AJP - Heart and Circulatory Physiology, Vol 243, Issue 4 499-H504, Copyright © 1982 by American Physiological Society
Coherence of cardiac output with rate changes
J. Melbin, D. K. Detweiler, R. A. Riffle and A. Noordergraaf
In awake or lightly anesthetized dogs increases in heart rate (HR) induced
by atrial pacing affect cardiac output (CO) and stroke volume (SV) in a
predictable way that is represented by a SV-HR relationship (dSV/dHR).
Under our experimental conditions where normal regulation of atrial rate
was bypassed, atrial rate was the independent variable and CO and SV were
dependent variables. As HR is increased, CO and SV are modified by reflex
and other circulatory regulators. The dSV/dHR relation characterized the
circulatory response to increasing HR. A single dSV/dHR curve consistently
predicted responses under a number of different conditions (standing,
recumbent, awake, various anesthetics, beta-adrenergic stimulation, or
depression) and thus appeared as an expression of cardiac function.
Alterations of the circulation by stellate ganglion or vagal stimulation,
volume loading, aortic compression, and ventricular pacing were not
represented by the same dSV/dHR function. The dSV/dHR function (including
its linear version as reported by others for anesthetized dogs) showed
that, when SVs were larger at low rates, maximum CO occurred at a higher
HR. Recognition of this arithmetic-based feature resolves apparent
contradictory findings reported in the literature.
