Minute-to-minute covariations in cardiovascular activity of conscious dogs

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Abstract
Cardiovascular activity of chronically instrumented conscious dogs was monitored continuously during daily sessions of rest or of intermittent aversive stimulation. Analysis of minute-to-minute averages revealed that cardiovascular variables changed in patterns, rather than as isolated independent events. Variations in cardiac output were highly positively correlated with concurrent variations in heart rate in all subjects under both conditions (mean r [correlation coefficient] = +0.93). Variations in heart rate were 2-5 times as great as stroke volume, which was remarkably constant (coefficient of variation averaged 4.6%). Variations in mean arterial pressure were consistently correlated with the variations in cardiac output (mean r = +0.66) and heart rate (mean r = +0.68), but were poorly correlated with small changes in stroke volume (mean r = -0.17) and total peripheral resistance (mean r = -0.16).