[Functional indices of the heart conduction system in patients with normal atrioventricular conduction]

A total of 16 patients with normal atrioventricular conduction were studied by the method of intracardiac electrophysiologic study. Time intervals of the conduction through the atria and the His-Purkinje system did not change during frequent atrial stimulation. The conduction time through the atrioventricular node increased, the periodical block with a location in the very node developing at a stimulation frequency of 181+/-18 beats/min. The duration of functional and effective refractory periods of the atria and the atrioventricular node depended upon heart rate. A complete block of retrograde conduction through the node was revealed in 5 of 13 patients by stimulating their ventricles. A frequency dependence of the conduction through the atrioventricular node and periodic block in relatively low stimulation frequency were observed in the others. The findings determine normal values of the indices studied and make a basis for the identification of anomalous pathways of atrioventricular conduction.