Endovascular stent grafting in the presence of aortic neck filling defects: early clinical experience

Thrombosis in the pathogenesis of abdominal aortic aneurysm

Background

Abdominal aortic aneurysms (AAAs) are a relatively common vascular pathology of the elderly with high morbidity potential. Irreversible degeneration of the aortic wall leads to lethal rupture if left untreated. Nearly all AAAs contain intraluminal thrombus (ILT) to a varying degree, yet the mechanisms explaining how thrombosis is disturbed in AAA are relatively unknown. This review examined the thrombotic complications associated with AAA, the impact of thrombosis on AAA surgical outcomes and AAA pathogenesis, and the use of antithrombotic therapy in the management of this disease.

Methods

A literature search of the PubMed database was conducted using relevant keywords related to thrombosis and AAAs.

Results

Thrombotic complications are relatively infrequent in AAA yet carry significant morbidity risks. The ILT can impact endovascular aneurysm repair by limiting anatomic suitability and influence the risk of endoleaks. Many of the pathologic mechanisms involved in AAA development, including hemodynamics, inflammation, oxidative stress, and aortic wall remodeling, contain pathways that interact with thrombosis. Conversely, the ILT can also be a source of biochemical stress and exacerbate these aneurysmal processes. In animal AAA models, antithrombotic therapies have shown favorable results in preventing and stabilizing AAA. Antiplatelet agents may be beneficial for reducing risks of major adverse cardiovascular events in AAA patients; however, neither antiplatelet nor anticoagulation is currently used solely for the management of AAA.

Conclusions

Thrombosis and ILT may have detrimental effects on AAA growth, rupture risk, and patient outcomes, yet there is limited understanding of the pathologic thrombotic mechanisms in aneurysmal disease at the molecular level. Preventing ILT using platelet and coagulation inhibitors may be a reasonable theoretical target for aneurysm progression and stability; however, the practical benefits of current antithrombotic therapies in AAA are unclear. Further research is needed to demonstrate the extent to which thrombosis impacts AAA pathogenesis and to develop novel pharmacologic strategies for the medical management of this disease.

Open abdominal aortic aneurysm repair is still necessary in an era of advanced endovascular repair

OBJECTIVE

Recent advances in endovascular aneurysm repair have overcome substantial anatomic barriers associated with short and challenging necks. With greater range to treat more difficult anatomy from an endovascular approach, one would assume the need of open surgical repair (OSR) would be diminished. The purpose of our study was to determine the need for OSR for abdominal aortic aneurysms, in a tertiary academic setting, with a moderate volume (10-15 cases/year) of fenestrated endografting being performed.

METHODS

An Institutional Review Board approved retrospective review was performed of all patients who underwent elective aortic aneurysm repair between January 2010 and July 2014. Computed tomography scans for patients who underwent OSR were reviewed and anatomic characteristics obtained. Instructions for use of (IFU) a commercially available fenestrated device (Cook Medical, Bloomington, Ind) were used to determine if open repair patients had anatomy amenable to advanced endovascular repair.

RESULTS

During the study interval, 415 patients underwent abdominal aortic aneurysm repair. Of those patients who underwent elective aneurysm repair, 105 patients had OSR. The study subsequently excluded 11 patients because they underwent secondary interventions after a failed endovascular repair and thus were not further evaluated. Also excluded were 18 patients who had OSR for an emergency intervention. The remaining 76 patients (35 female, 41 male; average age, 72 ± 8 years) had OSR and were outside the IFU of the fenestrated endovascular aneurysm repair (FEVAR) device. The average diameter of the abdominal aorta was 5.9 cm. Indications for OSR were an aneurysm neck <4 mm (71%), inclusion of at least 1 visceral vessel (69.7%), unilateral iliac artery aneurysms (15.5%), bilateral iliac artery aneurysms (14.3%), iliac artery tortuosity >40° of angulation (37.6%), extensive aortic thrombus (23.2%), and aortic neck angulation >45° (11.8%). Rejected patients had an average of 1.7 ± 0.8 anatomic constraints (range 1-4) that prevented use of the FEVAR device.

CONCLUSIONS

With evidence to support the strict adherence to IFU protocols of the FEVAR device in patients, our institution's practice has been to continue to perform open abdominal aortic aneurysm repair for patients with anatomy outside device protocols. Although it was thought that the decreased requirement of aortic neck required to deploy an endograft would lead to an increased patient population amenable to endovascular repair, there is still a clinically significant need for open aortic surgery.

