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INTRODUCTION: Low amplitude rhythmic contractions (LARC) have been identified in detrusor smooth muscle. Although LARC function is not well−understood, they may play a role in overactive bladder (OAB). The purpose of this study was to correlate in vitro LARC in strips of human bladder with in vivo LARC identified during urodynamics.
MATERIALS AND METHODS: In vitro analysis of LARC was examined by obtaining full thickness bladder strips from uninvolved cystectomy portions in 6 patients. Steady-state tension data were analyzed by fast Fourier transform (FFT) to quantify LARC. In vivo analysis of LARC was examined through retrospective review of 100 consecutive blinded urodynamics tracings for signs of LARC on the vesicular (P_ves) tracing that were not also identified on the abdominal (P_abd) tracing. Pressure data was normalized and underwent FFT analysis. Identified frequencies were considered distinct if > 3 standard deviations in amplitude above the mean normalized P_abd amplitude.
RESULTS: In vitro analysis of LARC using bladder strips identified distinct frequencies at 0.039±0.015 Hz. In vivo analysis of LARC in urodynamics studies identified 35 studies that visually displayed LARC. In 12/35 (34%), a distinct frequency of 0.039±0.006 Hz was observed. LARC frequencies were similar in both in vivo (bladder strips) and in vitro (urodynamics) studies (p=0.92).
CONCLUSIONS: Analysis of LARC identified an underlying bladder frequency of 0.039Hz that was nearly identical in both in vitro analysis of bladder strips and during in vivo clinical urodyanmics testing. Further refinements of this technique may help identify sub−sets of individuals with LARC−mediated OAB.