Sympathetic neural modulation of arterial stiffness in humans.

Elevated large-artery stiffness is recognized as an independent predictor of cardiovascular and all-cause mortality. The mechanisms responsible for such stiffening are incompletely understood. Several recent cross-sectional and acute experimental studies have examined whether sympathetic outflow, quantified by microneurographic measures of muscle sympathetic nerve activity (MSNA), can modulate large-artery stiffness in humans. A major methodological challenge of this research has been the capacity to evaluate the independent neural contribution without influencing the dynamic blood pressure dependence of arterial stiffness. The focus of this review is to summarize the evidence examining 1) the relationship between resting MSNA and large-artery stiffness, as determined by carotid-femoral pulse wave velocity or pulse wave reflection characteristics (i.e., augmentation index) in men and women; 2) the effects of acute sympathoexcitatory or sympathoinhibitory maneuvers on carotid-femoral pulse wave velocity and augmentation index; and 3) the influence of sustained increases or decreases in sympathetic neurotransmitter release or circulating catecholamines on large-artery stiffness. The present results highlight the growing evidence that the sympathetic nervous system is capable of modulating arterial stiffness independent of prevailing hemodynamics and vasomotor tone.