Barriers to Endovascular Aortic Aneurysm Repair: Past Experience and Implications for Future Device Development

Despite improvements in endovascular aortic aneurysm repair (EVAR) devices and techniques, significant anatomic constraints still preclude successful EVAR in a large number of patients. The authors sought to identify the current barriers to EVAR and examine their evolution over time. Patients were evaluated for potential endovascular repair by computed tomography angiography (CTA) with or without supplemental conventional arteriograms. The patient population was separated into 2 groups (A and B) based on early and late time periods in the experience with EVAR, corresponding to the availability of various devices. Group A (early) consisted of the Guidant Ancure, Medtronic Talent, and AneuRx devices and comprised patients presenting between April 1997 through June 2000. Group B (late) consisted of the Medtronic AneuRx, Cook Zenith, Edwards Lifepath, Gore Excluder, and Endologix PowerLink devices and comprised patients presenting between July 2000 and December 2003. Patient demographics and anatomic reasons for rejection were recorded in a database for statistical analysis. In total, 547 patients were evaluated (463 men, 84 women). Of these, 346 patients (63%; 312 men, 34 women) were deemed suitable candidates for EVAR and 201 (37%; 151 men, 50 women) were rejected. There was no significant difference in the overall rate of rejection in the early vs the late time period (34% A, 41% B, p= 0.08), but the number of exclusion criteria per patient decreased over time; patients rejected for EVAR had an overall average of 1.6 exclusion criteria (Group A, 1.9; Group B, 1.2). The reasons for rejection did significantly change over time. Specifically, rejection on the basis of inadequate arterial access, presence of extensive iliac artery aneurysms, or an inadequate proximal neck decreased. A disproportionate number of women were excluded throughout the study: Group A, 56% of women compared to 30% of men (p= 0.0003); Group B, 63% of women compared to 36% of men (p= 0.0022). Women were more likely than men to have inadequate arterial access routes. In addition, patients with high operative risk were also more likely to be excluded from EVAR, a finding that persisted over time. Anatomic constraints continue to pose significant challenges to aortic endografting. Progress has been made in that technological advances have conquered some of the previous anatomic challenges, chiefly those of arterial access and treatment of concomitant iliac aneurysm disease. However, the overall rate of rejection for EVAR remains the same. The chief anatomic barriers continue to be the difficult aortic neck and management of branched vascular segments.

Endovascular vs Open AAA Repair: Does Size Matter?

Since the natural tendency of the aorta is to increase in diameter and tortuosity with age and since abdominal aortic aneurysms (AAAs) increase in diameter and length over time, encroaching on the renal and hypogastric orifices, early repair of AAAs (when =4.0 cm) may allow greater applicability of the endovascular option because of more favorable aortoiliac morphology. Patients who present at an older age with larger AAAs should be more likely to be anatomically excluded from endovascular AAA repair. Over a 42-month period, 317 consecutive patients referred with aortoiliac aneurysms (infrarenal AAA =4.0 cm) were evaluated by one of the authors (SGL) for endovascular vs open repair based on computed tomography (CT) and angiographic imaging. The 10 anatomic exclusion criteria were those applicable to the Zenith ® endograft (Cook, Inc), which currently is the most anatomically inclusive of the aortic endografts in commercial use in the United States. Based on their aortoiliac morphology, 212 patients were excluded from endovascular repair and 105 were included as acceptable anatomic candidates. Age, AAA size, and the reason(s) for exclusion were recorded for each patient. By use of Student's t test and logistic and linear regression analyses, the groups were compared by age, AAA size, and age + size. There was no significant difference in patient age or AAA size distribution between the group of patients excluded from endovascular repair based on aortoiliac morphology compared to those who met the inclusion criteria. Patients with small AAAs (4.0–5.4 cm) had similar age distribution as those with large (=5.5 cm) AAAs. The majority of patients (87%) were excluded based on proximal aortic neck morphology. The presence of aortoiliac morphology that precludes endovascular repair is independent of patient age or AAA size at presentation. A patient presenting with a small (4.0–5.4 cm) AAA is not more likely to be a candidate for endovascular repair than a patient with a large AAA.

