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Karthikesalingam A, Thrumurthy SG, Jackson D, Choke E, Sayers RD, Loftus IM, Thompson MM, Holt PJ. Current Evidence Is Insufficient to Define an Optimal Threshold for Intervention in Isolated Type II Endoleak After Endovascular Aneurysm Repair. J Endovasc Ther 2012; 19:200-8. [DOI: 10.1583/11-3762r.1] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Georgakarakos E, Georgiadis GS, Ioannou CV, Kapoulas KC, Trellopoulos G, Lazarides M. Aneurysm sac shrinkage after endovascular treatment of the aorta: Beyond sac pressure and endoleaks. Vasc Med 2012; 17:168-73. [DOI: 10.1177/1358863x11431293] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The isolation of the aneurysm sac from systemic pressure and its consequent shrinkage are considered criteria of success after endovascular repair (EVAR). However, the process of shrinkage does not solely depend on the intrasac pressure, the predictive role of which remains ambiguous. This brief review summarizes the additional pathophysiological mechanisms that regulate the biomechanical properties of the aneurysm wall and may interfere with the process of aneurysm sac shrinkage.
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Affiliation(s)
- Efstratios Georgakarakos
- Department of Vascular Surgery, ‘Demokritus’ University of Thrace, University Hospital of Alexandroupolis, Alexandroupolis, Greece
| | - George S Georgiadis
- Department of Vascular Surgery, ‘Demokritus’ University of Thrace, University Hospital of Alexandroupolis, Alexandroupolis, Greece
| | - Christos V Ioannou
- Department of Vascular Surgery, University of Crete Medical School, University Hospital of Heraklion, Heraklion, Greece
| | - Konstantinos C Kapoulas
- Department of Vascular Surgery, ‘Demokritus’ University of Thrace, University Hospital of Alexandroupolis, Alexandroupolis, Greece
| | - George Trellopoulos
- First Surgical Clinic, General Hospital ‘G. Papanikolaou’, Exohi, Thessaloniki, Greece
| | - Miltos Lazarides
- Department of Vascular Surgery, ‘Demokritus’ University of Thrace, University Hospital of Alexandroupolis, Alexandroupolis, Greece
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Uhlenbrock AGD, Wintzer C, Imig H, Morlock M. Fluid transfer as a mechanism leading to endotension. Med Eng Phys 2010; 32:914-20. [DOI: 10.1016/j.medengphy.2010.06.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Revised: 04/15/2010] [Accepted: 06/27/2010] [Indexed: 11/25/2022]
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Endovascular aneurysm repair: current and future status. Cardiovasc Intervent Radiol 2008; 31:451-9. [PMID: 18231829 DOI: 10.1007/s00270-008-9295-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Revised: 12/01/2007] [Accepted: 12/06/2007] [Indexed: 10/22/2022]
Abstract
Endovascular aneurysm repair has rapidly expanded since its introduction in the early 1990s. Early experiences were associated with high rates of complications including conversion to open repair. Perioperative morbidity and mortality results have improved but these concerns have been replaced by questions about long-term durability. Gradually, too, these problems have been addressed. Challenges of today include the ability to roll out the endovascular technique to patients with adverse aneurysm morphology. Fenestrated and branch stent-graft technology is in its infancy. Only now are we beginning to fully understand the advantages, limitations, and complications of such technology. This paper outlines some of the concepts and discusses the controversies and challenges facing clinicians involved in endovascular aneurysm surgery today and in the future.
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Hinnen JW, Koning OHJ, van Bockel JH, Hamming JF. Aneurysm Sac Pressure after EVAR: The Role of Endoleak. Eur J Vasc Endovasc Surg 2007; 34:432-41; discussion 442-3. [PMID: 17669670 DOI: 10.1016/j.ejvs.2007.05.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Accepted: 05/27/2007] [Indexed: 10/23/2022]
Abstract
OBJECTIVE The relation between endoleak and aneurysm sac pressure is not completely clear. This review evaluates the effect of endoleaks on aneurysm sac pressure and summarizes the present knowledge regarding aneurysm sac pressure after EVAR. METHODS A systematic search of literature was carried out using MEDLINE, EMBASE and Web of Science. Studies were included if aneurysm sac pressure measurements as well as systemic pressure measurements were performed during or after EVAR. Mean pressure indices (MPI), ratio mean aneurysm sac pressure to mean systemic pressure), in the absence of endoleaks and in the presence of different type of endoleaks were compared. RESULTS Stent-graft deployment does not seem to result in immediate reduction of aneurysm sac in the absence of an endoleak. Aneurysm sac pressure is elevated in the presence of an endoleak. However, the MPIs differ widely between studies both in the absence and presence of an endoleak. CONCLUSION MPI is not specific to the type of endoleak. This implies that the same type of endoleak does not necessarily pose the same MPI and by this the same hazard of aneurysm rupture, because the aneurysm sac pressure is directly related to the aneurysm wall stress.
