Aneurysm enlargement following endovascular aneurysm repair: AneuRx clinical trial

A Systematic Review of the Recruitment and Outcome Reporting by Sex and Race/Ethnicity in Stent Device Development Trials for Endovascular Abdominal Aortic Aneurysm Repair

BACKGROUND

Women and racial/ethnic minority groups have been shown to experience poor outcomes after endovascular aortic aneurysm repair (EVAR). One potential reason is the rare inclusion of these populations in initial phases of device development. The objective of this systematic review is to understand enrollment and outcome reporting by sex and race/ethnicity in industry-funded EVAR device development trials.

METHODS

MEDLINE, PubMed, and Embase were searched from inception to January 2022 without language restrictions using the following terminology: "stent", "graft", "endograft", "device", and "abdominal aortic aneurysm" (AAA).

CLINICALTRIALS

gov was also searched from inception to January 2022 for "AAA." Two independent reviewers screened and extracted data. All phase I-III and postmarket evaluation trials that included patients ≥18 years of age, who underwent EVAR were assessed. Participation-to-prevalence ratios (PPRs) were calculated to estimate representation of participants by sex and race/ethnicity in trials compared with their share of disease burden.

RESULTS

Among the 4,780 retrieved articles, 55 industry-funded trials met inclusion criteria for this review. A total of 51 trials (93%) reported enrollment by sex/gender, and only 7 trials (13%) reported enrollment by race/ethnicity of the participants. A median of 19 (interquartile range [IQR]: 4.5, 51) women participants were recruited compared to 171 (IQR: 57, 311.5) men, and 17 (IQR: 7.5, 21.5) racial/minority patients were recruited compared to 241 (IQR: 123, 463.5) White participants. Women represent 16.6% of the disease population, and the median PPR is 0.62 (IQR: 0.42, 0.88), which has remained constant over time (Figure 1). None of the device trials reported outcomes based on sex/gender or race/ethnicity.

CONCLUSIONS

This systematic review highlights the disparities in recruitment and outcome reporting based on sex and race/ethnicity in EVAR device development trials. While most trials may be underpowered to study these differences, recent registry studies show differential outcomes based on sex and race/ethnicity of vascular patients. Therefore, it is imperative to include and report outcomes in these participants, starting from the initial device development phases to improve generalizability of device-use and understand sources of variation in device performance.

Endograft Technology: Highlights of the past 10 Years

The past decade has seen the evolution of an exciting technology that has changed forever the treatment of aortic aneurysmal disease. From rather crude homemade stent-grafts constructed in the surgical suite to elegant commercially manufactured devices in a variety of configurations and sizes, the aortic endograft has experienced a meteoric rise in popularity to become a beneficial, minimally invasive therapy that can obviate the risk of rupture and death. There are now 3 approved endovascular devices on the market for infrarenal abdominal aortic aneurysm repair, and it is likely that additional and improved devices will become available in the future. This review revisits the developmental history of the aortic endograft, noting the ongoing refinements that have arisen from our experiences with the growing population of stent-graft patients. Although research continues to search for solutions to the problems of endoleak and migration, long-term results even with the earlier second and third-generation devices are better than has been achieved with open surgical repair.

Midterm Results of Endovascular Infrarenal Abdominal Aortic Aneurysm Repair in High-Risk Patients

Short-term and midterm clinical outcomes after endovascular repair of abdominal aortic aneurysms (AAAs) have been well documented. Evaluation of longer term outcomes is now possible. Here we describe our initial 100 high-risk patients treated with endovascular aneurysm repair (EVAR), all with a minimum of 5 years of follow-up. A retrospective review of prospectively recorded data in a departmental database was undertaken for the first 100 consecutive EVAR patients with a minimum of 5 years (range, 60-105 months) of follow-up performed between December 1997 and June 2001. Information was obtained from surgical follow-up visits and family doctors' offices. Endovascular repair of AAA in high-risk patients can be achieved with acceptably low postoperative mortality and morbidity. Longer term results in this high-risk cohort suggest that EVAR is effective in preventing aneurysm-related deaths at 5 years and beyond. All late mortalities were due to patients' comorbid diseases.

Early Elective Conversion for Failing Evar

Background:

The aim of the study was to assess the long term results of endovascular aneurysm repair (EVAR) of abdominal aortic aneurysms at the Helsinki University Central Hospital 1996–2004 with a special emphasis on elective conversion procedures and their outcome.

Methods:

Treatment results and follow-up data of all 110 elective EVAR procedures performed in our institution were gathered prospectively and evaluated.

Results:

Conversion to open surgery was performed in 23 (21%) of 110 EVAR patients. 30-day mortality after elective stent-graft deployment was 0% as it was also on elective conversions (n = 20). Secondary elective conversions were performed due to infection in two and after failing stent-graft treatment in 12 patients. Six of the conversions were performed primarily. Three urgent conversions (3% overall) were performed: two of these patients died, corresponding to an overall mortality of 9% (2/23) in all conversions. Five-year aneurysm-related mortality after EVAR among patients with elective conversion was 0% and 19% in patients with secondary procedures other than elective conversions.

