| 1. |
- Roos, Håkan, 1967, et al.
(författare)
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Displacement Forces in Iliac Landing Zones and Stent Graft Interconnections in Endovascular Aortic Repair: An Experimental Study
- 2014
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 47:3, s. 262-267
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Stent graft migration influences the long-term durability of endovascular aortic repair. Flow-induced displacement forces acting on the attachment zones may contribute to migration. Proximal fixation of aortic stent grafts has been improved by using hooks, while distal fixation and stent graft interconnections depend on self-expansion forces only. We hypothesized that flow-induced displacement forces would be significant at the distal end, and would correlate with graft movements. Methods: As part of an experimental study, an iliac limb stent graft was inserted in a pulsatile flow model similar to aortic invivo conditions, and fixed-mounted at its proximal and distal ends to strain gauge load cells. Peak displacement forces at both ends and pulsatile graft movement were recorded at different graft angulations (0-90°), perfusion pressures (145/80, 170/90, or 195/100mmHg), and stroke frequencies (60-100b.p.m.). Results: Flow-induced forces were of the same magnitude at the proximal and distal end of the stent graft (peak 1.8N). Both the forces and graft movement increased with angulation and perfusion pressure, but not with stroke rate. Graft movement reached a maximum of 0.29±0.01mm per stroke despite fixed ends. There were strong correlations between proximal and distal displacement forces (r=0.97, p<.001), and between displacement forces and graft movement (r=0.98, p<.001). Conclusions: Pulsatile flow through a tubular untapered stent graft causes forces of similar magnitude at both ends and induces pulsatile graft movements in its unsupported mid-section. Peak forces are close to those previously reported to be required to extract a stent graft. The forces and movements increase with increasing graft angulation and perfusion pressure. Improved anchoring of the distal end of stent grafts may be considered. © 2013 European Society for Vascular Surgery.
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| 2. |
- Roos, Håkan, 1967, et al.
(författare)
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Displacement Forces in Stent Grafts: Influence of Diameter Variation and Curvature Asymmetry
- 2016
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 52:2, s. 150-156
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Long-term durability after endovascular aortic repair is influenced by stent graft migration causing types I and III endoleaks. Flow induced displacement forces have been shown to have the potential to cause migration. In this study, the influence of the distal diameter of iliac limb stent grafts and the shape of graft curvature on flow induced displacement forces, were investigated. Methods: In an experimental pulsatile flow model mimicking aortic conditions in vivo, flow induced displacement forces at the proximal and distal ends of iliac limb stent grafts were studied at different angles (0-90 degrees) and perfusion pressures (145/80, 170/90, 195/100 mmHg). Bell-bottomed, tapered, and non-tapered stent grafts and also asymmetric stent graft curvatures at 90 bend were studied. Measurements of graft movement were performed at all studied angulations and graft shapes. Results: For all stent graft diameters, flow induced displacement forces increased with higher pressure and increased stent graft angulation. Forces in the bell-bottom graft were considerably higher than in tapered and non-tapered grafts, with a markedly elevated peak force at the distal end (proximal end, 2.3 +/- 0.06 N and distal end, 6.9 +/- 0.05 N compared with 1.7 +/- 0.08 N and 1.6 +/- 0.08 N in non-tapered grafts; p <.001 both). Peak forces in tapered and non-tapered grafts were not significantly different between the proximal and distal end. In asymmetric stent graft curvatures, a significant increase in displacement forces was observed in the attachment zone that was closest to the stent graft bend. Graft movement increased with greater displacement forces. Conclusion: Flow induced displacement forces in iliac limb stent grafts are significant and are influenced by distal stent graft diameter and the shape of the graft curvature. The displacement forces are particularly high at the large distal end of bell-bottom grafts. Wide iliac arteries treated with bell-bottom stent grafts may require more vigilant surveillance and improved stent graft fixation.
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| 3. |
- Tokarev, Mikhail, 1982, et al.
