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Soo Hoo AJ, Fitzgibbon JJ, Hussain MA, Scully RE, Servais AB, Nguyen LL, Gravereaux EC, Semel ME, Marcaccio EJ, Menard MT, Ozaki CK, Belkin M. Contemporary Indications for Open Abdominal Aortic Aneurysm Repair in the Endovascular Era. J Vasc Surg 2022; 76:923-931.e1. [PMID: 35367568 DOI: 10.1016/j.jvs.2022.03.866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 03/21/2022] [Indexed: 10/18/2022]
Abstract
INTRODUCTION AND OBJECTIVES Despite the emergence of endovascular aneurysm repair (EVAR) as the most common approach to abdominal aortic aneurysm repair, open aneurysm repair (OAR) remains an important option. This study seeks to define the indications for OAR in the EVAR era and how these indications effect outcomes. METHODS A retrospective cohort study was performed of all OAR at a single institution from 2004 to 2019. Pre-operative computed tomography scans and operative records were assessed to determine the indication for OAR. These reasons were categorized into anatomical contraindications; systemic factors (connective tissue disorders, contraindication to contrast dye); and patient/surgeon preference (patients who were candidates for both EVAR and OAR). Perioperative and long-term outcomes were compared between the groups. RESULTS 370 patients were included in the analysis; 71.6% (265/370) had at least one anatomic contraindication to EVAR; 36% had two or more contraindications. The most common anatomic contraindications were short aortic neck length (51.6%), inadequate distal seal zone (19.2%), and inadequate access vessels (15.7%). The major perioperative complication rate was 18.1% and the 30-day mortality was 3.0%. No single anatomic factor was identified as a predictor of perioperative complications. Sixty-one patients (16.5%) had OAR based on patient/surgeon preference; these patients were younger; had lower incidences of coronary artery disease and chronic obstructive pulmonary disease; and they were less likely to require suprarenal cross clamping compared with patients who had anatomic and/or systemic contraindications to EVAR. The patient/surgeon preference group had a lower incidence of perioperative major complications (8.2% versus 20.1%, p=0.034), shorter length of stay (6 versus 8 days, p<0.001) and zero 30-day mortalities. The multivariable adjusted risk for 15-year mortality was lower for patient/surgeon preference patients (adjusted hazard ratio 0.44 [95% confidence interval 0.24-0.80], p=0.007) compared to those anatomic/systemic contraindications. CONCLUSIONS Within a population of patients who did not meet instruction for use (IFU) criteria for EVAR, no single anatomic contraindication was a marker for worse outcomes with OAR. Patients who were candidates for both aortic repair approaches but elected to have open surgical repair due to patient/surgeon preference have very low 30-day mortality and morbidity, and superior long-term survival rates compared with those patients who had OAR due to anatomic and/or systemic contraindications to EVAR.
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Affiliation(s)
- Andrew J Soo Hoo
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA
| | - James J Fitzgibbon
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA
| | - Mohamad A Hussain
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA; Centre for Surgery and Public Health, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Rebecca E Scully
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA
| | - Andrew B Servais
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA
| | - Louis L Nguyen
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA
| | - Edwin C Gravereaux
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA
| | - Marcus E Semel
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA
| | - Edward J Marcaccio
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA
| | - Matthew T Menard
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA
| | - C Keith Ozaki
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA
| | - Michael Belkin
- Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA
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Goudeketting SR, Schuurmann RCL, Slump CH, de Vries JPPM. Changes in Apposition of Endograft Limbs in the Iliac Arteries After Endovascular Aneurysm Repair: Determination With New Computed Tomography-Applied Software. J Endovasc Ther 2019; 26:843-852. [PMID: 31402731 DOI: 10.1177/1526602819867430] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Purpose: To validate new computed tomography (CT)-applied software used to determine endograft limb position and apposition after endovascular aneurysm repair (EVAR). Materials and Methods: Twelve EVAR patients (mean age 81±6 years; 10 men) with distal stent-graft extensions for 15 (3 bilateral) type Ib endoleaks during follow-up were selected based on the availability of the following CT studies: pre-EVAR, 1 month, and the penultimate scan prior to the scan disclosing the type Ib endoleak. Twelve patients (mean age 82±7 years; 11 men) without endoleak and a similar interval between the primary EVAR procedure and the penultimate CT scan of the endoleak group were selected as controls using measurements from both endograft limbs (n=21, 3 excluded). Prototype Vascular Imaging Analysis software was adapted to calculate 6 parameters for the distal apposition zone: fabric distance, shortest apposition length, endograft diameter, iliac seal surface (ISS), iliac endograft apposition surface (IEAS), and percentage of iliac surface coverage (IEAS/ISS × 100). Measurements were performed on the preoperative, first postoperative, and penultimate/matched follow-up CT scans. Interobserver variability was assessed with the intraclass correlation coefficient (ICC). Continuous data are presented as the median [interquartile range (IQR) Q1, Q3]. Results: CTA follow-up was not significantly different between the endoleak and control groups [30 months (IQR 18, 58) vs 36 months (IQR 21, 59), p=0.843]. Interobserver agreement was good to excellent for all parameters (ICC 0.879-0.985). Preoperative anatomy and endograft dimensions on the first follow-up CTA scan did not differ significantly between the groups. When the penultimate CTA scan was compared with the first postoperative CT scan, endograft dimensions had significantly changed in the endoleak group; importantly, apposition was significantly decreased, and fabric distance was significantly increased, indicating limb retraction. Differences in changes in endograft dimensions were significant between the groups. Conclusion: New CT-applied software was introduced to visualize apposition and position changes of endograft limbs during follow-up. The software demonstrated good-to-excellent interobserver agreement and enabled accurate analysis of post-EVAR endograft dimensions. Significant changes in apposition and position were observed with the software on the penultimate CT scan prior to diagnosis of type Ib endoleak.