Conclusions:

As conversions seem to be hazardous only when performed in urgent situations, elective conversion could be an alternative treatment method in complex failing first-generation stent-grafts as it may reduce mortality associated with urgent conversions or repeated attempts to maintain graft integrity with endovascular procedures.

Systolic Sac Pressure Index for the Prediction of Persistent Type II Endoleak for 12 Months After Endovascular Abdominal Aortic Aneurysm Repair

PURPOSE

To assess the relationship between the systolic sac pressure index (SPI) and the presence of endoleaks 12 months after endovascular abdominal aortic aneurysm repair (EVAR).

MATERIALS AND METHODS

We performed a single-center prospective trial of consecutively treated patients. SPI (calculated as systolic sac pressure/systolic aortic pressure) was measured by catheterization immediately after EVAR. Contrast-enhanced computed tomography was scheduled 12 months after EVAR to detect possible endoleaks.

RESULTS

Data were available for 34 patients who underwent EVAR for an AAA. Persisting type II endoleak was found in 8 patients (endoleak-positive group) but not in the other 26 patients (endoleak-negative group). The mean ± standard deviation SPI was significantly greater in the endoleak-positive group than in the endoleak-negative group (0.692 ± 0.048 vs. 0.505 ± 0.081, respectively; P = .001). Receiver-operating characteristic curve analysis revealed that an SPI of 0.638 was the optimum cutoff value for predicting a persistent endoleak at 12 months with high accuracy (0.971; 33/34), sensitivity (1.00), and specificity (0.962) values. The mean change in AAA diameter was -4.28 ± 5.03 mm and 2.22 ± 4.54 mm in patients with SPI of <0.638 or ≥0.638, respectively (P = .002).

CONCLUSION

Patients with an SPI of ≥0.638 immediately after EVAR were more likely to have a persistent type II endoleak at 12 months with an accuracy of 0.971, and showed increases in aneurysm sac diameter compared with patients with an SPI of <0.638.

Aneurysmal degeneration and type Ib endoleak with proximal aneurysm rupture: A case report, review of literature and technical suggestions

INTRODUCTION

Despite the reduction in mortality incidences of AAA in proportion to increased use of EVAR, the natural history of aneurysms with the presence of an endoleak post EVAR remains unclear. With a cumulative AAA rupture incidence of 2% at six years post EVAR, the lack of an immediate endoleak is not an indicator of success.

CASE REPORT

We present a case of an 80-year-old man who presented to the emergency department with generalised abdominal pain and hypotension. Four years earlier he had underwent an EVAR for a 6 cm infra-renal AAA. The computed tomography angiogram (CTA) illustrated aneurysmal dilatation of the left common iliac artery with extensive retroperitoneal haemorrhage. The patient was transferred to the operating room for an endovascular repair but due to significant episodes of haemodynamic instability, an emergency exploratory laparotomy was performed. To our surprise, there was a left-sided infra-renal anterolateral rupture of the aneurysm sac. The stent was explanted with difficulty from its fixed proximal aortic section down to left-sided common iliac artery. The fixed bare portion of the stent in the proximal aorta and in the right common iliac artery was left in-situ and the rest was integrated to a trouser graft with an end-to-end technique.

DISCUSSION

On detection of an endoleak, the aim should focus on their endovascular management, as open conversions are associated with high mortality and morbidity.

CONCLUSION

If open conversion is indicated, all technical aspects of the repair including partial stent extraction should be considered for best outcome.

Type II endoleak after endovascular aneurysm repair

Background

The aim was to assess the risk of rupture, and determine the benefits of intervention for the treatment of type II endoleak after endovascular abdominal aortic aneurysm repair (EVAR).

Methods

This systematic review was done according to PRISMA guidelines. Outcome data included incidence, spontaneous resolution, sac expansion, interventions, clinical success, and complications including conversion to open repair, and rupture.

Results

Thirty-two non-randomized retrospective studies were included, totalling 21 744 patients who underwent EVAR. There were 1515 type II endoleaks and 393 interventions. Type II endoleak was seen in 10·2 per cent of patients after EVAR; 35·4 per cent resolved spontaneously. Fourteen patients (0·9 per cent) with isolated type II endoleak had ruptured abdominal aortic aneurysm; six of these did not have known aneurysm sac expansion. Of 393 interventions for type II endoleak, 28·5 per cent were unsuccessful. Translumbar embolization had a higher clinical success rate than transarterial embolization (81 versus 62·5 per cent respectively; P = 0·024) and fewer recurrent endoleaks were reported (19 versus 35·8 per cent; P = 0·036). Transarterial embolization also had a higher rate of complications (9·2 per cent versus none; P = 0·043).

Conclusion

Aortic aneurysm rupture after EVAR secondary to an isolated type II endoleak is rare (less than 1 per cent), but over a third occur in the absence of sac expansion. Translumbar embolization had a higher success rate with a lower risk of complications.

AAA stent-grafts: past problems and future prospects

Endovascular aneurysm repair (EVAR) has quickly gained popularity for infrarenal abdominal aortic aneurysm repair during the last two decades. The improvement of available EVAR devices is critical for the advancement of patient care in vascular surgery. Problems are still associated with the grafts, many of which can necessitate the conversion of the patient to open repair, or even result in rupture of the aneurysm. This review attempts to address these problems, by highlighting why they occur and what the failings of the currently available stent grafts are, respectively. In addition, the review gives critical appraisal as to the novel methods required for dealing with these problems and identifies the new generation of stent grafts that are being or need to be designed and constructed in order to overcome the issues that are associated with the existing first- and second-generation devices.

