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Detection of isolated hook fractures 36 months after implantation of the Ancure endograft: A cautionary note
Abstract
Two cases of delayed (36-month) Ancure hook fracture are reported in patients who experienced a decrease in aneurysm size and no evidence of endoleak. Both devices used redesigned hooks and are otherwise identical to those devices currently used in clinical practice. Notably, hook fractures were not visualized on all abdominal radiographic views, nor were they noted on the final "institutional" report by the reviewing radiologist. Careful clinical follow-up with multiple-view abdominal radiographs remains essential for all patients treated with an endovascular graft, with particular attention directed to the integrity of the metal components. The broader clinical significance of this observation with respect to the Ancure endograft remains to be defined.
... Type III endoleak is an unusual complication; however, metal fatigue and fabric erosion can create a type III endoleak, a long-term problem. 12,13 A fracture of the proximal attachment hooks has been also reported. 12 Reports of fabric erosion leading to type IIIb endoleak are rare, whereas type IIIa endoleak, defined as disconnection of the modular limb of a stent graft, is more common and leads to pressurization of the aneurysm sac and risk of rupture and death. ...
... 12,13 A fracture of the proximal attachment hooks has been also reported. 12 Reports of fabric erosion leading to type IIIb endoleak are rare, whereas type IIIa endoleak, defined as disconnection of the modular limb of a stent graft, is more common and leads to pressurization of the aneurysm sac and risk of rupture and death. 14 In a 2003 European Collaborators on Stent-Graft Techniques for AAA and Thoracic Aortic Aneurysm and Dissection Repair (EUROSTAR) study, 15 29% of ruptured AAAs after EVAR had type III endoleaks, so that modular separation or defects in stent graft fabric due to material fatigue remain an issue to be addressed by the industry in stent graft design. ...
Endoprosthesis fabric tear leading to abdominal aortic aneurysm rupture is a rare event. In this report, we describe a patient who presented with an abdominal aortic aneurysm rupture after a tear in the fabric of the Gore Excluder endoprosthesis (W. L. Gore and Associationes, Flagstaff, Ariz) 5 years after implantation. The reason for the fabric tear was unknown. The complication was successfully treated by relining the endograft with an aortic cuff and two iliac limbs. The patient experienced an uneventful recovery after the intervention.
... 1,2 In the era when stent grafts are placed in younger individuals with a longer life span, data on longterm material durability of the devices are still lacking. 3 Contemporary incidents of type IIIB endoleak complications involving material failure may be underappreciated. ...
Background:
Type IIIB endoleak from material failure can lead to aneurysmal sac enlargement and latent rupture after endovascular repair of abdominal aortic aneurysm. Long-term durability of the endovascular stent graft is largely unknown, and the complication rate from device failure due to material fatigue may be underappreciated. In addition, even with advancement in imaging techniques, recognition of type IIIB endoleak can be challenging, which can lead to delay in intervention.
Methods:
A review of the literature was performed in PubMed and Google Scholar, yielding 23 articles with 46 case reports of type IIIB endoleak from various Food and Drug Administration-approved stent grafts after endovascular repair of infrarenal abdominal aortic aneurysm.
Results:
The most common location of type IIIB endoleak occurred in the main body (34.8%), followed by the area of the flow divider (32.6%). Sac growth was identified in 63% (29/46) of cases. Diagnosis of the endoleak occurred an average of 54.3 months after the index operation. Endovascular repair was the primary approach for elective repair of type IIIB endoleak (61.3% vs 13.3%). Perioperative mortality was higher in ruptured or symptomatic patients compared with patients undergoing elective repair (33.3% vs 6.5%).
Conclusions:
The actual incidence of type IIIB endoleak is still lacking, and the etiology may be multifactorial. Therefore, suspicion of type IIIB endoleak requires appropriate imaging techniques and prompt intervention to reduce the perioperative mortality rate.
... [1][2][3] The Ancure (Guidant) was abandoned due to fractures of the proximal anchoring hooks. 4 Fractures of the metallic frame in the LifePath (Edwards) were also observed. 5 The Stentor and Vanguard devices originally manufactured by Mintec and subsequently by Boston Scientific demonstrated several failure modes: polypropylene suture breaks, failure and abrasion of the fabrics, and very extensive corrosion of the Nitinol wires in the early devices. ...
Since the introduction of stent-grafts to isolate aneurysms by Parodi in the 1980's, nitinol has proven to be the material of choice for the supportive metal frame of self-expanding devices. However, the present implant retrieval study involving dogs and humans has demonstrated evidence of nitinol corrosion, with the concomitant release of nickel ions. While the concentration of such ions has not been quantified, their presence is sufficient to raise questions about how innocuous nitinol is in the long term. With a view to establishing its level of biostability, this study compared the potential genotoxicity of nitinol to other metals and alloys commonly used in medicine. The results showed that the genotoxicity of exposure to nitinol is equivalent to that of 316L stainless steel, and is less severe than that of cigarette smoking. While the devices discussed in this study are no longer commercially available due to less than optimal clinical results, We nevertheless believe that nitinol is an appropriate material for implantation. Efforts should continue to ensure that the titanium oxide surface layer is continuous and free from nickel ions that might escape into the surrounding tissue and blood stream. Some manufacturers have already demonstrated that well controlled surface polishing techniques can significantly improve nitinol's resistance to corrosion.
... [1][2][3] The Ancure (Guidant) was abandoned due to fractures of the proximal anchoring hooks. 4 Fractures of the metallic frame in the LifePath (Edwards) were also observed. 5 The Stentor and Vanguard devices originally manufactured by Mintec and subsequently by Boston Scientific demonstrated several failure modes: polypropylene suture breaks, failure and abrasion of the fabrics, and very extensive corrosion of the Nitinol wires in the early devices. ...
The biodurability of the Nitinol wires used in stent-grafts retrieved from reoperations and autopsy was analyzed to assess the possible causes of fracture and/or corrosion of the stents. The Nitinol wires of six explanted devices presented a corrosion-free surface after in vivo service. The drawing lines in the control wires were still present, but neither burrs nor flakes were observed. Pits and crevices were rare, but some shallow ones were present. Some abrasions of the surfaces of the Nitinol wires were also observed. The chemical composition of the explanted devices showed the presence of organic contamination that covered the thick layer of titanium oxide before reaching the Nitinol itself. The durability of the Nitinol employed in the manufacture of the Talent stent-grafts was confirmed; the results of this study show the Nitinol to be resistant to corrosion. We have also concluded that the fractures of the Nitinol wires in two devices were unique adverse incidents caused by compression and bending related to the sharp angle of the Nitinol wires.
... Device performance has been carefully regulated both in the US and Europe, which has led to the detection of device failure and resulted in either withdrawal or modification of the device. For example, the early designs for the Ancure device had fixational hook fractures reported (Najibi 2001); and the AneuRx (Medtronic) stent gra , a modular heavily stented and sutured device, su ered from reports of endoleak in the follow-up period and was withdrawn from the market (Katzen 2005). ...
The UK prevalence of thoracic aneurysm is estimated at 10.4 per 100,000 person-years. Progressive and unpredictable enlargement can lead to rupture. Endovascular repair of thoracic aortic aneurysms involves a stent graft system being introduced via the femoral artery and manipulated within the aorta under radiological guidance. Following endograft deployment, a seal is formed at the proximal and distal landing zones to exclude the aneurysm sac from the circulation. With the increasing popularity of endovascular repair there has been an increase in the number of commercially available stent graft designs on the market.
This review aimed to assess the different stent graft types for endovascular repair of thoracic aortic aneurysms.
The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator (TSC) searched the Specialised Register (last searched November 2012) and CENTRAL (2012, Issue 11). Trial databases were searched by the TSC for details of ongoing and unpublished studies.
All published and unpublished randomised controlled trials (RCTs) of stent graft types in the repair of thoracic aortic aneurysms were sought without language restriction.
Data collection and analysis was conducted in accordance with the Cochrane Handbook for Systematic Reviews of Interventions.
No studies were identified that met the inclusion criteria.
Unfortunately, no data exist regarding direct comparisons of the performance of different stent graft types. Therefore, this review cannot recommend guidance to clinicians in their selection of stent graft types. High quality RCTs evaluating stent graft types in thoracic endovascular aneurysm repair are required.
... Endovascular abdominal aortic aneurysm (AAA) repair (EVAR) was one such medical technology that may have had an initial "irrational utilization." 1 We have observed a steady increase in the endovascular repair of infrarenal AAAs since the first case reported by Parodi in 1991 2 until midterm reports of EVAR uttered a cautionary note in the early 2000s. 3,4 Multiple problems or failure modes for EVAR have been described, such as proximal endograft migration, [5][6][7] endograft stent or hook fractures, 8 fabric fatigue and mic-roleaks, 9,10 late ruptures, 11 and a significant incidence of secondary procedures. 12 Newer-generation endografts were developed in response to these problems. ...
This study evaluated longitudinal trends in abdominal aortic aneurysm (AAA) management after later-generation endografts became available.
We retrospectively analyzed non-suprarenal AAA repairs between January 1, 1996, and December 31, 2008, performed at a single institution. Patients were stratified by endovascular AAA repair (EVAR) or open repair and the presence or absence of rupture. Thirty-day mortality rates were compared with the Fisher exact test.
