A study of repeated measures of hemodynamics, muscle sympathetic nerve activity and their spectral oscillations

V. K. Somers, P. Van De Borne, N. Montano, M. Pagani, B. Zimmerman

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Background: Low-frequency (LF) and high-frequency (HF) components of RR interval (RR) variability are widely used as indirect markers of cardiac autonomic control but their reproducibility is unknown. We determined the intra-class correlation coefficients (ICC) of repeated measures of the mean levels and variability of RR and muscle sympathetic nerve activity (MSNA) in 7 normal subjects. We also determined whether spontaneous fluctuations in RR and MSNA over repeated measurements were mirrored by fluctuations in spectral components of these variables. Methods: Twenty minute recordings of respiration, RR, blood pressure (BP) and MSNA were performed at day 1, 1 week, 1 month and 3 months. Comparison between these recordings determined the long-term reliability. Results: The long-term reliability of the variability of RR was comparable to the variability of MSNA (range of ICC: .34 - .52). Spontaneous decreases in RR during the repeated recordings were paralleled by increases in the ratio of low-frequency to high-frequency variability (LF:HF ratio) of RR interval (r=-.43, p<.01) and by increases in MSNA (r=-.36, p=.01). The spontaneous changes in the LF:HF ratio of RR were mirrored by parallel changes in the LF:HF ratio of MSNA (r=+.30, p<.05). Spontaneous decreases in BP were accompanied by increases in the LF:HF ratio of MSNA (r=-.52; p=.0001). Conclusion: Spontaneous fluctuations in repeated measurements of resting blood pressure and RR interval over the long term are accompanied by parallel changes in the normalized spectral components of RR and MSNA variability.

Original languageEnglish (US)
Pages (from-to)A455
JournalFASEB Journal
Issue number3
StatePublished - 1997

ASJC Scopus subject areas

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics


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