Spectral change in heart rate variability in response to mental arithmetic before and after the beta-adrenoceptor blocker, carteolol.

Spectral analysis of heart rate fluctuation was evaluated before and after administration of carteolol, a non-selective beta-adrenoceptor-blocker, to investigate the neural regulatory mechanisms underlying the haemodynamic changes induced by mental stress. Mental stress increased blood pressure and heart rate, with an increased low frequency band, and low frequency/high frequency ratio of the power spectral analysis which are indices of sympathetic activity. Carteolol did not change basal and pre-mental stress measurements of blood pressure, heart rate and spectral density. However, carteolol altered the response to mental stress with a decrease in spectral density of the low frequency band and low frequency/high frequency ratio, and an increase in the high frequency component. These results confirm that mental stress elevates blood pressure by activating the sympathetic nervous system, and suggest that blockade of the beta-adrenoceptor attenuates the pressor response by preventing the autonomic responses to mental stress.