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Affiliation(s)
- Seline R Goudeketting
- Department of Vascular Surgery, St Antonius Hospital, Nieuwegein, the Netherlands.,Technical Medical Centre, University of Twente, Enschede, the Netherlands
| | - Richte C L Schuurmann
- Department of Surgery, Division of Vascular Surgery, University Medical Centre Groningen, the Netherlands
| | - Cornelis H Slump
- Technical Medical Centre, University of Twente, Enschede, the Netherlands
| | - Jean-Paul P M de Vries
- Department of Surgery, Division of Vascular Surgery, University Medical Centre Groningen, the Netherlands
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Goudeketting SR, Vermeulen JJM, van Noort K, te Riet o. g. Scholten G, Kuipers H, Slump CH, de Vries JPPM. Effect of Different EndoAnchor Configurations on Aortic Endograft Displacement Resistance: An Experimental Study. J Endovasc Ther 2019; 26:704-713. [DOI: 10.1177/1526602819857586] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Purpose: This study investigated the effect of different EndoAnchor configurations on aortic endograft displacement resistance in an in vitro model. Materials and Methods: An in vitro model was developed and validated to perform displacement force measurements on different EndoAnchor configurations within an endograft and silicone tube. Five EndoAnchor configurations were created: (1) 6 circumferentially deployed EndoAnchors, (2) 5 EndoAnchors within 120° of the circumference and 1 additional, contralateral EndoAnchor, (3) 4 circumferentially deployed EndoAnchors, (4) 2 rows of 4 circumferentially deployed EndoAnchors, and (5) a configuration of 2 columns of 3 EndoAnchors. An experienced vascular surgeon deployed EndoAnchors under C-arm guidance at the proximal sealing zone of the endograft. A constant force with increments of 1 newton (N) was applied to the distal end of the endograft. The force necessary to displace a part of the endograft by 3 mm was defined as the endograft displacement force (EDF). Two video cameras recorded the measurements. Videos were examined to determine the exact moment 3-mm migration had occurred at part of the endograft. Five measurements were performed after each deployed EndoAnchor for each configuration. Measurements are given as the median and interquartile range (IQR) Q1, Q3. Results: Baseline displacement force measurement of the endograft without EndoAnchors resulted in a median EDF of 5.1 N (IQR 4.8, 5.2). The circumferential distribution of 6 EndoAnchors resulted in a median EDF of 53.7 N (IQR 49.0, 59.0), whereas configurations 2 through 5 demonstrated substantially lower EDFs of 29.0 N (IQR 28.5, 30.1), 24.6 N (IQR 21.9, 27.2), 36.7 N, and 9.6 N (IQR 9.4, 10.0), respectively. Decreasing the distance between the EndoAnchors over the circumference of the endograft increased the displacement resistance. Conclusion: This in vitro study demonstrates the influence EndoAnchor configurations have on the displacement resistance of an aortic endograft. Parts of the endograft where no EndoAnchor has been deployed remain sensitive to migration. In the current model, the only configuration that rivaled a hand-sewn anastomosis was the one with 6 EndoAnchors. A circumferential distribution of EndoAnchors with small distances between EndoAnchors should be pursued, if possible. This study provides a quantification of different EndoAnchor configurations that clinicians may have to adopt in clinical practice, which can help them make a measured decision on where to deploy EndoAnchors to ensure good endograft fixation.
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Affiliation(s)
- Seline R. Goudeketting
- Department of Vascular Surgery, St Antonius Hospital, Nieuwegein, the Netherlands
- MIRA Institute of Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
| | - Jenske J. M. Vermeulen
- Department of Vascular Surgery, St Antonius Hospital, Nieuwegein, the Netherlands
- MIRA Institute of Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
| | - Kim van Noort
- Department of Vascular Surgery, St Antonius Hospital, Nieuwegein, the Netherlands
- MIRA Institute of Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
| | - Gerben te Riet o. g. Scholten
- Robotics and Mechatronics, Faculty of Electrical Engineering, Mathematics & Computer Science, University of Twente, Enschede, the Netherlands
| | - Henny Kuipers
- Robotics and Mechatronics, Faculty of Electrical Engineering, Mathematics & Computer Science, University of Twente, Enschede, the Netherlands
| | - Cornelis H. Slump
- MIRA Institute of Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
| | - Jean-Paul P. M. de Vries
- Department of Surgery, Division of Vascular Surgery, University Medical Centre Groningen, the Netherlands
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Experimental Evaluation of Endovascular Fenestration Scissors in an Ovine Model of Aortic Dissection. Eur J Vasc Endovasc Surg 2018; 56:373-380. [DOI: 10.1016/j.ejvs.2018.05.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 05/23/2018] [Indexed: 11/21/2022]
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Bastos Gonçalves F, Oliveira N, Josee van Rijn M, Ultee K, Hoeks S, Ten Raa S, Stolker R, Verhagen H. Iliac Seal Zone Dynamics and Clinical Consequences After Endovascular Aneurysm Repair. Eur J Vasc Endovasc Surg 2017; 53:185-192. [DOI: 10.1016/j.ejvs.2016.11.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 11/03/2016] [Indexed: 11/30/2022]
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Animal Models Used to Explore Abdominal Aortic Aneurysms: A Systematic Review. Eur J Vasc Endovasc Surg 2016; 52:487-499. [DOI: 10.1016/j.ejvs.2016.07.004] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Accepted: 07/01/2016] [Indexed: 01/09/2023]
