Review article
Sympathetic rhythms and cardiovascular oscillations

https://doi.org/10.1016/S1566-0702(01)00264-8Get rights and content

Abstract

Spectral analysis of heart rate and arterial pressure variabilities is a powerful noninvasive tool, which is increasingly used to infer alterations of cardiovascular autonomic regulation in a variety of physiological and pathophysiological conditions, such as hypertension, myocardial infarction and congestive heart failure. A most important methodological issue to properly interpret the results obtained by the spectral analysis of cardiovascular variability signals is represented by the attribution of neurophysiological correlates to these spectral components. In this regard, recent applications of spectral techniques to the evaluation of the oscillatory properties of sympathetic efferent activity in animals, as well as in humans, offer a new approach to a better understanding of the relationship between cardiovascular oscillations and autonomic regulation.

Section snippets

LF and HF oscillations in motor and premotor sympathetic neurons

In an earlier study (Montano et al., 1992) performed on decerebrate, artificially ventilated cats, we observed the presence of the two main rhythms, LF and HF, in the variability of the discharge of cardiac sympathetic efferent fibers. Both these oscillatory components were highly coherent with the similar spectral components detectable in the variability of RR interval and systolic arterial pressure (SAP), and underwent parallel changes during hemodynamic maneuvers. Briefly, increases in

LF and HF oscillations and sympathetic spinal network

Since the neural regulation of cardiovascular function is integrated not only at supraspinal but also at spinal level, thereby including sympatho-sympathetic reflexes Malliani et al., 1975, Coote, 1988, we wondered whether LF and HF rhythmicities could be found also in sympathetic spinal outflow. Indeed, it has long been known that spinal structures provide a tonic sympathetic discharge compatible with resting blood pressure within a physiological range Sherrington, 1906, Beacham and Perl, 1964

Independence of LF of HRV from hemodynamic oscillations

The capability of central structures generating an LF rhythm is strongly suggested also by a study (Cooley et al., 1998) performed on two patients with severe congestive heart failure (CHF), who underwent the implantation of a left ventricular assist device (LVAD). This device, used as a bridge to cardiac transplantation in intractable heart failure, obtains oxygenated blood from the native left ventricle and sends it to the arterial circulation. Thus, these patients represent a unique model in

LF and HF oscillations in muscle sympathetic nerve activity

The advent in recent years of direct intraneural microneurographic recordings of efferent sympathetic nerve traffic, to both muscle blood vessels (MSNA) and skin blood vessels (SSNA), has allowed us to address this issue also in human beings Wallin, 1983, Mark et al., 1985.

Previous studies in human healthy volunteers reported the presence of both LF and HF oscillations in spectral profile of MSNA Eckberg et al., 1985, Saul et al., 1990. However, they did not investigate the correlation between

Conclusions

In numerous circumstances, the increase in sympathetic activity seems to be associated with a simultaneous enhancement of its LF rhythm and, conversely, with a decrease of its HF component. The reciprocal organization seems to be a fundamental characteristic of central autonomic cardiovascular control.

The relative distribution of power between these two oscillatory frequencies is tightly linked to changes in the strength of the signal, so that one oscillatory frequency is a marker of excitation

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