Evaluation of a Wireless Pressure Sensor in a Canine Model of Retrograde-Collateral (Type II) Endoleak

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RABIH A. CHAER, MD, Susan Trocciola, MD, Stephanie Lin, MD, Brian DeRubertis, MD, Mathew Pierce, BA, Naveen Kumar, MD, Robert Hynecek, MD, Keith Ozaki, MD, K Craig Kent, MD, Peter L. Faries, MD.
New York Presbyterian Hospital, New York, NY, USA.

BACKGROUND:The accuracy of implantable wireless pressure transducers in determining intraaneurysmal pressure in the presence of endoleak has not been established. In this study, the accuracy of the CardioMEMS transducer in the presence of thrombus associated with type II endoleak was measured.
METHODS:Type II endoleaks were created in 4 mongrel dogs by implanting four collateral arterial side branches (caudal mesenteric, lumbar) as a Carrel patch onto a 3cm prosthetic PTFE abdominal aortic aneurysm (AAA). The aneurysm was then excluded from antegrade perfusion by a stent graft (Viabahn). The CardioMEMS wireless pressure sensor was deployed in the AAA external to the stent graft. An intraluminal solid-state strain-gauge pressure transducer (Konigsberg) that is accurate in the presence of thrombus served as the control to determine actual AAA pressure. The transducers were implanted 180 degrees apart opposite form the endoleak channel. Intra-aneurysmal pressure resulting from the type II endoleak was measured for 4 weeks using both transducers. Intraaneurysmal pressure was indexed to the systemic pressure (systemic=1) that was simultaneously measured by a strain-gauge pressure transducer implanted in the native aorta (Figure).
RESULTS:The intraaneurysmal pressure produced by the type II endoleak was significantly lower than systemic pressure in all animals (P<0.001), (Table). Close correlation between the wireless transducer and the control strain-gauge transducer was observed (R=0.71-0.83, P<0.001). Arteriography, cine MRA and Doppler ultrasound documented retrograde flow through the aneurysm side branches and persistent endoleak patency up to the time of euthanasia. Pathological analysis demonstrated the endoleak channel to be patent and separated from the transducers by thrombus, which surrounded both transducers.
CONCLUSIONS:Intraaneurysmal pressure generated by type II endoleaks may be accurately measured through thrombus using the CardioMEMS wireless pressure sensor in the canine model. The wireless sensor may potentially be used clinically to diagnose and characterize type II endoleaks.