Outcomes of Endovascular AAA Repair in Patients with Hostile Neck Anatomy Using Adjunctive Balloon-Expandable Stents

Hostile neck anatomy remains the predominant reason that patients are denied endovascular aneurysm repair (EVAR). We reviewed our experience of EVAR with use of prophylactic adjunctive proximal balloon-expandable stents in patients with hostile neck anatomy and adjunctive proximal balloon-expandable stents in patients with type I endoleaks. Of 140 patients who underwent EVAR between 2000 and 2004, we reviewed data for 19 patients in whom we used proximal balloon-expandable stents. By high-resolution computed tomography scan or angiography, hostile neck anatomy was classified as length <15 mm, neck diameters = 26 mm, circumferential thrombus at the proximal neck, angulated neck =60 degrees, and neck bulge or reverse taper necks. Patients were considered to have hostile anatomy if they met 1 or more of the above-cited criteria. All patients underwent AAA repair with commercially available endograft systems, Zenith (Cook, Bloomington, IN) and AneuRx (Medtronic/AVE, Minneapolis, MN). Balloon-expandable stents utilized included Cordis-Palmaz stents (17/19) and eV3 Max stents (2/19). Stents were deployed in the proximal graft with transrenal extension. AneuRx (18/19) and Zenith (1/19) endografts were used in all of the patients. Of the 19 patients, 15 had prophylactic stent placement for known hostile neck anatomy and 4 patients had stent placement for type I endoleak. Assisted primary technical success was achieved in all patients. Three patients had maldeployment of the endograft or proximal stent requiring additional endovascular interventions at the time of surgery. No endografts were deployed too low requiring stent placement. Procedure-related complications occurred in 2 of 19 patients. These included 1 operative death secondary to pneumonia and 1 patient who developed progressive renal failure. Short-term clinical success was achieved in 17 of 19 patients. Two patients required secondary interventions, 1 due to device migration with secondary conversion to open repair, and an endoleak, which, on angiogram, was a large type II endoleak successfully treated with coiling of the inferior mesenteric artery. One patient was observed to have a type II endoleak with no associated aneurysm enlargement. Short-term results suggest the use of prophylactic adjunctive balloon-expandable stents may decrease the incidence of secondary interventions related to hostile neck anatomy when used as an adjunctive measure with EVAR. Based on our experience, we feel EVAR may be offered to an expanded patient population with hostile neck anatomy with use of prophylactic balloon-expandable stents.

Device-Specific Resistance to in Vivo Displacement of Stent-Grafts Implanted with Maximum Iliac Fixation

Purpose:

To compare the in vivo device-specific downward displacement force of various externally supported endografts implanted with maximum iliac fixation.

Methods:

Twenty female sheep had aneurysms created with a graft patch in the infrarenal aorta. In 12 animals, a fully supported modular bifurcated stent-graft [AneuRx (n=4), Talent (n=4), or Zenith (n=4)] was deployed; in the other 8, a bifurcated aortic graft was surgically anastomosed to the infrarenal aorta. All grafts were displaced in vivo by applying downward traction to a guidewire brought out both femoral arteries. The peak force to cause initial stent-graft migration or disruption of the sutured anastomosis was recorded and compared.

Results:

There was no difference in animal size, aortic neck diameter or length, aneurysm size, or iliac artery diameter for animals receiving the AneuRx, Talent, or Zenith stent-grafts and those undergoing surgical repair. The mean length of iliac fixation was 31.0±0.3 mm, 30.8±0.5 mm, and 31.3±0.6 mm for the AneuRx, Talent, and Zenith devices, respectively (p=NS). Peak force to initiate migration was 30.2=5.5 N (range 25–38) for the AneuRx, 44.8±5.5 N (range 40–53) for the Talent, 46.7±5.4 N (range 38–55) for the Zenith, and 40.6±7.5 N (range 31–50) for the surgical anastomosis (p=0.01). There was no difference detected in the peak force to initiate migration between the suprarenally affixed Talent and Zenith stent-grafts and the surgical anastomosis (p=0.55).

Conclusion:

Devices with a suprarenal component require significantly greater force to cause downward displacement compared to infrarenal devices. The force required to displace a suprarenal device with maximal iliac fixation was equivalent to the force required to disrupt a surgical anastomosis.

Thromboembolic complications after endovascular repair of abdominal aortic aneurysm with neck thrombus

OBJECTIVE

To evaluate outcomes after endovascular aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA) with neck thrombus.

