Background:
Sympathetic activation and arterial baroreflex (ABR) dysfunction typify chronic heart failure (CHF). In addition, decreased oscillatory pattern of muscle sympathetic nerve activity (MSNA, LF
MSNA
/HF
MSNA
) seems to contribute to sympathetic exacerbation in patients with CHF. Unknown is whether the LF
MSNA
/HF
MSNA
is associated with ABR dysfunction in CHF patients. To answer this question, we investigated the association between gain, latency and coupling of ABR function and LF
MSNA
/HF
MSNA
in CHF patients.
Methods and Results:
Forty-three CHF patients, Functional Class II to III, NYHA, ejection fraction ≤40% were allocated into two groups according to the level of LF
MSNA
/HF
MSNA
index: 1) Higher LF
MSNA
/HF
MSNA
(n=21, 52±2 years) and 2) Lower LF
MSNA
/HF
MSNA
(n=22, 54±1 years). Blood pressure (BP, oscillometric beat-to-beat basis) and MSNA (microneurography technique) were recorded during 10 min at rest. Spectral and cross-spectral analyses of BP and MSNA variabilities were conducted to assess the LF
MSNA
/HF
MSNA
and the gain, latency and coupling between BP and MSNA of ABR function. Etiology, ejection fraction, gain and latency of ABR function were similar between groups. However, the patients with lower LF
MSNA
/HF
MSNA
had increased MSNA bursts frequency (53±2vs. 39±3 bursts/min, P<0.01) and total activity (180±15 vs. 126±17 a.u, P=0.03) compared to the patients with higher LF
MSNA
/HF
MSNA
. In contrast, the patients with lower LF
MSNA
/HF
MSNA
had reduced coupling of ABR function (69±3 vs. 80±2 %, P<0.01). Further analysis showed a significant association between the coupling of ABR function and LF
MSNA
/HF
MSNA
(R=0.36, P=0.02).
Conclusions:
There is an inverse association between the LF
MSNA
/HF
MSNA
index and sympathetic nerve activity. In addition, there is a direct association between the LF
MSNA
/HF
MSNA
index and the coupling of ABR, which suggests that the ABR dysfunction explains, at least in part, the augmented sympathetic nerve activity in CHF patients.