Changes in myocardial blood volume with graded coronary stenosis:
an experimental evaluation using myocardial contrast
echocardiography.
Lindner, Jonathan R., Danny M. Skyba, Norman C. Goodman, Ananda R.
Jayaweera, Sanjiv Kaul.
Cardiovascular Division, University of Virginia School of Medicine,
Char lottesville, Virginia
APStracts 3:0313H, 1996.
Vasodilation of the microvessels distal to a stenosis results in an
increase in myocardial blood volume (MBV). The purpose of this study
was to study the changes in MBV induced by graded coronary artery
stenoses using myocardial contrast echocardiography (MCE). According
ly, 21 dogs underwent progressive stenosis of a coronary artery in a
random order, the severity of which was judged by the pressure distal
to it. Total myocardial blood flow (MBF) to the bed distal to the
artery (both anterograde and collateral) was measured using
radiolabeled micro spheres injected into the left atrium. In 7 dogs,
anterograde and total MBF was measured at each stenosis stage by
injection of different microspheres into the left atrium and directly
into the coronary artery, respectively. MBV was calculated by
dividing MBF by the mean transit rate of microbubbles injected
directly into the coronary artery during MCE. The perfusion bed size
of the artery was also measured using MCE. Our major findings are: a)
there is a nonlinear increase in MBV with increasing degrees of
coronary stenosis until the coronary stenosis becomes critical; b) at
moderate levels of coronary stenosis, MBV remains constant despite
ongoing autoregulation because of reduction in the size of the
perfusion bed supplied by the stenotic vessel; and, c) after
exhaustion of autoregulation, a decrease in MBV is noted with
increasing levels of stenosis. We conclude that assessment of MBV
provides insights into myocardial perfusion distal to a coronary
stenosis above and beyond that provided by the measurement of MBF
alone.
Received 16 April 1996; accepted in final form 8 July 1996.
APS Manuscript Number H344-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 August 1996