METHODS

We retrospectively reviewed patients who underwent EVAR for AAA at our institution from 2007 to 2011. Patients with ruptured AAA, chronic renal failure, or hostile neck characteristics other than thrombus were excluded. Patients were divided into 2 groups: group T (with neck thrombus) and group N (without neck thrombus). We compared complications and mid-term outcomes.

RESULTS

There were no differences in success rates between the groups, but there were higher rates of thromboembolic complications such as distal embolization (20% vs 0%, P = .02) and renal dysfunction (36.8% vs 11.1%, P = .03) in group T than in group N. Suprarenal thrombus and suprarenal fixation in the presence of suprarenal thrombus were associated with postoperative renal dysfunction (P = .01).

CONCLUSION

The EVAR for AAA with neck thrombus is associated with thromboembolic complications.

Endografts with suprarenal fixation do not perform better than those with infrarenal fixation in the treatment of patients with short straight proximal aortic necks

OBJECTIVE

To determine if there are any differences in outcomes between infrarenal fixation (IF) and suprarenal fixation (SF) endograft systems for the endovascular treatment (endovascular aneurysm repair [EVAR]) of abdominal aortic aneurysms (AAAs) with short, straight proximal aortic necks (<1.5 cm).

METHODS

A retrospective review of 1379 EVAR procedures was performed between the years of 2002 and 2009 at a single institution. The charts and radiographic images of all patients were reviewed. Patients who underwent EVAR with AAA morphology with short proximal necks were stratified into two groups: IF, Gore Excluder (W. L. Gore, Flagstaff, Ariz) group and SF, Cook Zenith (Cook, Bloomington, Ind) group. The primary end point for the study was the presence of proximal type 1 endoleaks. Secondary end points were graft migration at 1- and 2-year follow-up and aneurysm sac regression. The groups' demographics and comorbidities were also compared.

RESULTS

A total of 1379 EVARS were performed during the study period and 84 were identified as having a short proximal aortic neck. Sixty patients were in the IF group and 24 in the SF group. The average follow-up period was 18.6 months (IF) and 18.5 months (SF). There was no difference in the average proximal neck length (1.19 cm IF vs 1.14 cm SF; P = not significant [NS]) or the preoperative AAA size (5.8 cm IF vs 5.9 cm SF; P = NS). There were no significant differences in age (76.6 years IF vs 74.8 years SF; P = .32), gender (IF 66.7% vs SF 21.88% men; P = .053), or length of stay (2.2 days IF vs 1.9 days SF; P = .39). The comorbidities (diabetes, hypertension, and warfarin use) were also similar. There were five type 1a endoleaks in group IF and one in group SF (P = .44) identified at the 1-month follow-up; however, only one patient in the IF group underwent intervention for enlargement of the AAA sac. At 1 year, there was persistence of one type 1a endoleak in both groups, but these were deemed dead-end leaks as they did not fill the sac nor lead to aneurysm growth. There were no migrations (>0.5 cm) noted in either group. Sac regression was observed at an average rate of 0.24 cm/year in the IF group and 0.26 cm/year in the SF group (P = NS). There were no aneurysm ruptures during the study period.

CONCLUSIONS

There are no significant differences in endograft migration or in the incidence of early and late type 1a endoleaks between endografts that use IF (Gore Excluder) and SF (Cook Zenith) fixation for patients with short aortic necks undergoing EVAR.

The influence of thrombus, calcification, angulation, and tortuosity of attachment sites on the time to the first graft-related complication after endovascular aneurysm repair

PURPOSE

Endovascular aneurysm repair (EVAR) is associated with high graft-related complication rates during follow-up. Anatomical fit between patient and endograft could be an important factor for successful treatment. Aim was to assess whether extent of thrombus, calcification, angulation, and tortuosity are associated with occurrence of complications after EVAR.

MATERIALS AND METHODS

Patients in either United Kingdom EVAR trial 1 or 2 were included if they had undergone EVAR within 6 months of randomization and had a preoperative computed tomography (CT) scan of adequate quality in the core laboratory. Three-dimensional CT imaging was used to assess extent of preoperative thrombus, calcification, angulation, and tortuosity in aneurysm neck and iliac segments. Cox regression modeling, adjusted for the variables tested and for known confounding variables, was used to investigate whether these factors were associated with increased rates of reported first complications.

