Study design, materials and methods
Individuals with and without urgency based on ICIq-OAB survey question 5a were prospectively enrolled in a urodynamics (UD) study. Participants were grouped as no/low OAB (5a=0-2) or high OAB (5a=3-4). Vesical and abdominal pressure tracings from these studies were analyzed iteratively throughout the entire filling phase to determine which volume regions contained significant rhythmic amplitude (≥1cm-H2O) in vesical pressure in the frequency range of 1.75 to 8.0 cycles/minute that was independent of rhythmic activity in abdominal pressure (S&I) using an established algorithm [3]. The maximum SRC amplitude and the corresponding frequency were recorded, along with the volumes at which S&I SRC was detected. Individuals were grouped based on whether S&I SRC occurred 1) only during the first half of filling (<50% cystometric capacity, “First Half Only”) or 2) during only the second half of filling or throughout filling (“Second Half or Throughout”).
Results
Data from 143 consecutive participants with sufficient data were analyzed and 49 (34%) were found to have S&I SRC, and these were grouped based on OAB (no/low OAB: n=31/98, 32% or high OAB: n=18/45, 40%). The maximum S&I SRC amplitude was elevated in the high OAB group compared to the no/low OAB group (12.6 cm-H20 and 5.7 cm-H20, respectively, t-test, p<0.05), but the corresponding frequencies were not different (3.85 cycles/minutes and 4.72 cycles/minute, respectively, p>0.05). Of those found to have S&I SRC in the First Half Only of filling, only 1/14 had high OAB (Fig 1). The presence of S&I SRC during the First Half Only was significantly associated with no/low OAB (Fisher’s exact test, p<0.05, Fig 1, *).
Interpretation of results
In this study, S&I SRC was identified in several participants with and without high OAB based on the symptom of urgency, suggesting 1) that not all quantifiable contractile activity, or DO, during UD filling necessarily leads to OAB symptoms or 2) that SRC may be an artifact of UD in some participants. Specifically, individuals with S&I SRC in the First Half Only did not have high OAB (13/14, 93%), suggesting that SRC during the First Half Only of filling may not be clinically relevant. In contrast, individuals with high OAB had S&I SRC either in the Second Half or Throughout filling.