title: Evaluation of the accuracy of a wireless pressure sensor in a canine model of retrograde-collateral (type II) endoleak and correlation with histologic analysis.
abstract: BACKGROUND
  The utility of intra-aneurysmal pressure determination is dependent on the ability to measure pressure in the presence of endoleak and thrombosis. In this study, the accuracy of a CardioMEMS wireless pressure sensor (CardioMEMS, Atlanta, Ga) transducer in the presence of thrombus associated with type II endoleak was measured.
  
  
  METHODS
  Type II endoleaks were created in four mongrel dogs by implanting four collateral arterial side branches (lumbar and caudal mesenteric arteries) as a Carrel patch onto a 3-cm prosthetic polytetrafluoroethylene abdominal aortic aneurysm (AAA). The aneurysm was excluded 2 weeks later from antegrade perfusion by a stent graft. The wireless pressure sensor was positioned in the AAA external to the stent graft. A Konigsberg intraluminal solid-state strain-gauge pressure transducer (Konigsberg Instruments, Pasadena, Calif) that is accurate in the presence of thrombus served as the control to determine AAA pressure. Both of the transducers were implanted on the luminal surface of the aneurysm, 180 degrees opposite from the Carrel patch and endoleak channel. Intra-aneurysmal pressure resulting from the type II endoleak was measured twice daily for 4 weeks using both transducers. A total of 56 pre-exclusion and 224 post-exclusion distinct pressure determinations were made. Intra-aneurysmal pressure was indexed to the systemic pressure that was simultaneously measured by a strain-gauge pressure transducer implanted in the native aorta. Histologic analysis of the aneurysm contents was performed with hematoxylin and eosin.
  
  
  RESULTS
  The intra-aneurysmal systolic, mean, and pulse pressures produced by the type II endoleak were significantly lower than systemic pressure in all animals and were < 60% of systemic pressure (P < .001). Close correlation between the wireless transducer and the control strain-gauge transducer was observed (R = 0.83, P < .001). Arteriography and Doppler ultrasound documented retrograde flow through the aneurysm side branches and persistent endoleak patency up to the time of euthanasia. Pathologic analysis demonstrated the endoleak channel to be patent and separated from the transducers by thrombus, which surrounded both transducers.
  
  
  CONCLUSIONS
  Intra-aneurysmal pressure generated by type II endoleaks may be accurately measured through thrombus using a wireless pressure sensor in the canine model. The wireless sensor has the potential for clinical applicability in diagnosing and characterizing type II endoleaks.
authors.affiliation: Division of Vascular Surgery, New York Presbyterian Hospital, Cornell University, Weill Medical School and Columbia University, College of Physicians and Surgeons, New York, NY 10021, USA.
authors.forename: Rabih A
authors.initials: RA
authors.lastname: Chaer
authors.forename: Susan
authors.initials: S
authors.lastname: Trocciola
authors.forename: Brian
authors.initials: B
authors.lastname: DeRubertis
authors.forename: Robert
authors.initials: R
authors.lastname: Hynecek
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xu
authors.forename: Russell
authors.initials: R
authors.lastname: Lam
authors.forename: K Craig
authors.initials: KC
authors.lastname: Kent
authors.forename: Peter L
authors.initials: PL
authors.lastname: Faries
mesh_terms: D017130:Angioplasty; D000818:Animals; D017544:Aortic Aneurysm, Abdominal / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D001027:Aortography; D001794:Blood Pressure; D001795:Blood Pressure Determination / Q000295:instrumentation; D004195:Disease Models, Animal; D004285:Dogs; D005069:Evaluation Studies as Topic; D018810:Magnetic Resonance Angiography; D019028:Magnetic Resonance Imaging, Cine; D011475:Prosthesis Failure; D015641:Radiography, Interventional; D015203:Reproducibility of Results; D015607:Stents; D013997:Time Factors; D014160:Transducers, Pressure; D014654:Vascular Patency