(författare)
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DIC for Surface Motion Analysis Applied to Displacement of a Stent Graft for Abdominal Aortic Repair in a Pulsating Flow
- 2015
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Ingår i: PIV15; 11th International Symposium on Particle Image Velocimetry, Santa Barbara, California, USA, September 14-16, 2015. ; , s. 1-12
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Stent graft migration has been recognized to influence the long-term durability of endovascular aortic repair. Flow-induced displacement forces acting on the attachment zones may contribute to this migration. An experimental perfusion model consisting of the flow loop described by Roos et al. 2014 was used for further characterization of the pulsating flow induced stent graft movements with monocular and stereoscopic configurations of an optical imaging system. This paper adds new information on displacement measurement accuracy and 3D deformation analysis of the stent graft, which is used for abdominal aortic aneurysm treatment. The work describes used modification of Soloff’s Stereo PIV reconstruction algorithm for surface motion analysis. It was found that the oscillation of the stent graft’s body in the perpendicular direction to the front plane was 5 times less than side movements of the bent stent graft. These results can be used for further studies on different stent graft geometrical configurations and CFD simulations using fluid-structure interaction approach.
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| 4. |
- Andersson, Mattias, et al.
(författare)
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A population-based study of post-endovascular aortic repair rupture during 15 years
- 2021
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Ingår i: Journal of Vascular Surgery. - : Elsevier BV. - 0741-5214 .- 1097-6809. ; 74:3
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The devastating event of a ruptured abdominal aortic aneurysm (rAAA) in patients who have survived a previous AAA repair, either elective or urgent, is a feared and quite uncommon event. It has been suggested to partly explain the loss of the early survival benefit for endovascular aortic repair (EVAR) vs open surgical repair (OSR). The main objective of this study was to report the national incidence rate, risk factors and outcome of post-EVAR ruptures. Secondarily, the national incidence rate of ruptures after OSR (post-OSR ruptures) was investigated. Methods: We conducted a nationwide, population-based, retrospective cohort study using the inpatient and outpatient entries for all patients >40 years of age, receiving their first (index) surgical procedure for AAA, from 2001 to 2015. Only patients surviving their index procedure were included. The primary outcome was rAAA, registered after discharge from the index procedure (EVAR or OSR), identified in the Swedish National Patient Registry and the Cause of Death Registry. Results: In total, 14,859 patients survived their primary (index) AAA procedure. There were 6470 EVAR procedures, 5893 for intact AAA (iAAA) and 577 for rAAA. Of the 6470 EVAR patients, 86 cases of post-EVAR rupture were identified, corresponding with a cumulative incidence of 1.3% over a mean follow-up time of 3.9 years. The incidence rate was 3.4 (95% confidence interval [CI], 2.7-4.2)/1000 person-years. The independent risk factors identified for post-EVAR rupture were rAAA at index surgery HR 2.4 (95% CI, 1.4-4.1, p 0.002) and age (hazard ratio, 1.1; 95% CI, 1.0-1.1; P <.001). Freedom from post-EVAR rupture was 99%, 98%, and 96% at 3, 5, and 10 years, respectively. Total and postoperative mortality after post-EVAR rupture were 42% and 17% (30 days), 45% and 22% (90 days), and 53% and 33% (1 year). The incidence rate of post-OSR rupture was 0.9/1000 person-years (95% CI, 0.7-1.2). Conclusions: Post-EVAR rupture is a rare complication that can occur at any time after the index EVAR procedure. This finding may have implications for the discussion of limited follow-up programs and for the choice of procedure in patients with an AAA with a long life expectancy. An rAAA as the indication for the index surgery and age were identified as risk factors for post-EVAR rupture. The mortality associated with post-EVAR rupture is high, but lower than that of primary rAAA. The much lower risk of post-OSR rupture was confirmed, but must not be neglected as a possible late complication. © 2021 The Authors
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| 5. |
- Andersson, Mattias, et al.