During a 13-year period, 721 patients underwent AAA repair, comprising 410 (56.9%) with EVAR and 311 (43.1%) with open repair. A bimodal distribution of EVAR usage was observed, with initial escalation in the 1990s to 70%. A nadir of EVAR occurred in the early 2000s (40%), correlating with more conservative EVAR use after the limitations of first-generation endografts were understood. Between 2005 and 2008, average EVAR use increased to 84%. The overall 30-day mortality rate for the entire cohort, including ruptured AAA, was 3.8%: 2.0% (8 of 410) for EVAR and 6.1% (19 of 311) for open repair (P < .05). Ruptured AAA had a mortality rate of 0% (0 of 8) for EVAR vs 31% (9 of 29) for open (P = .16). Non-ruptured AAA mortality was 2.0% (8 of 402) for EVAR vs 3.6% (10 of 282) for open (P = .23). EVAR and open repair both had reductions in mortality in the latter half of the series, combining to provide a significant decrease in overall mortality to 1.8% for patients treated from 2003 to 2008 compared with 4.9% for 1996 to 2002 (P < .05). Open AAA repair became more complex during the study period. The average rate for juxtarenal open AAA repair was 17.7% (range, 6.5%-34.6%) between 1996 and 2002 compared with 55.6% (range, 29.6%-100%) between 2003 and 2008 (P < .05).
AAA treatment has undergone a profound and sustained paradigm shift, now averaging 84% of repairs performed with EVAR between 2005 and 2008. Overall mortality from AAA repair, including ruptures, was reduced 64% (from 4.9% to 1.8%) during the 13-year study period. Although EVAR and open repair both had improved mortality in the latter half of the series, the primary driver in reduced mortality for AAA repair has been the shift to EVAR.
... Defects such as graft fabric tears, suture breaks and stent/hook/barb fractures have been reported in many studies after EVAR. 5,53,56,[78][79][80][81] They are most likely due to fatigue loading that occurs with every pulse of the heart. Zarins et al. 82 reported stent fractures and suture breaks in the AneuRx stent graft (figure 2). ...
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.
... These two patients have been reported separately. 15 An illustration of one patient is presented in Fig 6. No clinical untoward effects have been noted so far in these two patients. ...
Late complications and graft failures have recently cast serious doubts on the durability of endovascular repair of abdominal aortic aneurysms (AAA). The results of a multicenter trial comparing a bifurcated endograft (AB) with standard open repair (OR) were reviewed to assess the late findings of both methods of AAA treatment.
In a multicenter study of AB versus OR conducted from December 1995 to February 1998, 242 patients with AAA successfully treated with an AB and 111 control patients treated concurrently with OR were followed up at least yearly. Twenty-five immediate conversions were excluded from late follow-up. All imaging modalities obtained during follow-up were reviewed by a core laboratory for AAA size, endoleaks, migration, and device integrity. Clinical outcomes at the yearly visits were compared. All death reports were reviewed to classify the cause of death.
Average follow-up for the AB group was 36 months, with 194 patients at 3 years and 55 patients at 4 years. The cumulative mortality rate was similar between the AB (15.7%) and OR groups (12.6%; P =.59). The significant early benefit to the AB group in cardiopulmonary complications was no longer evident by 3 years. However, the AB advantage in total and bowel complications, as well as the higher renal complication rates, persisted. At 3 years, 73.7% of patients showed a significant reduction of their AAA size, whereas 25.7% still had an endoleak. One migration and two single hook fractures were noted. Graftrelated reinterventions were performed in 50 patients (20%) without any deaths. Twenty-eight patients (11.6%) underwent interventions for limb flow compromise, whereas 25 were treated for endoleak. Late conversion to OR was required in five patients (2%). No AAA ruptures were encountered in either group.
Rupture-free survival rates after treatment of AAA with the bifurcated AB are similar to those of the OR group. Notably the proximal attachment system is relatively stable and the AAA shrinks in three of four patients treated. Reinterventions are nonetheless required in nearly one of five patients. Although most late procedures are percutaneous, counseling regarding possible future interventions is necessary.
... As many of the initial patients approach the long-term follow-up period, the number of reported deficiencies associated with this new technology is accumulating. 6,[9][10][11][12] In addition, that many patients will need secondary procedures to maintain either patency of the endograft or exclusion of the aneurysm is becoming clear. Laheij and colleagues 3 evaluated the EUROSTAR data and found reintervention rates similar to our results. ...
The purpose of this study was to evaluate the incidence, distribution, and indications of secondary procedures after endovascular aortic aneurysm repair (EAR).
At a single institution, 179 patients underwent EAR with four different endografts (AneuRx, n = 117; Zenith, n = 49; Ancure, n = 12; and Talent, n = 1). The vascular section database was queried for patients who needed secondary procedures after the original EAR. The mean time from EAR to the termination of the study was 27.0 +/- 16.7 months. Type I or III endoleaks were treated aggressively. Type II endoleaks were treated only in the presence of aneurysm expansion.
Thirty-five (35/179; 19.6%) secondary procedures were performed in 32 patients. Indications for secondary procedures included 14 limb occlusions or stenoses (40.0%), 13 endoleaks (37.1%), six endograft migrations (17.1%), one delayed aneurysm rupture (2.8%), and one device malfunction (2.8%). Seven of the 10 early (<90 days) limb failures (70%) occurred within the first 60 patients. At that time, a protocol with aggressive external iliac artery evaluation was adopted. In the next 125 patients, the rate of early limb occlusion or stenosis was 2.4% (P =.025, with Fisher exact test). Distribution of secondary procedures included 23 endoluminal interventions (65.7%; angioplasty +/- stent placement, thrombolysis, endocuff placement, embolization), eight traditional peripheral procedures (22.9%; femoral-femoral bypass, thrombectomy), two laparoscopic interventions (5.7%; inferior mesenteric artery ligation), and two laparotomies (5.7%; delayed conversions). Interventions for limb occlusion or stenosis occurred earliest (3.5 +/- 5.4 months; P <.05, with analysis of variance), followed by treatment of endoleaks (14.3 +/- 12.9 months) and migration (27.5 +/- 10.4 months). The one delayed rupture occurred at 15.3 months.
Secondary procedures after EAR are common. Reinterventions can be grouped temporally on the basis of indication. Treatment for limb ischemia is predominately early (>/=3 months), whereas treatment for endoleaks occurs at approximately 1 year and interventions for migration predominate after 2 years.
... Elgiloy fractures were initially reported in the hooks of first generation EVT devices during the early phase of the EVT trial. 17 Even though the hooks were remodeled to a more gradual angle to decrease the stress applied across the hook, Najibi et al 22 reported two cases of hook fractures identified 36 months after implantation of the remodeled Ancure device. Although the EVT device in this study had High-resolution explant radiograph of Gore TAG stent graft that was used to repair thoracic aortic aneurysm. ...
The first endovascular stent graft was implanted to treat an abdominal aortic aneurysm more than a decade ago. This technique has evolved dramatically with the growing understanding of metallurgic and fabric sciences and improved device designs. However the potential for stent graft material failure remains. This investigation describes the incidence of material failure, potential modes of device fatigue, and the clinical significance of these failures.
Six hundred eighty-six endovascular stent grafts were used to treat patients with aortic aneurysms. Device fatigue in the form of stent, suture fracture, or graft wear was identified with an analysis of follow-up radiographs and explanted stent grafts. A review of patient clinical histories, spiral computed tomographic scan studies, scanning electron microscopy, and energy dispersion spectroscopy of explanted devices was conducted to evaluate the modes and consequences of failure.
Sixty patients were identified with device fatigue, 49 of whom had abdominal endovascular repairs and 11 of whom had thoracic repairs. Of the 60 patients with stent graft fatigue, 43 patients had metallic stent fractures, 14 had suture disruptions, and three had graft holes. These material failures occurred within seven distinct stent graft designs. The average time to the recognition of failure was 19 months, with a mean follow-up period of 8 months since the event was identified. Eleven patients died, and one was lost to follow-up 2 years after identification of a stent fracture. The remaining patients are presently being followed eoyj physical examination, plain film radiograph, and computed tomographic scans for clinical sequelae of device fatigue.
Endovascular stent graft fatigue has been recognized in numerous devices after aortic implantation. Fatigue may take the form of stent, graft, or suture failure, with certain modes unique to specific stent graft devices. The clinical significance of stent graft material failure remains uncertain.
... Additionally, device corrosion has also been observed clinically. So far, there is no model which can predict such device deteriorations [33]. The reason is the serious lack of time-dependent clinical data due to short follow-ups, especially for the second generation of stentgrafts. ...
Since the introduction of endovascular techniques in the early 1990s for the treatment of abdominal aortic aneurysms (AAAs), the insertion of an endovascular graft (EVG) into the affected artery segment has been greatly successful for a certain group of AAA patients and is continuously evolving. However, although minimally invasive endovascular aneurysm repair (EVAR) is very attractive, post-operative complications may occur. Typically, they are the result of excessive fluid-structure interaction dynamics, possibly leading to EVG migration. Considering a 3D stented AAA, a coupled fluid flow and solid mechanics solver was employed to simulate and analyze the interactive dynamics, i.e., pulsatile blood flow in the EVG lumen, pressure levels in the stagnant blood filling the AAA cavity, as well as stresses and displacements in the EVG and AAA walls. The validated numerical results show that a securely placed EVG shields the diseased AAA wall from the pulsatile blood pressure and hence keeps the maximum wall stress 20 times below the wall stress value in the non-stented AAA. The sac pressure is reduced significantly but remains non-zero and transient, caused by the complex fluid-structure interactions between luminal blood flow, EVG wall, stagnant sac blood, and aneurysm wall. The time-varying drag force on the EVG exerted by physiological blood flow is unavoidable, where for patients with severe hypertension the risk of EVG migration is very high.
Background
There are no recognized pharmacological treatments for abdominal aortic aneurysms (AAA), although statins are suggested to be beneficial. We sought to summarize the literature regarding the effects of statins on human AAA growth, rupture, and 30‐day mortality.
