Study of autonomic nervous system through heart rate variability in idiopathic vesical hyperactivity syndrome

Objective: Several studies have suggested a defective automatic nervous system (ANS) in idiopathic vesical hyperactivity syndrome. The study of heart rate variability (HRV) is a non-invasive and validated method for measuring ANS activity. We therefore used this method for vesical filling in a control population (women with stress urinary incontinence : SUI) and in female patients with idiopathic vesical hyperactivity syndrome. Materials and methods: We included 7 women with pure SUI and 3 with idiopathic vesical hyperactivity syndrome. Continuous ECG recording was performed over 10 minutes with an empty bladder and during artificial bladder filling. Heart rate variations were measured by frequential indices: low frequency, which mainly reflected sympathetic modulation, and high frequency, which is related to the parasympathetic system. Results: In the control group, no significant changes in heart rate variations during filling were noted. However, in the idiopathic vesical hyperactivity group, cardiac neurovegetative control was different from the control group, and varied during filling, going from empty bladder parasympathetic hypertonia to sympathetic hypertonia at the end of filling. At the end of filling, when vesical continence is ensured by the sympathetic system, we noted a significant increase in sympathetic tone (P = 0.001), associated with a reduction in cardiac parasympathetic tone (P < 0.0001). These results demonstrate vegetative balance dysfunction in idiopathic vesical hyperactivity syndrome. Conclusion: This preliminary study demonstrates a predominance of parasympathetic activity with an empty bladder and a predominance of sympathetic activity at the end of bladder filling in OAB. The results suggest a defective autonomic nervous system with idiopathic OAB. Further studies in a larger OAB population compared with normal urinary-symptom free patients are necessary to confirm this hypothesis.