Assessment of the autonomic control of the cardiovascular system by a frequency domain approach

In the current chapter we shall present the crucial features making the frequency domain approach to cardiovascular and sympathetic postganglionic discharge (i.e., muscle sympathetic nerve activity, MSNA) variability an effective tool to assess the baroreceptor and autonomic changes attending different physiological and pathophysiological conditions. It will be given evidence about the suitability of spectrum analysis techniques to address the effects of respiration on heart rate, blood pressure, and MSNA and to evaluate side-related differences in the baroreceptor function during carotid baroreceptor rhythmic stimulation in healthy individuals. Finally, it will be shown how frequency domain-based techniques can assess baroreceptor capability to synchronize heart rate, blood pressure, and MSNA spontaneous variability according to a 10-s rhythmicity. Such a sympathetic discharge pattern seems to be a feature necessary to arterial vessel to properly vasoconstrict in response to the sympathetic activation attending the upright position.