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Tokunaga S, Ihara T, Banno H, Kodama A, Sugimoto M, Komori K. The Relationship between Temporal Changes in Proximal Neck Angulation and Stent-Graft Migration after Endovascular Abdominal Aortic Aneurysm Repair. Ann Vasc Surg 2016; 39:119-127. [PMID: 27565407 DOI: 10.1016/j.avsg.2016.05.128] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 05/09/2016] [Accepted: 05/26/2016] [Indexed: 11/17/2022]
Abstract
BACKGROUND In recent years, endovascular abdominal aortic aneurysm repair (EVAR) for treating abdominal aortic aneurysms (AAA) has become quite prevalent in Japan. Though little information is available about temporal changes in proximal neck angulation due to the difficulties encountered in measuring the angle. Therefore, we examined temporal changes in proximal neck angulation and its relationship to stent-graft migration after EVAR. METHODS Between June 2007 and March 2010, 159 patients underwent EVAR for treatment of fusiform AAAs at our hospital. This study focuses on the 80 patients among this group whose treatment sites and subsequent stent grafts were examined by contrast computed tomographic angiography before surgery, directly after surgery (within 4 days), as well as 1 year and 2 years thereafter. We created curved planar reconstruction (CPR) images and measured the length of migration and neck angle using our method. RESULTS At 2 years after EVAR, the average length of proximal landing zone was 21.4 ± 9.2 mm. The average length of stent migration after 2 years was 1.41 ± 2.68 mm. The average neck angle was 33.9° preoperatively and 29.9° directly after surgery yielding a significant difference. However, 1 and 2 years after surgery the average neck angle was 28.2° and 28.4°, respectively. The number of patients experiencing a change >6° in the angle of the proximal neck between the preoperative condition and that directly after surgery was 16 (34.8%) with the use of Zenith stent grafts (n = 46) and 14 (41.2%) with the use of Excluder stent grafts (n = 34). There was no correlation between the proximal neck angle and migration of the proximal stent graft. In addition, there was no correlation between the changes in proximal neck angle and the secondary intervention rate and the occurrence of endoleak. CONCLUSIONS There was a significant change in the neck angle between the preoperative condition and the immediate postoperative condition. However, there was no clear relationship found between the angle of the neck and the proximal stent-graft migration. Postoperative changes in the proximal neck angle just after EVAR and subsequent temporal changes during a 2-year follow-up period do not appear to predict stent-graft migration, secondary intervention rates, or the occurrence of endoleak.
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Affiliation(s)
- Seisaku Tokunaga
- Division of Vascular Surgery, Department of Surgery, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan.
| | - Tsutomu Ihara
- Division of Vascular Surgery, Department of Surgery, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan
| | - Hiroshi Banno
- Division of Vascular Surgery, Department of Surgery, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan
| | - Akio Kodama
- Division of Vascular Surgery, Department of Surgery, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan
| | - Masayuki Sugimoto
- Division of Vascular Surgery, Department of Surgery, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan
| | - Kimihiro Komori
- Division of Vascular Surgery, Department of Surgery, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan
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Murphy EH, Johnson ED, Arko FR. Device-Specific Resistance to in Vivo Displacement of Stent-Grafts Implanted with Maximum Iliac Fixation. J Endovasc Ther 2016; 14:585-92. [PMID: 17696636 DOI: 10.1177/152660280701400422] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Purpose: To compare the in vivo device-specific downward displacement force of various externally supported endografts implanted with maximum iliac fixation. Methods: Twenty female sheep had aneurysms created with a graft patch in the infrarenal aorta. In 12 animals, a fully supported modular bifurcated stent-graft [AneuRx (n=4), Talent (n=4), or Zenith (n=4)] was deployed; in the other 8, a bifurcated aortic graft was surgically anastomosed to the infrarenal aorta. All grafts were displaced in vivo by applying downward traction to a guidewire brought out both femoral arteries. The peak force to cause initial stent-graft migration or disruption of the sutured anastomosis was recorded and compared. Results: There was no difference in animal size, aortic neck diameter or length, aneurysm size, or iliac artery diameter for animals receiving the AneuRx, Talent, or Zenith stent-grafts and those undergoing surgical repair. The mean length of iliac fixation was 31.0±0.3 mm, 30.8±0.5 mm, and 31.3±0.6 mm for the AneuRx, Talent, and Zenith devices, respectively (p=NS). Peak force to initiate migration was 30.2=5.5 N (range 25–38) for the AneuRx, 44.8±5.5 N (range 40–53) for the Talent, 46.7±5.4 N (range 38–55) for the Zenith, and 40.6±7.5 N (range 31–50) for the surgical anastomosis (p=0.01). There was no difference detected in the peak force to initiate migration between the suprarenally affixed Talent and Zenith stent-grafts and the surgical anastomosis (p=0.55). Conclusion: Devices with a suprarenal component require significantly greater force to cause downward displacement compared to infrarenal devices. The force required to displace a suprarenal device with maximal iliac fixation was equivalent to the force required to disrupt a surgical anastomosis.
