Role of cardiac output in mediating arterial blood pressure
oscillations.
O'leary, Donal S., and Dixon J. Woodbury.
Department of Physiology, Wayne State University School of
Medicine, Detroit, MI 48201
APStracts 3:0108R, 1996.
The objective of this study was to determine the role of cardiac
output (CO) in mediating spontaneous fluctuations in mean arterial
pressure (MAP) in conscious dogs. Dogs were chronically instrumented
to monitor MAP and CO. Atrioventricular block was induced and left
ventricular and right atrial electrodes were implanted. After
recovery, MAP was observed for 5 minutes under two conditions: 1)
normal variation in heart rate and CO via triggering the ventricular
stimulator with each atrial depolarization (effectively reversing the
atrioventricular block, termed AV-linked stimulation) and 2) computer
control of ventricular rate to maintain CO constant on a beat-by-beat
basis at the same level as observed during normal variations in heart
rate and CO. When CO was held constant, large amplitude low frequency
oscillations in MAP were readily apparent. Spectral analysis by fast
fourier transform revealed that during constant CO the power observed
at low frequencies in the MAP spectrum represented 95.0 +/- 2.7% of
the total power as compared to 75.5 +/- 4.6% during normal variations
in heart rate and cardiac output (p < 0.05). In addition, when CO was
held constant, the power observed at higher frequencies markedly
decreased from 24.5 +/- 4.6% of total power during AV-linked
stimulation to only 5.0 +/- 2.7% of total power during constant CO (p
< 0.05). We conclude that low frequency oscillations in MAP are due
to changes in peripheral resistance whereas a significant amount of
high frequency changes in MAP stems from spontaneous changes in
cardiac output.
Received 18 January 1996; accepted in final form 8 March 1996.
APS Manuscript Number R27-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 27 March 96