Methods and Results
We conducted a systematic review and meta‐analysis of randomized and observational studies using the Cochrane CENTRAL database, MEDLINE, and EMBASE up to June 15, 2018. Review, abstraction, and quality assessment were conducted by 2 independent reviewers, and a third author resolved discrepancies. Pooled mean differences and odds ratios with 95% confidence intervals were calculated using random effects models. Heterogeneity was quantified using the I² statistic, and publication bias was assessed using funnel plots. Our search yielded 911 articles. One case‐control and 21 cohort studies involving 80 428 patients were included. The risk of bias was low to moderate. Statin use was associated with a mean AAA growth rate reduction of 0.82 mm/y (95% confidence interval 0.33, 1.32, P=0.001, I²=86%). Statins were also associated with a lower rupture risk (odds ratio 0.63, 95% confidence interval 0.51, 0.78, P<0.0001, I²=27%), and preoperative statin use was associated with a lower 30‐day mortality following elective AAA repair (odds ratio 0.55, 95% confidence interval 0.36, 0.83, P=0.005, I²=57%).
Conclusions
Statin therapy may be associated with reduction in AAA progression, rupture, and lower rates of perioperative mortality following elective AAA repair. These data argue for widespread statin use in AAA patients.
Clinical Trial Registration
URL: http://www.crd.york.ac.uk. Unique identifier: CRD42017056480.
Background
The UK prevalence of abdominal aortic aneurysm (AAA) is estimated at 4.9% in over 65-year olds. Progressive and unpredictable enlargement can lead to rupture. Endovascular repair of AAAs involves a stent graft system being introduced via the femoral artery and manipulated within the aorta under radiological guidance. Following endograft deployment, a seal is formed at the proximal and distal landing zones to exclude the aneurysm sac from the circulation. With the increasing popularity of endovascular repair there has been an increase in the number of commercially available stent graft designs on the market. This is an update of the review first published in 2013.
Objectives
This review aimed to assess the different stent graft types for endovascular repair of AAA.
Search methods
The Cochrane Vascular Group Trials Search Co-ordinator (TSC) searched the Specialised Register (last searched February 2015) and the Cochrane Register of Studies (2015, Issue 1). Trial databases were searched by the TSC for details of ongoing and unpublished studies.
Selection criteria
All published and unpublished randomised controlled trials (RCTs) of stent graft types in the repair of AAAs were sought without language restriction and in consultation with the Cochrane Vascular Group TSC.
Data collection and analysis
We planned to conduct data collection and analysis in accordance with the Cochrane Handbook for Systematic Reviews of Interventions.
Main results
No studies were identified that met the inclusion criteria. It was not possible to review the quality of the evidence in the absence of studies eligible for inclusion in the review.
Authors' conclusions
Unfortunately, no data exist regarding direct comparisons of the performance of different stent graft types. High quality randomised controlled trials evaluating stent graft types in abdominal endovascular aneurysm repair are required.
Plain language summary
Different stent grafts for repair of abdominal aortic aneurysms
Background
An aneurysm is a localised widening of an artery. The abdominal aorta is the largest artery in the body, delivering blood from the heart to the organs in the abdomen and the legs. If an aneurysm occurs in the abdominal aorta it can expand and may rupture, resulting in death. Open surgery can treat these aneurysms; this involves opening the abdomen and placing an artificial graft over the widening. A new alternative treatment involves an artifical stent graft, delivered through an arterial blood vessel in the groin, fixed over the widening. This technique is called endovascular repair. There are many different types of stent graft available. They differ in how they are inserted in/access the blood vessel, how they attach to the walls of the artery and the design and materials they are made from.
Study characteristics and key results
We searched for evidence directly comparing the different types of stent grafts in aneurysm repair (current until February 2015). This review found no randomised controlled trial evidence investigating if any specific stent graft performs better than another type of stent graft. More research is required to help surgeons decide which specific type of stent graft to use.
Quality of the evidence
It was not possible to review the quality of the evidence in the absence of studies eligible for inclusion in the review.
Background
The UK prevalence of thoracic aneurysm is estimated at 10.4 per 100,000 person-years. Progressive and unpredictable enlargement can lead to rupture. Endovascular repair of thoracic aortic aneurysms involves a stent graft system being introduced via the femoral artery and manipulated within the aorta under radiological guidance. Following endograft deployment, a seal is formed at the proximal and distal landing zones to exclude the aneurysm sac from the circulation. With the increasing popularity of endovascular repair there has been an increase in the number of commercially available stent graft designs on the market. This is an update of the review first published in 2013.
Objectives
This review aimed to assess the different stent graft types for endovascular repair of thoracic aortic aneurysms.
Search methods
The Cochrane Vascular Group Trials Search Co-ordinator (TSC) searched the Specialised Register (last searched February 2015) and the Cochrane Register of Studies CENTRAL (2015, Issue 1). Trial databases were searched by the TSC for details of ongoing and unpublished studies.
Selection criteria
All published and unpublished randomised controlled trials (RCTs) of stent graft types in the repair of thoracic aortic aneurysms were sought without language restriction.
Data collection and analysis
Data collection and analysis was conducted in accordance with the Cochrane Handbook for Systematic Reviews of Interventions.
Main results
No studies were identified that met the inclusion criteria. It was not possible to assess the quality of the evidence in the absence of studies eligible for inclusion in the review.
Authors' conclusions
Unfortunately, no data exist regarding direct comparisons of the performance of different stent graft types. High quality RCTs evaluating stent graft types in thoracic endovascular aneurysm repair are required.
Plain language summary
Different stent graft types to repair thoracic aortic aneurysms
Background
An aneurysm is a localised widening of an artery. The thoracic aorta is the largest artery in the body, delivering blood from the heart to the arms and head. If an aneurysm occurs in the thoracic aorta it can expand and may rupture, resulting in death. Open surgery can treat these aneurysms, which involves opening the chest and placing an artificial graft over the widening. A new alternative treatment involves an artificial stent graft, delivered through an arterial blood vessel in the groin, fixed over the widening. This technique is called endovascular repair. There are many different types of stent grafts available. They differ in how they are inserted into/access the blood vessel, how they attach to the walls of the artery and the design and materials they are made from.
Study characteristics and key results
We searched for evidence directly comparing the different types of stent grafts in aneurysm repair (current until February 2015). This review found no evidence from randomised controlled trials to determine if any specific stent graft performs better than another type of stent graft. More research is required to help surgeons decide which specific type of stent graft to use.
Quality of the evidence
It was not possible to assess the quality of the evidence in the absence of studies eligible for inclusion in the review.
Endovascular treatment of abdominal aortic aneurysms (AAA) is a promising new alternative to the traditional surgical repair. However, the endovascular approach suffers problems such as stent graft migration, endoleaks and stent mechanism breakage. Fatigue failure is believed to be the major cause of stent graft migration and device breakage. Knowledge of the in vivo forces acting on such devices is a basic requirement for the design of a successful endovascular device. Using a Fourier series trigonometric fit of a typical pressure and flow relationship, a mathematical model, using the control volume method, was developed to predict the pulsatile drag forces acting on various bifurcated stent graft geometries. It was found that for an iliac angle of 30°, a proximal diameter of 24 mm and an iliac diameter of 12 mm, the drag force varied, over the cardiac cycle, between 3.9 and 5.5 N in the axial direction. It was noted that for a specific iliac angle the drag force variation with proximal diameter approximates a quadratic fit, with an increase in proximal diameter producing an increase in drag force. The more compliant the aorta the higher the drag force. Previously published results demonstrated the axial loads (axial drag forces) required for stent graft migration for certain stents types are lower than the drag forces calculated in this study. It is believed that the results of this study can provide guidelines for the quantitative analyses of the in vivo drag forces experienced by stent grafts and could therefore be used as design criteria for such devices.
The evolution of vascular surgery toward minimally invasive approaches appears to be inevitable. Thus, innovative and reliable minimally invasive anastomosis techniques are needed to facilitate minimally invasive vascular surgery. Current endovascular anastomosis techniques are limited by their reliance on suitable arteries for access and attachment. Their dependency on the fate of the arterial attachment sites is greater than for the conventionally sutured anastomosis. These limitations will be difficult to over come. Videoscopic anastomosis techniques may offer both the advantages of endovascular surgery in terms of rapid postoperative recovery and reliability of open-sutured anastomosis. With improved training and instrumentation, such as robots, semiautomatic or automatic anastomotic devices, the video scopic approaches will likely become technically easier. The chief disadvan tage of current open-sutured anastomoses is the invasive exposure required, elevated morbidity and mortality, and associated prolonged hospital stay and convalescence period. Development of automatic or semiautomatic anastomosis techniques could decrease the invasiveness of these operations. Further research will help understand the interaction of the artificial agents with the arterial wall and will define what constitutes a perfect and durable anastomosis. This, in turn, will allow for the ideal anastomosis technique to become reality, and for widespread application of minimally invasive approaches in vascular surgery.
The UK prevalence of abdominal aortic aneurysm (AAA) is estimated at 4.9% in over 65-year olds. Progressive and unpredictable enlargement can lead to rupture. Endovascular repair of AAAs involves a stent graft system being introduced via the femoral artery and manipulated within the aorta under radiological guidance. Following endograft deployment, a seal is formed at the proximal and distal landing zones to exclude the aneurysm sac from the circulation. With the increasing popularity of endovascular repair there has been an increase in the number of commercially available stent graft designs on the market.
This review aimed to assess the different stent graft types for endovascular repair of AAA.
The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator (TSC) searched the Specialised Register (last searched November 2012) and CENTRAL (2012, Issue 10). Trial databases were searched by the TSC for details of ongoing and unpublished studies.