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Affiliation(s)
- Erin H Murphy
- Division of Vascular Surgery, Department of Surgery, UT Southwestern Medical Center, Dallas, TX 75390-9157, USA
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Batagini NC, Hardy D, Clair DG, Kirksey L. Nellix EndoVascular Aneurysm Sealing System: Device description, technique of implantation, and literature review. Semin Vasc Surg 2016; 29:55-60. [PMID: 27823591 DOI: 10.1053/j.semvascsurg.2016.04.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Clinical outcome reports document that from 30% to 60% of endovascular aneurysm repair procedures are performed outside of US Food and Drug Administration-approved Instruction for Use, or "off label." Endovascular aneurysm repair performed outside of Instruction for Use has a significantly higher rate of device failure, potentially requiring device reintervention and even planned or emergent explant. The Nellix device has the potential to reduce the rate of aneurysm device failure through its novel design. The objective of this article was to introduce the Nellix EndoVascular Aneurysm Sealing System and indications for use and describe the technique of implantation. We describe various modes of endovascular aneurysm repair failure and how the Nellix system can reduce these unplanned adverse outcomes. Additional clinical applications and theoretical shortcomings of endovascular aneurysm sealing devices are detailed.
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Affiliation(s)
- Nayara Cioffi Batagini
- Vascular Surgery Department, The Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195.
| | - David Hardy
- Vascular Surgery Department, The Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195
| | - Daniel G Clair
- Vascular Surgery Department, The Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195
| | - Lee Kirksey
- Vascular Surgery Department, The Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195
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Coulston J, Baigent A, Selvachandran H, Jones S, Torella F, Fisher R. Lack of Iliac Engagement Correlates With Iliac Limb Complications Following Standard EVAR. Vasc Endovascular Surg 2015; 49:201-5. [DOI: 10.1177/1538574415614403] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Objective: An adequate distal sealing zone is a prerequisite for successful endovascular aneurysm repair (EVAR). Poor engagement of iliac limbs within the common iliac artery potentially increases the risk of limb-related complications. The aim of this study was to investigate the proportion of common iliac artery used for distal sealing as a predictor of iliac limb complications following standard EVAR. Methods: This was a retrospective case controlled study where an iliac complication group was compared to a larger control group from the unit database. Core analysis of postoperative computed tomography scans was used to ascertain the percentage engagement of the iliac limb of the stent graft within the native iliac artery in both groups. Results: There were 240 limbs in the control group and 33 limbs in the complications group. Complications included 10 endoleaks, 1 iliac limb dislocation, 2 insufficient engagement, 4 occlusions, and 16 kinks. The proportion of common iliac artery engagement was significantly higher in the control group compared with the complications group (75.3:68.6%, P = .003). Conclusions: Increased engagement in the common iliac artery following standard EVAR reduces the risks of limb complications. A clinical guide utilization of more than 70% of the total length of common iliac artery could be used as this was associated with a significantly lower rate of iliac limb complications following standard EVAR.
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Affiliation(s)
- James Coulston
- Liverpool Vascular and Endovascular Service, Regional Vascular Unit, Royal Liverpool Hospital, Liverpool, England
| | - Amy Baigent
- Liverpool Vascular and Endovascular Service, Regional Vascular Unit, Royal Liverpool Hospital, Liverpool, England
| | - Haran Selvachandran
- Liverpool Vascular and Endovascular Service, Regional Vascular Unit, Royal Liverpool Hospital, Liverpool, England
| | - Steven Jones
- Liverpool Vascular and Endovascular Service, Regional Vascular Unit, Royal Liverpool Hospital, Liverpool, England
| | - Francesco Torella
- Liverpool Vascular and Endovascular Service, Regional Vascular Unit, Royal Liverpool Hospital, Liverpool, England
| | - Robert Fisher
- Liverpool Vascular and Endovascular Service, Regional Vascular Unit, Royal Liverpool Hospital, Liverpool, England
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Kratzberg JA, Golzarian J, Raghavan ML. Role of graft oversizing in the fixation strength of barbed endovascular grafts. J Vasc Surg 2014; 49:1543-53. [PMID: 19497518 DOI: 10.1016/j.jvs.2009.01.069] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2008] [Revised: 01/25/2009] [Accepted: 01/31/2009] [Indexed: 10/20/2022]
Abstract
PURPOSE The role of endovascular graft oversizing on risk of distal graft migration following endovascular aneurysm repair for abdominal aortic aneurysm is poorly understood. A controlled in vitro investigation of the role of oversizing in graft-aorta attachment strength for endovascular grafts (EVGs) with barbs was performed. METHODS Barbed stent grafts (N = 20) with controlled graft oversizing varying from 4-45% were fabricated while maintaining other design variables unchanged. A flow loop with physiological flow characteristics and a biosynthetic aortic aneurysm phantom (synthetic aneurysm model with a bovine aortic neck) were developed. The stent grafts were deployed into the aortic neck of the bio-synthetic aortic aneurysm phantom under realistic flow conditions. Computed tomography imaging of the graft-aorta complex was used to document attachment characteristics such as graft apposition, number of barbs penetrated, and penetration depth and angle. The strength of graft attachment to the aortic neck was assessed using mechanical pullout testing. Stent grafts were categorized into four groups based on oversizing: 4-10%; 11-20%; 21-30%; and greater than 30% oversizing. RESULTS Pullout force, a measure of post-deployment fixation strength was not different between 4-10% (6.23 +/- 1.90 N), 11-20% (6.25 +/- 1.84 N) and 20-30% (5.85 +/- 1.89 N) groups, but significantly lower for the group with greater than 30% oversizing (3.67 +/- 1.41 N). Increasing oversizing caused a proportional decrease in the number of barbs penetrating the aortic wall (correlation = -0.83). Of the 14 barbs available in the stent graft, 89% of the barbs (12.5 of 14 on average) penetrated the aortic wall in the 4-10% oversizing group while only 38% (5.25 of 14) did for the greater than 30% group (P < .001). Also, the stent grafts with greater than 30% oversizing showed significantly poorer apposition characteristics such as eccentric compression or folding of the graft perimeter. The number and depth of barb penetration were found to be positively correlated to pullout force. CONCLUSION Greater than 30% graft oversizing affects both barb penetration and graft apposition adversely resulting in a low pullout force in this in vitro model. Barbed stent grafts with excessive oversizing are likely to result in poor fixation and increased risk of migration.
