Microheterogeneity of myocardial blood flow in rabbit heart during
the normoxic and hypoxic states.
Matsumoto, Takeshi, Masami Goto, Hiroyuki Tachibana, Yasuo Ogasawara,
Katsuhiko Tsujioka, Fumihiko Kajiya.
Department of Medical Engineering and Systems Cardiology, Kawasaki
Medical School, 577 Matsushima, Kurashiki, Okayama 701-01 Japan
APStracts 2:0352H, 1995.
The goal of this study was to evaluate microheterogeneity of
myocardial blood flow and its dependence on arterial oxygen tension
(PaO2). We measured within-layer distribution of regional blood flows
in the left ventricles of anesthetized rabbits both in the normoxic
and in the hypoxic states with myocardial region sizes in the range
of 0.01 to 1.0 mm2. A novel method of digital-radiography combined
with the technique of 3H-labeled desmethylimipramine deposition
enabled us to visualize and accurately quantitate regional blood flow
at such high levels of resolution. To analyze myocardial blood flow
patterns, we computed the coefficient of variation () and the
correlation between adjacent regional flows (). The values were
larger in the hypoxic state (PaO2=26+/-5 mmHg) than in the normoxic
state (PaO2=97+/-20 mmHg) at all levels of resolution (p<0.001).
In the normoxic state, there was a transmural difference in
(p<0.001); increased with depth of the left ventricle (from
subepicardium to subendocardium). However, the relation between and
the depth of the left ventricle was not statistically significant in
the hypoxic state. The values were smaller in the hypoxic state than
in the normoxic state at all levels of resolution (p<0.001).
When the degree of resolution was reduced from 0.01 mm2 to 1.0 mm2,
decreased by 75% in the normoxic and by 69% in the hypoxic state.
Thus, we conclude: 1) The decrease in PaO2 increases similarity of
blood flows in nearby regions and decreases myocardial blood flow
heterogeneity. 2) Similarity of regional blood flows increases with
depth of the left ventricle in the normoxic state, but this
transmural difference disappears in the hypoxic state.
Received 17 April 1995; accepted in final form 26 July 1995.
APS Manuscript Number H364-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 August 1995.