Dissociation between microneurographic and heart rate variability estimates of sympathetic tone in normal subjects and patients with heart failure

1999 ◽  
Vol 96 (6) ◽  
pp. 557-565 ◽  
Author(s):  
Catherine F. NOTARIUS ◽  
Gary C. BUTLER ◽  
Shin-ichi ANDO ◽  
Michael J. POLLARD ◽  
Beverley L. SENN ◽  
...  
Keyword(s):  
Heart Failure ◽  
Heart Rate ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Low Frequency ◽  
Normal Subjects ◽  
Left Ventricular ◽  
Nerve Activity ◽  
Heart Failure Patients ◽  
Sympathetic Nervous

The concept that spectral analysis of heart rate variability (HRV) can estimate cardiac sympathetic nerve traffic in subjects with both normal and impaired left ventricular systolic function has not been validated against muscle sympathetic nerve activity (MSNA). We used coarse-graining spectral analysis to quantify the harmonic and non-harmonic, or fractal, components of HRV and to determine low-frequency (0.0–0.15 Hz; PL) and high-frequency (0.15–0.5 Hz; PH) harmonic power. To test the hypothesis that MSNA and HRV representations of sympathetic nerve activity (PL and PL/PH) increase in parallel in heart failure, we recorded heart rate and MSNA during supine rest in 35 patients (age 52.4±2 years; mean±S.E.M.), with a mean left ventricular ejection fraction of 22±2%, and in 34 age-matched normal subjects. Power density was log10 transformed. Mean MSNA was 52.9±2.6 bursts/min in heart failure patients and 34.9±1.9 bursts/min in normal subjects (P < 0.0001). In normal subjects, but not in heart failure patients, total power (PT) (r = -0.41; P = 0.02) and fractal power (PF) (r = -0.36; P = 0.04) were inversely related to age. In heart failure patients, total and fractal power were reduced (P < 0.009 for both), and were inversely related to MSNA burst frequency (r = -0.55, P = 0.001 and r = -0.60, P = 0.0003 respectively). In normal subjects, there was no relationship between MSNA and either PL or PH. In heart failure patients, as anticipated, PH was inversely related to MSNA (r = -0.41; P < 0.02). However, PL was also inversely rather than directly related to MSNA (r = 0.44 for 1/log10 PL; P < 0.01). There was no relationship between other sympathetic (PL/PH) or parasympathetic (PH/PT) indices and MSNA in either heart failure patients or normal subjects. The lack of concordance between these direct and indirect estimates of sympathetic nervous system activity indicates that this component of HRV cannot be used for between-subject comparisons of central sympathetic nervous outflow. It is the absence of low-frequency power that relates most closely to sympathetic activation in heart failure.

Dynamics of muscle sympathetic nerve activity in advanced heart failure patients

1996 ◽  
Vol 271 (5) ◽  
pp. H1962-H1969
Author(s):  
A. H. Nguyen ◽  
A. Garfinkel ◽  
D. O. Walter ◽  
M. A. Hamilton ◽  
G. C. Fonarow ◽  
...  
Keyword(s):  
Heart Failure ◽  
Heart Rate ◽  
Frequency Modulation ◽  
Healthy Subjects ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Low Frequency ◽  
Nerve Activity ◽  
Heart Failure Patients ◽  
Patients With Heart Failure

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.

Relation between QT interval variability and muscle sympathetic nerve activity in normal subjects

2015 ◽  
Vol 309 (7) ◽  
pp. H1218-H1224 ◽  
Author(s):  
Fatima El-Hamad ◽  
Elisabeth Lambert ◽  
Derek Abbott ◽  
Mathias Baumert
Keyword(s):  
Supine Position ◽  
Sympathetic Nerve ◽  
Qt Interval ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Low Frequency ◽  
Normal Subjects ◽  
Nerve Activity ◽  
Head Up Tilt ◽  
Low Frequency Power

Beat-to-beat variability of the QT interval (QTV) is sought to provide an indirect noninvasive measure of sympathetic nerve activity, but a formal quantification of this relationship has not been provided. In this study we used power contribution analysis to study the relationship between QTV and muscle sympathetic nerve activity (MSNA). ECG and MSNA were recorded in 10 healthy subjects in the supine position and after 40° head-up tilt. Power spectrum analysis was performed using a linear autoregressive model with two external inputs: heart period (RR interval) variability (RRV) and MSNA. Total and low-frequency power of QTV was decomposed into contributions by RRV, MSNA, and sources independent of RRV and MSNA. Results show that the percentage of MSNA power contribution to QT is very small and does not change with tilt. RRV power contribution to QT power is notable and decreases with tilt, while the greatest percentage of QTV is independent of RRV and MSNA in the supine position and after 40° head-up tilt. In conclusion, beat-to-beat QTV in normal subjects does not appear to be significantly affected by the rhythmic modulations in MSNA following low to moderate orthostatic stimulation. Therefore, MSNA oscillations may not represent a useful surrogate for cardiac sympathetic nerve activity at moderate levels of activation, or, alternatively, sympathetic influences on QTV are complex and not quantifiable with linear shift-invariant autoregressive models.

