[Autonomic nervous system activity in IBS patients estimated by heart rate variability (HRV)]

The mixed irritable bowel syndrome (IBS) is a functional disorder concerned with diarrhea and constipation without organic changes. The etiology of IBS is complex, concerning with the changing psychological factors and associated with the autonomic dysfunction ultimately. The aim of the study was the estimation of the autonomic nervous system (ANS) activity in IBS patients using time and frequency domain analysis parameters of heart rate variability.

10 patients (47.3 +/- 12.5 years) with typical IBS symptoms in mixed form (diarrhoea and constipation) and 10 healthy persons (49.1 +/- 8 yrs) were studied. The control group was matched by age and gender. Each subject underwent 5-minutes, resting heart rate variability recording, during deep breathing (DB) test (6 breath/min) and 24-hour ECG monitoring using Holter equipment. In each case time and spectral domain analysis HRV parameters were obtained.

Short-term HRV recording: In IBS patients we noted the decrease of the all parameters of the HRV spectral domain analysis in comparison to the control group (VLF--468.1 [ms2] vs. 906.3 [ms2]; LF--437.1 [ms2] vs. 811.6 [ms2]; HF--271.5 [ms2] vs. 854.6 [ms2]; p < 0.05 respectively). During DB test increase of LF power (2005.2 [ms2] vs. 6652.1 [ms2]; p < 0.05) and HF power (328.8 [ms2] vs. 901.7 [ms2]; p < 0.05) was observed in both group, however the response was lower in IBS patients. Circadian HRV recording: In IBS patients normalised parameter nHF was increased in both day and night periods in comparison to the control (35.5 [n.u.] and 38.5 [n.u.] vs. 22.0 [n.u.] and 25.7 [n.u.] respectively) while normalised nLF parameter was in both periods of registration lower in IBS patients of approximately 50% (the day--37.9 [n.u.] vs. 76.9 [n.u.]; the night--40.7 [n.u.] vs. 71.6 [n.u.]; p < 0.05).

Our results indicate changes of the circadian ANS activity in patients with mixed IBS: the increase of the parasympathetic and the decrease of the sympathetic activity. However the ANS response to parasympathetic stimulation in DB test was diminished.