AJP - Heart and Circulatory Physiology, Vol 252, Issue 3 529-H535, Copyright © 1987 by American Physiological Society
Temperature distribution cannot predict local cardiac metabolism
P. Duijst, G. Elzinga and N. Westerhof
The objective of this study was to investigate if local myocardial
metabolism can be determined from the transmural temperature distribution.
Heat produced metabolically in the myocardium is carried away by the
coronary blood and by diffusion. Transport by coronary flow (convectional
heat loss) was determined from the coronary blood flow and the
transcoronary temperature difference. This measured value was compared with
one predicted from measured oxygen consumption, assuming a slab of tissue
for the left ventricular free wall with homogeneous flow distribution and
homogeneous metabolism. Measured and predicted convectional heat loss could
not be shown to differ. Endocardial and epicardial heat production were
estimated in two ways: 1) from the transmural temperature distribution (AT)
and 2) from local flow (radioactive microspheres) and oxygen consumption
(AO2). Ideally the ratio AT/AO2 should be unity. For flows in the resting
physiological state (up to 100 ml X min-1 X 100 g-1) this ratio was not
statistically different from one for both endocardium and epicardium: 0.86
+/- 0.11 and 1.09 +/- 0.07 (SE), respectively. For larger flows the ratio
reduced to 0.66 +/- 0.08 endocardially. It is concluded that overall left
ventricular metabolism can be predicted from conventional heat loss and
that for physiological, but not for increased flow, the transmural
temperature distribution predicts local metabolism.
