Arterial Stiffness and the Sympathetic Nervous System

Abstract

This chapter addresses the complex relationship between sympathetic activity and the main factors affecting arterial distensibility. Sympathetic nervous system is considered one of the major elements involved in the regulation of mean arterial pressure, affecting heart rate, left ventricular contractility, and systemic vascular resistance. Actually, in hypertensive patients a permanent increase in mean arterial pressure may cause structural changes in viscoelastic properties of arterial wall, causing a permanent reduction in arterial distensibility. Moreover, heart rate, left ventricular function, and mean arterial pressure can also be considered major functional factors which can cause transient changes in arterial viscoelastic properties. Evidence is available that sympathetic activity plays a major role in modulating the mechanical properties of muscular arteries. This explains the reduction in distensibility of muscular arteries shown under particular conditions of stress, such as exposure to high altitude and, in general, to hypoxia. Changes in sympathetic activity may be influenced by baroreflex regulation of cardiovascular homeostasis. Reflex changes of arterial tone and modifications of cardiac output are the result of this regulation. A carotid and aortic stiffness may be associated with reduced cardiovagal baroreflex sensitivity, with a consequent increase in blood pressure variability, and also with a higher speed of changes in beat-to-beat systolic blood pressure fluctuations typical of hypertension.