Abstract
AIMS: To describe parameters from urodynamic pressure recordings that describe urinary bladder contractility through the use of principles of muscle mechanics. METHODS: Subtracted detrusor pressure and voided flow were recorded from patients undergoing filling cystometry. The isovolumetric increase of detrusor pressure, P, of a voluntary bladder contraction before voiding was used to generate a plot of (dP/dt)/P versus P. Extrapolation of the plot to the y-axis and the x-axis generated a contractility parameter, v(CE) (the maximum rate of pressure development) and the maximum isovolumetric pressure, P(0) , respectively. Similar curves were obtained in ex vivo pig bladders with different concentrations of the inotropic agent carbachol and shown in a supplement. RESULTS: Values of v(CE) , but not P(0) , diminished with age in female subjects. v(CE) was most significantly associated with the 20-80% duration of isovolumetric contraction t(20-80) ; and a weaker association with maximum flow rate and BCI in women. P(0) was not associated with any urodynamic variable in women, but in men was with t(20-80) and isovolumetric pressure indices. CONCLUSIONS: The rate of isovolumetric subtracted detrusor pressure (t(20-80) ) increase shows a very significant association with indices of bladder contractility as derived from a derived force-velocity curve. We propose that t(20-80) is a detrusor contractility parameter (DCP). Neurourol. Urodynam. 36:1009-1014, 2017. © 2016 Wiley Periodicals, Inc.