All published and unpublished randomised controlled trials (RCTs) of stent graft types in the repair of AAAs were sought without language restriction and in consultation with the Peripheral Vascular Disease Group TSC.
We planned to conduct data collection and analysis in accordance with the Cochrane Handbook for Systematic Reviews of Interventions.
No studies were identified that met the inclusion criteria.
Unfortunately, no data exist regarding direct comparisons of the performance of different stent graft types. Therefore, this review cannot recommend guidance to clinicians in their selection of stent graft types. High quality randomised controlled trials evaluating stent graft types in abdominal endovascular aneurysm repair are required.
Endovascular aneurysm repair (EVAR) is widely accepted as a safe technique for treatment of aortic diseases since the concept was first pioneered by Volodos in 1986 and Parodi in 1991. Numerous registries have shown that this minimally invasive technique is associated with lower mortality when compared to open surgery in short and mid-term follow-up. The first pioneer devices had a high failure rate due to stent migration. This led to the creation of the first generation stent-grafts, which were associated with complications such as thrombosis of the limbs, graft migration and major endoleaks. The majority of these endostents are now withdrawn from the commercial market. However, these patients need lifelong surveillance because of a considerable risk of late complications. The materials used in the stent-graft vary with each manufacturer. Low porous fabric, suprarenal fixation and low profile devices led to the development of the second generation stent-grafts. The improvements with regards to the delivery systems, enabled reposition of the top-stent following deployment in some devices. The number of devices commercially available increased with the second generation. The third generation of stent-grafts, allowed treatment of complex aortic disease. Custom made solutions incorporate small openings, fenestrations for vessels involved in the aneurysmal disease and is already built in today's technology and available as CE marked devices. The device can be built with combinations of various branches and fenestrations in order to best accommodate the aortic anatomy of the patient. However, many issues remain with the development of this technology. There is a need for durable systems with less complicated deployment mechanics in order to be applied and more widespread. In conclusion, the third generation endografts in challenging anatomy has yielded encouraging results. With regards to short and midterm outcome and need for secondary interventions, evaluations shows comparable results with all devices performing well.
The long-term success of the endovascular procedure for the treatment of Abdominal Aortic Aneurysms (AAAs ) depends on the secure fixation of the proximal end and the geometry of the stent-graft (SG) device. Variations in SG types can affect proximal fixation and SG hemodynamics. Such hemodynamic variations can have a catastrophic effect on the vascular system and may result from a SG/arterial wall compliance mismatch and the sudden decrease in cross-sectional area at the bifurcation, which may result in decreased distal perfusion, increased pressure wave reflection and increased stress at the interface between the stented and non-stented portion of the vessel. To examine this compliance mismatch, a commercial SG device was tested experimentally under a physiological pressure condition in a silicone AAA model based on computed tomography scans. There was a considerable reduction in compliance of 54% and an increase in the pulse wave velocity of 21%, with a significant amount of the forward pressure wave being reflected. To examine the SG geometrical effects, a commercial bifurcated geometry was compared computationally and experimentally with a geometrical taper in the form of a blended section, which provided a smooth transition from the proximal end to both iliac legs. The sudden contraction of commercial SG at the bifurcation region causes flow separation within the iliac legs, which is known to cause SG occlusion and increased proximal pressure. The blended section along the bifurcation region promotes a greater uniformity of the fluid flow field within the distal legs, especially, during the deceleration phase with reduced boundary layer reversal. In order to reduce the foregoing losses, abrupt changes of cross-section should be avoided. Geometrical tapers could lead to improved clinical outcomes for AAA SGs.
In 1991, when Parodi first published his experience with placement of a balloon-expandable endograft for the treatment of
abdominal aortic aneurysms in patients deemed unsuitable for open surgery, 1 interest grew in the field of endovascular approaches
to the treatment of aortic aneurysms. Since that initial report, tremendous advancements have made this methodology commonplace,
and more importantly, widely accepted as a viable alternative to the traditional open repair. Furthermore, refinements in
the newer devices have expanded the inclusion criteria for patients previously thought to be unsuitable for endovascular repair,
greatly increasing its versatility and applicability.
Six Talent stent-grafts were harvested at reoperations (N=5) and autopsy (N=1). The explants were observed nondestructively, including gross morphology, X-rays, CT scans and closed pressure system analysis. The Nitinol frames in three devices harvested at reoperations and another harvested at autopsy were intact. One had a stent fracture of the proximal bare stent, and one had a wire fracture of a thin proximal external supporting stent as well as a hole in the fabric just above the bifurcation. For the three devices structurally intact, reoperations were performed for a type 1A endoleak (one patient) and aorto-enteric fistulas (two patients). The healing characteristics were poor or absent. The fabric in the main body of the grafts harvested after aorto-enteric fistula was devoid of biological deposits. Two of the grafts harvested at reoperation demonstrated fabric holes of up to 4 mm 2. The device obtained at autopsy showed an almost continuous internal capsule with variable thickness. The luminal surface was smooth, but the capsule detached easily. The devices explanted at reoperations showed various levels of impaired biofunctionality associated with adverse outcomes. The stent-graft retrieved from autopsy was intact.
To evaluate the effects of type II endoleaks and sac pressurization on stent-graft displacement following endovascular aneurysm repair (EVAR).
Experimental silicone infrarenal aneurysm (6-cm) models were "treated" with a Talent stent-graft deployed with 20-mm proximal and distal landing zones. Inflow and outflow vessels were created as part of the silicone model to control flow into the aneurysm sac. All aneurysm models were uniform, with a diameter neck of 31 mm, a neck length of 20 mm, and iliac artery diameters of 16 mm. The aortic model was secured in a water bath to a pulsatile pump under physiological conditions; the output phase ratio (%systole/%diastole) was set at 65/35 with a pump rate of 80 beats per minute. Commercially available bifurcated stent-grafts were then displaced in vitro utilizing a linear motion apparatus attached to a force gauge. The mean arterial pressure (MAP) and pulse pressure (PP) at the aortic inflow were 60.1 ± 3.1 and 38.3 ± 7.8 mmHg, respectively. Peak force to cause initial stent-graft migration with and without a type II endoleak was recorded and compared.
In aneurysm sacs with no endoleak, the MAP and sac PP were 32 ± 6.4 and 6 ± 1.3 mmHg, respectively (p<0.01). In aneurysm sacs with a type II endoleak, the MAP and sac PP were 54.1 ± 9.7 and 16.1 ± 4.1 mmHg, respectively (p<0.02). Peak force to initiate migration was 16.0 ± 1.41 N (range 15-18) with no endoleak vs. 23.2 ± 2.2 N (range 20-25) in those with a type IIa endoleak and 23.5 ± 2.5 N (range 20-26) in those with a type IIb endoleak (p<0.001).
Type II endoleaks are associated with a significantly increased sac pressure. Increased sac pressurization from type II endoleaks results in a significantly greater force to displace a stent-graft longitudinally. Type II endoleaks may therefore inhibit migration and offer a benefit following EVAR; however, clinical correlation of these results is required.
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.
The first commercially available stent grafts were unable to withstand the hemodynamic forces of the vascular environment. The past 15 years have seen a gradual improvement in long-term stent graft performance as designs evolved through the elimination of features associated with late failure and the replication of features associated with durable success. Clinical experience provides the following principles on which to base device design and implantation techniques. Few patients have an adequate length of non-dilated aorta distal to the aneurysm to allow implantation of an aorto-aortic stent graft; bifurcated stent grafts are usually required for AAA repair. Friction, column strength and tissue ingrowth do not prevent migration of the stent graft from its attachment within the neck into the aneurysm; some form of active fixation is required, usually in the form of barbs. Any movement between the apex of a stent and the overlying graft material will erode the fabric; stents and grafts need to move as a single unit. Nitinol is versatile, but fragile; Nitinol components must be polished to eliminate all surface irregularities and they cannot be subjected to compression loading, or excessive pulsatile movement. The neck of an aneurysm is unstable; it will dilate unless protected by a securely fixed, non-compliant stent graft. The aneurysm does not heal; freedom from risk of rupture depends on durable depressurization of the sac. The sole objective of image-based follow-up is the early detection, and catheter-based correction, of device failure. Once any given design has been in use long enough to identify its failure modes, the frequency of follow-up studies can be adjusted accordingly. However, it takes a long time to identify all the potential forms of late failure, and pre-clinical testing remains an imprecise science. New, or recently modified, devices cannot necessarily be assumed to be as durable as their predecessors.
To retrospectively evaluate the safety and effectiveness of the use of bivalirudin, a direct thrombin antagonist, compared with unfractionated heparin in endovascular aneurysm repair (EVAR).
Between March 1994 and September 2007, 740 consecutive patients (mean age, 75.7 y +/- 7.7; 69 women) underwent elective EVAR for infrarenal abdominal aortic aneurysm. Bivalirudin was used in 98 of these 740 (13.2%) and unfractioned heparin was used in the other 642 (86.8%). Complications were classified according to the Society of Vascular Surgery/International Society for Cardiovascular Surgery criteria. Major bleeding was defined as clinically overt blood loss resulting in a decrease of hemoglobin of more than 3 g/dL, any decrease in hemoglobin of more than 4 g/dL, transfusion of 2 U or more of red blood cells, or intracranial or retroperitoneal hemorrhage.
