AJP - Heart and Circulatory Physiology, Vol 244, Issue 1 60-H67, Copyright © 1983 by American Physiological Society
Myocardial blood flow and function during gradual coronary occlusion in awake dog
R. C. Hill, L. H. Kleinman, W. H. Tiller Jr, W. R. Chitwood Jr, J. C. Rembert, J. C. Greenfield Jr and A. S. Wechsler
The purpose of this study was to correlate dimensions and transmural blood
flow in a segment of myocardium supplied by a coronary artery undergoing
gradual closure. Nine adult dogs were instrumented with an electromagnetic
flow probe, pneumatic occluder, and an ameroid constrictor on the
circumflex coronary artery. Ultrasonic crystals were implanted 10 mm from
the external surface of the left ventricle in a segment perfused by the
circumflex artery. Regional blood flow was determined with 7- to 10-microns
radiolabeled microspheres. Data were collected in the awake state at rest
before closure began (control), during partial closure, and immediately
after total closure. Seven of the nine animals were studied after occlusion
during treadmill exercise. During both partial and total closure at rest
the rate and extent of systolic shortening as well as the transmural blood
flow were unchanged from control. During treadmill exercise mean flow
increased. However, flow was redistributed away from the inner two layers
causing deterioration in both the rate and extent of shortening of this
segment. These data suggest that, although regional myocardial function and
flow can be maintained at rest by the immature canine collateral
circulation, these parameters are impaired markedly during augmented flow
with exercise.
