AJP - Regulatory, Integrative and Comparative Physiology, Vol 243, Issue 1 152-R158, Copyright © 1982 by American Physiological Society
Increased cardiac output following occlusion of the descending thoracic aorta in dogs
J. K. Stene, B. Burns, S. Permutt, P. Caldini and M. Shanoff
Occlusion of the thoracic aorta (AO) in dogs with a constant volume right
ventricular extracorporeal bypass increased cardiac output (Q) by 43% and
mean arterial pressure by 46%, while mean systemic pressure (MSP) was
unchanged. We compared AO with occlusion of the brachiocephalic and left
subclavian arteries (BSO) which decreased cardiac output by 5%, increased
mean arterial pressure by 32%, and increased MSP by 11%. We feel these
results confirm that AO elevates preload by transferring blood volume from
the splanchnic veins to the vascular system drained by the superior vena
cava. If the heart is competent to keep right arterial pressure at or near
zero, this increase in preload will elevate Q above control levels.
Comparing our data with results of other authors who have not controlled
right atrial pressure, emphasizes the importance of a competent right
ventricle in allowing venous return to determine Q.
