Affiliation:
1. Instituto de Bioflsiea, Universidade do Brasil, Rio de Janeiro, Brasil
Abstract
Electrophysiologic mapping experiments on the excitation of the A-V node of isolated rabbit heart have been performed with intracellular microelectrodes. An area of tissue showing peculiar physiologic characteristics was shown to coincide, at least in part, with the histologic A-V node and His bundle. Three functional regions have been determined in the physiologic mapping of the A-V node. The middle layer (N) shows signs of decremental conduction and is the site of the slowest propagation velocity in the A-V node. The other layers are transitional regions between the N layer and atrium (AN) or the His bundle (NH). The AN layer shows a progressively slower propagation velocity as the N region is approached. The same holds for the NH region. A precise correlation between these findings and the 3 existent histologic layers remains to be determined. The existence of an area of peculiar tissue just above the A-V valves and encircling the A-V orifice has been confirmed. This area is continuous with the AN layer of the functional A-V node and has been named the atrioventricular ring (AVR) on the assumption that it is a remnant of the embryonic A-V ring. Wenckebach cycles and A-V block of nodal origin are tentatively explained as resulting from increased decrement in the middle nodal layer (N).
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
Cited by
219 articles.
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