Grade 1 major complications were observed in 161 of 642 patients (25.2%) in the heparin group and 12 of 98 patients (12.2%) in the bivalirudin group (P = .0046), whereas the incidences of grade 3 major complications were not significantly different between groups (P = .57). The rate of total complications was higher in the heparin group than in the bivalirudin group (247 of 642 [38.5%] vs 21 of 98 [21.4%]; P = .001). Major bleeding occurred in 10 of 98 patients (10.2%) receiving bivalirudin and in 91 of 642 patients (14.2%) receiving heparin (P = .34). One of 21 major complications (4.76%) in the bivalirudin group and 12 of 247 major complications (4.86%) in the heparin group were attributable to thrombosis (P = 1.0).
Bivalirudin is a safe and feasible alternative to unfractionated heparin in patients undergoing EVAR.
Purpose of this study was to compare the correlation of statin use with long-term mortality in patients with abdominal (AAA) and thoracic aortic aneurysm (TAA).
We compared long-term survival of 731 AAA and 59 TAA patients undergoing elective endovascular repair (EVAR). Kaplan-Meier survival curves were compared by the log-rank method. Propensity score-adjusted multivariable logistic regression models were used to determine independent associations of statin use on vital status after EVAR.
Statin use was associated with decreased long-term mortality in AAA patients in bivariate and multivariable regression analysis, in which the effect of propensity to receive a statin was considered (adjusted HR: .613, 95%-CI: .379- .993, p = .047) whereas mortality of TAA patients was not associated with use of statins (adjusted HR: 1.795, 95%-CI: .147 -21.942, p = .647).
Use of statins is an independent predictor of decreased mortality after elective EVAR in AAA, but not in TAA patients. These findings indirectly support the concept of a distinct pathogenesis of AAA and TAA.
To report a case of endograft disintegration misinterpreted as a type II endoleak.
An 86-year-old man underwent successful Vanguard stent-graft implantation for a 49-mm abdominal aortic aneurysm. At 1 month, a distal type I endoleak was repaired, but another endoleak thought to arise from the lumbar or inferior mesenteric arteries remained. Multiple interventions to embolize the feeding arteries were unsuccessful, and the endoleak persisted. At 1 year, the leak was still present, and the aneurysm had increased to 69 mm. After failing to demonstrate the source of the leak radiographically, surgery was performed. At operation, the endoleak was traced to small holes in the graft fabric. The endograft was removed without difficulty, and the flow was re-established with an aortobi-iliac woven graft.
Chronically implanted stent-grafts can show signs of failure that are confusing or misleading. Correct diagnosis of endoleaks may be difficult, but every effort must be made to identify their source. It is vital that no enlarging aneurysm be left untreated.
After the introduction of endovascular repair of abdominal aortic aneurysms (AAA), both benefits and drawbacks of this new technique have been reported. To assess whether the new technique is an adequate substitute of conventional AAA repair, a randomised study is due. The Dutch Randomised Endovascular Aneurysm Management (DREAM) trial is a randomised multicenter trial enrolling patients eligible for elective treatment of infrarenal AAAs. In this study, the cost-effectiveness of endovascular aneurysm repair (EAR) is compared with that of conventional transabdominal surgery, in patients that are considered suitable for both types of treatment. The primary endpoint is combined operative mortality and morbidity. Secondary endpoints and additional assessments include event free survival, quality of life, length of hospital stay and costs. It is expected that the DREAM-trial will lead to a safe and controlled introduction of a new technology. Also, the medical community will obtain valid scientific evidence of the merits of endovascular AAA repair. Finally, policy makers will be provided with accurate cost-effectiveness data for the Dutch healthcare system. The aim of the present paper is to describe the background, methods and design of the DREAM-trial.
The purpose of this study was to assess the short-term and mid-term results of endovascular aneurysm repair with the Zenith stent graft in a single-center prospective study.
Between October 1998 and July 2001, we used the Zenith stent graft for elective endovascular aneurysm repair in 116 patients, six of whom were women. The mean age was 75 years, and the mean aneurysm diameter was 60.3 +/- 8.8 mm. Stent grafts were oversized 10% to 20% relative to computed tomographic (CT) scan-based diameter measurements. All repairs were performed in the operating room through surgically exposed femoral arteries. The results were assessed before discharge with three-phase, contrast-enhanced CT scan and plain abdominal radiograph. These studies were repeated at 1, 6, 12, and 24 months after operation. Follow-up periods ranged from 1 to 34 months.
No failed insertions and no conversions to open surgery occurred. The diameter of the main body of the stent graft was 28 mm or more in 73 patients (63%). Additional stents were inserted during surgery to treat kinking in eight patients (6.9%) and renal artery encroachment in two patients (1.7%). Mean fluoroscopy time was 35.1 +/- 18.3 minutes, contrast load was 146 +/- 53 mL (350 mg/mL), and estimated blood loss was 249 +/- 407 mL. The major complication rate was 9.5%, and the minor complication rate was 10.3%. The perioperative complications were myocardial infarction in four patients, arrythmia in four patients, and pulmonary embolism, renal failure, stroke, small bowel obstruction, femoral stenosis, digital embolism, and graft limb thrombosis in one patient each. All 116 patients went home from the hospital, but one patient died 2 weeks later of a combination of pulmonary embolism and myocardial infarction. Endoleak was seen on the first CT scan in 16 patients (15%); 15 were type II, and one was type III. No endoleaks of type I or IV were seen. Additional interventions were performed for each of the following conditions: type II endoleak (n = 4), type III endoleak (n = 1), femoral clamp injury (n = 1), renal artery stenosis (n = 1), and graft limb occlusion (n = 1). One patient had acute aneurysm dilatation and rupture caused by a type II endoleak through the inferior mesenteric artery 6 months after stent graft implantation. No cases were seen of late graft occlusion, stent graft migration, stent fracture, barb fracture, or secondary endoleak.
The Zenith device is safe, versatile, and effective in the short to medium term. Most patients need wide stent grafts (>or=28 mm proximally and >or=16 mm distally) to achieve 10% to 20% oversizing to prevent type I endoleak.
Positional stability of the endograft is essential for long-term durability after endovascular abdominal aortic aneurysm repair (EAR). However, the cumulative risk of delayed endograft migration has been sparsely reported.
A total of 91 patients studied underwent EAR with the AneuRx endograft with a minimum 1 year from implantation. Data from a prospective database were assessed for proximal endograft migration, defined as > or = 5 mm change from the initial endograft position. Multiple anatomic characteristics were also examined. Sixty-nine patients were alive, with complete follow-up at 1 year, with a mean time from implantation of 33.2 +/- 1.1 months. Data are mean +/- SEM.
Endograft migration occurred in 15 patients, giving a cumulative event rate of 7.2% (5/69) at 1 year, 20.4% (10/49) at 2 years, 42.1% (8/19) at 3 years, and 66.7% (2/3) at 4 years post-EAR (P =.01). Although the initial aortic neck diameter did not differ between the groups (21.5 +/- 0.6 mm vs 21.8 +/- 0.3 mm, P =.61), significant (P <.05), late aortic neck enlargement was seen in patients with migration (25.0 +/- 1.6 mm, 26.2 +/- 1.2 mm, and 27.0 +/- 1.0 mm at 1,2, and 3 years, respectively) but not in nonmigrators. Regression analysis demonstrated a statistically significant (P <.05) correlation between endograft oversizing and late aortic neck dilation. Overall migration risk was 29.2% in patients oversized >20% and 18.6% in patients oversized < or = 20%. Aortic neck angulation (23.4 +/- 6.6 degrees vs 23.5 +/- 3.3 degrees, P =.99), aortic neck length (25.9 +/- 2.5 mm vs 27.0 +/- 1.6 mm, P =.74), initial endograft/aortic neck overlap (18.6 +/- 2.6 mm vs 19.4 +/- 1.4 mm, P =.80) and size of abdominal aortic aneurysm (55.5 +/- 1.5 mm vs 54.9 +/- 1.4 mm, P =.84) were similar between migrators and nonmigrators, respectively. Secondary endovascular treatment with aortic cuffs was required in five patients with device migration.
Device migration after EAR with the AneuRx endograft occurred with significant frequency, the incidence of which increased with the length of follow-up. Late aortic neck dilation was significantly associated with migration. Oversizing of the endograft of >20% may accelerate this late aortic neck dilation. However, the etiologies of endograft migration were likely multifactorial, as the majority (8/15) of patients experiencing migration were oversized <20%. Although endovascular repair of these migrations is usually possible, the long-term durability of these secondary procedures is unknown. Careful surveillance for this endograft failure mode must be an essential component of post-EAR follow-up.
Since the first US report of endovascular repair of abdominal aortic aneurysm in 1995, many lessons have been learned from the growing reports of successes and failures. This article combines experience with 6 endograft types plus examples from the literature to summarize lessons learned from a variety of stent graft failures classified according to (1) failure of patient selection, (2) procedural failure, and (3) failure of the endovascular device.
Over the last decade, more than 25,000 endovascular stent grafts have been used to treat aortic aneurysms. Although results have been promising thus far, problems with endoleaks, material failure, device migration, and aneurysm rupture continue to be reported. Improvements in device material and design have contributed to the rapid growth and utility of these devices; however, material failure still remains a concerning mode for potential procedure failure. A review of the authors'experience with material failure and a review of the literature was conducted to help understand and comprehend the magnitude of this problem and try to determine its clinical significance.
Enthusiasm for endovascular aortic repair (EVAR) has been tempered by midterm outcomes that raise valid concern about long-term durability.
This article compares outcome data from a prospective nonrandomized comparison of a less-invasive open surgical repair technique-minimal incision aortic surgery (MIAS)-and EVAR.
MIAS and EVAR had comparable intensive care unit stays (1 day or less), quick return to general dietary feeding (2 days), and comparable hospital length of stay (4.8 days [3.4 days for uncomplicated cases MIAS] and 2.0 days for EVAR). Overall morbidity and mortality for MIAS and EVAR were comparable (18% versus 27%). MIAS was more cost effective than EVAR (net revenue MIAS = +8,445 US dollars, EVAR -7,263 US dollars).
