AJP - Heart and Circulatory Physiology, Vol 249, Issue 2 249-H254, Copyright © 1985 by American Physiological Society
Effect of pacing on oxygen supply-to-consumption ratio in ischemic myocardium
G. J. Grover and H. R. Weiss
This study was performed to determine if the partially occluded myocardium
could maintain its O2 supply-to-consumption ratio during atrial pacing. In
14 open-chest anesthetized dogs, the left anterior descending coronary
artery was occluded to 50% of base-line flow, and in half of the dogs the
hearts were paced to 50% above base-line heart rate. Blood flows were
determined by use of microspheres before and after occlusion, and O2
supply-consumption variables were determined by use of
microspectrophotometry. After occlusion in control and paced groups, blood
flow was depressed in the ischemic region compared with the nonischemic
region. In paced animals, blood flows in all regions were significantly
higher compared with their respective values in nonpaced animals. After
pacing, mean O2 consumption was 34% higher (53% in the occluded region)
compared with control animals. The O2 supply-to-consumption ratio was
similar in the occluded region of paced animals compared with the same
region in controls. This ratio was lower in ischemic regions of both groups
compared with their respective nonischemic regions. This indicates that,
despite a reduced O2 supply-to-consumption ratio in the ischemic area, an
unutilized reserve of flow exists.