RESULTS

A total of 217 patients with 53 first graft-related complications were analyzed after a mean follow-up of 3.6 years. Adjusted hazard ratios (95% confidence intervals, P values) for complications per unit increase of variable were 0.96 (0.92-0.99, 0.018) for neck thrombus, 1.06 (1.00-1.12, 0.044) for neck calcification, 1.02 (1.00-1.05, 0.079) for neck angulation, 1.04 (1.01-1.06, 0.011) for common iliac thrombus, 0.96 (0.93-1.00, 0.033) for common iliac calcification, and 5.96 (1.53-23.28, 0.010) for common iliac tortuosity.

CONCLUSION

Increased neck angulation and calcification and common iliac thrombus and tortuosity are associated with higher rates of graft-related complications after EVAR. Increased neck thrombus and common iliac calcification appear to protect against complications. Careful evaluation of these factors prior to EVAR might lead to lower complication rates.

Clinical outcomes for hostile versus favorable aortic neck anatomy in endovascular aortic aneurysm repair using modular devices

BACKGROUND

Endovascular aneurysm repair (EVAR) is not generally recommended for patients with hostile neck anatomy. This study analyzed the clinical implications of various clinical features of proximal aortic neck anatomy.

METHODS

Prospectively collected data from 258 EVAR patients using modular devices were analyzed. Patients were classified as having favorable neck anatomy (FNA) or hostile neck anatomy (HNA). HNA was defined as any or all of length of <10 mm, angle of >60°, diameter of >28 mm, ≥50% circumferential thrombus, ≥50% calcified neck, and reverse taper. Univariate, multivariate, and Kaplan-Meier analyses were used to compare early and late clinical outcomes.

RESULTS

FNA was present in 37% and HNA was present in 63%. Clinical and demographic characteristics were comparable. Technical success was 99%. Mean follow-up was 22 months (range, 1-78 months). Perioperative complication rates were 3% for FNA vs 16% for HNA (P = .0027). Perioperative deaths were 0% for FNA and 3% for HNA (P = .2997). Proximal type I early endoleaks (intraoperative) occurred in 9% of FNA vs 22% for HNA (P = .0202). Intraoperative proximal aortic cuffs were used to seal endoleaks in 9% of FNA vs 22% of HNA (P = .0093). At late follow-up, abdominal aortic aneurysm expansion was noted in 6% of FNA vs 7% of HNA (P = .8509). Rates of freedom from late type I endoleaks at 1, 2, 3, and 4 years were 97%, 97%, 97%, and 90% for FNA vs 89%, 89%, 89%, and 89% for HNA (P = .1224); rates for late interventions were 95%, 90%, 90%, and 90% for FNA vs 95%, 93%, 91%, and 85% for HNA (P = .6902). Graft patency at 1, 2, and 3 years was 99%, 99%, and 99% for FNA vs 97%, 92%, and 90% for HNA (P = .0925). The survival rates were 93%, 84%, 76%, and 76% for FNA vs 88%, 82%, 74%, and 66% for HNA (P = .2631). Reverse taper was a significant predictor for early type I endoleak (odds ratio [OR], 5.25, P < .0001), reverse taper (OR, 5.95; P < .0001) and neck length (OR, 4.15; P = .0146) were for aortic cuff use; circumferential thrombus (OR, 2.44; P = .0448), and neck angle (OR, 3.38; P = .009) were for perioperative complications.

CONCLUSIONS

Patients with HNA can be treated with EVAR, but with higher rates of early (intraoperative) type I endoleak and intervention. The midterm outcomes are similar to FNA.

Early in Vivo Analysis of an Endovascular Stapler During Endovascular Aneurysm Repair

The objective of this article is to describe the use and technique of a novel endostapling device used in an in vivo animal model. Six ovine underwent implantation of a Dacron endograft into the thoracic aorta followed by placement of endoclips proximally and distally. The animals were survived 35 days to evaluate the performance and safety of the endoclip in an animal model prior to clinical trials. The mean time for securing both the proximal and the distal anastomosis was 22 minutes (range 17–31 minutes). All staples were deployed, without the need for repositioning, on the first attempt. There were no complications related to the implant procedure or indwelling clips. Additionally, no endograft migration occurred. At the time of expiant, staples were evaluated for depth of penetration and accuracy of placement. The staples had fully penetrated the endograft and vessel wall through the adventitia in 89% (64 of 72) of clips deployed. The staples were placed accurately, within 10 mm of the endograft proximal and distal attachments in 94% (68 of 72) of the clips deployed. Furthermore, endothelialization of the staples was present without surrounding thrombus. Implant sites were scored as normal without surrounding tissue damage by an independent pathologist. The endoclip performed well in creating proximal and distal fixation of the endograft. There were no adverse outcomes related to the endostaple. Future clinical trials should be undertaken to assess its clinical utility during endovascular aneurysm repair.

