Effects of Major Endoleaks on a Stented Abdominal Aortic Aneurysm

Insertion of a stent-graft into an aneurysm, especially abdominal aortic aneurysms (AAAs), is a very attractive surgical intervention; however, it is not without major postoperative complications, such as endoleaks. An endoleak is the transient accumulation of blood in the AAA cavity, which is formed by the stent-graft and AAA walls. Of the four blood pathways, a type I endoleak constitutes the major one. Thus, focusing on both proximal and distal type I endoleaks, i.e., the minute net influx of blood past the attachment points of a stent-graft into the AAA cavity, the transient three-dimensional interactions between luminal blood flow, stent-graft wall, leakage flow, and AAA wall are computationally simulated. For different type I endoleak scenarios and inlet pressure wave forms, the impact of type I endoleaks on cavity pressure, wall stress, and stent-graft migration force is analyzed. The results indicate that both proximal type I-a and distal type I-b endoleaks may cause cavity pressures close to a patient’s systemic pressure; however, with reduced pulsatility. As a result, the AAA-wall stress is elevated up to the level of a nonstented AAA and, hence, such endoleaks render the implant useless in protecting the AAA from possible rupture. Interestingly enough, the net downward force acting on the implant is significantly reduced; thus, in the presence of endoleaks, the risk of stent-graft migration may be mitigated.

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Modeling Endoleaks and Collateral Reperfusion following Endovascular AAA Exclusion

Journal of Endovascular Therapy ◽

10.1177/152660280301000305 ◽

2003 ◽

Vol 10 (3) ◽

pp. 424-432 ◽

Cited By ~ 10

Author(s):

Chuh K. Chong ◽

Thien V. How ◽

Geoffrey L. Gilling-Smith ◽

Peter L. Harris

Keyword(s):

Stent Graft ◽

Aortic Pressure ◽

Type I ◽

Type Ii ◽

Pump System ◽

Type Ii Endoleak ◽

Type I Endoleak ◽

The Impact ◽

Mean Aortic Pressure

Purpose: To investigate the effect on intrasac pressure of stent-graft deployment within a life-size silicone rubber model of an abdominal aortic aneurysm (AAA) maintained under physiological conditions of pressure and flow. Methods: A commercial bifurcated device with the polyester fabric preclotted with gelatin was deployed in the AAA model. A pump system generated physiological flow. Mean and pulse aortic and intrasac pressures were measured simultaneously using pressure transducers. To simulate a type I endoleak, plastic tubing was placed between the aortic wall and the stent-graft at the proximal anchoring site. Type II endoleak was simulated by means of side branches with set inflow and outflow pressures and perfusion rates. Type IV endoleak was replicated by removal of gelatin from the graft fabric. Results: With no endoleak, the coated graft reduced the mean and pulse sac pressures to negligible values. When a type I endoleak was present, mean sac pressure reached a value similar to mean aortic pressure. When net flow through the sac due to a type II endoleak was present, mean sac pressure was a function of the inlet pressure, while pulse pressure in the sac was dependent on both inlet and outlet pressures. As perfusion rates increased, both mean and pulse sac pressures decreased. When there was no outflow, mean sac pressure was similar to mean aortic pressure. In the presence of both type I and type II endoleaks, mean sac pressure reached mean aortic pressure when the net perfusion rate was low. Conclusions: In vitro studies are useful in gaining an understanding of the impact of different types of endoleaks, in isolation and in combination, on intrasac pressure after aortic stent-graft deployment.

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Wall Stresses Before and After Endovascular Repair of Abdominal Aortic Aneurysms

Advances in Bioengineering ◽

10.1115/imece2004-61556 ◽

2004 ◽

Cited By ~ 5

Author(s):

Elena S. Di Martino ◽

Ajay Bohra ◽

Christine Scotti ◽

Ender Finol ◽

David A. Vorp

Keyword(s):

Endovascular Aneurysm Repair ◽

Three Dimensional ◽

Invasive Procedure ◽

Aortic Aneurysms ◽

Aortic Tissue ◽

Type I ◽

Abdominal Aortic ◽

Before And After ◽

Anchoring System ◽

Three Dimensional Finite Element

Endovascular aneurysm repair (EVAR) technique is a minimally invasive procedure approach to abdominal aortic aneurysm (AAA) repair. Following EVAR, isolated aortic tissue starts remodeling after the new blood path is established. The commercially available endovascular grafts (EVG) have been found to be prone to Type I endoleak, which is re-pressurization of the degenerated AAA sac following a breach in the seal mechanism of the EVG or migration due to failure of the mechanism holding the graft in place (Chuter, 2002) These inadequacies of EVGs might be attributed to the effect of non-optimal design of graft anchoring system. In the present study, we utilized pre-operative and post-operative computer tomography (CT) data with previously derived material properties to construct three-dimensional finite element (FE) models for AAA before and after the EVAR procedure. We studied the nature of stresses acting on the aorta before and after EVAR. In particular we investigated the physical forces acting on the EVG and how they are transferred to the aortic wall at graft anchoring sites.