Discharge Pattern of Renal Sympathetic Nerve Activity in the Conscious Rat: Spectral Analysis of Integrated Activity

2000 ◽  
Vol 84 (6) ◽  
pp. 2859-2867 ◽  
Author(s):  
Takato Kunitake ◽  
Hiroshi Kannan
Keyword(s):  
Heart Rate ◽  
Power Spectrum ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Low Frequency ◽  
Heart Beat ◽  
Nerve Activity ◽  
Renal Sympathetic Nerve Activity ◽  
Conscious Rats ◽  
Renal Sympathetic

We investigated the periodic characteristics of bursting discharge in renal sympathetic nerve activity (RSNA) in conscious rats. Employing a discrete fast Fourier transform algorithm, a power spectrum analysis was used to quantify periodicities present in rectified and integrated RSNA whose signal-to-noise ratio in the recordings was greater than six. In conscious rats with intact baroreceptors, RSNA was characterized by four frequency components occurring at about 0.5, 1.5, 6, and 12 Hz, which corresponded to the low-frequency fluctuation of heart rate, respiration, and frequency of heart beat, and its harmonics, respectively. After intravenous infusion of sodium nitroprusside (SNP) to elicit reflex increases in RSNA and heart rate, the power for the component at 6 Hz followed the changes in heart beat frequency and was significantly increased, while those for the three other components were attenuated or experienced no change. In sino-aortic denervated (SAD) conscious rats, all four components were abolished, and the power spectrum was well fitted by a flat or Lorentzian curve, suggesting an almost random pattern. Only a respiratory-related component, which suggested common central modulation, appeared sporadically for short periods but was absent for the most part. Therefore most of this component together with the low-frequency component was also likely due to the baroreceptor-dependent peripheral modulation. The activity was sorted in 15 subgroups on the basis of spike amplitudes in the RSNA. Each subgroup showed frequency characteristics similar to the whole nerve activity. These results suggest that all periodicity in the RSNA of conscious rats with intact baroreceptors is caused by the baroreceptor input.

Exercise training reduces sympathetic nerve activity in heart failure patients treated with carvedilol

2007 ◽  
Vol 9 (6-7) ◽  
pp. 630-636 ◽  
Author(s):  
Raffael Fraga ◽  
Fábio G. Franco ◽  
Fabiana Roveda ◽  
Luciana N.J. de Matos ◽  
Ana M.F.W. Braga ◽  
...  
Keyword(s):  
Heart Failure ◽  
Exercise Training ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Nerve Activity ◽  
Heart Failure Patients

Continual recordings of cardiac sympathetic nerve activity in conscious sheep

2002 ◽  
Vol 282 (1) ◽  
pp. H93-H99 ◽  
Author(s):  
David L. Jardine ◽  
Christopher J. Charles ◽  
Ian C. Melton ◽  
Clive N. May ◽  
Melanie D. Forrester ◽  
...  
Keyword(s):  
Heart Rate ◽  
Cardiac Disease ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Low Frequency ◽  
Cardiac Sympathetic Nerve ◽  
Nerve Activity ◽  
Recording Time ◽  
Cardiac Sympathetic Nerve Activity ◽  
Conscious Sheep

Cardiac sympathetic nerve activity (CSNA) is of major importance in the etiology of heart disease but is impossible to measure directly in humans. Ovine and human cardiovascular systems are similar; therefore, we have developed a method for the daily recording of CSNA in conscious sheep. After thoracotomy, electrodes were glued into the left thoracic cardiac nerve and CSNA, blood pressure (BP), and heart rate were recorded daily. Satisfactory recordings ≥7 days of CSNA were obtained in 11 of 28 sheep (40%), mean recording time 10.6 days, range 7-47. During the first week, CSNA decreased gradually from 78 ± 8 at baseline to 60 ± 7 bursts/min on day 5( P = 0.02) or from 76 ± 9 to 57 ± 7 bursts/100 beats on day 7 ( P = 0.04). Similarly, BP decreased from 103 ± 4 to 94 ± 4 mmHg ( P = 0.03). Low-frequency heart rate variability decreased from 0.12 ± 0.02 to 0.06 ± 0.02 ms2on day 6 ( P = 0.004) but was not correlated to CSNA. In conclusion, CSNA that can be continually recorded in conscious sheep decreases during the first week postsurgery and, thereafter, stabilizes. This model should provide valuable insights in future investigations of cardiac disease.

Absence of Low-Frequency Variability of Sympathetic Nerve Activity in Severe Heart Failure

Circulation ◽  
1997 ◽  
Vol 95 (6) ◽  
pp. 1449-1454 ◽  
Author(s):  
Philippe van de Borne ◽  
Nicola Montano ◽  
Massimo Pagani ◽  
Ron Oren ◽  
Virend K. Somers
Keyword(s):  
Heart Failure ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Severe Heart Failure ◽  
Low Frequency ◽  
Nerve Activity ◽  
Low Frequency Variability
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