(författare)
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Editor's Choice – Structured Computed Tomography Analysis can Identify the Majority of Patients at Risk of Post-Endovascular Aortic Repair Rupture
- 2022
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 64, s. 166-174
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The main objective was to report mechanisms and precursors for post-endovascular aneurysm repair (EVAR) rupture. The second was to apply a structured protocol to explore whether these factors were identifiable on follow up computed tomography (CT) prior to rupture. The third objective was to study the incidence, treatment, and outcome of post-EVAR rupture. Methods: This was a multicentre, retrospective study of patients treated with standard EVAR at five Swedish hospitals from 2008 to 2018. Patients were identified from the Swedvasc registry. Medical records were reviewed up to 2020. Index EVAR and follow up data were recorded. The primary endpoint was post-EVAR rupture. CT at follow up and at post-EVAR rupture were studied, using a structured protocol, to determine rupture mechanisms and identifiable precursors. Results: In 1 805 patients treated by EVAR, 45 post-EVAR ruptures occurred in 43 patients. The cumulative incidence was 2.5% over a mean follow up of 5.2 years. The incidence rate was 4.5/1 000 person years. Median time to post-EVAR rupture was 4.1 years. A further six cases of post-EVAR rupture in five patients found outside the main cohort were included in the analysis of rupture mechanisms only. The rupture mechanism was type IA in 20 of 51 cases (39%), IB in 20 of 51 (39%) and IIIA/B in 11 of 51 (22%). One of these had type IA + IB combined. One patient had an aortoduodenal fistula without another mechanism being identified. Precursors had been noted on CT follow up prior to post-EVAR rupture in 16 of 51 (31%). Retrospectively, using the structured protocol, precursors could be identified in 43 of 51 (84%). In 17 of 27 (63%) cases missed on follow up but retrospectively identifiable, the mechanisms were type IB/III. Overall, the 30 day mortality rate after post-EVAR rupture was 47% (n = 24/51) and the post-operative mortality rate was 21% (n = 7/33). Conclusions: Most precursors of post-EVAR rupture are underdiagnosed but identifiable before rupture using a structured follow up CT protocol. Precursors of type IB and III failures caused the majority of post-EVAR ruptures.
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| 6. |
- Falkenberg, Mårten, 1959, et al.
(författare)
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Ethylene vinyl alcohol copolymer (Onyx) to seal type 1 endoleak. A new technique.
- 2011
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Ingår i: Vascular. - : SAGE Publications. - 1708-5381 .- 1708-539X. ; 19:2, s. 77-81
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate whether the liquid embolic agent Onyx, an ethylene vinyl alcohol copolymer, can be used to seal type 1 endoleaks during endovascular aortic repair (EVAR). Six patients with large aortic aneurysms and remaining type 1 endoleaks during or after EVAR were treated with Onyx embolization through a microcatheter placed in the proximal neck in five cases and in the distal neck in one case. Four of the patients were treated using the chimney technique. The type 1 endoleak was primarily sealed by Onyx in all six patients. There was no distal embolization. Two patients had complications during follow-up. One patient had occlusions of chimney grafts to the renal arteries and to one leg extension. These occlusions were not anatomically related to Onyx embolization. One patient had late stentgraft migration of the Onyx-treated distal neck with aneurysm rupture 18 months after treatment. Early experience of Onyx embolization as a bailout solution of type 1 endoleaks after complicated EVAR is promising. However, effective seal with Onyx does not prevent late stentgraft migration. More reported patients and longer follow-up are necessary to evaluate this new technique.
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| 7. |
- Nordanstig, Joakim, et al.
(författare)
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Deep Femoral Vein Reconstruction of the Abdominal Aorta and Adaptation of the Neo-Aortoiliac System Bypass Technique in an Endovascular Era.
- 2019
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Ingår i: Vascular and endovascular surgery. - : SAGE Publications. - 1938-9116 .- 1538-5744. ; 53:1, s. 28-34
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Tidskriftsartikel (refereegranskat)abstract
- Primary infection of the abdominal aorta is a rare pathology that may threaten the integrity of the aortic wall, while secondary aortic prosthesis infection represents a devastating complication to open surgical and endovascular aortic surgery. Curative treatment is achievable by removal of all infected prosthetic material followed by a vascular reconstruction.Twelve consecutive patients treated with the neo-aortoiliac system bypass (NAIS) procedure were reviewed. Nine were treated for a secondary aortic prosthesis infection (tube graft n = 3, bifurcated graft n = 4, endovascular aortic repair (EVAR) stent graft n = 1, and fenestrated EVAR [FEVAR] stent graft n = 1), while 3 patients underwent NAIS repair due to an emergent primary mycotic aortoiliac aneurysm. Primary Results: Ten of 12 patients survived 30 days. Three patients were operated on acutely, and 9 patients had elective or subacute NAIS surgery. Two of 3 patients operated acutely died within 30 days, whereas no 30-day or 1-year mortality was observed in patients undergoing elective or subacute surgery. The median time from primary reconstruction to the NAIS procedure was 11 months (range: 0-201 months). Stent grafts (n = 5 of 12) were in 4 cases explanted using endovascular balloon clamping. Of the explanted endografts, 2 patients presented with a secondary graft infection after EVAR/FEVAR, while 3 patients had been emergently treated with endovascular cuffs as a "bridge-to-surgery" procedure due to aortoenteric fistula (AEF). Patients who received a "bridge-to-surgery" regimen were treated with the NAIS procedure within 8 weeks (median 27 days, range: 27-60) after receiving emergency stent grafting.Aortic balloon-clamping during explantation of infected aortic prosthetic endografts is feasible and facilitates complete endograft removal. Endovascular bridging procedures could be beneficiary in the treatment of AEF or anastomotic dehiscence due to graft infection, offering a possibility to convert the acute setting to an elective definitive reconstructive procedure with a higher overall success rate.