Complete Endograft Collapse 9½ Years Following Endograft Repair of an Abdominal Aortic Aneurysm

Endografts are a common method of treating abdominal aortic aneurysms (AAA) because of the short-term benefits of endovascular aneurysm repair (EVAR). However, the short-term benefits of endovascular repair must be balanced against long-term complications, such as the need for conversion to open repair, device migration, persistent or de novo endoleaks, and most concerning the potential for subsequent rupture of the aneurysm. Lifelong postimplantation surveillance is mandatory because the incidence of some complications increases over time. This report describes our recent experience in a patient in whom complete endograft collapse was discovered 9½ years following EVAR necessitating conversion to open repair.

Durability of endovascular infrarenal aneurysm repair: when does late failure occur and why?

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.

A comparison between standard and high density Resilient AneuRx in reducing aneurysm sac pressure in a chronic canine model

OBJECTIVES

Low intra-aneurysm sac pressure has been shown to correlate with sac shrinkage following endovascular aneurysm repair (EVAR) whereas high pressure results in sac enlargement. The Resilient AneuRx (RSA) has higher density Dacron compared with the standard AneuRx (STA) and was developed in an attempt to reduce type 4 and 5 endoleaks, thereby more effectively reducing sac pressure. The purpose of this study is to compare the ability of RSA and STA in reducing sac pressure in a chronic canine aneurysm model.

MATERIALS AND METHODS

Artificial polytetrafluoroethylene (PTFE) aneurysm (26 x 50 mm) with an Endosure wireless pressure sensor (CardioMEMS, Atlanta, Ga) attached to the inner surface was implanted in the abdominal aorta of 10 mongrel dogs. Two weeks after creation of the aneurysm, each animal underwent EVAR with either STA (n = 5) or RSA (n = 5). Following EVAR, intra-sac pressure was measured with the implanted wireless pressure sensor up to 3 months postoperatively when the animals were sacrificed.

RESULTS

EVAR was successful with no signs of an endoleak in all 10 dogs. Pressure sensing with the wireless sensor was also successful in each animal until the end of the study. Systolic intra-sac pressure remained at a high level in the STA group, whereas it gradually lowered over time in the RSA group. This difference reached statistical significance at 2 months and lasted to 3 months. No endoleak was detected in either group at the time of sacrifice. Gross analysis confirmed that all the aneurysm sacs were thrombosed without any flow inside the sac.

CONCLUSION

Despite absence of an endoleak, intra-sac pressure remained high in the STA group. RSA effectively reduced sac pressure over time. Graft porosity appears to be an important factor that may determine the outcome of EVAR. These findings may be useful in designing improved endograft.

Article Commentary: Managing Dissections of the Thoracic Aorta

Thoracic aortic dissection is associated with substantial morbidity and mortality, and it requires timely and accurate diagnosis and treatment. Long-term antihypertensive therapy remains critical for the treatment of this disease. Surgical intervention, although still a formidable undertaking, has evolved to better address both acute and chronic dissection, and the results have improved. Basic and clinical research, as well as technological advances, have increased our understanding of this challenging disease state.

Persistent type 2 endoleak after endovascular repair of abdominal aortic aneurysm is associated with adverse late outcomes

OBJECTIVE

Type 2 endoleak occurs in up to 20% of patients after endovascular aneurysm repair (EVAR), but its long-term significance is debated. We reviewed our experience to evaluate late outcomes associated with type 2 endoleak.

METHODS

During the interval January 1994 to December 2005, 873 patients underwent EVAR. Computed tomography (CT) scan assessment was performed < or =1 month of the operation and at least annually thereafter. Sequential 6-month CT scan follow-up was adopted for those patients with persistent type 2 endoleaks, and reintervention was limited to those with sac enlargement >5 mm. Study end points included overall survival, aneurysm sac growth, reintervention rate, conversion to open repair, and abdominal aortic aneurysm (AAA) rupture. Preoperative variables and anatomic factors potentially associated with these endpoints were assessed using multivariate analysis.

RESULTS

We identified 164 (18.9%) patients with early (at the first follow-up CT scan) type 2 endoleaks. Mean follow-up was 32.6 months. In 131 (79.9%) early type 2 endoleaks, complete and permanent leak resolution occurred < or =6 months. Endoleaks persisted in 33 patients (3.8% of total patients; 20.1% of early type 2 endoleaks) for >6 months. Transient type 2 endoleak (those that resolved < or =6 months of EVAR) was not associated with adverse late outcomes. In contrast, persistent endoleak was associated with several adverse outcomes. AAA-related death was not significantly different between patients with and without a type 2 endoleak (P = .78). When evaluating patients with no early endoleak vs persistent endoleak, freedom from sac expansion at 1, 3, and 5 years was 99.2%, 97.6%, and 94.9% (no leak) vs 88.1%, 48.0%, and 28.0% (persistent) (P < .001). Patients with persistent endoleak were at increased risk for aneurysm sac growth vs patients without endoleak (odds ratio [OR], 25.9; 95% confidence interval [CI] 11.8 to 57.4; P < .001). Patients with a persistent endoleak also had a significantly increased rate of reintervention (OR, 19.0; 95% CI, 8.0 to 44.7); P < .001). Finally, aneurysm rupture occurred in 4 patients with type 2 endoleaks. Freedom from rupture at 1, 3, and 5 years for patients with a persistent type 2 endoleak was 96.8%, 96.8%, and 91.1% vs 99.8%, 98.5%, and 97.4% for patients without a type 2 endoleak. Multivariate analysis demonstrated persistent type 2 endoleak to be a significant predictor of aneurysm rupture (P = .03).

