AJP - Heart and Circulatory Physiology, Vol 241, Issue 4 564-H570, Copyright © 1981 by American Physiological Society
Effects of experimental volume-overload hypertrophy on myocardial blood flow and cardiac function
F. R. Badke, F. C. White, M. Le Winter, J. Covell, J. Andres and C. Bloor
To examine the effects of volume-overload hypertrophy on regional
myocardial perfusion, we determined myocardial blood flows with
microspheres at rest, during exercise, and during exercise with adenosine
infusion in dogs with aortocaval fistulas for 12 wk (group 2) and
sham-operated controls (group 1). A subgroup of six animals (group 3) was
studied both before and after shunt closure in order to separate the
influences of hypertrophy from the hemodynamic effects of the fistula.
Epicardial blood flows in animals with patent fistulas were significantly
greater than in controls under all conditions (P less than 0.05). However,
endocardial blood flows were lower at maximal exercise and with adenosine,
so that the endocardial-to-epicardial blood flow ratios were reduced 36 and
28%, respectively(P less than 0.05). These flow abnormalities were reversed
by closing the fistula prior to regression of hypertrophy. Moreover,
coronary resistance per unit of myocardium was not different for the three
groups. These results suggest that the blood-flow abnormalities seen in the
exercising dog with an aortocaval fistula are secondary to hemodynamic
considerations and not to hypertrophy itself. Low aortic diastolic
pressures and high myocardial oxygen demands during exercise may combine to
produce subendocardial hypoperfusion in this model.