Long-term results of balloon-expandable LifePath endografts in abdominal aortic aneurysm: a single-center experience

OBJECTIVE

This retrospective single-center study analyzed long-term results after LifePath (Edwards Lifesciences LLC, Irvine, Calif) endoprosthesis implantation for abdominal aortic aneurysm (AAA), primarily focusing on the wire form fracture issue and consecutive endoleak rate.

METHODS

Between 1999 and 2004, all consecutive patients with LifePath AAA devices in our institution were included in the retrospective analysis. All patients had computed tomography angiography (CTA) imaging preoperatively and image postprocessing. The follow-up using CTA imaging specifically addressed material fatigue (wire form fractures) resulting in migrations and type I endoleaks.

RESULTS

During the 6-year study period, which included the 1-year withdrawal and redesign of the device, 51 patients were treated with LifePath AAA endografts. The 30-day mortality was 0%. The perioperative 30-day morbidity was 9.8%. One patient required a primary conversion due to misdeployment of the iliac limbs within the graft main body. The primary endoleak rate was 20.56% (type I, 2%; type II, 19.6%). During the mean follow-up of 40.7 months, 12 patients died, six were lost to follow-up, and 32 underwent subsequent CTA imaging. Eight patients (25%) demonstrated a proximal type I endoleak, seven (22%) had a type II endoleak, and three had a type III endoleak (9%). In nine patients (28.1%), wire form fractures could be detected at image postprocessing. Four patients required a secondary conversion due to endoleak and aneurysm growth (2 type I endoleaks and 2 type III endoleaks).

CONCLUSION

Wire form fracture is the major structural problem in the LifePath balloon-expandable endograft device, resulting in a significant endoleak rate. We must caution those patients with a LifePath device in-situ that careful follow-up must be performed due to material fatigue and they should consider secondary conversion.

Aortic Aneurysm, Thoracoabdominal Aneurysm, Juxtarenal Aneurysm, Fenestrated Endografts, Branched Endografts, and Endovascular Aneurysm Repair

The development of endovascular devices to treat aneurysms that abut or involve the visceral vessels has occurred in an effort to reduce the significant procedural morbidity and mortality associated with conventional repair. To accomplish this, three systems have been trialed. The first technique was developed to treat juxtarenal aneurysms and involves the placement of customized fenestrations strategically placed within the fabric of the graft. These are aligned with the ostia of the visceral vessels incorporated by the repair and supplemented by the placement of a balloon expandable stent. In a similar fashion, aneurysms that involve the visceral vessels can be treated with a fenestrated graft where the fenestration is reinforced with a nitinol ring. This is then mated with a balloon-expandable stentgraft, allowing the devices to seal at the level of the nitinol ring. An alternative means of incorporating the visceral vessels is to use directional branches where one or more additional limbs (typically 8 mm) are anastomosed to the aortic graft, through which access into the visceral vessel is attained. Mating stentgrafts for the later design can be of a self-expanding or balloon expandable nature. The experience with fenestrated devices is mature and associated with a low perioperative mortality (<2%) without many long-term complications. The treatment of thoracoabdominal aneurysms with branches has provided us with optimism regarding the technique, but results are only short term in nature. Further device development is ongoing and dissemination of this technology is now occurring in Europe, Australia and Canada.

Influence of Infrarenal Neck Length on Outcome of Endovascular Abdominal Aortic Aneurysm Repair

PURPOSE

To evaluate the influence of the infrarenal neck length on clinical outcome after endovascular abdominal aortic aneurysm repair (EVAR).

METHODS

Data were analyzed from 3499 patients enrolled in the EUROSTAR registry between January 1999 and April 2005 who underwent EVAR with a Talent or Zenith endograft and had detailed morphological data recorded. The study cohort was divided into 3 groups according to infrarenal neck length: >15 mm (reference group A, n=2822), 11 to 15 mm (group B, n=485), and < or =10 mm (group C, n=192). Uni- and multivariate analyses were performed to evaluate differences in clinical outcomes among the study groups.