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Affiliation(s)
- J W Hinnen
- Section of Vascular Surgery, Department of Surgery, Leiden University Medical Center, Leiden, The Netherlands.
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Kleinstreuer C, Li Z, Farber MA. Fluid-Structure Interaction Analyses of Stented Abdominal Aortic Aneurysms. Annu Rev Biomed Eng 2007; 9:169-204. [PMID: 17362195 DOI: 10.1146/annurev.bioeng.9.060906.151853] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Rupture of abdominal aortic aneurysms (AAAs) alone is the thirteenth leading cause of death in the United States. Thus, reliable AAA-rupture risk prediction is an important advancement. If repair becomes necessary, the minimally invasive technique of inserting a stent-graft (SG), commonly referred to as endovascular aneurysm repair (EVAR), is a viable option in many cases. However, postoperative complications, such as endoleaks and/or SG migration, may occur. Computational fluid-structure interaction simulations provide physical insight into the hemodynamics coupled with multi-wall mechanics' function as an assessment tool for optimal SG placement and improved device design.
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Affiliation(s)
- C Kleinstreuer
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA.
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Mozes G, Kinnick RR, Gloviczki P, Bruhnke RE, Carmo M, Hoskin TL, Bennet KE, Greenleaf JF. Noninvasive measurement of aortic aneurysm sac tension with vibrometry. J Vasc Surg 2005; 42:963-71. [PMID: 16275455 DOI: 10.1016/j.jvs.2005.07.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2005] [Accepted: 07/02/2005] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Currently, the risk of aneurysm sac rupture after endovascular abdominal aortic aneurysm repair (EVAR) is estimated by using a group of anatomic variables. Available techniques for pressure monitoring include either direct measurement using catheter-based techniques or indirect measurement requiring implantation of a pressure sensor during aneurysm repair. None of these methods is without limitations. Radiation pressure, such as that generated by a modulated ultrasound (US) beam, can induce surface vibration at a distance. The velocity of the resulting surface waves depends on the tensile stress of the vibrated surface. By measuring the change in wave velocity, it is possible to detect the change in tensile stress and calculate the pressure through the vibrated surface. We tested this concept in an in vitro aneurysm model. METHODS Rubber tubes and explanted porcine abdominal aortas were used to model an aneurysm sac. The surface of the model was vibrated with an amplitude-modulated US beam. The resulting motion was detected either by reflected laser light or by Doppler US. The phase of the propagating wave was measured to assess changes in velocity with different pressures. RESULTS Increasing hydrostatic pressure in the rubber model correlated well with the cumulative phase shift (R(2) = 0.96-0.99; P < .0001). By using a pump to generate dynamic pressure (between 110 and 200 mm Hg), the cumulative phase shift correlated well with the square of the mean pressure (R(2) = 0.92; P < .0001); however, the correlation with pulse pressure was poor (24-36 mm Hg; r = 0.38; P < .02). In the porcine in vitro aortic sac model, the cumulative phase shift detected with both laser (r = 0.94-0.99; P < .0001) and Doppler (r = 0.96-0.99; P < .0001) correlated well with the aneurysm pressure. CONCLUSIONS Application of vibrometry for noninvasive measurement of aortic aneurysm sac tension is feasible in an in vitro setting. The concept of vibrometry may be used to detect endotension noninvasively after EVAR. Vibrometry may also be used to estimate wall stress in native aneurysms, and it may predict the risk of aneurysm rupture. CLINICAL RELEVANCE Vibrometry may offer a technique for completely noninvasive monitoring of aneurysm sac pressure after EVAR. Vibrometry is based on the following principles: radiation pressure, such as that generated by modulated US, can induce surface vibration at a distance; by measuring the change in wave velocity of vibration, it is possible to detect changes in tensile stress and calculate the pressure through the vibrated surface. We tested this concept in an in vitro model and found that application of vibrometry for noninvasive measurement of aortic aneurysm sac tension is feasible. Vibrometry may also be used to estimate wall stress in native aneurysms.
