Role of urethral electromyography in predicting outcome of Burch retropubic urethropexy.

OBJECTIVE: To establish preoperative urethral electromyographic parameters that predict which women are unlikely to be cured of genuine stress incontinence by Burch retropubic urethropexy procedures. STUDY
DESIGN: Eighty-nine women who underwent preoperative urodynamic testing with urethral electromyography and retropubic urethropexy for genuine stress incontinence were prospectively studied. Raw electromyographic signals were processed by an electromyographic instrument equipped with automated motor unit analysis software programs. Quantitative electromyographic software was used to analyze the electrical activity of the urethral sphincter with use of mean rectified voltage (MRV)-mean amplitude calculated over the entire tracing after the waveform is rectified-with women at rest and during voluntary urethral squeezing, repetitive coughing, and bladder filling. Objective outcomes were determined 3 months after the operation with single-channel cystometrograms performed while subjects were standing. Nonparametric statistical analyses included the chi(2) test of association for nominal data and the Mann-Whitney test for comparison of population medians.
RESULTS: All women had urethral hypermobility and met our standard clinical criteria for retropubic urethropexy. Fifteen women had incomplete follow-up data and were excluded from final analysis. Fifty-nine of 74 women (80%) were objectively cured, and 15 women had persistent genuine stress incontinence. Women who were cured did not differ from those who were not cured in age, parity, menopausal status, maximum urethral closure pressure, Valsalva leak point pressure, maximum cystometric capacity, detrusor instability, or prolapse stage. Women with persistent genuine stress incontinence were more likely to have had previous pelvic operations (P =.01). There were no differences in any electromyographic parameters at rest, with urethral squeezing, or during bladder filling between the groups. Women who were objectively cured had larger MRV values with repetitive coughing (P =.05) and larger increases from resting MRV values (DeltaMRV) with repetitive coughing (P =.04). Twenty-seven of 30 women with MRV values > or =25 microV with repetitive coughing were cured (positive predictive value [PPV] = 90%; negative predictive value [NPV] = 32%), and 22 of 24 women with more than a 10-microV increase in resting MRV values with repetitive coughing (DeltaMRV > 10 microV) were cured (PPV = 92%; NPV = 29%). If women had both an MRV value > or =25 microV and a DeltaMRV value >10 microV, the PPV was 100%; however, the NPV remained at 30%.
CONCLUSION: Women who were cured of genuine stress incontinence with Burch retropubic urethropexy procedures had better motor unit action potential activation with repetitive coughing than women with persistent genuine stress incontinence. Urethral electromyography may be used to assess the neuromuscular integrity of the striated urethral sphincter and to help predict which women will have successful retropubic urethropexy procedures.