Spectral heart rate variability analysis in experimental obstructive and chemical overactive bladder models.

BACKGROUND Overactive bladder (OAB) is a clinical entity with complex, still incompletely understood pathophysiology, involving central and peripheral autonomic nervous system (ANS) disturbances. OBJECTIVES The aim of the study was to estimate ANS activity using spectral analysis of heart rate variability (HRV) in two experimental overactive bladder models: chemical, evoked by cyclophosphamide treatment (COAB), and obstructive, produced by proximal partial bladder outlet obstruction (OOAB). MATERIAL AND METHODS 10 COAB rats and 10 OOAB rats with appropriate control groups were studied (40 animals total were enrolled in the study). In all groups studied, resting HRV recordings were performed. Standard spectral HRV parameters were analysed. The bladder overactivity was confirmed by urodynamic recordings and histological assessment. RESULTS In COAB, all non-normalized spectral HRV parameters were diminished, while OOAB rats were mostly characterized by pronounced LF (Low Frequency) and HF (High Frequency) decrease. Normalized (nLF and nHF) parameters achieved similar values in both COAB and OOAB. In the analysis of percentages of the individual components in the total HRV power, the OOAB group showed almost double VLF (Very Low Frequency) percentage as compared to the control. OOAB rats also displayed the highest disproportion between VLF and both HF and LF percentages. Contrary to the OOAB, there were small differences in the percentage participation of the separate HRV components in COAB. CONCLUSIONS For both COAB and OOAB models, the authors demonstrated a decrease in the values of spectral HRV parameters, which may reflect ANS disturbances. Moreover, in OOAB animals, apart from total HRV power reduction, exaggerated differences between VLF percentage and the remaining components were revealed. In authors' opinion, their findings concerning VLF differences may reflect increased autonomic disturbances in the OOAB model.