Does the atrioventricular node conduct?

Abstract

There can be no doubt about the importance of electrotonus as the mechanism of otherwise inexplicable arrhythmias. In this presentation the atrioventricular node is regarded as a biological oscillator and electrotonus induced by organised atrial or ventricular excitation as the mechanism by which the oscillator can be entrained. The concept of the atrioventricular node as an oscillator/pacemaker influenced by electrotonus is in keeping with the functions of the atrioventricular node and offers a rational explanation for the varying atrioventricular nodal delay during sinus rhythm, the protection the atrioventricular node affords in the presence of atrial tachycardias and fibrillation, and for atrioventricular nodal automaticity as an escape mechanism. The concept accords with clinical and experimental observations that classically have been attributed to the 'conducting' properties of the atrioventricular junction. It also offers a rational explanation for the relatively short PR intervals in large mammals such as elephants and whales, as well as for several atrioventricular 'conduction' abnormalities and arrhythmias. In fact, the assumption that conduction and automaticity are properties of the atrioventricular node tends to complicate rather than to clarify the understanding of atrioventricular nodal function under varying physiological and pathological influences. The question whether the atrioventricular node conducts in the traditional meaning of the word warrants further investigation.