RESULTS

After correction for confounders, proximal type I endoleak within 30 days occurred in 10.9% of group C compared to 2.6% of group A (OR 4.46, 95% CI 2.61 to 7.61). Within 48 months of follow-up (median 12 months), the incidence of proximal endoleaks was higher in groups B (9.6%; HR 1.98, 95% CI 1.16 to 3.38) and C (11.3%; HR 2.132, 95% CI 1.17 to 4.60) compared to group A (3.4%).

CONCLUSION

Our study indicates that endovascular treatment of abdominal aortic aneurysms with infrarenal neck length <15 mm is associated with significantly increased risk of short- and midterm proximal endoleaks after EVAR. The greater risk of proximal endoleaks should be weighed against the risks of alternative treatment modalities.

Outcomes of Endovascular Abdominal Aortic Aneurysm Repair in Patients with Hostile Neck Anatomy

PURPOSE

The principal anatomic contraindication to endovascular aneurysm repair (EVR) is an unfavorable proximal aortic neck. With increasing experience, a greater proportion of patients with unfavorable neck anatomy are being offered EVR. This study aimed to evaluate outcomes in patients with challenging proximal aortic neck anatomy.

METHODS

Prospectively collected data from 147 consecutive patients who underwent EVR between December 1997 and April 2005 were supplemented with a retrospective review of medical records and radiological images. Unfavorable anatomic features were defined as neck diameter >28 mm, angulation >60 degrees, circumferential thrombus >50%, and length <10 mm. Eighty-seven patients with 0 adverse features (good necks) were compared with 60 patients with one or more adverse features (hostile necks).

RESULTS

Comparing the good neck with the hostile neck group, there were no significant differences in the incidence of primary technical success (p = 0.15), intraoperative adjunctive procedures (p = 0.22), early proximal type I endoleak (<30 days) (p = 1.0), late proximal type I endoleak (>30 days) (p = 0.57), distal type I endoleak (p = 0.40), type III endoleak (p = 0.51), secondary interventions (p = 1.0), aneurysm sac expansion (p = 0.44), or 30 day mortality (p = 0.70). The good neck group had a significantly increased incidence of type II endoleak (p = 0.023). By multivariate analysis, the incidence of intraoperative adjunctive procedures was significantly increased in the presence of severe angulation (p = 0.041, OR 3.08, 95% CI 1.05-9.04).

CONCLUSION

Patients with severely hostile proximal aortic neck anatomy may be treated with EVR, although severely angulated necks require additional intraoperative procedures. Early outcomes are encouraging and suggest that indications for EVR may be expanded to include patients with hostile neck anatomy.

Suprarenal Endograft Fixation Avoids Adverse Outcomes Associated with Aortic Neck Angulation

The advent of endovascular therapy has had a profound impact on repair of abdominal aortic aneurysms (AAA). Prudent patient selection, particularly in regard to unfavorable anatomy, is emerging as perhaps the most important determinant of endovascular abdominal aortic aneurysm repair (EVAR) outcome. The aim of this study was to examine the association of one such anatomic factor, proximal aortic neck angulation, with the incidence of adverse events following EVAR. Prospectively collected data on 289 EVAR repairs with the Talent endograft (Medtronic, Inc., Minneapolis, MN) from March 1998 to June 2000 were analyzed. Stent graft-specific adverse events studied were migration, endoleak, kinking, thrombosis, and AAA expansion. Computed tomography (CT) scanning with three-dimensional post-processing and/or aortography was used to measure aortic neck angle. Patients were categorized into one of four groups according to their neck angle: I (0-10 degrees); II (11-39 degrees); III (40-59 degrees); or IV (60-85 degrees). Outcomes were evaluated by chi-squared analysis and ANOVA. There was a direct correlation between AAA diameter and neck angle (p = 0.002). There was no difference in endoleak rate (p = 0.877), stent migration (p = 0.850), or AAA expansion rate (p = 0.599) between groups. Device kinking >45 degrees was associated with neck angulation > or = 60 degrees (p = 0.013), but not with other adverse outcomes. The average neck angle was 30 degrees in patients with endoleaks and 31 degrees in patients without endoleaks. Increasing aortic neck angulation was not associated with the selected adverse outcomes within 1 year following EVAR with the Talent stent graft using suprarenal fixation with the exception of graft kinking. This may be related to the graft design that permits suprarenal aortic fixatiou of the proximal stent graft, Whether severe degrees of angulation of 60 degrees or greater can be safely treated with suprarenal fixation requires further study.