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Affiliation(s)
- Geza Mozes
- Division of Vascular Surgery, Mayo Clinic, Mayo Medical School, Rochester, MN 55905, USA
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Li Z, Kleinstreuer C. Computational analysis of type II endoleaks in a stented abdominal aortic aneurysm model. J Biomech 2005; 39:2573-82. [PMID: 16221475 DOI: 10.1016/j.jbiomech.2005.09.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Accepted: 09/01/2005] [Indexed: 11/25/2022]
Abstract
Insertion of a stent-graft into an aneurysm to form a new (synthetic) blood vessel and prevent the weakened artery wall from rupture is an attractive surgical intervention when compared to traditional open surgery. However, focusing on a stented abdominal aortic aneurysm (AAA), post-operative complications such as endoleaks may occur. An endoleak is the net influx of blood during the cardiac cycle into the cavity (or sac) formed by the stent-graft and the AAA wall. A natural endoleak source may stem from one or two secondary branches leading to and from the aneurysm, labeled types IIa and IIb endoleaks. Employing experimentally validated fluid-structure interaction solvers, the transient 3-D lumen and cavity blood flows, wall movements, pressure variations, maximum wall stresses and migration forces were computed for types IIa and IIb endoleaks. Simulation results indicate that the sac pressure caused by these endoleaks depends largely on the inlet branch pressure, where the branch inlet pressure increases, the sac pressure may reach the systemic level and AAA-rupture is possible. The maximum wall stress is typically located near the anterior-distal side in this model, while the maximum stent-graft stress occurs near the bifurcating point, in both cases, due to local stress concentrations. The time-varying leakage rate depends on the pressure difference between AAA sac and inlet branch. In contrast, the stent-graft migration force is reduced by type II endoleaks because it greatly depends on the pressure difference between the stent-graft and the aneurysm cavity.
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Affiliation(s)
- Z Li
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695-7910, USA
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Wright IA, Gordon MK, Buckenham TM. SPECTRAL DOPPLER CHARACTERIZATION OF ENDOLEAKS FOLLOWING ENDOLUMINAL ABDOMINAL AORTIC ANEURYSM REPAIR. ANZ J Surg 2005; 75:118-23. [PMID: 15777387 DOI: 10.1111/j.1445-2197.2005.03313.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Colour Doppler ultrasound of endoluminal abdominal aortic aneurysm repair is becoming an established imaging technique in identifying endoleak. Management and treatment of endoleak is determined in part by the exact nature of the endoleak, namely its type and whether it has single or multiple vessel inflow and outflow. To date, spectral Doppler waveform analysis has provided some information about the propensity for spontaneous seal of isolated type II endoleaks, rather than assisting in their classification. METHODS We present a collection of three case reports outlining the directionality/phasicity of the Doppler waveform profile associated with endoleaks whose type and subtype (uni- /or multi-conduital) were angiographically determined. RESULTS In all three cases uniconduital type II endoleak demonstrated a to-and-fro waveform on Doppler ultrasound imaging. CONCLUSIONS To-and-fro Doppler waveforms may be associated with uniconduital type II endoleaks. If upon investigation of further cases this is found to be the case, this waveform classification may facilitate determination of the subtype (uni- or multi-conduital) of endoleak, thus identifying those cases which may be more amenable to percutaneous repair.
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Affiliation(s)
- Isabel A Wright
- Department of Surgery, Christchurch Public Hospital, Christchurch, New Zealand.
