AJP - Regulatory, Integrative and Comparative Physiology, Vol 271, Issue 3 641-R646, Copyright © 1996 by American Physiological Society

ARTICLES

Role of cardiac output in mediating arterial blood pressure oscillations

D. S. O'Leary and D. J. Woodbury
Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA. doleary@med.wayne.edu

The objective of this study was to determine the role of cardiac output in mediating spontaneous fluctuations in mean arterial pressure (MAP) conscious dogs. Dogs were chronically instrumented to monitor MAP and cardiac output. Atrioventricular (AV) block was induced, and left ventricular and right atrial electrodes were implanted. After recovery, MAP was observed for 5 min under two conditions: 1) normal variation in heart rate and cardiac output via triggering the ventricular stimulator with each atrial depolarization (effectively reversing the AV block, AV-linked stimulation) and 2) computer control of ventricular rate to maintain cardiac output constant on a by-beat basis at the same level as observed during normal variations in heart rate and cardiac output. When cardiac output was held constant, large-amplitude, low-frequency oscillations in MAP were readily apparent. Spectral analysis by fast Fourier transform revealed that during constant cardiac output the power observed at low frequencies in the MAP spectrum represented 95.0 +/- 2.7% of the total power compared with 75.5 +/- 4.6% during normal variations in heart rate and cardiac output (P < 0.05). In addition, when cardiac output 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 cardiac output (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.

This article has been cited by other articles:

				M. P. Tulppo, A. J. Hautala, T. H. Makikallio, R. T. Laukkanen, S. Nissila, R. L. Hughson, and H. V. Huikuri Effects of aerobic training on heart rate dynamics in sedentary subjects J Appl Physiol, July 1, 2003; 95(1): 364 - 372. [Abstract] [Full Text] [PDF]

				B. N. Van Vliet, F. Belforti, and J.-P. Montani Baroreflex stabilization of the double (pressure-rate) product at 0.05 Hz in conscious rabbits Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2002; 282(6): R1746 - R1753. [Abstract] [Full Text] [PDF]

				J. V. Ringwood and S. C. Malpas Slow oscillations in blood pressure via a nonlinear feedback model Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2001; 280(4): R1105 - R1115. [Abstract] [Full Text] [PDF]

				J. A. Taylor, T. D. Williams, D. R. Seals, and K. P. Davy Low-frequency arterial pressure fluctuations do not reflect sympathetic outflow: gender and age differences Am J Physiol Heart Circ Physiol, April 1, 1998; 274(4): H1194 - H1201. [Abstract] [Full Text] [PDF]

				L. A. Lipsitz, R. Morin, M. Gagnon, D. Kiely, and A. Medina Vasomotor instability preceding tilt-induced syncope: does respiration play a role? J Appl Physiol, August 1, 1997; 83(2): 383 - 390. [Abstract] [Full Text] [PDF]