Journal of Applied Physiology, Vol 38, Issue 3 485-490, Copyright © 1975 by American Physiological Society
Specificity of autonomic influences on cardiac responses during myocardial ischemia
R. L. Kaspar, G. E. Barnes, D. F. Peterson and V. S. Bishop
A possible role of the autonomic nervous system in the left ventricular
response to acute regional myocardial ischemia was sought in conscious dogs
instrumented for measurement of left ventricular pressure, internal
diameter, and aortic flow. Ischemia produced by occluding the left
circumflex coronary artery caused tachycardia and reduced contractility.
Changes during control occlusions were compared with those during
occlusion.s after beta-adrenergic blockade, parasympathetic blockade, and
combined sympathetic and parasymphatetic blockade. Beta-blockade did reduce
the tachycardia and slightly reduced left ventricular diameter changes in
response to coronary occlusion. Results obtained in animals following
surgical cardiac sympathectomy indicated reduced tachycardia and no effects
on other parameters. The principal effect of parasympathetic blockade was
to augment the increase in end diastolic diameter during occlusion Right
atrial pacing indicated this change was due to higher initial heart rates.
Combined parasympathetic and sympathetic blockade did not alter inotropic
responses to coronary occlusion. Results indicated that inotropic support
due to changes in activity in autonomic nerves is not increased during
acute occlusion of the left circumflex coronary artery.
