Assessment of human sympathetic nervous system activity from measurements of norepinephrine turnover.

Cardiac autonomic modulation and incidence of late potentials in essential hypertension: role of age, sex, ventricular mass and remodeling

“…This phenomenon, observed in a large cohort of patients, extends previous findings which demonstrated a reduction in HRV and sympathetic modulation to the cardiac activity in elderly normotensive subjects, 47 as well as in aged hypertensive patients. 46 However, an age-related decline of sympathetic and parasympathetic response to tilt was described in normotensive subjects 43 but not in hypertensive patients.…”

Sympathetic nervous system behavior in human obesity

“…Unfortunately, the general applicability of plasma NE concentrations suffers from some important limitations. First, the NE entering circulation comprises only a small fraction of that released from presynaptic sympathetic varicosities and plasma NE concentrations do not provide insight into regional behavior of the SNS (Esler et al, 1988). Second, plasma NE concentrations are dependent on the rate of clearance from the circulation and not simply the rate of NE release (Esler et al, 1988).…”

What will be the role of I-123 MIBG in improving the outcome of medically treated heart failure patients?

“…Plasma norepinephrine levels are altered by a wide variety of physical and emotional stimuli that affect norepinephrine release, as well as changes in cardiac output and regional blood flow that vary the rate of removal of norepinephrine from the plasma. 50 Heart rate variability is an indirect method for assessing cardiac sympathetic nerve activity and has been associated with HF outcomes in several studies. 51 Reduced heart rate variability reflects sympathetic autonomic activity, but is also influenced by parasympathetic tone, chemoreceptor function, respiratory rate and tidal volume, mechanical factors (e.g., stretch of the atria from changes in cardiac filling and thoracic pressure), and level of physical activity.…”