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 PS196. Endotension: Net Flow Through an Endoleak Determines Its Visibility

Stuart Blackwood2, Doran Mix1, Mallory Wingate1, Ankur Chandra1, Alan Dietzek2
1Cardiovascular Engineering Lab (CVEL), Division of Vascular Surgery, University of Rochester, Rochester, NY; 2Department of Vascular Surgery, Danbury Hospital, Danbury, CT.

OBJECTIVES: Unexplained aneurysm growth despite multimodality imaging following EVAR is often attributed to endotension. We tested a hypothesis that endotension may be from a type 1a endoleak (EL) pressurizing the aneurysm sac without net forward flow, not visualized on standard angiographic imaging.

METHODS: A patient-specific aortic aneurysm phantom was constructed of polyvinyl alcohol using 3-D molding techniques. A bifurcated stent graft was implanted and the phantom connected to a hemodynamic simulator for testing. Type 1a ELs were created using 7 Fr catheters. Three scenarios were studied: complete exclusion (no EL); inflow with no sac outflow; and inflow with sac outflow. DSA imaging was performed at 48kvP at 5fps followed by delayed imaging (1 frame/min) over 30 minutes.

RESULTS: With no EL, the systemic MAP (sMAP) averaged 113mmHg and Aneurysm Sac MAP (asMAP) averaged 101mmHg (Table 1). With EL without outflow, the sMAP averaged 116mmHg and asMAP averaged 120mmHg. EL flow was bidirectional with no net forward flow. With EL with aneurysm sac outflow, the sMAP averaged 119mmHg and asMAP averaged 105.5mmHg. EL flow was 39cc/minutes across the EL channel. With DSA imaging, the EL with no outflow was noted after >9 minutes of delayed imaging.

CONCLUSIONS: Our model demonstrated a type 1a EL in the absence of aneurysm sac outflow resulting in full pressurization of the aneurysm sac with biphasic (zero net) flow. This EL was not visible on standard contrast DSA until >9 minutes. This model may serve as a first step in explaining both the mystery of endotension and in vivo aneurysm sac growth with no detectable ELs using current standard imaging modalities.

AUTHOR DISCLOSURES: S. Blackwood: Nothing to disclose; A. Chandra: Nothing to disclose; A. Dietzek: Nothing to disclose; D. Mix: Nothing to disclose; M. Wingate: Nothing to disclose.

Table 1

Systemic MAP / Aneurysm MAP (mmHg)
Systemic PP / Aneurysm PP (mmHg)
Net Endoleak Flow (cc/min)
Standard Angiography / Delayed Imaging (Positive/Negative after 30mins)
No Endoleak
113 / 101
80 / 10
not applicable
negative / negative
Type 1a Endoleak no Outflow
116 / 120
84 / 17
negative / positive
Type 1a Endoleak with Outflow
119 / 105.5
86 / 12
positive / positive

Summary of Endoleak channel flow, Radiographic Detection of the Endoleak, Sac Pressurization as Mean Arterial Pressure (MAP) and Pulse Pressure (PP)
Posted April 2013

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