FUNCTIONAL UNIDIRECTIONAL BLOCK BETWEEN TWO LAYERS OF CARDIAC CONDUCTING TISSUE

Abstract

Unidirectional block is a fundamental component in the initiation of a reentrant cardiac arrhythmia. The activation sequences of the adult rabbit (n=10) or canine (n=5) left anterior papillary muscle were mapped two-dimensionally using multiple monopolar extracellular electrodes with computerized data acquisition and analysis. Isochronal maps were then made to determine the activation patterns of the superficial Purkinje (P) layer or the underlying ventricular (V) layer during stimulation of an attached P strand or the apical V surface. The P cell layer extends over most of the surface of the left papillary muscle, but the direct propagation from the P layer into the underlying V layer is limited to several relatively discrete basal sites. We have additionally demonstrated sites located more apically which allow propagation in only one direction; namely, from the underlying V layer into the P layer. This phenomenon occurs because of a proposed resistive barrier between the two layers which is spatially inhomogeneous, with the junctional resistivity between the P and V layer increasing from base to apex. These sites of potential unidirectional conduction could have functional significance under abnormal conditions when the available sites of P-to-V conduction are reduced. This property could, therefore, operate as one of the mechanisms of cardiac reentrant arrhythmias.

Log in or create a free account to read this content

Gain free access to this article, as well as selected content from this journal and more on nature.com

Access through your institution

or

Sign in or create an account

Continue with Google

Continue with ORCiD