Transients in myocardial oxygen consumption following abrupt
changes in perfusion pressure in the goat.
Dankelman, Jenny, Catharina P. B. Van Der Ploeg, Jos A. E. Spaan.
Department of Medical Physics and Informatics, Academic Medical
Center, University of Amsterdam, PO Box 22700, 1100 DE Amsterdam,
Laboratory for Measurement and Control, Delft University of
Technology, Mekelweg 2, 2628 CD Delft, The Netherlands
APStracts 2:0395H, 1995.
Previously we reported that glibenclamide decelerates the rate of
coronary flow regulation by a factor of four (8). The dynamic oxygen
content differences were analyzed in the present study. The left main
coronary artery of the open chest anesthetized goat was perfused at
constant pressure (Pp). Pp(t), arterial flow (Qa(t)) and the arterio
-venous oxygen content difference (AVo2(t)) were averaged per beat.
The AVo2 signal was corrected for mixing processes in the capillaries
and transport time from capillaries to the venous measuring site
(AVo2*(t)). A change in Pp of 20 mmHg induced a temporary change in
MVo2, referred to as dynamic Gregg effect. With an increase in Pp,
the maximal change of myocardial oxygen consumption
(MVo2(t)=Qa(t)xAVo2*(t)) was 15.0+3.6% (mean+SE) during control and
31.3+2.3% with glibenclamide. With a decrease in Pp these changes
were 16.3+2.9% and 21.0+1.1%. During control, the t50 for the rate of
return of the MVo2 response was 4.2+0.8 s for an increase and 4.0+1.0
s for a decrease in Pp. With glibenclamide these values were 16.9+2.2
s and 22.6+2.0 s. This study confirms that during steady state the
perfusion pressure induced oxygen consumption (steady state Gregg
effect) is diminished by autoregulation. However, it is concluded
that during transients following abrupt changes in perfusion pressure
large changes in MVo2 occur depending on the rate of regulation
(dynamic Gregg effect).
Received 3 November 1994; accepted in final form 2 August 1995.
APS Manuscript Number H979-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.