AJP - Heart and Circulatory Physiology, Vol 271, Issue 5 1962-H1969, Copyright © 1996 by American Physiological Society
Dynamics of muscle sympathetic nerve activity in advanced heart failure patients
A. H. Nguyen, A. Garfinkel, D. O. Walter, M. A. Hamilton, G. C. Fonarow, J. D. Moriguchi, A. Hage, J. N. Weiss and H. R. Middlekauff
Division of Cardiology, University of California Los Angeles (UCLA) School of Medicine 90095, USA.
Muscle sympathetic nerve activity (MSNA) is increased in patients with
heart failure compared with healthy subjects. We applied spectral and
correlation techniques to determine if qualitative as well as quantitative
differences in MSNA differentiate heart failure patients from healthy
subjects. We recorded MSNA, heart rate, and respiration in 11 heart failure
patients and 10 healthy humans. Our results are as follows. 1)
Statistically significant low-frequency modulation of MSNA at 0.029 +/-
0.002 Hz (mean +/- SE; range 0.026-0.038 Hz) was found in 10 of 11 heart
failure patients but in only 2 of 10 healthy controls (differences between
groups, P < 0.01; chi 2 test). 2) Heart rate and respiration also
demonstrated significant low-frequency modulation in a similar range. 3)
Spectral and correlation techniques revealed that low-frequency modulation
of MSNA was highly correlated with low-frequency modulation of respiration
in heart failure patients, but not in healthy subjects. In contrast,
low-frequency modulation of MSNA did not correlate well with low-frequency
modulation of heart rate. In summary, low-frequency modulation of
respiration is coupled to low-frequency modulation of MSNA in heart failure
patients, but not in normal subjects. We speculate that this low-frequency
modulation of respiration may represent subclinical Cheyne-Stokes
breathing, which has marked qualitative effects on MSNA in patients with
heart failure.