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Affiliation(s)
- Jarin A Kratzberg
- Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa 52242-1527, USA
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12
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von Sachsen S, Senf B, Burgert O, Meixensberger J, Florek HJ, Mohr FW, Etz CD. Stent graft visualization and planning tool for endovascular surgery using finite element analysis. Int J Comput Assist Radiol Surg 2013; 9:617-33. [PMID: 24170574 DOI: 10.1007/s11548-013-0943-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 09/03/2013] [Indexed: 11/26/2022]
Abstract
PURPOSE A new approach to optimize stent graft selection for endovascular aortic repair is the use of finite element analysis. Once the finite element model is created and solved, a software module is needed to view the simulation results in the clinical work environment. A new tool for interpretation of simulation results, named Medical Postprocessor, that enables comparison of different stent graft configurations and products was designed, implemented and tested. METHODS Aortic endovascular stent graft ring forces and sealing states in the vessel landing zone of three different configurations were provided in a surgical planning software using the Medical Imaging Interaction Tool Kit (MITK) software system. For data interpretation, software modules for 2D and 3D presentations were implemented. Ten surgeons evaluated the software features of the Medical Postprocessor. These surgeons performed usability tests and answered questionnaires based on their experience with the system. RESULTS The Medical Postprocessor visualization system enabled vascular surgeons to determine the configuration with the highest overall fixation force in 16+/-6 s, best proximal sealing in 56+/-24s and highest proximal fixation force in 38+/- s. The majority considered the multiformat data provided helpful and found the Medical Postprocessor to be an efficient decision support system for stent graft selection. The evaluation of the user interface results in an ISONORM-conform user interface (113.5 points). CONCLUSION The Medical Postprocessor visualization software tool for analyzing stent graft properties was evaluated by vascular surgeons. The results show that the software can assist the interpretation of simulation results to optimize stent graft configuration and sizing.
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Affiliation(s)
- S von Sachsen
- Innovation Center Computer Assisted Surgery (ICCAS), University of Leipzig, Leipzig, Germany,
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Prasad A, Xiao N, Gong XY, Zarins CK, Figueroa CA. A computational framework for investigating the positional stability of aortic endografts. Biomech Model Mechanobiol 2013; 12:869-87. [PMID: 23143353 PMCID: PMC3638896 DOI: 10.1007/s10237-012-0450-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 10/19/2012] [Indexed: 10/27/2022]
Abstract
Endovascular aneurysm repair (Greenhalgh in N Engl J Med 362(20):1863-1871, 2010) techniques have revolutionized the treatment of thoracic and abdominal aortic aneurysm disease, greatly reducing the perioperative mortality and morbidity associated with open surgical repair techniques. However, EVAR is not free of important complications such as late device migration, endoleak formation and fracture of device components that may result in adverse events such as aneurysm enlargement, need for long-term imaging surveillance and secondary interventions or even death. These complications result from the device inability to withstand the hemodynamics of blood flow and to keep its originally intended post-operative position over time. Understanding the in vivo biomechanical working environment experienced by endografts is a critical factor in improving their long-term performance. To date, no study has investigated the mechanics of contact between device and aorta in a three-dimensional setting. In this work, we developed a comprehensive Computational Solid Mechanics and Computational Fluid Dynamics framework to investigate the mechanics of endograft positional stability. The main building blocks of this framework are: (1) Three-dimensional non-planar aortic and stent-graft geometrical models, (2) Realistic multi-material constitutive laws for aorta, stent, and graft, (3) Physiological values for blood flow and pressure, and (4) Frictional model to describe the contact between the endograft and the aorta. We introduce a new metric for numerical quantification of the positional stability of the endograft. Lastly, in the results section, we test the framework by investigating the impact of several factors that are clinically known to affect endograft stability.