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Dias NV, Ivancev K, Malina M, Resch T, Lindblad B, Sonesson B. Intra-aneurysm sac pressure measurements after endovascular aneurysm repair: differences between shrinking, unchanged, and expanding aneurysms with and without endoleaks. J Vasc Surg 2004; 39:1229-35. [PMID: 15192561 DOI: 10.1016/j.jvs.2004.02.041] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE Our objective was to study intra-aneurysm pressure after endovascular aneurysm repair (EVAR) in shrinking, unchanged, and expanding abdominal aortic aneurysms (AAAs) with and without endoleaks. METHODS Direct intra-aneurysm sac pressure measurement (DISP) by percutaneous translumbar puncture of the AAA under fluoroscopic guidance was performed 46 times during the follow-up of 37 patients (30 men; median age, 73 years [range, 58-82 years]; AAA diameter: median, 60 mm [range, 48-84 mm]). Three patients were included in two different groups because DISP was performed more than once with different indications. Tip-pressure sensors mounted on 0.014-inch guidewires were used for simultaneous measurement of systemic and AAA sac pressures. Mean pressure index (MPI) was calculated as the percentage of mean intra-aneurysm pressure relative to the simultaneous mean intra-aortic pressure. RESULTS Median MPI was 19% in shrinking (11 patients), 30% in unchanged (10 patients), and 59% in expanding (9 patients) aneurysms without endoleaks. Pulse pressure was also higher in expanding (10 mm Hg) compared with shrinking (2 mm Hg; P <.0001) AAAs. Four of the nine patients with expanding AAAs underwent five repeated DISPs later in the follow-up, and MPIs were consistently elevated. Seven of the 10 patients with unchanged AAAs without endoleaks underwent further computed tomography follow-up after DISP; 2 expanded (MPI, 47%-63%), 4 shrank (MPI, 21%-30%), and 1 remained unchanged (MPI, 14%). Type II endoleaks (6 patients, 7 DISPs) were associated with wide range of MPI (22%-92%). Successful endoleak embolization (n = 4) resulted in pressure reduction. CONCLUSIONS Intra-aneurysm sac pressure measurement is an important adjunctive for EVAR evaluation, possibly allowing early detection of failures. High pressure is associated with AAA expansion and low pressure with shrinkage. Type II endoleaks can be responsible for AAA pressurization, and successful embolization appears to result in pressure reduction.
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Affiliation(s)
- Nuno V Dias
- Endovascular Center, Department of Radiology, UMAS, Malmö University Hospital, S-205 02 Malmö, Sweden.
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Sekhri AR, Lees WR, Adiseshiah M. Measurement of Aortic Compliance in Abdominal Aortic Aneurysms Before and After Open and Endoluminal Repair:Preliminary Results. J Endovasc Ther 2004; 11:472-82. [PMID: 15298497 DOI: 10.1583/04-1243.1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
PURPOSE To assess aortic wall compliance as a portent of rupture risk in patients with abdominal aortic aneurysms. METHODS In this pilot study, 38 patients (32 men; median age 78 years, range 63-95) underwent an ultrasound scan: 20 pre-repair and 24 post-repair (18 endovascular [EVR] and 6 open). Six patients from the pre-repair group were included in a post repair study after EVR. Cine loop images were analyzed offsite using wall tracking software, which measured aortic diameter changes during cardiac cycles. Brachial blood pressure was measured, and elastic modulus (Ep) and stiffness (beta) were calculated. Preop Ep and beta were determined at the neck, inflection points (IP), and mid sac levels. Postop Ep and beta were calculated in mid sac only for technical reasons. RESULTS Preoperative Ep and beta were significantly higher at IP compared with neck (median Ep 24.22 versus 12.95 N/cm(2), p<0.003; median beta 16.27 versus 8.65, p<0.003). At the mid sac, Ep and beta were also significantly higher compared with neck: Ep 26.41 versus 12.95 N/cm(2), p=0.001; beta 17.94 versus 8.65, p=0.001. The values for IP and mid sac were Ep 24.22 versus 26.41 N/cm(2), p=0.64; beta 16.27 versus 17.94, p=0.64. In the postop cases (n=24), Ep and beta in successful endovascular repair (n=12) were significantly higher than in open repair, respectively: median Ep 34.31 versus 12.33 N/cm(2), p<0.001; median beta 23.18 versus 8.24, p<0.001. Patients with endoleaks or endotension (n=6) had significantly elevated Ep and beta compared with those without endoleaks (n=12): median Ep 79.79 versus 34.31 N/ cm(2), p=0.002; median beta 51.52 versus 23.18, p<0.002. Six patients scanned before and after EVR showed a decrease of Ep and beta in 3, no change in 1, and an increase in 2. An increase greater than 2 fold was noted in a patient with a gross type II endoleak. CONCLUSIONS This pilot study shows that estimates of aortic wall compliance agree well with known values for wall stress distribution. EVR leaves patients with greater wall stiffness than those undergoing open repair, a situation accentuated by endoleaks. Wall compliance and stiffness measurement promises to be useful for the evaluation of success of endovascular repair.
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Affiliation(s)
- Amine R Sekhri
- Medical Imaging, The Middlesex Hospital, University College London Hospitals and University College London, England, UK
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Affiliation(s)
- John J Ricotta
- Department of Surgery, State University of New York at Stony Brook, Room 020, University Hospital, Stony Brook, NY 11794, USA
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