CONCLUSIONS

Persistent type 2 endoleak is associated with an increased incidence of adverse outcomes, including aneurysm sac growth, the need for conversion to open repair, reintervention rate, and rupture. These data suggest that patients with persistent type 2 endoleak (>6 months) should be considered for more frequent follow-up or a more aggressive approach to reintervention.

Endovascular conversion with femorofemoral bypass as a treatment of endotension and aneurysm sac enlargement

We report a case of a patient treated with a Gore Excluder endograft for AAA in November 2003 with subsequent aneurysm sac enlargement in the absence of an identified endoleak. The patient had a Type I endoleak treated with a Palmaz stent at the neck and later developed a Type II endoleak treated with translumbar coil embolization. This was successful with absence of pressure in the sac after the procedure and stable aneurysm size over the next nine months. Surveillance of the patient with both CT and ultrasound then revealed an increase in the aortic sac diameter in the absence of endoleak. A Cook Zenith converter was used to reline this PTFE endograft. Subsequently, imaging showed aneurysm sac shrinkage. This is a report of endotension with aneurysm expansion following Gore Excluder placement which was treated successfully with a dacron endograft.

Complications of Endovascular Repair of Abdominal Aortic Aneurysms: A Review

The endovascular procedure for repair of abdominal aortic aneurysms has had an enormous impact on the treatment of this challenging disease. Complications, however, do occur and it is important to have a thorough understanding of the array of complications and appropriate management strategies. In this review of endovascular complications, we describe early and late complications paying particular attention to preventive, treatment and surveillance strategies.

The importance of iliac fixation in prevention of stent graft migration

OBJECTIVE

Secure proximal fixation of endografts to the infrarenal aortic neck is known to be important in the short- and long-term success of endovascular aneurysm repair. We sought to determine the relative importance of distal iliac fixation in preventing endograft migration and adverse clinical events after endovascular aneurysm repair.

METHODS

We reviewed the outcome of 173 patients treated from 1996 to 2003 at Stanford University Medical Center with an externally supported stent graft. Quantitative image analysis of the postimplantation computed tomography scan was performed to determine the proximal aortic and distal iliac fixation lengths and the proximity the distal end of the stent graft to the iliac bifurcation. Subsequent follow-up computed tomography scans were reviewed for evidence of stent graft migration. Patients were grouped according to good (>15 mm), intermediate, or bad (<10 mm) aortic fixation and good (iliac fixation length > or =25 mm and iliac limbs <10 mm from iliac bifurcation), intermediate, or bad (<25-mm fixation length) iliac fixation.

RESULTS

Stent graft migration of 10 mm or more was seen in 17 patients (10%) during the 23 +/- 19-month follow-up period. Patients with no migration had a greater iliac fixation length (30 +/- 12 mm) than those with migration (22 +/- 8 mm; P = .01), and the distal ends of the iliac limbs were closer to the iliac bifurcation (15 +/- 12 mm) than in patients with migration (25 +/- 10 mm; P < .001). Patients with no migration also had a greater proximal aortic fixation length (23 +/- 12 mm) than migration patients (13 +/- 7 mm; P = .001). There were no migrations among patients with good iliac fixation whether aortic fixation was good, intermediate, or bad (0/63; 0%). Among patients with bad/intermediate iliac and good aortic fixation, there were 5 (9%) of 58 patients had migrations. Patients with both bad/intermediate iliac and bad/intermediate aortic fixation had the highest migration rate (12/52; 23%). Cox proportional hazards regression modeling revealed that the significant factors predicting migration were poor proximity of the distal end of the iliac limbs to the iliac bifurcation (odds ratio 17.2; P = .01) and aortic fixation length (odds ratio 2.0; p = 0.007 for each centimeter). Iliac extender modules were placed in 9 patients with bad iliac fixation and migration, with no further migration during a mean follow-up of 12 months. Patients with good iliac and aortic fixation and no endoleak on the initial postprocedure computed tomography scan (n = 43) had no migrations, secondary procedures, or adverse clinical events over a 2-year follow-up period.

CONCLUSIONS

Iliac fixation, along with proximal aortic fixation, is an important factor in preventing the migration of stent grafts that have longitudinal columnar support. Patients with good iliac fixation did not experience migration even in the presence of suboptimal proximal aortic fixation. Close proximity of the distal end of the stent graft to the iliac bifurcation seems to provide stability against migration.