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Affiliation(s)
- Anamika Prasad
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Nan Xiao
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Department of Biomedical Engineering, King’s College London, London SE1 7EH, UK
| | - Xiao-Yan Gong
- Medical Implant Mechanics LLC, 26895 Aliso Creek Road, Aliso Viejo, CA 92656, USA
| | | | - C. Alberto Figueroa
- Department of Biomedical Engineering, King’s College London, London SE1 7EH, UK
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Georgakarakos E, Xenakis A, Manopoulos C, Georgiadis GS, Tsangaris S, Lazarides M. Geometric Factors Affecting the Displacement Forces in an Aortic Endograft With Crossed Limbs: A Computational Study. J Endovasc Ther 2013; 20:191-9. [DOI: 10.1583/1545-1550-20.2.191] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Melas N, Perdikides T, Saratzis A, Saratzis N, Kiskinis D, Deaton DH. Helical EndoStaples enhance endograft fixation in an experimental model using human cadaveric aortas. J Vasc Surg 2012; 55:1726-33. [DOI: 10.1016/j.jvs.2011.11.048] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Revised: 11/02/2011] [Accepted: 11/05/2011] [Indexed: 11/27/2022]
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Vad S, Eskinazi A, Corbett T, McGloughlin T, Vande Geest JP. Determination of coefficient of friction for self-expanding stent-grafts. J Biomech Eng 2011; 132:121007. [PMID: 21142321 DOI: 10.1115/1.4002798] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Migration of stent-grafts (SGs) after endovascular aneurysm repair of abdominal aortic aneurysms is a serious complication that may require secondary intervention. Experimental, analytical, and computational studies have been carried out in the past to understand the factors responsible for migration. In an experimental setting, it can be very challenging to correctly capture and understand the interaction between a SG and an artery. Quantities such as coefficient of friction (COF) and contact pressures that characterize this interaction are difficult to measure using an experimental approach. This behavior can be investigated with good accuracy using finite element modeling. Although finite element models are able to incorporate frictional behavior of SGs, the absence of reliable values of coefficient of friction make these simulations unreliable. The aim of this paper is to demonstrate a method for determining the coefficients of friction of a self-expanding endovascular stent-graft. The methodology is demonstrated by considering three commercially available self-expanding SGs, labeled as A, B, and C. The SGs were compressed, expanded, and pulled out of polymeric cylinders of varying diameters and the pullout force was recorded in each case. The SG geometries were recreated using computer-aided design modeling and the entire experiment was simulated in ABAQUS 6.8/STANDARD. An optimization procedure was carried out for each SG oversize configuration to determine the COF that generated a frictional force corresponding to that measured in the experiment. The experimental pullout force and analytically determined COF for SGs A, B, and C were in the range of 6-9 N, 3-12 N, and 3-9 N and 0.08-0.16, 0.22-0.46, and 0.012-0.018, respectively. The computational model predicted COFs in the range of 0.00025-0.0055, 0.025-0.07, and 0.00025-0.006 for SGs A, B, and C, respectively. Our results suggest that for SGs A and B, which are exoskeleton based devices, the pullout forces increase upto a particular oversize beyond which they plateau, while pullout forces showed a continuous increase with oversize for SG C, which is an endoskeleton based device. The COF decreased with oversizing for both types of SGs. The proposed methodology will be useful for determining the COF between self-expanding stent-grafts from pullout tests on human arterial tissue.
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Affiliation(s)
- Siddharth Vad
- Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, AZ 85721, USA
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17
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Initial clinical experience with a sac-anchoring endoprosthesis for aortic aneurysm repair. J Vasc Surg 2011; 53:574-82. [DOI: 10.1016/j.jvs.2010.09.009] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Revised: 08/10/2010] [Accepted: 09/01/2010] [Indexed: 11/21/2022]
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Computational Analysis of Displacement Forces Acting on Endografts Used to Treat Aortic Aneurysms. STUDIES IN MECHANOBIOLOGY, TISSUE ENGINEERING AND BIOMATERIALS 2011. [DOI: 10.1007/8415_2011_73] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Corbett TJ, Molony DS, Callanan A, McGloughlin TM. The effect of vessel material properties and pulsatile wall motion on the fixation of a proximal stent of an endovascular graft. Med Eng Phys 2010; 33:106-11. [PMID: 20947409 DOI: 10.1016/j.medengphy.2010.09.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Revised: 09/21/2010] [Accepted: 09/22/2010] [Indexed: 10/18/2022]
Abstract
Migration is a serious failure mechanism associated with endovascular abdominal aortic aneurysm (AAA) repair (EVAR). The effect of vessel material properties and pulsatile wall motion on stent fixation has not been previously investigated. A proximal stent from a commercially available stent graft was implanted into the proximal neck of silicone rubber abdominal aortic aneurysm models of varying proximal neck stiffness (β=25.39 and 20.44). The stent was then dislodged by placing distal force on the stent struts. The peak force to completely dislodge the stent was measured using a loadcell. Dislodgment was performed at ambient pressure with no flow (NF) and during pulsatile flow (PF) at pressures of 120/80 mmHg and 140/100 mmHg to determine if pulsatile wall motions affected the dislodgement force. An imaging analysis was performed at ambient pressure and at pressures of 120 mmHg and 140 mmHg to investigate diameter changes on the model due to the radial force of the stent and internal pressurisation. Stent displacement forces were ~50% higher in the stiffer model (7.16-8.4 N) than in the more compliant model (3.67-4.21 N). The mean displacement force was significantly reduced by 10.95-12.83% from the case of NF to the case of PF at 120/80 mmHg. A further increase in pressure to 140/120 mmHg had no significant effect on the displacement force. The imaging analysis showed that the diameter in the region of the stent was 0.37 mm greater in the less stiff model at all the pressures which could reduce the fixation of the stent. The results suggest that the fixation of passively fixated aortic stents could be comprised in more compliant walls and that pulsatile motions of the wall can reduce the maximum stent fixation.
