known. In this study refractoriness of ventricular muscle and of the HPS was evaluated in 30 patients with normal intraventricular conduction by the ventricular extrastimulus (V2) technique during constant cycle length (method I) and during abrupt cycle length changes (method II). During method II the cycle length immediately before V2 was identical to the constant cycle length of method I and therefore was designated as the reference cycle length (CLR); however, the cycle length preceding (CLP) CLR was either longer than CLR (method IIA) by 100 to 300 msec in 11 patients or shorter than CLR (method IIB) by 100 to 300 msec in 30 patients. Results showed that compared with method I, method IIA shortened the relative refractory period (RRP) of the HPS from 350 +/- 29 to 344 +/- 29 msec (p less than .04), whe...Continue Reading

Mentioned in this Paper

Myocardial Contraction
Structure of Purkinje Fibers
Left Ventricular Structure
Left Bundle Branch of His
Refractory Period, Electrophysiological
Refractory Period
Cardiac Conduction System
Electrophysiology (Science)
Heart Ventricle
Cardiac Pacing, Artificial

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