Computed tomography versus magnetic resonance imaging of endoleaks after EVAR

AIM

The aim of study was to compare the sensitivity of MRI and CTA for endoleak detection and classification after EVAR.

PATIENTS & METHODS

Twenty-eight patients, between 2 days and 65 months after EVAR, were evaluated with both CT and MRI. Twenty-five patients had an Ancure graft and the other three had an Excluder. The MRI protocol for endoleak evaluation included: a T1-weighted spin echo, a high-resolution 3D CE-MRA, and a post-contrast T1-weighted spin echo. In total 40 ml Gadolinium was administered. The CT protocol consisted of a blank survey followed by a spiral CT angiography (CTA) using 140 ml of Ultravist. An experienced, blinded observer evaluated all CTs and MRIs.

RESULTS

Using MRI and MRA techniques significantly more endoleaks (23/35) were detected than with CTA (11/35) (p=0.01, Chi-Square). CT could not determine the type of endoleak in 3 of the 11 endoleaks detected and was uncertain in one. MRI was uncertain about the type in 14 of the 23 endoleaks detected. All endoleaks visible on CT were visible by MRI as well.

CONCLUSIONS

MRI techniques are more sensitive for the detection of endoleak after endovascular AAA repair than CT.

Progressive growth of a pelvic collection five years after endovascular aneurysm repair: an atypical presentation of an asymptomatic contained rupture

We report a case of an unusual and late presentation of an asymptomatic contained rupture after modular stent-graft implantation to treat an aortobiiliac aneurysm. Follow-up computed tomography (CT) scans 4 and 5 years after endovascular aneurysm repair showed a homogeneous, nonenhancing, but clearly growing, pelvic collection. CT-guided drainage of the collection was performed, and cultures of the evacuated brown fluid were negative for any infection. Control CT scan after drainage showed a complete collapse of both the collection and the previously excluded iliac aneurysms. A direct communication between the sterile pelvic collection and the excluded iliac aneurysm was suggested on this CT imaging and confirmed afterwards by surgery. From these imaging and surgical findings, this pelvic collection can be considered as an atypical presentation of an asymptomatic contained rupture of the excluded aneurysm.

Initial and Midterm Results for Repair of Aortic Diseases With Handmade Stent Grafts

BACKGROUND

The purpose of this study was to determine the initial and midterm results for repair of thoracic and abdominal aortic diseases using handmade stent-grafts (SGs).

METHODS AND RESULTS

Between 1999 and 2004, 41 consecutive patients (31 patients with thoracic and 10 patients with abdominal aortic disease) underwent endovascular stent-graft repair using handmade SGs. The follow-up averaged 24.8+/-17.6 months. The technical and initial clinical success rates were 82.9% (34/41) and 80.5% (33/41), respectively. Primary type I or III endoleaks occurred in 12.2% (5/41) of the patients. The hospital mortality rate was 4.9% (2/41). Persistent type I or III endoleaks occurred in 9.8% (4/41) and SG migrations occurred in 4.9% (2/41) of the patients. Open surgical conversion was undertaken in 12.2% (5/41) of the patients because of an endoleak and/or migration. The mean change observed in the aneurysm diameter was -6.2+/-10.5 mm, and shrinkage in the diameter occurred in 51.4% (18/35) of the cases. There was 1 patient death because of aneurysm rupture. Neither stent fracture nor graft hole was observed. The overall clinical success rate during follow-up was 78.0% (32/41).

CONCLUSION

The initial and midterm results obtained after repair of the aortic diseases using handmade SGs were considered to be satisfactory. More surgical experience and long-term patient follow-up are both required to further reassess the effect of this treatment.

The development of endotension is associated with increased transmission of pressure and serous components in porous expanded polytetrafluoroethylene stent-grafts: Characterization using a canine model

OBJECTIVE

This study used a canine model of abdominal aortic aneurysms (AAAs) to compare intra-aneurysmal pressure and thrombus formation after exclusion with Dacron and expanded polytetrafluoroethylene (ePTFE) stent-grafts.

METHODS

Prosthetic AAAs with implanted strain-gauge pressure transducers were treated by stent-graft exclusion using Food and Drug Administration-approved devices in 10 mongrel dogs: five Dacron (AneuRx) and five ePTFE (original Excluder). Intra-aneurysmal pressure was measured over 4 weeks after AAA exclusion and indexed to the systemic pressure, represented as a percentage of a simultaneously obtained systemic pressure (value = 1.0). Magnetic resonance imaging (MRI) of the intra-aneurysmal thrombus was performed at 1, 2, and 4 weeks after exclusion and expressed as a signal-to-noise ratio (S:N) to control for background signal intensity. Comparisons of pressures and S:N between the two stent-grafts was analyzed with the Student's t test. Intra-aneurysmal thrombus was characterized histologically.

