SYMPATHETIC MODULATION OF RADIAL ARTERY COMPLIANCE IN CONGESTIVE-HEART-FAILURE

Animal studies have suggested that arterial compliance can be modulate d by adrenergic influences. Whether this adrenergic modulation also oc curs in humans is still a matter of debate. In the present article we address this issue by examining the relationships between sympathetic tone and arterial compliance in a variety of physiological and pathoph ysiological conditions. We have found that cigarette smoking, ie, an a ction that produces a marked sympathetic activation, causes a signific ant reduction in radial artery compliance, as measured by an echotrack ing device capable of providing continuous beat-to-beat evaluation of this hemodynamic variable. When expressed as compliance index, ie, as the ratio between the area under the compliance-pressure curve and pul se pressure, the reduction amounted to 35.7+/-4.8% (mean+/-SEM) and wa s independent of the smoking-related blood pressure increase. Furtherm ore, pharmacological stimulation of adrenergic receptors located in th e arterial wall was also shown to affect arterial compliance because t he radial artery compliance index was markedly reduced (-29.5+/-3.9%) during phenylephrine infusion in the brachial artery at doses devoid o f any systemic blood pressure effect. Evidence was also obtained that the relationship between sympathetic activation and arterial complianc e has pathophysiological relevance, because in 17 patients with conges tive heart failure (New York Heart Association classes II through IV) there was a significant inverse correlation (r=.62, P<.01) between mus cle sympathetic nerve activity (directly measured by microneurography in the peroneal nerve) and radial artery compliance. Finally, we have recently observed that anesthesia of the brachial plexus, a maneuver t hat induces a transient blockade of nerve conduction to the upper limb , markedly increases radial artery compliance (change in compliance in dex, +30.0+/-5.0%). Thus, at least at the radial artery level arterial compliance is under a pronounced tonic restraint by sympathetic influ ences and can be modulated in either direction by reflex or central al terations in sympathetic drive. This modulation has pathophysiological implications.