Assessment of autonomic nervous activity in hand-arm vibration syndrome patients using time- and frequency-domain analyses of heart rate variation.

OBJECTIVES: The aim of the present study was to non-invasively assess autonomic nervous activity, using time- and frequency-domain analyses of heart rate variation (HRV), and to investigate the relationship between indices of HRV and duration of exposure to vibration (DEV), time since retirement from work involving vibration (TR) and time undergoing treatment (TT) in a group of patients with hand-arm vibration syndrome (HAVS). SUBJECTS AND METHODS: Twenty one HAVS patients who were no longer exposed to vibration and were undergoing standard treatment for HAVS, and 10 healthy control subjects, similar to the patients in age, height, weight and number of current smokers and drinkers, volunteered for this study. Indices of HRV [time-domain indices (the mean of R-R intervals, standard deviation and coefficient of variation) and normalized units of frequency-domain indices [low frequency (LF) and high frequency (HF) components], indicating parasympathetic nervous activity, were calculated from 2 min electrocardiographic data recorded during spontaneous breathing by subjects in supine rest.
RESULTS: The LF and HF components of the patients were significantly lower than those of the healthy controls (P < 0.05). When Pearson correlation analysis was applied for the patient group, using indices of HRV with age, weight, height, DEV, TR and TT, the LF components positively related to TR and TT (P < 0.01). The patients were thus divided into three groups as follows, according to TR: group A (</=1 year), group B (>1 to <5 years) and group C (>/=5 to </=10 years), or according to TT: group X (</=1 year), group Y (>1 to <5 years) and group Z (>/=5 to </=10 years). The LF components of the groups A and X were significantly lower than that of the healthy controls (P < 0.01). The HF components of the groups A and X were also significantly lower than that of the healthy controls (P < 0.05).
CONCLUSIONS: The findings of the present study indicate decreased cardiac parasympathetic activity in the HAVS patients in comparison to the healthy controls. The TT and TR significantly influenced the HRV results in these patients; however, the DEV did not. The findings also indicate that treatment and cessation of exposure to vibration might have a beneficial effect on the cardiac parasympathetic activity in HAVS patients.