Background: Pelvic Floor EMG LagTime (PFELT), is defined as the time between pelvic floor relaxation (first stage of normal volitional voiding) and start of Urine flow measured on Uroflow/EMG (average PFELT normally 2-6 seconds). As originally reported, when <2sec there was high correlation with detrusor overactivity (DO) and >6sec, with Primary Bladder neck dysfunction (PBND), findings validated on paired Videourodynamics for both conditions. With increasing confidence in diagnostic reliability with Uroflow/EMG/PFELT, videourodynamics can be reserved for more complicated cases, and PFELT, a valuable tool monitoring treatment response, as successful treatment results in PFELT and other uroflow parameters returning to normal, paired with clinical improvements. Most importantly, PFELT measurements are not singularly diagnostic. They are contextual, drawing greatest significance from the circumstances underwhich Uroflow/EMG was performed, associated uroflow parameters and goodness of fit with clinical history. However, despite increasing utilization some questions have arisen regarding measurement that warrant addressing. Methods: A qualitative study involved semi-structured interviews with advanced practice providers at 3 centers who regularly perform uroflow/EMG studies was conducted to elicit concerns regarding PFELT measurement/interpretation. Uroflow/EMG studies of concern at each center were also reviewed. From these interviews, points of confusion regarding how to correctly measure PFELT and pitfalls in interpretation were identified and discussed. Results: Caveats to accurately measure PFELT and avoid mis/over interpretation: 1) There needs a discernable point of demarcation between increased EMG activity/pelvic floor muscle recruitment and volitional relaxation prior to the start of flow (ideally EMG remains quiet from that point, but short intermittent spikes in response to movement/straining should be ignored); if there is no PF muscle recruitment PFELT cannot be measured; 2) Proper EMG Patch placement (margin of external anal sphincter) to minimize electrical artefact and appropriate EMG sensitivity scales to avoid over/under magnifying EMG appearance; 3) Study should be performed when there’s definite urge to void and adequate bladder volume mirroring the sensation and volume they most typically toilet; 4) When a short PFELT (≤ 2sec) is noted it should be paired with urgency at that moment and consistent with the clinical history and usually paired with early maximum flow rate (Fig.1A); if PFELT is normal, it doesn’t exclude the patient having DO, only that it was not occurring at that time (i.e. volume insufficient to trigger, or DO had been successfully aborted just prior). 5) Likewise, prolonged PFELT (typically ≥double normal range) in PBND should be paired with historical hesitancy and/or straining to initiate/sustain voiding and typically associated with more depressed flow and maximum flow occurring late (Fig.1B).
Conclusions: With attention to performance detail, Caveats of measurement and awareness of pitfalls in interpretation, PFELT demonstrates its greatest value diagnostically and monitoring clinical response in DO and PBND, particularly in children where the nature of their voiding disorder can be obscure, and symptoms and flow pattern without EMG alone can be misleading.