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| 8. |
- Roos, Håkan, 1967, et al.
(författare)
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Predisposing Factors for Re-interventions with Additional Iliac Stent Grafts After Endovascular Aortic Repair.
- 2017
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Ingår i: European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery. - : Elsevier BV. - 1532-2165. ; 53:1, s. 89-94
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Tidskriftsartikel (refereegranskat)abstract
- Endoleaks of type Ib and III are relatively common causes of re-intervention after EVAR. The aim was to determine underlying causes and identify anatomical factors associated with these re-interventions.A total of 444 patients with standard bifurcated stent grafts were included in a retrospective observational study. Patients requiring additional iliac stent grafts (n=24) were compared to those who did not (n=420). Pre- and post-operative CT examinations were reviewed in patients with additional iliac stents. Reasons for re-interventions were defined as migration (>5mmat the distal end or at interconnections), progression of disease (iliac artery diameter exceeding graft diameter), inadequate distal seal length at primary repair, or a combination of these factors.Twenty-four patients received 31 additional grafts in 30 limbs after a median 46 months (range 2-92 months). Five re-interventions (21%) were due to rupture. Re-intervened limbs had a larger iliac artery diameter 18mm (25th and 75th percentile 20-25) versus 15mm (13-18mm), p<.001. The degree of iliac limb oversizing at primary EVAR was lower in re-intervened patients (11% (8-18%) versus 18% (12-26%), p=.003). In re-intervened patients, iliac attachment zones were shorter in treated limbs than in untreated 23mm (11-34) versus 34mm (25-44), p<.001). Sixteen of 31 re-interventions (51%) were caused by migration (10at the distal landing site, 6at interconnections), nine of 31 (29%) by disease progression, and nine of 31 (29%) had inadequate initial stent graft placement. Three of 31 re-interventions (10%) were done as proactive procedures.Additional iliac stent grafting occurred late after primary repair; a considerable number were caused by rupture. A low degree of oversizing, migration at the distal landing site, separation of stent graft interconnections, disease progression at the distal landing site, and inadequate initial stent graft placement may all contribute. Patients with large iliac dimensions and short attachment zones may need a larger degree of oversizing and more vigorous surveillance.