RESULTS

In animals excluded with both Dacron and ePTFE stent-grafts, the intra-aneurysmal pressure was nonpulsatile and reduced to <30% of systemic pressure. Significantly greater pressure transmission was observed after AAA exclusion using ePTFE compared with Dacron stent grafts (systolic pressure: ePTFE, 0.28 +/- 0.12 vs Dacron, 0.11 +/- 0.02, P < .001; mean pressure: ePTFE, 0.16 +/- 0.08 vs Dacron, 0.06 +/- 0.02, P < .001). MRI confirmed the absence of perfusion in all aneurysms. The T1-weighted signal intensity remained persistently elevated (S:N at 1 week, 2.7 +/- 0.4 vs 2 weeks, 4.0 +/- 0.2 vs 4 weeks, 5.4 +/- 1.3) in ePTFE-treated intra-aneurysmal thrombus, suggesting an absence of thrombus organization. In contrast, progressive evolution of T1 signal intensity in aneurysms excluded by Dacron stent-grafts was consistent with maturation from intact red blood cells (S:N at 1 week, 3.3 +/- 0.4) to methemoglobin (S:N at 2 weeks, 6.1 +/- 0.8), and then hemosiderin and ferritin (S:N at 4 weeks, 2.4 +/- 0.5). Histologically, ePTFE-excluded aneurysms contained poorly organized thrombus with red blood cell fragments and haphazardly arranged fibrin deposition indicative of active remodeling and continued influx of transudated serum. In aneurysms excluded by Dacron stent-grafts, dense, mature collagenous connective tissue and organized fibrin were present, indicative of greater thrombus organization.

CONCLUSIONS

Stent-graft treatment reduces intra-aneurysmal pressure to <30% of systemic pressure when no endoleak is present; however, significantly greater pressure is present in aneurysms treated with porous ePTFE stent-grafts than Dacron grafts. Histologic and MRI imaging analysis suggest that active transudation of serous blood components may be contributing to this increased intra-aneurysmal pressure.

Clinical Significance of Type II Endoleak after Endovascular Repair of Abdominal Aortic Aneurysm

Type II endoleaks after endovascular repair of abdominal aortic aneurysm (EVAR) are a result of retrograde flow from arterial branches (e.g., lumbar and inferior mesenteric) refilling the aneurysm sac, which has been excluded by the stent graft. Controversy continues with regard to the clinical significance and treatment of type II endoleaks. To develop recommendations for management, we analyzed outcome data from 10 EVAR trials completed over the last 5 years involving a total of 2,617 cases. The incidence of type II endoleak at discharge or 30 days was 6-17%, at 6 months 4.5-8%, and at 1 year 1-5%. Successful resolution of endoleak following secondary interventions was observed in 11-100% of cases. There were 10 conversions to open repair and no ruptures related to type II endoleak. In patients observed for 12 months with computed tomography and/or ultrasound, approximately one-half of type II endoleaks disappeared spontaneously. In the absence of a type I endoleak, our analysis of the current literature suggests that intervention for type II endoleak should be undertaken for abdominal aortic aneurysm sac enlargement occurring after 6 months, persistence for >12 months without abdominal aortic aneurysm sac enlargement, or an aneurysm sac pressure >20% of systolic blood pressure; translumbar aneurysm sac thrombosis and intra-arterial feeding vessel occlusion appear to be prudent management options.

Secondary conversion of the Gore Excluder to operative abdominal aortic aneurysm repair

OBJECTIVE

Reports continue to document the occurrence of major adverse events after endovascular aortic aneurysm repair. Although many of these problems can be successfully managed through endovascular salvage, operative conversion with explantation of the endoprosthesis remains necessary in some patients. We report herein a review of all patients initially enrolled in multicenter US clinical trials of the Excluder endograft who underwent secondary conversion to open surgical repair.

METHODS

Clinical data and relevant medical records of patients enrolled in phase I and II multicenter US clinical trials of the Excluder endograft were retrospectively reviewed for adverse events and further narrowed to those patients who underwent secondary operative conversion. Hospital records, operative and anesthesia reports, and all imaging studies were analyzed at initial implantation and at the time of subsequent open surgical repair.

RESULTS

Late open conversion was performed in 16 (2.7%) of the 594 patients enrolled in the Excluder clinical trials. Presumed endotension accounted for 8 of 16 of secondary conversions. In two of these patients, however, an endoleak was identified at the time of open surgical repair. Of the remaining eight patients, two underwent conversion for device infection, five for persistent endoleak, and one for aneurysm rupture. The overall 30-day mortality was 6.25% (1/16), with one death occurring in a patient with a ruptured aneurysm. Of patients who underwent conversion because of endotension, the maximal abdominal aortic aneurysm diameter (mean +/- SD) at the time of initial implantation and subsequent graft removal was 61 +/- 11 mm and 70 +/- 10 mm, respectively. The mean time to open conversion for treatment of endotension was 37 +/- 12 months (range, 20-50 months; median, 42 months). Freedom from conversion was 98.6% and 96.7% at 24 and 48 months, respectively.

CONCLUSIONS

Endotension in the absence of a demonstrable endoleak has been a major indication for late surgical conversion in patients treated with the Excluder endograft. Given the potential presence of an undetected endoleak and the possible effects of progressive sac enlargement on long-term device stability, continued close surveillance of patients with assumed endotension is required. Should changes in device design eliminate endotension, a further reduction in the already low incidence of late open conversion of the Excluder endograft can be anticipated.

