Influence of Arterial Baroreceptors on Heart Rate Variability

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Abstract
Objective: Fluctuations in heart rate, blood pressure and other circulatory parameters have been described since the last century, but only recently the observation that changes in these fluctuations are associated with changes in the sympathovagal balance and with the activity of the arterial baroreflexes has led to the practical use of analysis of cardiovascular variability as a marker of autonomic function. The present review reports the various hypotheses on the origin of fluctuations in cardiovascular variability and the possibility to apply these observations to the clinical field. Method: Two main oscillatory components have been described in the cardiovascular system: one is related to the respiratory activity; a second component whose period is ∼10 s is independent of respiration. These can be accurately quantified by computerized methods based on spectral analysis. These fluctuations might not only be used as a marker of vagal and sympathetic activity, but also provide information on the activity of the arterial baroreflex. A practical approach to obtain this data is discussed. Results: Practical implications of this methodology involve the non-invasive assessment of baroreflex activity and sympathovagal balance under a large number of physiologic and pathologic conditions. In this article the application to the autonomic assessment during physical exercise and after cardiac transplantation is reviewed in depth. Conclusions: The arterial baroreceptors exert a strong, though not exclusive influence on the cardiovascular fluctuations, through both sympathetic and vagal activity. These might be conveniently evaluated by non-invasive techniques involving spectral analysis of cardiovascular variability.