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Deployment Finesse of the Cook Zenith Stent Graft

10.1093/med/9780199986071.003.0001 ◽

2018 ◽

Author(s):

John Fritz Angle

Keyword(s):

Abdominal Aortic Aneurysm ◽

Aortic Aneurysm ◽

Stent Graft ◽

Evidence Based ◽

Type I ◽

Stent Grafts ◽

Standards Of Practice ◽

Abdominal Aortic ◽

Type I Endoleak

For all abdominal aortic aneurysm endografts, the major challenge is minimizing the risk of a type I endoleak. Percutaneous placement of an abdominal aortic endograft has become a widely-performed procedure. With several devices available on the market, there are many device-specific and experience-based considerations in planning and performing these procedures safely and with good outcomes. Although not always evidence-based, reviewing some case-specific scenarios can introduce techniques or lead to standards of practice that reduce suboptimal outcomes or prevent complications in future procedures. This chapter discusses deployment finesse of the Cook Zenith Flex and Zenith LP stent grafts, but many of the described concepts apply to other abdominal endografts and even thoracic endograft procedures.

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Anisotropic Wall Mechanics of Abdominal Aortic Aneurysms

ASME 2008 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2008-192265 ◽

2008 ◽

Author(s):

Giampaolo Martufi ◽

Jose F. Rodriguez ◽

Ender A. Finol

Keyword(s):

Three Dimensional ◽

Wall Stress ◽

Aortic Aneurysms ◽

Constitutive Law ◽

Intraluminal Pressure ◽

Aortic Tissue ◽

Unruptured Aneurysms ◽

Abdominal Aortic ◽

Dimensional Reconstruction ◽

Tissue Specimens

The prevalence of AAA is growing along with population age and according to different studies AAA rupture is the 13th most common cause of death in the U.S., causing an estimated 15,000 deaths per year. In biomechanical terms, AAA rupture is a phenomenon that occurs when the developing mechanical stresses within the aneurysm inner wall, as a result of the exerted intraluminal pressure, exceed the failure strength of the aortic tissue. To obtain a reliable estimation of wall stress, it is necessary to perform an accurate three-dimensional reconstruction of the AAA geometry and model an appropriate constitutive law for the aneurysmal tissue material characterization. In this regard, a recent study on the biaxial mechanical behavior of human AAA tissue specimens [1] demonstrates that aneurysmal arterial tissue behaves mechanically anisotropic. The objectives of the present work are to determine the effect of material anisotropy of the aneurysmal abdominal aorta on wall stress distribution and to establish a comparison of wall mechanics between ruptured and unruptured aneurysms.

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Uncovered Chimney Stent Graft for Renal Arteries With the Nellix Endovascular Aneurysm Sealing Technique

Vascular and Endovascular Surgery ◽

10.1177/1538574417747175 ◽

2017 ◽

Vol 52 (2) ◽

pp. 148-153 ◽

Cited By ~ 1

Author(s):

Luca Garriboli ◽

Antonio Maria Jannello

Keyword(s):

Aortic Aneurysms ◽

Type I ◽

Abdominal Aortic ◽

Vessel Patency ◽

Type I Endoleak ◽

Procedural Costs ◽

Endovascular Approach ◽

Access Complications

Purpose: To describe the application of uncovered chimney stent grafts with the Nellix endovascular aneurysm sealing technique (ChEVAS) for juxtarenal abdominal aortic aneurysms (JAAAs). Case Report: Two patients with JAAA and multiple comorbidities were considered unfit for open surgery and were selected for an endovascular approach. Fenestrated and branched endografts were too expensive, and a chimney endovascular approach was considered inappropriate for the relatively high incidence of proximal type I endoleak and graft migration. ChEVAS was performed successfully with the novel addition of uncovered chimney stents to further reduce costs and possibly improve target vessel patency. JAAA exclusion and visceral vessel patency was confirmed at 18-month follow-up. Conclusion: ChEVAS with bare chimney stents is technically less complex, potentially reduces access complications and procedural costs, and may improve long-term patency compared to alternative techniques. Results at 18 months seem promising, but strict follow-up is necessary as the long-term durability is unknown.