Endovascular Aneurysm Repair versus Open Aneurysm Repair: Comparison of Treatment Outcome and Procedure-Related Reintervention Rate

We conducted a retrospective study to compare treatment outcome and procedure-related reintervention rates of endovascular aneurysm repair (EVAR) with those of open repair. Clinical and radiological data of patients treated at the Rijnstate Hospital (Arnhem, The Netherlands) for nonsymptomatic aortic abdominal aneurysm during October 1998-January 2004 were reviewed and analyzed for demographic data, aneurysm specifics, comorbid condition status, and perioperative outcome. There were 99 patients treated with EVAR and 116 patients treated with open repair. Significant differences in age were seen between treatment groups, patients under the age of 80 being more likely to have open repair (p < 0.004). The EVAR group consisted of significantly fewer women (p < 0.029). Of seven comorbid conditions, four reached significant differences between treatment groups; patients with ischemic heart disease (p < 0.044), heart failure (p < 0.006), renal failure (p < 0.033), or peripheral arterial disease (p < 0.006) were more likely to have EVAR. Comparison of aneurysm anatomy showed no difference in size between EVAR (mean 57.7 mm, 95% CI 55.9-59.5 mm) and open repair (mean 60.1 mm, 95% CI 57.9-62.3 mm). Significant differences were seen in aneurysm neck length and diameter. Operative outcome showed differences in length of hospital stay (median, EVAR 7 vs. open repair 11 days), 30-day mortality (p < 0.048), postoperative hematoma (p < 0.001), and postoperative pulmonary infections (p < 0.001), all in favor of EVAR. Follow-up of the EVAR group showed a decrease (mean 10 mm, 95% CI 7-14 mm) of aneurysm diameter in 15% of cases during follow-up (mean 18 months, range 1-66). Despite higher age and more comorbidity of patients undergoing EVAR, 30-day mortality, postoperative pulmonary infection rate, and length of hospital stay were lower than for those undergoing open repair. Both EVAR and open repair can be performed on a subset of patients with low mortality, complication, and reintervention rates.

Systematic review of recent evidence for the safety and efficacy of elective endovascular repair in the management of infrarenal abdominal aortic aneurysm

Background

Conventional management of abdominal aortic aneurysm (AAA) is by open repair and is associated with a mortality rate of 2–6 per cent. Endovascular aneurysm repair (EVAR) is an alternative technique first introduced in 1991. A systematic review was undertaken of the evidence for the safety and efficacy of elective EVAR in the management of asymptomatic infrarenal AAA.

Methods

Thirteen electronic bibliographical databases were searched, covering biomedical, health-related, science and social science literature. Outcomes were assessed with respect to efficacy (successful deployment, technical success, conversion rates and secondary intervention rates) and safety (30-day mortality rate, procedure morbidity rates and technical issues—endoleaks, graft thrombosis, stenosis and migration).

Results

Of 606 reports identified, 61 met the inclusion criteria (three randomized and 15 non-randomized controlled trials, and 43 uncontrolled studies). There were 29 059 participants in total; 19 804 underwent EVAR. Deployment was successful in 97·6 per cent of cases. Technical success (complete aneurysm exclusion) was 81·9 per cent at discharge and 88·8 per cent at 30 days. Secondary intervention to treat endoleak or maintain graft patency was required in 16·2 per cent of patients. Mean stay in the intensive care unit and mean hospital stay were significantly shorter following EVAR. The 30-day mortality rate for EVAR was 1·6 per cent (randomized controlled trials) and 2·0 per cent in nonrandomized trials and case series. Technical complications comprised stent migration (4·0 per cent), graft limb thrombosis (3·9 per cent), endoleak (type I, 6·8 per cent; type II, 10·3 per cent; type III, 4·2 per cent) and access artery injury (4·8 per cent).

Discussion

EVAR is technically effective and safe, with lower short-term morbidity and mortality rates than open surgery. However, there is a need for extended follow-up as the long-term success of EVAR in preventing aneurysm-related deaths is not yet known.

Endograft technology: highlights of the past 10 years

The past decade has seen the evolution of an exciting technology that has changed forever the treatment of aortic aneurysmal disease. From rather crude homemade stent-grafts constructed in the surgical suite to elegant commercially manufactured devices in a variety of configurations and sizes, the aortic endograft has experienced a meteoric rise in popularity to become a beneficial, minimally invasive therapy that can obviate the risk of rupture and death. There are now 3 approved endovascular devices on the market for infrarenal abdominal aortic aneurysm repair, and it is likely that additional and improved devices will become available in the future. This review revisits the developmental history of the aortic endograft, noting the ongoing refinements that have arisen from our experiences with the growing population of stent-graft patients. Although research continues to search for solutions to the problems of endoleak and migration, long-term results even with the earlier second and third-generation devices are better than has been achieved with open surgical repair.

