Baroreflex Sensitivity: Measurement and Clinical Implications

Abstract

Alterations of the baroreceptor-heart rate reflex (baroreflex sensitivity, BRS) contribute to the reciprocal reduction of parasympathetic activity and increase of sympathetic activity that accompany the development and progression of cardiovascular diseases. Therefore, the measurement of the baroreflex is a source of valuable information in the clinical management of cardiac disease patients, particularly in risk stratification. This article briefly recalls the pathophysiological background of baroreflex control, and reviews the most relevant methods that have been developed so far for the measurement of BRS. They include three "classic" methods: (i) the use of vasoactive drugs, particularly the α-adrenoreceptor agonist phenylephrine, (ii) the Valsalva maneuver, which produces a natural challenge for the baroreceptors by voluntarily increasing intrathoracic and abdominal pressure through straining, and (iii) the neck chamber technique, which allows a selective activation/deactivation of carotid baroreceptors by application of a negative/positive pressure to the neck region. Two more recent methods based on the analysis of spontaneous oscillations of systolic arterial pressure and RR interval are also reviewed: (i) the sequence method, which analyzes the relationship between increasing/decreasing ramps of blood pressure and related increasing/decreasing changes in RR interval through linear regression, and (ii) spectral methods, which assess the relationship (in terms of gain) between specific oscillatory components of the two signals. The limitations of the coherence criterion for the computation of spectral BRS are discussed, and recent proposals for overcoming them are presented. Most relevant clinical applications of BRS measurement are finally reviewed with particular reference to patients with myocardial infarction and heart failure. Ann Noninvasive Electrocardiol 2008;13(2):191-207baroreceptors; baroreflex sensitivity; autonomic nervous systemThe evaluation of baroreflex sensitivity (BRS) is an established tool for the assessment of autonomic control of the cardiovascular system. Besides the well-acknowledged physiological role in the maintenance of circulatory homeostasis, evidence has been accumulated that changes in the characteristics of baroreflex function reflect alterations in autonomic control of the cardiovascular system. 1 Thus, measuring the baroreflex has been shown to be a source of valuable information in the clinical management, particularly in prognostic evaluation and assessment of treatment effect, in a variety of cardiac diseases. Although several methods have been developed to study baroreflex function in humans, most of these techniques are of limited value for a daily practice in the clinical setting. This article will briefly address the pathophysiological background of baroreflex control, will focus on the advantages and limitations of the different methodologies in the quantification of baroreflex activity, and will discuss the main clinical findings and the most relevant implicati...

Brain nitric oxide production by a proline-rich decapeptide from Bothrops jararaca venom improves baroreflex sensitivity of spontaneously hypertensive rats

“…Clinical evidence has associated arterial baroreflex dysfunction with many cardiovascular diseases, the sudden death of patients suffering acute myocardial infarction and mortality in patients with congestive heart failure. 17 Changes in neural-cardiovascular integration due to NO deficiency may be the main cause of autonomic abnormalities in several models of experimental hypertension 2 as a consequence of impaired arterial baroreflex. 3,18 As a result of augmented ASS activity, an enzyme also expressed in the CNS, 6 and central effects on the control of blood pressure 11,14 in the presence of Bj-PRO-10c, we expected to observe increased NO production in the brain and improved arterial baroreflex function in conscious SHRs.…”

Endogenous leptin contributes to baroreflex suppression within the solitary tract nucleus of aged rats

“…HR was derived from the AP wave. The evoked BRS was measured by the Oxford method in which randomized, intravenous boluses of graded doses of phenylephrine or sodium nitroprusside (2, 5, and 10 g/kg in 0.9% NaCl) are given to increase or decrease pressure, respectively (26). The BRS was determined for each animal as the slope of the relationship between changes in MAP and the pulse interval (60,000/HR).…”

Maternal Diabetes Increases Small Conductance Ca2+-Activated K+(SK) Currents That Alter Action Potential Properties and Excitability of Cardiac Motoneurons in the Nucleus Ambiguus

“…Recently Wichi et al (2005) found that maternal diabetes impairs baroreflex control of heart rate (HR) in offspring of STZ-induced diabetic mothers. Because attenuation of baroreflex sensitivity is associated with many cardiovascular diseases including sudden death (La Rovere et al 2008), it is critically important to study the effects of maternal diabetes on the neural components within the baroreflex circuitry.…”