Chronic heart failure was associated with significantly higher resting muscle sympathetic nerve activity (62 vs 39 bursts per minute; P<0.01) and absent low-frequency variability compared to controls.
Observational (n=33)
The absence of low-frequency variability in sympathetic nerve activity in severe heart failure suggests central autonomic regulatory impairment and is associated with worse clinical parameters and mortality.
Absolute Event Rate: 62% vs 39%
p-value: p=<.01
BACKGROUND: In normal humans, variability of blood pressure, RR interval, and sympathetic activity occurs predominantly at a low frequency (LF; 0.04 to 0.14 Hz) and a high frequency (HF; +/-0.25 Hz). In conditions that increase sympathetic activation in normal humans, the LF component is increased relative to the HF component. Patients with heart failure have high levels of sympathetic activity. We tested the hypothesis that the LF component of sympathetic nerve activity variability is increased in heart failure. METHODS AND RESULTS: We performed spectral analysis of simultaneous recordings of resting muscle sympathetic nerve activity (MSNA) and RR interval in 21 patients with chronic heart failure and 12 age-matched control subjects. MSNA was higher in patients with heart failure (62 +/- 4 bursts per minute) than in the normal subjects (39 +/- 4 bursts per minute; P < .01). LF components of RR interval and MSNA variability were lower in the heart failure patients versus the control subjects (P < .01). HF variability of RR interval and MSNA was preserved, at least in part, in heart failure. There was close coherence between variability patterns of RR interval and MSNA. Furthermore, in 14 heart failure patients who had no LF variability in MSNA compared with 7 heart failure patients who did manifest LF variability in MSNA, RR interval was shorter, the variance of RR interval was lower, MSNA was higher, respiratory rate was faster, and left ventricular ejection fraction was lower (all P < .05). At a median follow-up of 12 months, 4 heart failure patients had died, all of whom had had absent LF oscillations in MSNA and RR interval. CONCLUSIONS: The LF variability of sympathetic nerve activity is absent in patients with severe heart failure. This disturbed pattern of variability is closely coherent with the abnormal variability of RR interval. These disturbances of rhythmic oscillations of autonomic outflow, evident in both RR interval and MSNA, suggest a central autonomic regulatory impairment in heart failure and may have important prognostic implications.
Borne et al. (1997) conducted an observational in Chronic heart failure (n=33). Chronic heart failure (exposure) vs. Age-matched normal control subjects was evaluated on Resting muscle sympathetic nerve activity (MSNA) bursts per minute (p=<.01). Chronic heart failure was associated with significantly higher resting muscle sympathetic nerve activity (62 vs 39 bursts per minute; P<0.01) and absent low-frequency variability compared to controls.
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