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Affiliation(s)
- T J Corbett
- Centre for Applied Biomedical Engineering Research (CABER), MSSi, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, Ireland
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Melas N, Saratzis A, Saratzis N, Lazaridis J, Psaroulis D, Trygonis K, Kiskinis D. Aortic and Iliac Fixation of Seven Endografts for Abdominal-aortic Aneurysm Repair in an Experimental Model Using Human Cadaveric Aortas. Eur J Vasc Endovasc Surg 2010; 40:429-35. [DOI: 10.1016/j.ejvs.2010.07.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Accepted: 07/03/2010] [Indexed: 10/19/2022]
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Corbett TJ, Callanan A, O'Donnell MR, McGloughlin TM. An Improved Methodology for Investigating the Parameters Influencing Migration Resistance of Abdominal Aortic Stent-Grafts. J Endovasc Ther 2010; 17:95-107. [DOI: 10.1583/09-2920.1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Figueroa CA, Taylor CA, Yeh V, Chiou AJ, Zarins CK. Effect of curvature on displacement forces acting on aortic endografts: a 3-dimensional computational analysis. J Endovasc Ther 2009; 16:284-94. [PMID: 19642787 DOI: 10.1583/08-2667.1] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
PURPOSE To determine the effect of curvature on the magnitude and direction of displacement forces acting on aortic endografts in 3-dimensional (3D) computational models. METHOD A 3D computer model was constructed based on magnetic resonance angiography data from a patient with an infrarenal aortic aneurysm. Computational fluid dynamics tools were used to simulate realistic flow and pressure conditions of the patient. An aortic endograft was deployed in the model, and the displacement forces acting on the endograft were calculated and expressed in Newtons (N). Additional models were created to determine the effects of reducing endograft curvature, neck angulation, and iliac angulation on displacement forces. RESULTS The aortic endograft had a curved configuration as a result of the patient's anatomy, with curvature in the anterolateral direction. Total displacement force acting on the endograft was 5.0 N, with 28% of the force in a downward (caudal) direction and 72% of the force in a sideways (anterolateral) direction. Elimination of endograft curvature (planar graft configuration) reduced total displacement force to 0.8 N, with the largest component of force (70%) acting in the sideways direction. Straightening the aortic neck in the curved endograft configuration reduced the total force acting on the endograft to 4.2 N, with a reduction of the sideways component to 55% of the total force. Straightening the iliac limbs of the endograft reduced the total force acting on the endograft to 2.1 N but increased the sideways component to 91% of the total force. CONCLUSION The largest component of the force acting on the aortic endograft is in the sideways direction, with respect to the blood flow, rather than in the downward (caudal) direction as is commonly assumed. Increased curvature of the aortic endograft increases the magnitude of the sideways displacement force. The degree of angulation of the proximal and distal ends of the endograft influence the magnitude and direction of displacement force. These factors may have a significant influence on the propensity of endografts to migrate in vivo.
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Affiliation(s)
- C Alberto Figueroa
- Department of Bioengineering, Stanford University, Stanford, California, USA
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Zarins CK, Taylor CA. Endovascular device design in the future: transformation from trial and error to computational design. J Endovasc Ther 2009; 16 Suppl 1:I12-21. [PMID: 19317584 DOI: 10.1583/08-2640.1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Endovascular devices have been designed by trial and error, with bench and animal testing followed by human clinical trials to determine whether the devices are safe and effective. Despite remarkable advances over the past 15 years, there are persistent concerns regarding the long-term durability of endovascular devices. This may be due to deficiencies in device design, which has lagged behind other industries in adopting computational methods that are now routinely used to design, develop, and test new aircraft and automobiles. Similar computational design and failure mode simulations that evaluate performance under stress conditions have not been widely applied in the development of endovascular devices. Advances in medical imaging and computational modeling now allow simulation of physiological conditions in patient-specific 3-dimensional vascular models, which can provide a framework to design and test the next generation of endovascular devices. This modeling will allow the prospective design of devices that can withstand the force variations in the cardiovascular system that occur during bending, coughing, and varying degrees of exercise, as well as the extremes encountered during sudden impact in contact sports. Utilization of computational design methodology that takes into consideration the physiology of the cardiovascular system will improve future endovascular devices so that they are safer and more effective and durable.
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Affiliation(s)
- Christopher K Zarins
- Stanford University School of Medicine and School of Engineering, Stanford, California, USA.
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Thomas B, Sanchez L. Proximal Migration and Endoleak: Impact of Endograft Design and Deployment Techniques. Semin Vasc Surg 2009; 22:201-6. [DOI: 10.1053/j.semvascsurg.2009.07.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Oshin OA, Bown MJ, McWilliams RG, Brennan JA, Vallabhaneni SR. Optimal technique for imaging iliac segments during endovascular repair of abdominal aortic aneurysms. J Endovasc Ther 2009; 16:373-9. [PMID: 19642797 DOI: 10.1583/09-2736.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
PURPOSE To determine if oblique angulation of the image intensifier is adequate to image the entire length of the common iliac artery during endovascular aneurysm repair or if additional caudal tilt is necessary. METHODS Using a 3D workstation, the apparent level of the iliac bifurcation (distal limit of the stent-graft) was determined on computed tomographic angiography by profiling the common iliac segment in oblique angulation only and repeated with a combination of oblique angulation and caudal tilt. Two independent observers measured twice the apparent length of the iliac segment in both profiles for 50 patients according to a set protocol. Intra- and interobserver variability was calculated using the Bland and Altman method; the differences between the two different profiles were tested using paired t tests. RESULTS Of the 50 CTA datasets reviewed, 2 datasets were excluded owing to extensive calcification of the iliac system that prevented accurate interpretation of the image. Of the 96 segments studied, the iliac segments appeared longer (better profiled) with a combination of caudal tilt and oblique angulation in 80%, with an average discrepancy of 9 mm for observer 1 (range -1 to +28) and 7 mm for observer 2 (0 to +26). The effect of caudal tilt was statistically significant for individual observers (p = 0.001 and 0.024, respectively). Forty-six percent of iliac segments measured by observer 1 and 35% by observer 2 showed that the addition of caudal tilt resulted in improved profiling by at least 10 mm. Although inter- and intraobserver variation was significant, the gain in apparent iliac length with the addition of caudal tilt was preserved. CONCLUSION When profiled with oblique angulation alone, the location of the iliac bifurcation may appear higher than its true location, resulting in underutilization of the iliac segment by >10 mm in over a third of the patients. The problem is corrected by employing additional caudal tilt.