MIAS is a safe, cost-effective alternative to endovascular aortic repair.
To review early results of endovascular repair of abdominal aortic aneurysms (AAAs).
The first 100 patients who underwent endovascular repair of AAA (EVAR) between June 26,1996, and October 31, 2001, at the Mayo Clinic in Rochester, Minn, were studied retrospectively to evaluate technical success, freedom from reinterventions, and early clinical outcome.
A total of 89 men and 11 women (mean +/- SD age, 76 +/- 7 years; range, 47-92 years) underwent EVAR. The procedure was successful in 97 patients. There was no early death. Major complications occurred in 25 patients. The 30-day technical success rate was 86% (95% confidence interval [CI], 77%-92%). The median intensive care unit stay was 1 day (range, 1-15 days), and the median hospital stay was 3 days (range, 1-35 days). Median follow-up was 7 months (range, 1-60 months). Endoleak (incomplete seal of the endovascular graft) at discharge was observed in 14 patients; 13 developed endoleak during follow-up. There were 23 reinterventions, 65% of which were percutaneous procedures. One aneurysm ruptured at 5 months, but the patient was successfully treated by open repair. Primary and secondary graft patency rates at 1 year were 83% (95% CI, 74%-93%) and 94% (95% CI, 87 %-99%), respectively. The freedom from reintervention rate at 1 year was 71% (95% CI, 59%-84%), with an overall success rate from EVAR of 92% (95% CI, 84%-100%). There were no differences in early patency, reinterventions, and success rates between unibody and modular devices.
EVAR can be performed with high technical success and low mortality rates; however, nonfatal complications and catheter-based reinterventions are frequent, and EVAR may not prevent aneurysm rupture. Although stent graft repair for high-risk patients is appealing, current data are insufficient to support EVAR as the preferred treatment of AAAs.
On November 23, 1992, the first endovascular stent graft (ESG) repair of an aortic aneurysm was performed in North America. Following the treatment of this patient, we have continued to evaluate ESG over the past 10 years in the treatment of 817 patients.
Abdominal (AAA) or thoracic (TAA) aortic aneurysms are a significant health concern traditionally treated by open surgical repair. ESG therapy may offer protection from aneurysm rupture with a reduction in procedure morbidity and mortality.
Over a 10-year period, 817 patients were treated with ESGs for AAA (723) or TAA (94). Patients received 1 of 12 different stent graft devices. Technical and clinical success of ESGs was reviewed, and the incidence of procedure-related complications was analyzed.
The mean age was 74.3 years (range, 25-95 years); 678 patients (83%) were men; 86% had 2 or more comorbid medical illnesses, 67% of which included coronary artery disease. Technical success, on an intent-to-treat basis was achieved in 93.8% of patients. Primary clinical success, which included freedom from aneurysm-related death, type I or III endoleak, graft infection or thrombosis, rupture, or conversion to open repair was 65 +/- 6% at 8 years. Of great importance, freedom from aneurysm rupture after ESG insertion was 98 +/- 1% at 9 years. There was a 2.3% incidence of perioperative mortality. One hundred seventy five patients died of causes not related to their aneurysm during a mean follow-up of 15.4 months.
Stent graft therapy for aortic aneurysms is a valuable alternative to open aortic repair, especially in older sicker patients with large aneurysms. Continued device improvements coupled with an enhanced understanding of the important role of aortic pathology in determining therapeutic success will eventually permit ESGs to be a more durable treatment of aortic aneurysms.
In summary, endovascular therapy represents a new and exiting paradigm in the treatment of abdominal aortic aneurysms. Its detractors have now largely been silenced, and a working knowledge of the devices and techniques is essential for all surgeons who care for patients with aneurysms. The first 25,000 stent-graft procedures have been attended by significant risks of implantation and endoleak, but the patients' acceptance of the technique has been heard loud and clear. The surgeon's task is not to convince the patient to undergo a more painful and invasive open procedure, but to advance the understanding, design, and implementation of this new technique such that its long-term results will someday rival those of the time-tested traditional operation.
new technology, such as endovascular abdominal aortic aneurysm repair (EVAR) may promote an 'irrational exuberance' for its application.
nonsuprarenal AAA repairs performed at a single institution over a 7 year period were retrospectively studied. Method of repair, 30-day mortality and EVAR aortic neck anatomy were assessed.
431 AAA repairs were performed between January 1996 and June 2002, 238 (55%) open and 193 (45%) EVAR. The percentage of EVAR increased steadily from approximately 20% in 1996 and 1997 to a peak of 69.5% in 2000. However, in 2001-2002 the percentage of EVAR fell to approximately 40% of total repairs. In this time period our selection criteria for EVAR became more conservative, with treatment of fewer patients with short aortic necks (12.8 vs. 28.9% with neck length < or = 20 mm, p = 0.05; 3.8 vs. 10.8% with neck length < or = 15 mm, p = 0.1) or highly angulated necks (3.8 vs. 28.9% with neck angulation > or = 40 degrees, p = 0.04) in 2001-2002 versus 1999-2000, respectively. Institutional volume of AAA repairs doubled over the study period (p = 0.001). 30-day mortality over the study period for nonruptured EVAR and open AAA repair was 2.6 and 3.3%, respectively (p = NS). The complexity of open repairs increased significantly during the final 3 years of the review. Conclusions: the application of EVAR has fallen from a high of 69.5% of our AAA repairs in 2000 to approximately 40% in 2001-2002. More prudent patient selection in recent years regarding unfavorable aortic neck anatomy was felt to be a primary etiology of changes in overall EVAR utilization. The anticipated improvement in long-term results from EVAR await multi-year follow-up.
Endovascular treatment of abdominal aortic aneurysms (AAA) is a promising new alternative to the traditional surgical repair. However, the endovascular approach suffers problems such as stent graft migration, endoleaks and stent mechanism breakage. Fatigue failure is believed to be the major cause of stent graft migration and device breakage. Knowledge of the in vivo forces acting on such devices is a basic requirement for the design of a successful endovascular device. Using a Fourier series trigonometric fit of a typical pressure and flow relationship, a mathematical model, using the control volume method, was developed to predict the pulsatile drag forces acting on various bifurcated stent graft geometries. It was found that for an iliac angle of 30 degrees, a proximal diameter of 24 mm and an iliac diameter of 12 mm, the drag force varied, over the cardiac cycle, between 3.9 and 5.5 N in the axial direction. It was noted that for a specific iliac angle the drag force variation with proximal diameter approximates a quadratic fit, with an increase in proximal diameter producing an increase in drag force. The more compliant the aorta the higher the drag force. Previously published results demonstrated the axial loads (axial drag forces) required for stent graft migration for certain stents types are lower than the drag forces calculated in this study. It is believed that the results of this study can provide guidelines for the quantitative analyses of the in vivo drag forces experienced by stent grafts and could therefore be used as design criteria for such devices.
Aneurysm sac shrinkage after endovascular aneurysm repair (EAR) provides objective evidence of successful aneurysm exclusion and absence of endotension. Attainment of this outcome parameter may be device-dependent. In this study, 169 patients underwent EAR with an AneuRx (n = 118) or Zenith (n = 51) endograft at a single institution. A prospectively maintained database was examined for significant changes in aneurysm sac diameter (> or = 5 mm) on the basis of computed tomography (CT) measurements at 6 and 12 months follow-up. Significant aneurysm sac shrinkage (> or = 5 mm) occurred in 73.1 % (19/26) vs. 43.1% (28/65) of patients in the Zenith and AneuRx groups, respectively, at 12 months (p = 0.03). At 6 months follow-up, sac shrinkage rates were 51.4% (19/37) vs. 25.8% (16/62) in the Zenith and AneuRx groups, respectively (p = 0.04). Mean reduction of sac diameter at 12 months was -7.6 +/- 1.6 mm vs. -3.5 +/- 0.8 mm in the Zenith and AneuRx groups, respectively (p = 0.01). There was a trend toward fewer Type I and III endoleaks at 1 month in the Zenith group (0 vs. 8.3%) that did not achieve statistical significance (p = 0.067). The presence of any endoleak (> or = 1 month) was associated with reduced 12 month shrink rates from 47.1% (25/51) to 28% (4/14) in the AneuRx group (p = 0.35) and from 77.3% (17/22) to 50% (2/4) in the Zenith group (p = 0.25). Patients treated with the Zenith endograft demonstrated a significantly higher rate and amount of aneurysm sac shrinkage than patients treated with an AneuRx device. Endoleaks appeared to negatively influence shrink rates with both endografts.
Stent fatigue fractures, fabric holes, and suture breaks were found in most explanted AneuRx stent grafts. These structural findings were not significantly related to pre-explant aneurysm enlargement or endoleak; however, longer studies with larger sample sizes are needed to confirm these results. Pre-explant device migration was associated with a greater number of explant stent fractures and fabric holes. Although “for cause” explants had a greater number of structural abnormalities than did “incidental” explants, these differences may be explained by differences in duration of device implantation. Most devices explanted “for cause” had evidence of insecure proximal, distal, or junctional fixation, which could account for the adverse clinical event. Thus a clear relationship to explant structural findings could not be established. Longer studies are needed to fully determine the significance of these explant findings.
