Simultaneous measurements of cardiac noradrenaline spillover and sympathetic outflow to skeletal muscle in humans.

Abstract

SUMMARY1. Muscle sympathetic nerve activity (MSA) was recorded in the peroneal nerve at the knee by microneurography in ten healthy subjects and determinations were made simultaneously of intra-arterial blood pressure, and whole-body and cardiac noradrenaline spillover to plasma. Measurements were made at rest, during isometric handgrip at 30% of maximum power and during stress induced by forced mental arithmetic.2. At rest there were significant positive correlations between spontaneous MSA (expressed as number of sympathetic bursts min-) and both spillover of noradrenaline from the heart and concentration of noradrenaline in coronary sinus venous plasma.3. Both isometric handgrip and mental arithmetic led to sustained increases of blood pressure, heart rate and MSA. Plasma concentrations of noradrenaline and spillover of noradrenaline (total body and cardiac) increased. In general the effects were more pronounced during handgrip than during stress. 4. When comparing effects during handgrip and stress the ratio between the fractional increases of MSA and cardiac noradrenaline spillover were significantly greater during handgrip.5. The data suggest (a) that there are proportional interindividual differences in the strength of resting sympathetic activity to heart and skeletal muscle which are determined by a common mechanism and (b) that handgrip and mental stress are associated with differences in balance between sympathetic outflows to heart and skeletal muscle.

Sympathetic Nerve Activity in the Congenital Long-QT Syndrome

“…Support for the concept of a reduction in cardiac sympathetic drive in patients with LQTS emerges: first, from the slower heart rates; second, from the lower LF and LF/HF of RR variability; and third, from evidence that lower levels of MSNA are consistently and strongly associated with low levels of cardiac norepinephrine spillover 13,14 and decreased levels of coronary sinus norepinephrine. 13 Thus, this constellation of findings is very suggestive of a decreased level of cardiac sympathetic drive in patients with untreated LQTS.…”

The effect of gender on the sympathetic nerve hyperactivity of essential hypertension

“…8 However, in normal subjects a correlation has been reported between MSNA and the sympathetic drive to the heart and the kidney as assessed by norepinephrine spillover rate. 37,38 Also, in EHT patients an increase of MSNA as well as the sympathetic drive to the heart and the kidney have been reported 8 indicating a generalized activation of the sympathetic drive. Indeed, there have been reports using indirect indices of sympathetic nerve activity showing that men have a predominance of sympathetic effects on the heart interval using spectral analysis, 39,40 and higher circulating catecholamine levels than women.…”

Low-Dose Atropine Attenuates Muscle Sympathetic Nerve Activity in Healthy Humans.

“…There is a relationship between rising blood pressure and heightened MSNA (27). Wallin et al reported that there were significantly positive correlations between spontaneous MSNA and both spillover of noradrenaline from the heart and concentration of noradrenaline in coronary sinus venous plasma (28). Thus, measurement of MSNA is a useful method for determining the sympathetic nerve activity in human hypertension, whereas it provides no direct information regarding sympathetic nerve activity to other organs such as the kidney and heart.…”