AJP - Heart and Circulatory Physiology, Vol 243, Issue 5 754-H760, Copyright © 1982 by American Physiological Society
Atrioventricular nodal conduction during atrial fibrillation in rabbit heart
T. Mazgalev, L. S. Dreifus, J. Bianchi and E. L. Michelson
Atrial fibrillation was induced in 15 superfused rabbit
atrial-atrioventricular nodal preparations in which surface bipolar
electrograms were recorded simultaneously from the crista terminalis,
interatrial septum, and His bundle along with microelectrode action
potentials from cells in the atrionodal (AN), nodal (N), and nodal-His (NH)
regions of the atrioventricular node. Effective engagement of the
atrioventricular node with propagation to the His bundle was critically
dependent on the relative timing of activation at the crista terminalis and
interatrial septal input regions of the atrioventricular node. Conduction
through the AN and N regions appeared dependent on the relative timing of
activation wave fronts emerging from the two input regions. Asynchronous
engagement of AN and N regions resulted in both distortion of action
potentials and concealed conduction, with delayed conduction and block to
the NH region and His bundle. Successful engagement of the NH region always
produced a 1:1 NH-to-His bundle relationship. It is concluded that during
atrial fibrillation 1) activation of the AN region occurs as a result of
the variable interaction of inputs from the crista terminalis and
interatrial septum; 2) predictably, effective synchronous engagement of the
AN and consequently the N region is responsible for conduction to the NH
and His bundle regions; 3) conversely, asynchronous activation inputs from
the crista terminalis and interatrial septum result in fragmented,
asynchronous as well as concealed conduction within the AN and N regions
with block in the atrioventricular node and variable conduction to the His
bundle.