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A standardized aortic aneurysm model for the assessment of endovascular stent-graft technology

Vascular ◽

10.1258/vasc.2010.oa0262 ◽

2011 ◽

Vol 19 (2) ◽

pp. 82-88 ◽

Cited By ~ 2

Author(s):

J A Macierewicz ◽

J-N Albertini ◽

R J Hinchliffe

Keyword(s):

Stent Graft ◽

Duplex Ultrasound ◽

Aortic Aneurysms ◽

Straight Tube ◽

Type I ◽

Infrarenal Aorta ◽

Endovascular Stent ◽

Ovine Model ◽

Endovascular Stent Graft ◽

Type I Endoleak

Reliable models of aortic aneurysms are required to test endovascular stent-graft technology prior to human use. We describe the creation of a standardized prosthetic aneurysm in an ovine model to assess endovascular technology. In an adult ovine model under general anesthesia, a polyester sphere measuring 6 cm across was sutured onto the infrarenal aorta following aortotomy. Two weeks later an endovascular stent-graft was deployed in the aorta. Exclusion was confirmed on monthly ultrasound duplex and during angiography at three months and under terminal anesthesia at six months. Autopsy along with histology of the specimen were then performed. A total of 10 sheep underwent aneurysm implantation. Nine received a straight tube endovascular stent-graft (Lombard Medical, Abingdon, Oxon, UK) and seven completed the study. Five prosthetic aneurysms shrank during serial imaging with duplex ultrasound and angiography. However, two remained the same size. One of these had a type I endoleak whereas the other had endotension (type I endoleak confirmed at autopsy). This animal model provides a reliable and reproducible method of creating prosthetic aneurysms for assessing endovascular stent-grafts. It was possible to assess aneurysm exclusion non-invasively using duplex ultrasound. Aneurysms effectively excluded from the circulation shrank whereas those with an endoleak did not.

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Intraoperative Proximal Endoleaks during AAA Stent-Graft Repair: Evaluation of Risk Factors and Treatment with Palmaz Stents

Journal of Endovascular Therapy ◽

10.1177/152660280100800306 ◽

2001 ◽

Vol 8 (3) ◽

pp. 268-273 ◽

Cited By ~ 33

Author(s):

Nuno V. Dias ◽

Timothy Resch ◽

Martin Malina ◽

Bengt Lindblad ◽

Krassi Ivancev

Keyword(s):

Stent Graft ◽

Therapeutic Option ◽

Balloon Dilation ◽

Aortic Aneurysms ◽

Type I ◽

Aneurysm Neck ◽

Custom Made ◽

Type I Endoleak ◽

Stent Graft Repair ◽

Palmaz Stents

Purpose: To study factors that might contribute to intraoperative proximal type I endoleak and to evaluate the placement of giant Palmaz stents as a therapeutic option. Methods: Thirty-three patients (30 men; median age 72 years, range 50–85) with abdominal aortic aneurysms underwent implantation of fully supported Gianturco Z-stent—based endografts (12 custom-made aortomonoiliac and 21 bifurcated Zenith devices). Ten (30%) patients were treated for intraoperative proximal endoleaks. Stent-graft oversizing and neck angulation, length, and shape were compared between patients with and without leaks. Results: In 9 cases, the endoleaks were successfully treated with intraoperative placement of Palmaz stents without complications. In 1 patient, a leak that was resolved intraoperatively with balloon dilation reappeared 1 month later; a Palmaz stent was deployed successfully. Stent-graft oversizing did not differ significantly between patients who developed proximal endoleaks and those who did not (median 4.0 mm in both groups, p = 0.47). Median neck length was 21.0 mm in patients with endoleak and 28.0 mm in those without (p > 0.99). Median neck angulation was 30° in both groups (p = 0.33), and the presence of a conical aneurysm neck was not significantly different (2/10 versus 6/23, p > 0.99). All aneurysms remained excluded at a median follow-up of 13 months (range 6–24). Conclusions: Stent-graft oversizing and neck morphology (length, angulation, and conical shape) do not seem to correlate with the incidence of proximal type I endoleaks. Palmaz stent placement appears to be a feasible and safe treatment option for this complication.