Strict morphologic criteria must be used for patient selection to achieve durable success with endovascular aortic aneurysm repair (EVAR). The goal of this study was to assess morphologic suitability (MS) of abdominal aortic aneurysms (AAAs) for 2 currently approved bifurcated stent grafts and identify reasons for exclusion from EVAR. The authors reviewed the electronic charts of 1,795 consecutive patients who were diagnosed as having AAA between January 1999 and July 2001 at their institution. Three hundred and twenty patients had an AAA with a diameter of > or = 5.0 cm, measured on computed tomography (CT). The records of 301 patients, 254 men, 47 women, with a mean age of 74 years were available for review, and these patients constituted the study cohort. Criteria used for MS included a proximal neck length > or = 15 mm; neck diameter between 18 and 26 mm; neck angulation < or = 60 degrees ; common or external iliac artery (CIA or EIA) diameters of 7-16 mm and 8-13 mm, respectively, for AneuRx (Medtronic Ave, Santa Rosa, CA) and Ancure (Guidant Cardiac and Vascular Division, Menlo Park, CA) bifurcated grafts. AAAs were suitable for AneuRx device in 14% of patients (43 of 301; 95% CI = 11-19%) and for Ancure in 5% (16 of 301; 95% CI = 3.1-9%). The main reason for exclusion was an inadequate proximal aortic neck (73%). The neck was too short in 49.5%, too wide in 64% and badly angulated in 12% of the patients. Iliac artery morphology precluded EVAR with AneuRx and Ancure devices in 52% and 80%. Both CIAs were too wide for EVAR in 43% and 77%, respectively. When iliac artery diameter < or = 20 mm was accepted, iliac suitability for AneuRx increased from 49% to 70% and overall suitability increased from 14% to 20%. When more permissive criteria were used for MS (neck length > or = 10 mm, neck diameter < or = 30 mm, CIA < or = 20), 39% of patients became candidates for EVAR. More than three fourths of the patients with an AAA > or = 5.0 cm in size, seen in a tertiary referral center, are morphologically not suitable for EVAR using 2 currently approved bifurcated endografts. The main reasons for exclusion are a short or wide proximal aortic neck. Considerable changes in size of the devices and in proximal attachment techniques have to occur before most AAAs will be suitable for EVAR.
A variety of structural defects or failures have appeared in the majority of commercially developed stentgrafts for endoluminal abdominal aortic aneurysm (AAA) repair. Some have resulted in device withdrawal; others have been dealt with by device modification. Newer devices have been designed to avoid some of these failure modes but, because many have not become apparent until as late as 2 years, these corrective measures will require long-term follow-up to establish device durability. Typically, routine surveillance has missed these problems or discovered them late and, when fully investigated, most structural problems have been more prevalent than initially suspected and/or increased with time. However, analyses documenting the full extent and clinical consequences of these structural failures have not been openly reported. This lack of information, and the nature of the structural failures themselves, have undermined confidence in the durability of endovascular aneurysm repair (EVAR), mandated indefinite periodic surveillance, and further increased its costs. Prospects for controlling the described failure modes in the future are good in terms of most device- and operator-specific causes, but aneurysm-specific causes may be more difficult to overcome. Until durability is established by improved technology and long-term follow-up, a more conservative application of EVAR has been suggested, with its use limited primarily to patients with large AAAs (>5.5 cm diameter), favorable anatomy for EVAR, and associated comorbidities that significantly increase the patient's risk for open repair as well as decrease their longevity outlook. The history of these structural failures and the corrective measures taken, as well as their current impact on EVAR are presented in this article.
We sought to determine the effectiveness of uncovered stents with aneurysm transstent coil embolization compared with endografts for percutaneous abdominal aortic aneurysm (AAA) repair. Thirty-six patients with AAA considered inoperable underwent endovascular repair using the Ancure bifurcated endograft or overlapping uncovered stents with transstent coil embolization. Procedural success, outcomes, serial aneurysm size, aneurysm blood flow, and growth ratios were compared between groups. One patient in each group died due to the procedure and two patients in the endograft cohort required acute surgical repair. After 2.0 +/- 0.8 years of follow-up, three patients required endograft placement, four surgical repair, three had AAA rupture, with two AAA-related deaths in the uncovered stent group. No late deaths or surgical conversion occurred in the endograft group. The primary AAA flow exclusion and aneurysm expansion rate and growth were superior in the endograft group and during follow-up. In high-risk patients with AAA, the use of endografts was superior compared to uncovered stents with transstent coil embolization for endovascular repair.
Since the world was first introduced to the concept of endovascular aneurysm repair by Parodi's landmark procedures in 1990, stent-grafts have assumed a prominent role in the management of abdominal aortic aneurysm. Most modern systems are trackable, accurate, and secure. The resulting endovascular procedure is safe, durable, effective, and versatile. Perhaps the most significant increment in the applicability of the endovascular technique was achieved by the development of bifurcated stent-grafts, which dispensed with inadequate distal aortic implantation sites. Additional branches and fenestrations now permit endovascular repair in cases of thoracoabdominal, pararenal, juxtarenal, and bilateral iliac aneurysms. These advances in device performance have been accompanied by a rapid dissemination of necessary skills, leading to the development of a new superspecialty of vascular therapy, with elements of vascular surgery, interventional radiology, and interventional cardiology.
To investigate if stents with hooks and barbs will improve stent-graft fixation in the abdominal aorta.
Sixteen- to 24-mm-diameter Dacron grafts were deployed inside cadaveric aortas. The grafts were anchored by stents as in endovascular abdominal aortic aneurysm repair. One hundred thirty-seven stent-graft deployments were carried out with modified self-expanding Z-stents with (A) no hooks and barbs (n = 75), (B) 4 5-mm-long hooks and barbs (n = 39), (C) 8 10-mm-long, strengthened hooks and barbs (n = 19), or (D) hooks only (n = 4). Increasing longitudinal traction was applied to determine the displacement force needed to extract the stent-grafts. The radial force of the stents was measured and correlated to the displacement force.
The median (interquartile range) displacement force needed to extract grafts anchored by stent A was 2.5 N (2.0 to 3.4), stent B 7.8 N (7.4 to 10.8), and stent C 22.5 N (17.1 to 27.9), p < 0.001. Both hooks and barbs added anchoring strength. During traction, the weaker barbs were distorted or caused intimal tears. The stronger barbs engaged the entire aortic wall. The radial force of the stents had no impact on fixation, while aortic calcification and graft oversizing had marginal effects.
Stent barbs and hooks increased the fixation of stent-grafts tenfold, while the radial force of stents had no impact. These data may prove important in future endograft development to prevent stent-graft migration after aneurysm exclusion.
Fatigue fracture and wear have been identified as some of the major problems associated with implant failure of medical devices. The actual in vivo mechanisms are complex and involve the hostile body environment. The response of the host tissue to wear debris is a real issue. Fatigue-wear corrosion and environmental stress cracking are common. Although fatigue fracture and wear are frequently reported in orthopaedic applications such as hip joint prostheses, they can be fatal in mechanical heart valves. While it is not possible to avoid failure, recent work has focused on predictive tools to enable more accurate prediction so as to avoid catastrophic failure in vivo. This paper presents an overview of fatigue fracture problems in metallic, polymeric and ceramic implant materials, looks at some recent techniques of testing and discusses the future development of fracture and wear resistant biomaterials.
Purpose: This report describes the results of a phase 1 trial of endovascular repair of abdominal aortic aneurysm, conducted under FDA protocol in 13 U.S. medical centers from February 1993 to December 1994.
Methods: Forty-six patients 54 to 84 years of age underwent endovascular repair of abdominal aortic aneurysm (diameter, 3.8 to 7.1 cm). Fifteen were treated with the original device (EGS-I), and 31 with a revised over-the-wire system (EGS-II). All patients were periodically observed with contrast-enhanced computed tomographic scan, colorflow duplex scan, and plain abdominal films to evaluate the stability of prosthetic location and to detect any vascular communication with or entry of blood into the aneurysm sac or change in aneurysm size.
Results: Thirty-nine implants (85%) were successful; average operating time was 194 minutes. Seven attempts were unsuccessful and were converted to open repair without complication (EGS-I,5 of 15;EGS-II, 2 of 31). Conversions were caused by iliac stenosis in four patients, subintimal deployment in one, proximal displacement in one, and short distal neck in one. No patients died within 30 days of surgery. Complications included myocardial infarction in one patient, iliofemoral arterial injury in eight, wound infection in seven, required transfusion in eight, transient unexplained fever in nine, and minor emboli with foot petechiae in two. There were no amputations, major emboli, or episodes of mesenteric ischemia. Contrast enhancement outside the graft but within the aneurysm sac was detected initially in 17 grafts (44%), of which nine (53%) resolved spontaneously. Of eight persistent leaks into the aneurysm sac, one was controlled with transluminal balloon angioplasty and one required surgical explantation because of aneurysm enlargement. Six patients continued to have contrast enhancement, but had no evidence of aneurysm enlargement from 6 to 27 months after surgery. Hospital stay averaged 3.8 days (range, 1 to 13 days). Follow-up extends to 27 months, with one non-device related death of respiratory failure at 6 months. Metallic attachment system fracture, a device-related malfunction, was identified in nine implants (23%), which led to one removal; the remaining eight functioned normally with no untoward sequelae. The program was suspended while the defect was corrected. Preparations are complete for the phase 2 portion of the trial.
Conclusions: Endovascular repair of abdominal aortic aneurysm appears to be safe and efficacious. Long-term results and late consequences of attachment system fracture have yet to be determined. The long-term results of perigraft leak into the aneurysm sac are unknown but worrisome in view of adverse outcomes reported by other investigators.
