title: Intrasac pressure waveforms after endovascular aneurysm repair (EVAR) are a reliable marker of type I endoleaks, but not type II or combined types: an experimental study.
abstract: OBJECTIVE
  To ascertain the nature of the pressure wave transmitted through aneurysm thrombus and the changes produced after endovascular repair and the development of type I and II endoleaks.
  
  
  METHODS
  A 25 mm Talent endovascular graft was deployed in a latex model of an abdominal aortic aneurysm, which was incorporated in a pulsatile flow unit. The graft was surrounded by thrombus analogue to simulate conditions in vivo. Pressure waveforms in the sac were captured over 5s at 1000 Hz in these settings: (i) no endoleaks (baseline), after introduction of (ii) type I (iii) type II and (iv) combined type I and II endoleaks. The arterial blood pressure settings used were 140/100 and 130/90 mmHg, denoted the high and low settings, respectively. ANOVA in Minitab 13 was applied for statistical analysis.
  
  
  RESULTS
  Pulsatile waveforms were transmitted through the thrombus. Intrasac pressure after stent-grafting reduced to 110/107, 99/96 mmHg (p<0.001) (high, low settings, respectively). Introduction of a type I endoleak caused this to rise to 120/112, 115/107 mmHg (p<0.001, vs. baseline); after producing a type II endoleak these were 101/98, 91/88 mmHg (p<0.001, vs. baseline). A combined type I and II endoleak produced intrasac pressures identical to that of a type I endoleak.
  
  
  CONCLUSIONS
  Intrasac pressure waveforms following EVAR are easily defined following a type I endoleak. Waveforms obtained following type II endoleak simulation resemble the baseline waveform in an attenuated form. Intrasac pressures are, therefore, a reliable marker for type I, but not a type II endoleak. In the case of a combined endoleak, the type I endoleak waveform effectively masks that of the type II. Intrasac thrombus faithfully transmits intrasac pressures.
authors.affiliation: Vascular/Endovascular Unit, University College London Hospital, W1G 6DE London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Chaudhuri
authors.forename: L E
authors.initials: LE
authors.lastname: Ansdell
authors.forename: A J
authors.initials: AJ
authors.lastname: Grass
authors.forename: M
authors.initials: M
authors.lastname: Adiseshiah
mesh_terms: D017544:Aortic Aneurysm, Abdominal / Q000145:classification / Q000503:physiopathology* / Q000601:surgery*; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D019917:Blood Vessel Prosthesis Implantation; D006801:Humans; D008955:Models, Cardiovascular; D011183:Postoperative Complications / Q000145:classification / Q000209:etiology* / Q000503:physiopathology*; D011673:Pulsatile Flow; D015203:Reproducibility of Results; D015607:Stents; D016896:Treatment Outcome; D014656:Vascular Surgical Procedures