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PubMed · 1619751

[Heart rate variability].

Abstract

Heart rate variability (HRV) has become a useful parameter for the quantification of autonomic nervous function. HRV has been quantified, either by time domain or frequency domain analysis. Time domain measures, such as CVRR and RR50, are easy to calculate but they only provide information related to parasympathetic activity. The spectral analyses, on the other hand, give us information concerning 3 oscillatory components. The high frequency band (the frequency between 0.15-0.5 Hz) is known as the respiratory sinus arrhythmia (RSA), and the middle frequency band (0.88-0.15 Hz) is attributed to baroreflex components. The low frequency band (0.01-0.08 Hz) may be of various origins, such as blood flow rhythm, periodic respiration (including Cheyne-Stokes respiration), renin-angiotensin, and thermal regulation. The efferent nerve to the high frequency band is totally operated by the parasympathetic system. The low frequency band is regulated by both sympathetic and parasympathetic nervous systems. We demonstrated that the diurnal variation of HRV may afford additional information, such as ultradian changes of autonomic activity, possibly due to REM/NREM cycles. It is believed that simultaneous monitoring of other physiological parameters such as EEG, EOG, respiration, and blood pressures, might give us information concerning the dynamic nature of autonomic nervous function.

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BibTeXRIS

M Miyamoto, Y Ichimaru, S Katayama. 1992. [Heart rate variability].. https://pubmed.ncbi.nlm.nih.gov/1619751/

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Cardiovascular and cerebrovascular responses to lower body negative pressure in type 2 diabetic patients.

In diabetic patients, vascular disease and autonomic dysfunction might compromise cerebral autoregulation and contribute to orthostatic intolerance. The aim of our study was to determine whether impaired cerebral autoregulation contributes to orthostatic intolerance during lower body negative pressure in diabetic patients. Thirteen patients with early-stage type 2 diabetes were studied. We continuously recorded RR-interval, mean blood pressure and mean middle cerebral artery blood flow velocity at rest and during lower body negative pressure applied at -20 and -40 mm Hg. Spectral powers of RR-interval, blood pressure and cerebral blood flow velocity were analyzed in the sympathetically mediated low (LF: 0.04-0.15 Hz) and the high (HF: 0.15-0.5 Hz) frequency ranges. Cerebral autoregulation was assessed from the transfer function gain and phase shift between LF oscillations of blood pressure and cerebral blood flow velocity. In the diabetic patients, lower body negative pressure decreased the RR-interval, i.e. increased heart rate, while blood pressure and cerebral blood flow velocity decreased. Transfer function gain and phase shift remained stable. Lower body negative pressure did not induce the normal increase in sympathetically mediated LF-powers of blood pressure and cerebral blood flow velocity in our patients indicating sympathetic dysfunction. The stable phase shift, however, suggests intact cerebral autoregulation. The dying back pathology in diabetic neuropathy may explain an earlier and greater impairment of peripheral vasomotor than cerebrovascular control, thus maintaining cerebral blood flow constant and protecting patients from symptoms of presyncope.

Autonomic Nervous System Diseases↗