title: The impact of tension-free vaginal tape on the urethral closure function: mechanism of action.
abstract: OBJECTIVE
  To investigate if the tension-free vaginal tape (TVT) works by increasing the abdominal to urethral pressure impact ratio (APIR).
  
  
  METHODS
  Twenty one women with urodynamically proven stress urinary incontinence (SUI) were assessed by ICIQ-SF, pad-weighing test, incontinence diary and Urethral Pressure Reflectometry (UPR) before and after TVT. UPR was conducted during resting and increased intra-abdominal pressure (P(Abd)) by straining. Related values of P(Abd) and urethral opening pressure (P(o)) were plotted into an abdomino-urethral pressuregram. Linear regression of the values was conducted, and the slope of the line was found. The slope expresses the ratio of pressure increase in the urethra compared to the pressure increase in the abdomen and was called APIR.
  
  
  RESULTS
  The urethral opening pressure at rest (P(o-rest)) was unchanged after TVT, while APIR increased in all women (from 0.7 to 1.4, P < 0.0001).
  
  
  CONCLUSIONS
  The TVT seems to strengthen the urethral closure function by increasing the APIR while P(o-rest) is unchanged regardless of the type of pre-operative dysfunction. This confirms the theory of TVT's mechanism of action being mid-urethral support.
authors.affiliation: Department of Obstetrics and Gynecology, Herlev Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Marie-Louise
authors.initials: ML
authors.lastname: Saaby
authors.forename: Niels
authors.initials: N
authors.lastname: Klarskov
authors.forename: Gunnar
authors.initials: G
authors.lastname: Lose
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008875:Middle Aged; D011312:Pressure; D053825:Suburethral Slings; D014521:Urethra / Q000503:physiopathology*; D014549:Urinary Incontinence / Q000503:physiopathology* / Q000601:surgery; D014563:Urodynamics / Q000502:physiology*
keywords: APIR; PTR; SUI; TVT; UPR; closure function; closure mechanism; intra-abdominal pressure increase; pressure reflectometry; strain; tension-free vaginal tape; urethra; urinary incontinence; urodynamics