AJP - Heart and Circulatory Physiology, Vol 243, Issue 4 523-H527, Copyright © 1982 by American Physiological Society
Effects of autonomic activity and changes in heart rate on atrioventricular conduction
D. W. Wallick, P. J. Martin, Y. Masuda and M. N. Levy
The effects of autonomic neural stimulation and changes in atrial pacing
frequency on atrioventricular (AV) conduction were determined in
anesthetized open-chest dogs. Increases in vagal stimulation frequency and
in pacing rate significantly increased the AV interval, whereas increases
in sympathetic stimulation frequency reduced the AV interval. Vagal
stimulation (1.4 Hz) prolonged the AV interval by 17 ms when the atrial
pacing rate was 2 Hz. On the other hand, the same vagal stimulation
increased the AV interval by 29 ms when the pacing rate was 2.73 Hz. In
addition, sympathetic stimulation (1.2 Hz) reduced the AV interval by 29 ms
when the pacing rate was 2 Hz. In contrast, the same sympathetic
stimulation reduced the AV interval 54 ms when the pacing rate was 2.73 Hz.
However, the increase in vagal stimulation did not significantly alter the
positive dromotropic response of the AV node to sympathetic stimulation.
Therefore, the response of AV conduction to combined sympathetic and vagal
stimulation was essentially the algebraic sum of the responses to the
individual stimulations. Furthermore, the level of activity in one
autonomic division did not alter appreciably the interaction between the
pacing rate and the activity in the other autonomic division; i.e., the
interaction between pacing rate, sympathetic stimulation, and vagal
stimulation was not significant.