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Three-Dimensional Analysis of Component Stability of the Nellix Endovascular Aneurysm Sealing System After Treatment of Infrarenal Abdominal Aortic Aneurysms

Journal of Endovascular Therapy ◽

10.1177/1526602816678201 ◽

2016 ◽

Vol 24 (2) ◽

pp. 201-209 ◽

Cited By ~ 11

Author(s):

Bernhard Dorweiler ◽

Christian Boedecker ◽

Friedrich Dünschede ◽

Christian F. Vahl ◽

Marwan Youssef

Keyword(s):

Stent Graft ◽

Conformational Changes ◽

Three Dimensional ◽

Aortic Aneurysms ◽

3D Analysis ◽

Short Term ◽

Abdominal Aortic ◽

Overall Stability ◽

Type Ia ◽

Instructions For Use

Purpose: To assess short-term stability and conformational changes of the Nellix EndoVascular Aneurysm Sealing (EVAS) System using 3-dimensional (3D) analysis. Methods: Postoperative computed tomography (CT) scans obtained at 0, 3, and 12 months in 24 patients (mean age 75±7 years; 22 men) who underwent EVAS between December 2013 and December 2014 for intact abdominal aortic aneurysm (within the instructions for use) were evaluated for stent-graft deviation in multiple planes using dedicated 3D analysis software. In addition, 2D analysis using an anatomically fixed reference landmark was performed to assess craniocaudal migration. Clinical and follow-up data of the patients were recorded and matched with results of the imaging analysis. Results: Overall stability of the Nellix endografts was promising. Relevant conformational changes in the majority of cases were limited to the iliac graft segment and were clinically benign in all cases. Conversely, the only deviation of the proximal stent-graft segment was found in a patient with type Ia endoleak. Additional 2D analysis found relevant (≥5 mm) caudal migration of the Nellix stent-graft in 6 patients, including the one with the type Ia endoleak. In 3 patients, 3D analysis demonstrated the absence of relevant conformational changes of the endografts despite caudal migration. Conclusion: Overall stability of the separate EVAS stent-grafts is promising in the short term. Relevant conformational changes (stent-graft deviation) in the majority of cases were benign and confined to the iliac segment.

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The use of EndoAnchors in endovascular repair of abdominal aortic aneurysms with challenging proximal neck: Single-centre experience

JRSM Cardiovascular Disease ◽

10.1177/2048004019845508 ◽

2019 ◽

Vol 8 ◽

pp. 204800401984550 ◽

Cited By ~ 1

Author(s):

Rocco Giudice ◽

Ottavia Borghese ◽

Giorgio Sbenaglia ◽

Carlo Coscarella ◽

Claudia De Gregorio ◽

...

Keyword(s):

Stent Graft ◽

Abdominal Aortic Aneurysms ◽

Aortic Aneurysms ◽

Single Centre ◽

Proximal Neck ◽

Abdominal Aortic ◽

Single Centre Experience ◽

Type Ia ◽

Graft Migration

Objectives The aim of this study was to present a single-centre experience with EndoAnchors in patients who underwent endovascular repair for abdominal aortic aneurysms with challenging proximal neck, both in the prevention and treatment of endograft migration and type Ia endoleaks. Methods We retrospectively analysed 17 consecutive patients treated with EndoAnchors between June 2015 and May 2018 at our institution. EndoAnchors were applied during the initial endovascular aneurysm repair procedure (primary implant) to prevent proximal neck complications in difficult anatomies (nine patients), and in the follow-up after aneurysm exclusion (secondary implant) to correct type Ia endoleak and/or stent-graft migration (eight patients). Results Mean time for anchors implant was 23 min (range 12–41), with a mean of 5 EndoAnchors deployed per patient. Six patients in the secondary implant group required a proximal cuff due to stent-graft migration ≥10 mm. Technical success was achieved in all cases, with no complications related to deployment of the anchors. At a median follow-up of 13 months (range 4–39, interquartile range 9–20), there were no aneurysm-related deaths or aneurysm ruptures, and all patients were free from reinterventions. CT-scan surveillance showed no evidence of type Ia endoleak, anchors dislodgement or stent-graft migration, with a mean reduction of aneurysm diameter of 0.4 mm (range 0–19); there was no sac growth or aortic neck enlargement in any case. Conclusions EndoAnchors can be safely used in the prevention and treatment of type Ia endoleaks in patients with challenging aortic necks, with good results in terms of sac exclusion and diameter reduction in the mid-term follow-up.

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