AJP - Heart and Circulatory Physiology, Vol 242, Issue 3 310-H313, Copyright © 1982 by American Physiological Society
Decrease in myocardial oxygen extraction with aortic constriction in the dog
D. Saito, S. Kusachi, O. Nishiyama, K. Yasuhara, S. Haraoka, H. Nagashima and R. A. Olsson
In the open-chest dog constriction of the descending thoracic aorta, which
raises central aortic pressure by 30-80 mmHg, increases cardiac oxygen
usage (MVO2) and coronary blood flow (CBF) but reduces heart rate and
myocardial oxygen extraction [(A-V)O2]. Pacing tachycardia superimposed on
aortic constriction further increases MVO2 and CBF but does not alter
(A-V)O2. Atropine or vagotomy abolishes the effect of aortic constriction
on (A-V)O2, whereas vagal stimulation in the presence of alpha- and
beta-adrenergic blockade reduces (A-V)O2. L-propranolol and
phenoxybenzamine fail to modify the effect of aortic constriction on
(A-V)O2. These results indicate that aortic constriction reduces (A-V)O2 by
eliciting parasympathetically-mediated coronary vasodilation.
