Sympathetic Neural Mechanisms in Human Cardiovascular Health and Disease

Abstract

The sympathetic nervous system plays a key role in regulating arterial blood pressure in humans. This review provides an overview of sympathetic neural control of the circulation and discusses the changes that occur in various disease states, including hypertension, heart failure, and obstructive sleep apnea. It focuses on measurements of sympathetic neural activity (SNA) obtained by microneurography, a technique that allows direct assessment of the electrical activity of sympathetic nerves in conscious human beings. Sympathetic neural activity is tightly linked to blood pressure via the baroreflex for each individual person. However, SNA can vary greatly among individuals and that variability is not related to resting blood pressure; that is, the blood pressure of a person with high SNA can be similar to that of a person with much lower SNA. In healthy normotensive persons, this finding appears to be related to a set of factors that balance the variability in SNA, including cardiac output and vascular adrenergic responsiveness. Measurements of SNA are very reproducible in a given person over a period of several months to a few years, but SNA increases progressively with healthy aging. Cardiovascular disease can be associated with substantial increases in SNA, as seen for example in patients with hypertension, obstructive sleep apnea, or heart failure. Obesity is also associated with an increase in SNA, but the increase in SNA among patients with obstructive sleep apnea appears to be independent of obesity per se. For several disease states, successful treatment is associated with both a decrease in sympathoexcitation and an improvement in prognosis. This finding points to an important link between altered sympathetic neural mechanisms and the fundamental processes of cardiovascular disease.

A comparison of the effects of hyperbaric and isobaric bupivacaine spinalanesthesia on hemodynamics and heart rate variability

“…Short-term regulation of arterial blood pressure is under control of the autonomous nervous system (24). HRV is a noninvasive and straightforward test that shows the balance between sympathetic and parasympathetic systems at the sinoatrial node level (25).…”

Translational Examination of Changes in Baroreflex Function After Renal Denervation in Hypertensive Rats and Humans

“…The class or type of antihypertensive medications may significantly impact BP outcome because they have varying effects on the basal SNA and BP. 41 Conducting scientific studies on patients with the RDN procedure, whether with the Symplicity or other available catheters, is currently problematic. First, there are no prescreening processes that would allow identification of BP responders.…”

Baroreflex sensitivity: mechanisms and measurement

“…Sensed by aortic and carotid baroreceptors, the afferent vagal and glossopharyngeal pathways convey burstlike information regarding every blood pressure (BP) pulsation to the brain stem. Efferent pathways also carry heart beat related nerve traffic: the parasympathetic, vagal limb of the reflex transports burst-like patterns, while the sympathetic limb shows inhibitory responses upon each BP pulsation [1]. Importantly, the heart is permanently under combined parasympathetic and sympathetic influence, which means that the electrophysiological properties of the entire heart, ventricular myocytes, conduction system, but also the atrium and sinus node, are modulated by these two antagonistic influences.…”