Heart rate variability: an objective measure of autonomic activity and bladder sensations during urodynamics

There are still controversies regarding the reproducibility of cystometric data and no objective measurement of bladder sensations is currently available. Additionally, very little information exists about autonomic activity during standard filling cystometry (FC). The aim of this study was to evaluate the use of heart rate variability (HRV) analysis as a reliable monitor of the autonomic nervous system and objective measure for bladder sensations during FC.

In a volunteer sample of healthy female subjects a standard FC at 25 ml/min was performed, using an 8 Fr microtip catheter with integrated pressure transducers. During FC, subjects had to indicate first sensation of filling (FSF), first desire to void (FDV) and strong desire to void (SDV). A 3-lead electrocardiogram was continuously recorded. After 5 h all measurements were repeated. Power spectrum analysis was used to analyse HRV, to obtain low frequency (LF) and high frequency (HF) parameters, from which the LF/HF ratio was derived.

12 subjects with a mean age of 23.3 +/- 2.3 years could be included. 11 of 12 subjects completed both measurement sessions. One subjects had to be excluded, due to irritating urethral discomfort following catheterisation. The LF/HF ratio showed a reproducible activation pattern in the healthy subjects with a stable sympathovagal balance until FDV. Before SDV was indicated, the sympathovagal balance started to shift towards sympathetic activation and caused a significant increase in LF/HF.

HRV analysis seems to be a useful indicator for the general activation pattern of the sympathovagal balance during FC, correlating the intensity of the bladder filling sensation to stress and sympathetic activation.