Regional vascular reserve in canine atria and ventricles during rest and exercise. Bauman, Robert P., Judith C. Rembert, Joseph C. Greenfield, Jr. Department of Medicine, Division of Cardiology, Duke University Medical Center 27710 and Medical Service (Cardiology Section) and Research and Development Service, Veterans Affairs Medical Center, 27705, Durham, North Carolina.
APStracts 2:0213H, 1995.
Vascular reserve, which defines the capacity for further vasodilation in a given physiologic or pathologic condition, has not been measured in the canine atria. This study defines, in normal dogs, the regional vascular reserve simultaneously measured in the atria (appendage, nonappendage regions) and in the ventricles during rest and two levels of exercise. Blood flow was determined using 11.4 + 0.1 [mu]m radiolabeled microspheres. Vascular reserve (percent for each region) is the ratio of vascular conductance during each condition to maximum vascular conductance. Maximum vascular conductance was estimated by infusing adenosine intravenously. For a given physiologic condition regional vascular conductance varied two to threefold. The vascular reserve of each of the regions decreased progressively from rest to mild exercise to moderate exercise. Regional vascular reserve for both atria, the right ventricle, and the epicardial layer of the left ventricle was essentially uniform for a given condition: rest 93 + 0.4%, mild exercise 81 + 1.2% and moderate exercise 69 + 1.5%. This similarity in vascular reserve implies that for a given physiologic condition a common mechanism precisely regulates myocardial perfusion in these cardiac regions as a function of the total vasodilator capacity. 

Received 14 October 1993; accepted in final form 11 May 1995.
APS Manuscript Number H571-3.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.