What is the significance of endoleaks and endotension

Endovascular repair has been used over a decade as a treatment of abdominal aortic aneurysm, and has become a widely accepted treatment method with a low rate of perioperative complications. Endoleak, perigraft blood flow outside endograft but within aneurysmsac, has been intensively studied during the last 10 years of endovascular aneurysm repair (EVR). The natural history of aneurysms with endoleak and the true clinical significance of various types of endoleaks remains unclear. Type I/III endoleak has been found to be associated with aneurysm rupture, while the risk of rupture of aneurysms with type II endoleak and endotension appears very small. In endotension, the aneurysm sac remains pressurized, even if there is no evidence of an endoleak. Currently,it is accepted that type I/III endoleaks should be corrected, preferably by endovascular means, due to the risk of rupture. If endovascular repair is not possible, then open conversion should be considered. The risk of conversion should be weighed against the risk of aneurysm rupture. Treatment of type II endoleaks and endotension is more controversial. In those with aneurysm enlargement,secondary interventions are often performed.

Post-Endograft Abdominal Aortic Aneurysm Shrinkage Varies Among Hospitals:Observations From Multicenter Trials

PURPOSE

To evaluate differences in abdominal aortic aneurysm (AAA) shrinkage among hospitals following protocol-driven patient selection and using endografts from a single manufacturer.

METHODS

Standardized inclusion criteria for the Talent endograft multicenter trials included AAA diameter >/=40 mm and proximal neck limits of length >/=5 mm, diameter 14 to 32 mm, and angle </=60 degrees. AAA reporting standards categories were used to classify distal aorta and common iliac artery involvement. Serial computed tomographic scans through 12-month follow-up were examined by independent core laboratory review. Significant shrinkage was defined as a >/=5-mm decrease in the AAA largest minor axis diameter. Trial sites with >10 complete study cases were selected for stepwise logistic regression analysis. In the 13 trial sites meeting this criterion, 323 patients (mean age 74; 93% men) were treated for aneurysms with a mean pretreatment diameter of 53 mm.

RESULTS

At 12 months, significant AAA shrinkage occurred in 192 (59%) cases. The AAA shrinkage rate was 71% to 82% at 3 sites, 60% to 64% at 4 sites, 45% to 50% at 4 sites, and 35% and 27% at the 2 remaining sites. In the multivariate analysis, the hospital site showed a strong, independent association with aneurysm shrinkage (p<0.04). Neck and pretreatment AAA diameters were also found to be important factors (p<0.04). Age, gender, AAA classification, neck length, and angle were not significant correlates. Sixty-four (20%) endoleaks (29 type I, 34 type II, and 1 type III) were observed. The incidence of proximal endoleak was significantly different among sites (p<0.001) and highest in the 3 sites with the lowest AAA shrinkage rate.

CONCLUSIONS

AAA shrinkage rates vary significantly among hospitals using the same endograft and protocol-defined patient selection criteria. Site-specific factors appear to be an important variable leading to successful endograft repair, as defined by post-endograft aneurysm shrinkage.

Explant analysis of AneuRx stent grafts: relationship between structural findings and clinical outcome

OBJECTIVE

We reviewed the structural findings of explanted AneuRx stent grafts used to treat abdominal aortic aneurysms, and relate the findings to clinical outcome measures.

METHODS

We reviewed data for all bifurcated AneuRx stent grafts explanted at surgery or autopsy and returned to the manufacturer from the US clinical trial and worldwide experience of more than 33,000 implants from 1996 to 2003. Devices implanted for more than 1 month with structural analysis are included in this article. Explant results were analyzed in relation to cause of explantation and pre-explant evidence of endoleak, enlargement, or device migration.

RESULTS

One hundred twenty explanted stent grafts, including 37 from the US clinical trial, were analyzed. Mean implant duration was 22 +/- 13 months (range, 1-61 months). Structural abnormalities included stent fatigue fractures, fabric abrasion holes, and suture breaks. The mean number of nitinol stent strut fractures per explanted device was 3 +/- 4, which represents less than 0.2% of the total number of stent struts in each device. The mean number of fabric holes per explanted device was 2 +/- 3, with a median hole size of 0.5 mm(2). Suture breaks were seen in most explanted devices, but composed less than 1.5% of the total number of sutures per device. "For cause" explants (n = 104) had a 10-month longer implant duration (P =.007) compared with "incidental" explants (n = 16). "For cause" explants had more fractures (3 +/- 5; P =.005) and fabric holes (2 +/- 3; P =.008) per device compared with "incidental" explants, but these differences were not significant (P =.3) when adjusted for duration of device implantation. Among clinical trial explants the number of fabric holes in grafts in patients with endoleak (2 +/- 3 per device) was no different from those without endoleak (3 +/- 4 per device; P = NS). The number of fatigue fractures or fabric holes was no different in grafts in clinical trial patients with pre-explant aneurysm enlargement compared with those without enlargement. Pre-explant stent-graft migration was associated with a greater number of stent strut fractures (5 +/- 7 per device; P =.04) and fabric holes (3 +/- 3 per bifurcation; P =.03) compared with explants without migration. Serial imaging studies revealed inadequate proximal, distal, or junctional device fixation as the probable cause of rupture or need for conversion to open surgery in 86% of "for cause" explants. Structural device abnormalities were usually remote from fixation sites, and no causal relationship between device findings and clinical outcome could be established.

CONCLUSIONS

Nitinol stent fatigue fractures, fabric holes, and suture breaks found in explanted AneuRx stent grafts do not appear to be related to clinical outcome measures. Longer term studies are needed to confirm these observations.