P129. Morphological changes of the vagus nerve are accompanied by changes of heart rat

Publication date: August 2018

Source: Clinical Neurophysiology, Volume 129, Issue 8

Author(s): D. Weise, J.O. Pelz, E. Belau

Background

The physiological regulation of the heart is determined by the interaction between the sympathetic and the parasympathetic nervous system. The parasympathetic efferent fibers originate from the nucleus ambiguous and the dorsal motor nucleus. Together with the afferent fibers from the spinal trigeminal nucleus and the solitary nucleus they form the vagus nerve (VN). The measurement of the heart rate variability (HRV) enables to assess the relative impact of the parasympathetic and sympathetic innervation on the heart with different impact of the right and left VN. Whether morphological changes of the right and left VN are accompanied by functional changes as indicated by altered HRV parameters is currently unknown.

Methods

Measurement of HRV was performed in 65 healthy subjects (38 women; mean age 52 years, range 23–76 years). RR intervals were measured on electrocardiograms at normal breathing for 10 min under resting and in supine position via the computer-based system ProSciCard (MedSet Medizintechnik GmbH, Hamburg, Germany). Besides heart rate at rest, several indices of the HRV were automatically computed: the standard deviation of RR-intervals (SDNN, higher index indicates higher variability), the root mean square of successive differences (RMSSD, estimate of short-term components of HRV), the number of all RR-intervals/maximal frequency (HRV index, higher index indicates higher variability). In addition, power spectral analyses in the low (ln(LF), 0.05–0.15 Hz) and in the high frequency spectrum (ln(HF), 0.15–0.5 Hz) were performed and the low frequency/high frequency ratio (ln(LF/HF) ratio) as a marker of sympatho-vagal interaction was calculated. In addition, the cross-sectional area (CSA) of the VN was sonographically measured at the level of the thyroid gland. Besides the lateralized assessment of the VN CSA, the ratio between the CSA of the right and left VN was calculated (VN-symmetry index).

Results

There was no correlation between the right or left VN CSA and heart rate at rest or any other HRV parameter in a correlation analyses adjusted for age and sex. However, we found a correlation between the VN-symmetry index and SDNN (0.30, p = 0.029), RMSSD (0.30, p = 0.027), HRV index (0.26, p = 0.055) and the ln(HF) (0.24, p = 0.085).

Conclusions

In a cohort of healthy subjects, morphological changes of both VN as represented by the VN-symmetry index are accompanied by functional changes mainly involving the parasympathetic nervous system. Further studies should examine whether this correlation is altered in (e.g.) neurodegenerative or inflammatory diseases involving the VN.

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