Evaluating the use of different waveforms for intravesical electrical stimulation: a study in the rat
Filip De Bock1, Joris Dirckx, Jean-Jacques Wyndaele
1Department of Urology, University of Antwerp and Antwerp University Hospital, Antwerp, Belgium.
Aim:
For decades, monophasic square wave pulses have been used for intravesical electrical stimulation (IVES) in diagnosis and treatment of lower urinary tract dysfunction. The use of other waveforms, more preferred by patients or more effective for neural stimulation, has hardly been studied before. This study compares the effect of several waveforms and derived parameters in IVES.
Methods:
IVES, performed in eight female Sprague-Dawley rats, was given for 300 sec with constant frequency (10 Hz) and current amplitude (6 mA) with unipolar square, biphasic square, asymmetric biphasic square, double square, unipolar exponential rise, biphasic exponential rise, and double-exponential rise wavepulses with different pulse durations (2 × 5 msec, 20 msec, or 2 × 20 msec). Bladder pressure was recorded. Average current and average power were calculated.
Results:
Stimulations with the different waveforms resulted in the same maximal pressure rise (all P>0.1). The average charge was zero for biphasic waveforms. For exponential rise pulse waveforms the total injected charge was lower than that for the monophasic square pulse waveform. The average power was the highest for biphasic waveforms and the lowest for monophasic double-exponential rise pulses waveform.
Conclusions:
Charge-balanced waveforms, which are more preferred by patients, are equally effective in evoking IVES-induced detrusor contraction as monophasic square pulse waveforms. Thus, it can be beneficial in clinical practice to replace the monophasic square pulse waveform for IVES by charge-balanced waveforms. Furthermore, the stimulation power and thus the requested energy can be reduced by changing the waveform. This can be important for electrical stimulation using implanted batteries.