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| 9. |
- Roos, Håkan, 1967
(författare)
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Re-interventions after endovascular aortic repair: clinical and experimental studies
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Endovascular aortic repair (EVAR) has lower morbidity and mortality than open surgery. Late complications and re-interventions are more common, however, and the timing of different re-interventions and their respective underlying causes are not fully understood. Aims: The overall aim was to describe re-interventions after EVAR and to identify possible underlying causes. Specific aims were as follows: 1. To describe re-interventions after EVAR, including incidence, indications, procedures, and outcome, concentrating especially on non-access-related re-interventions. 2. To determine underlying causes and to identify anatomical factors associated with additional iliac stent grafting. 3. To study flow-induced displacement forces in iliac limb stent grafts and the influence of stent graft angulation, fluid pressure, pulsation frequency, distal diameter of the stent graft, and asymmetric graft curvatures in an experimental aortic model. 4. To describe a new endovascular technique to close small entries that persist in the aortic arch. Materials and methods: Studies 1 and 2 were retrospective single-centre cohort studies of re-interventions after standard EVAR, focusing especially on non-access-related re-interventions. In Study 1, incidence, indications, procedures, and outcome were analyzed in 405 patients. In Study 2, 24 patients with additional iliac stent grafts after EVAR were studied. Computed tomography examinations were reviewed in detail regarding causes of re-intervention and underlying anatomic factors. These patients were compared with 420 patients treated with bifurcated EVAR during the same time period who did not require additional iliac stent grafts during follow-up, regarding patient characteristics and preoperative anatomic measurements. Studies 3 and 4 involved investigation of flow-induced displacement forces in iliac limb stent grafts in an experimental flow model mimicking physiologic conditions. In Study 3, the forces on a tubular stent graft with symmetric curvature were studied in relation to graft angulation, fluid pressure, and stroke rate. In Study 4 tapered, non-tapered, and bell-bottom grafts were studied at symmetric graft curvature and non-tapered grafts were studied at asymmetric curvature. Study 5 involved a new endovascular technique for closure of persistent small entries in selected patients with aneurysmal dilatation of chronic aortic dissections. Results: Study 1 showed that embolization of endoleak type II and placement of additional iliac stent grafts were the most common re-interventions after EVAR. These interventions were performed long after the initial intervention. Medium-term outcome in patients with re-intervention was comparable to that in patients without re-intervention. Study 2 showed that a considerable number of additional iliac stent grafting were caused by rupture. Migration at the distal landing site or graft interconnections was the most common cause, followed by disease progression. Study 3 demonstrated that flow-induced displacement forces were of similar magnitude at both ends of a non-tapered iliac stent graft, and the force increased with increasing graft angulation and fluid pressure but not with increasing pulse frequency. There was a high correlation between pulsatile graft movement and displacement forces. Study 4 showed that there were particularly high displacement forces in bell-bottom grafts, and that the forces were dependent on distal graft diameter and shape of the curvature. Study 5 showed that endovascular closure of persistent entries in chronic dissections is feasible, and in selected patients it may be an alternative to open surgery. Conclusions: Re-interventions are still common after EVAR, but most are percutaneous procedures and outcomes are generally good. Additional iliac stent grafting is one of the more frequent re-interventions, and in most cases it is related to stent graft migration, with a higher risk in patients with large iliac diameters and short attachment zones. Flow-induced displacement forces may have a role in the increased risk of migration. Patients with EVAR landing zones in wide iliac arteries may need improved graft fixation and more vigorous surveillance.
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| 10. |
- Sandström, Charlotte, et al.
(författare)
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Endovascular plugs to occlude proximal entries in chronic aortic dissection
- 2022
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Ingår i: Interactive Cardiovascular and Thoracic Surgery. - : Oxford University Press (OUP). - 1569-9293 .- 1569-9285. ; 35:3
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES Patients with expanding chronic aortic dissection and patent proximal entries are sometimes poor candidates for open surgery or TEVAR. Occlusion of proximal entries with endovascular plugs has previously been suggested in selected patients, but clinical results over time are unknown. This study analyses aortic remodelling and clinical outcome after proximal entry occlusion. METHODS Between 2007 and 2016, 14 patients, with expanding chronic aortic dissection, considered poor candidates for standard treatment, were treated with endovascular plugs in proximal entries located in the arch (n = 6) or descending aorta (n = 8). The Amplatzer (TM) Vascular Plug II was used for entries <= 4 mm and the Amplatzer (TM) Septal Occluder or Amplatzer (TM) Muscular VSD Occluder for entries 5-16 mm. Patients were followed for 0.5-13 years (median 7.3) with clinical visits and computed tomography. Diameters and cross-sectional areas along the aorta were measured. RESULTS Occlusion of proximal entries was achieved in 10/14 patients (71%), including 4 patients with an adjunctive reintervention needed for complete seal in the segment. Unchanged or reduced maximum thoracic aortic diameter was observed in all 10 patients with successful occlusion. In 4 patients, proximal occlusion was not achieved and early conversion to FET (n = 1), FET/TEVAR (n = 2) or TEVAR (n = 1) was performed. Two aorta-related deaths occurred during follow-up, both after early conversion. CONCLUSIONS Endovascular occlusion of proximal dissection entries of expanding chronic aortic dissections can induce favourable aortic remodelling and may be considered in selected patients with expanding chronic aortic dissection who are poor candidates for open surgery or stent graft repair.
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