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Affiliation(s)
- Olufemi A Oshin
- Regional Vascular Unit, Royal Liverpool University Hospital, Liverpool, UK
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Corbett TJ, Callanan A, Morris LG, Doyle BJ, Grace PA, Kavanagh EG, McGloughlin TM. A review of the in vivo and in vitro biomechanical behavior and performance of postoperative abdominal aortic aneurysms and implanted stent-grafts. J Endovasc Ther 2008; 15:468-84. [PMID: 18729555 DOI: 10.1583/08-2370.1] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Endovascular repair of abdominal aortic aneurysms has generated widespread interest since the procedure was first introduced two decades ago. It is frequently performed in patients who suffer from substantial comorbidities that may render them unsuitable for traditional open surgical repair. Although this minimally invasive technique substantially reduces operative risk, recovery time, and anesthesia usage in these patients, the endovascular method has been prone to a number of failure mechanisms not encountered with the open surgical method. Based on long-term results of second- and third-generation devices that are currently becoming available, this study sought to identify the most serious failure mechanisms, which may have a starting point in the morphological changes in the aneurysm and stent-graft. To investigate the "behavior" of the aneurysm after stent-graft repair, i.e., how its length, angulation, and diameter change, we utilized state-of-the-art ex vivo methods, which researchers worldwide are now using to recreate these failure modes.
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Affiliation(s)
- Timothy J Corbett
- Centre for Applied Biomedical Engineering Research, MSSI, Department of Mechanical and Aeronautical Engineering, University of Limerick, Ireland
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Feezor RJ, Huber TS, Berceli SA, Nelson PR, Seeger JM, Lee WA. Impact of endograft design and product line on the device cost of endovascular aneurysm repair. J Vasc Surg 2008; 47:499-503. [DOI: 10.1016/j.jvs.2007.10.051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Revised: 10/24/2007] [Accepted: 10/27/2007] [Indexed: 11/25/2022]
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Murphy EH, Johnson ED, Arko FR. Device-Specific Resistance to in Vivo Displacement of Stent-grafts Implanted With Maximum Iliac Fixation. J Endovasc Ther 2007. [DOI: 10.1583/1545-1550(2007)14[585:drtivd]2.0.co;2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Heikkinen MA, Alsac JM, Arko FR, Metsänoja R, Zvaigzne A, Zarins CK. The importance of iliac fixation in prevention of stent graft migration. J Vasc Surg 2006; 43:1130-7; discussion 1137. [PMID: 16765227 DOI: 10.1016/j.jvs.2006.01.031] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2005] [Accepted: 01/09/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVE Secure proximal fixation of endografts to the infrarenal aortic neck is known to be important in the short- and long-term success of endovascular aneurysm repair. We sought to determine the relative importance of distal iliac fixation in preventing endograft migration and adverse clinical events after endovascular aneurysm repair. METHODS We reviewed the outcome of 173 patients treated from 1996 to 2003 at Stanford University Medical Center with an externally supported stent graft. Quantitative image analysis of the postimplantation computed tomography scan was performed to determine the proximal aortic and distal iliac fixation lengths and the proximity the distal end of the stent graft to the iliac bifurcation. Subsequent follow-up computed tomography scans were reviewed for evidence of stent graft migration. Patients were grouped according to good (>15 mm), intermediate, or bad (<10 mm) aortic fixation and good (iliac fixation length > or =25 mm and iliac limbs <10 mm from iliac bifurcation), intermediate, or bad (<25-mm fixation length) iliac fixation. RESULTS Stent graft migration of 10 mm or more was seen in 17 patients (10%) during the 23 +/- 19-month follow-up period. Patients with no migration had a greater iliac fixation length (30 +/- 12 mm) than those with migration (22 +/- 8 mm; P = .01), and the distal ends of the iliac limbs were closer to the iliac bifurcation (15 +/- 12 mm) than in patients with migration (25 +/- 10 mm; P < .001). Patients with no migration also had a greater proximal aortic fixation length (23 +/- 12 mm) than migration patients (13 +/- 7 mm; P = .001). There were no migrations among patients with good iliac fixation whether aortic fixation was good, intermediate, or bad (0/63; 0%). Among patients with bad/intermediate iliac and good aortic fixation, there were 5 (9%) of 58 patients had migrations. Patients with both bad/intermediate iliac and bad/intermediate aortic fixation had the highest migration rate (12/52; 23%). Cox proportional hazards regression modeling revealed that the significant factors predicting migration were poor proximity of the distal end of the iliac limbs to the iliac bifurcation (odds ratio 17.2; P = .01) and aortic fixation length (odds ratio 2.0; p = 0.007 for each centimeter). Iliac extender modules were placed in 9 patients with bad iliac fixation and migration, with no further migration during a mean follow-up of 12 months. Patients with good iliac and aortic fixation and no endoleak on the initial postprocedure computed tomography scan (n = 43) had no migrations, secondary procedures, or adverse clinical events over a 2-year follow-up period. CONCLUSIONS Iliac fixation, along with proximal aortic fixation, is an important factor in preventing the migration of stent grafts that have longitudinal columnar support. Patients with good iliac fixation did not experience migration even in the presence of suboptimal proximal aortic fixation. Close proximity of the distal end of the stent graft to the iliac bifurcation seems to provide stability against migration.
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