Investigation of the correlation between heart rate and heart rate variability

Pathologic conditions are frequently associated with marked changes in heart rate (HR), which itself influences its variability (HRV). Accordingly, some researchers consider the HR and the HRV to be equivalent measures. The question was posed: Does the HRV afford different information than the HR itself? The HRV were investigated in ten patients during a normal autonomic tone and a pharmacological autonomic blockade, respectively. The results were analysed by calculation of the product-moment correlation coefficient and by means of linear regression of the HRV and the HR. Significant correlations were found between the HR and all of the HRV bands. The regression coefficients of the HR and HRV increased markedly after a sympathetic blockade. The extent of the regression decreased to nearly zero during a total vegetative blockade. It was concluded that (1) There is a significant negative correlation between the HR and the HRV; (2) The degree of this connection is influenced markedly by the actual tone of the autonomic nervous system, which means different information contents of the HR and its variability in the autonomic regulation of the circulation.