Despite a critical need to predict component life based on wire fatigue data, a survey of the literature indicates that no standard specimen exists for fatigue testing of fine wires. This article describes a plastically formed, precurved loop specimen developed to meet this need. The loop geometry localizes damage, permitting the use of in-situ, automated crack detection systems. The loop specimen is appropriate for wire diameters between a few hundred micrometres to a few millimetres, and for materials with a high elastic modulus. Material properties are presented for a cobalt-chromium-based alloy (Elgiloy) wire used as a practical example. Analytical and finite element stress analyses are presented which quantify the maximum stress at the loop apex. Fatigue life results using the present specimen are given for Elgiloy wire. Post-test SEM examinations are presented to show that fracture initiation takes place at the maximum stress location as predicted by the analyses. A fracture path and morphology characterization is also shown to be consistent with the anticipated stress regimes
Fatigue fracture and wear have been identified as some of the major problems associated with implant failure of medical devices. The actual in vivo mechanisms are complex and involve the hostile body environment. The response of the host tissue to wear debris is a real issue. Fatigue-wear corrosion and environmental stress cracking are common. Although fatigue fracture and wear are frequently reported in orthopaedic applications such as hip joint prostheses, they can be fatal in mechanical heart valves. While it is not possible to avoid failure, recent work has focused on predictive tools to enable more accurate prediction so as to avoid catastrophic failure in vivo. This paper presents an overview of fatigue fracture problems in metallic, polymeric and ceramic implant materials, looks at some recent techniques of testing and discusses the future development of fracture and wear resistant biomaterials.
The authors describe the initial clinical experience with a new device, approved by the FDA for investigation, for repair of abdominal aortic aneurysm by transfemoral endovascular insertion of an aortic graft.
Sixty-nine patients with abdominal aortic aneurysms were screened, and ten were found to be suitable for endovascular grafting. Repair was done in the operating room using general anesthesia. One femoral artery was surgically exposed, and the device, containing a premeasured graft with proximal and distal self-expanding fixation devices, was inserted with fluoroscopic control through an open arteriotomy.
Eight of ten patients underwent successful graft placement, and two patients required conversion to an open repair. On follow-up, six of eight patients who underwent graft placement functioned normally, with documented aneurysm thrombosis. Two patients who underwent graft placement functioned normally, with contrast computed tomography evidence of incomplete aneurysm thrombosis, but without further expansion.
Transfemoral repair is safe and appears to be effective. Phase II study currently is appropriate, with need for long-term follow-up.
This report describes the results of a phase 1 trial of endovascular repair of abdominal aortic aneurysm, conducted under FDA protocol in 13 U.S. medical centers from February 1993 to December 1994.
Forty-six patients 54 to 84 years of age underwent endovascular repair of abdominal aortic aneurysm (diameter, 3.8 to 7.1 cm). Fifteen were treated with the original device (EGS-I), and 31 with a revised over-the-wire system (EGS-II). All patients were periodically observed with contrast-enhanced computed tomographic scan, color-flow duplex scan, and plain abdominal films to evaluate the stability of prosthetic location and to detect any vascular communication with or entry of blood into the aneurysm sac or change in aneurysm size.
Thirty-nine implants (85%) were successful; average operating time was 194 minutes. Seven attempts were unsuccessful and were converted to open repair without complication (EGS-I, 5 of 15; EGS-II, 2 of 31). Conversions were caused by iliac stenosis in four patients, subintimal deployment in one, proximal displacement in one, and short distal neck in one. No patients died within 30 days of surgery. Complications included myocardial infarction in one patient, iliofemoral arterial injury in eight, wound infection in seven, required transfusion in eight, transient unexplained fever in nine, and minor emboli with foot petechiae in two. There were no amputations, major emboli, or episodes of mesenteric ischemia. Contrast enhancement outside the graft but within the aneurysm sac was detected initially in 17 grafts (44%), of which nine (53%) resolved spontaneously. Of eight persistent leaks into the aneurysm sac, one was controlled with transluminal balloon angioplasty and one required surgical explanation because of aneurysm enlargement. Six patients continued to have contrast enhancement, but had no evidence of aneurysm enlargement from 6 to 27 months after surgery. Hospital stay averaged 3.8 days (range, 1 to 13 days). Follow-up extends to 27 months, with one non-device related death of respiratory failure at 6 months. Metallic attachment system fracture, a device-related malfunction, was identified in nine implants (23%), which led to one removal; the remaining eight functioned normally with no untoward sequelae. The program was suspended while the defect was corrected. Preparations are complete for the phase 2 portion of the trial.
Endovascular repair of abdominal aortic aneurysm appears to be safe and efficacious. Long-term results and late consequences of attachment system fracture have yet to be determined. The long-term results of perigraft leak into the aneurysm sac are unknown but worrisome in view of adverse outcomes reported by other investigators.
The behavior of the ASTM F1058 wrought cobalt-chromium-nickel-molybdenum-iron alloy (commonly referred to as Elgiloy or Phynox) is evaluated in terms of mechanical properties, magnetic resonance imaging, corrosion resistance, and biocompatibility. The data found in the literature, the experimental corrosion and biocompatibility results presented in this article, and its long track record as an implant material demonstrate that the cobalt superalloy is an appropriate material for permanent surgical implants that require high yield strength and fatigue resistance combined with high elastic modulus, and that it can be safely imaged with magnetic resonance.
This paper investigates the radial deformation load of an aortic endoluminal prosthesis and determines the longitudinal load required to cause migration in a human cadaveric aorta of the endoprosthesis.
The endovascular prosthesis under investigation was a 24 mm diameter, nitinol, self-expanding aortoaortic device (InterVascular, Clearwater, Florida, U.S.A.). Initially, a motorised digital force gauge developed an incremental load which was applied to the ends of five stent-grafts, to a maximum of 10 mm (42%) compression. Secondly, using a simple bench model, each ends of four stent-grafts were deployed into 10 cadaveric experimental aneurysm necks and a longitudinal load applied to effect distraction.
Increasing load produced increasing percentage deformation of the stent-grafts. The mean longitudinal distraction load for an aneurysm neck of 20 mm was 409 g (200-480 g), for 15 mm was 277 g (130-410 g) and for 10 mm was 218 g (130-340 g). The aneurysm diameter and aortic calcification had p values of 0.002 and 0.047, respectively, while the p value for aneurysm neck length was less than 0.00001.
These results suggest that there is a theoretical advantage of oversizing an aortic prosthesis and that sufficient anchorage is achieved in an aortic neck of 10 mm to prevent migration when fully deployed.
The Ancure endografting system (Guidant Cardiac and Vascular Division, Menlo Park, Calif) features a unibody, nonsupported woven polyester graft designed to treat abdominal aortic aneurysms. It is constructed in tube, bifurcated, and aortoiliac configurations. The attachment system consists of a frame with four independent V-shaped double hooks that penetrate the arterial wall for fixation. There are separate attachment systems at the proximal and distal ends of the endoprosthesis. In September 1999, the Food and Drug Administration (FDA) approved the tube and bifurcated devices for general use. The aortoiliac device is under present consideration of the FDA. Phase II and III clinical trials of the system enrolled over 870 patients from the end of 1995 to the summer of 1999. The device was deployed successfully in 90% to 96% of cases, depending on the configuration and the phase of the trial. Mortality rates were similar to those of concurrent open surgical control rates, but serious morbidity was reduced. Long-term follow-up of the bifurcated group from phase II showed only one migration and no ruptures. Aneurysm size reduction in this group was noted in 51.3% of patients at 1 year and 68.5% at 2 years. In the same subset, type I endoleaks were noted in 2.7% at 1 year and 1.3% at 2 years. All postoperative imaging studies were reviewed by a core laboratory facility. The advantages of the ancure system include solid fixation, flexibility in accommodating morphologic changes, and excellent long-term clinical performance. The disadvantages include a large introducer system and the potential for limb obstruction by compression or angulation. However, limb compromise responds well to intraluminal stenting. The expected FDA approval of the aortoiliac device and a larger variety of graft sizes should expand the number of patients who can be treated with this system.
Vangaurd endoprosthesis: upper stent row separation with or without nitinol wire fracture Available from: www.medical-devices.gov.uk/da2001(01).htm 2001
- Device
Device alert. Vangaurd endoprosthesis: upper stent row separation with or without nitinol wire fracture. Available from: www.medical-devices.gov.uk/da2001(01).htm 2001. Accessed Feb 2001.
Forces on aortic stent grafts Proceedings of the 5th Annual Hilton Head Workshop on the Engineering of Human Tissues
- Delassus P Mcgloughlin
Morris W, Delassus P, McGloughlin T. Forces on aortic stent grafts. Proceedings of the 5th Annual Hilton Head Workshop on the Engineering of Human Tissues; 2001 Feb 22-25; Hilton Head, SC. Atlanta: Georgia Institute of Technology EKC for Tissue Engineering; 2001. p. 87.
Forces on aortic stent grafts
- W Morris
- P Delassus
- T Mcgloughlin
Morris W, Delassus P, McGloughlin T. Forces on aortic stent grafts.
Proceedings of the 5th Annual Hilton Head Workshop on the
Engineering of Human Tissues; 2001 Feb 22-25;
AneuRx stent graft system: nitinol frame fracture after implantation Available from: www.medical-devices.gov.uk
- Device
Device alert. AneuRx stent graft system: nitinol frame fracture after
implantation. Available from: www.medical-devices.gov.uk/da2000(06).
htm 2000. Accessed Feb 2001.
Atlanta: Georgia Institute of Technology EKC for Tissue Engineering
- Hilton Head
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Hilton Head, SC.
Atlanta: Georgia Institute of Technology EKC for Tissue Engineering;
2001. p. 87.
Forces on aortic stent grafts. Proceedings of the 5th Annual Hilton Head Workshop on the Engineering of Human Tissues
- Morris
Assessment of wrought ASTM F1058 cobalt alloy properties for permanent surgical implants
- Clerc