Embolization as cause of bowel ischemia after endovascular abdominal aortic aneurysm repair

OBJECTIVE

We investigated the incidence, cause, and outcome of large bowel and small bowel ischemia after endovascular abdominal aortic aneurysm (AAA) repair.

METHODS

Medical records for all patients undergoing endovascular AAA repair from December 1999 to December 2003 were reviewed. The incidence, cause, and outcome of clinically detected postoperative bowel ischemia were analyzed.

RESULTS

Seven hundred two endovascular AAA repairs were performed. In 10 patients (1.4%) acute bowel ischemia developed. Six of these patients sustained concurrent small bowel necrosis, and the remaining 4 had isolated colon ischemia. Seven patients underwent exploratory laparotomy. In 6 of these bowel resection was performed, and in 1 patient the ischemic bowel was unsalvageable. Of the 6 patients with small and large bowel ischemia, 4 had segmental or patchy necrosis, which was separated by normal-appearing intestine, and 1 had extensive ischemia that involved most of the small bowel and the entire colon, with pathologic evidence of microembolization. Three patients had preoperative occlusion of the inferior mesenteric artery. One had unilateral and 1 had bilateral hypogastric artery interruption. Five of the 6 patients with small bowel ischemia had thrombus or atheroma in the proximal aneurysmal necks. All patients with isolated colon ischemia survived. All 6 patients with concurrent small bowel ischemia died.

CONCLUSION

The total incidence of clinically evident bowel ischemia after endovascular AAA repair is similar to that after open surgery. However, small bowel ischemia occurs more commonly in patients with endovascular repair, and is associated with extremely high mortality. The direct pathologic evidence and the patterns of segmental, skipped, or patchy ischemia in most patients imply that microembolization has an important role.

Diameter of abdominal aortic aneurysm and outcome of endovascular aneurysm repair: does size matter? A report from EUROSTAR

OBJECTIVES

This study was undertaken to determine the effect of the preoperative diameter of abdominal aortic aneurysms on the midterm outcome after endovascular abdominal aneurysm repair (EVAR).

METHOD

The data for 4392 patients who had undergone EVAR were analyzed. Patients were enrolled over 6 years to June 2002 in the EUROSTAR database. Outcomes were compared between three groups defined by the preoperative diameter of the aneurysm: group A (n = 1962), 4.0 to 5.4 cm; group B (n = 1528), 5.5 to 6.4 cm; and group C (n = 902), 6.5 cm or larger. Patient characteristics, details of aortoiliac anatomy, operative procedures, old or current device generation, and postoperative complications in the three patient groups were compared. Outcome events included aneurysm-related death, unrelated death, conversion, and post-EVAR rupture of the aneurysm. Life table analysis and log-rank tests were used to compare outcome in the three study groups. Multivariate Cox models were used to determine whether baseline and follow-up variables were independently associated with adverse outcome events.

RESULTS

Patients in group C were significantly older than patients in groups A and B (73 years vs 70 and 72 years, respectively; P =.003 - P <.0001 for different group comparisons), and more frequently were at higher operative risk (American Society of Anesthesiologists classification >or=3; 63% vs 48% and 54%; P =.0002-P <.0001). Device-related (type I) endoleaks were more frequently observed at early postoperative arteriography in group C compared with groups A and B (9.9% vs 3.7% and 6.8%; P =.01-P <.0001). Postoperatively systemic complications were more frequently present in group C (17.4% vs 12.0% in group A and 12.6% in group B; P <.0001 and.001). The first-month mortality was approximately twice as high in group C compared with the other groups combined (4.1% vs 2.1%; P <.0001). Late rupture was most frequent in group C. Follow-up results at midterm were less favorable in groups C and B compared with group A (freedom from rupture, 90%, 98%, and 98% at 4 years in groups C, B, and A, respectively; P <.0001 for group C vs groups A and B). Aneurysm-related death was highest in group C (88% freedom at 4 years, compared with 95% in group B and 97% in A; P =.001 and P <.0001, respectively; group B vs A, P =.004). The annual rate of aneurysm-related death in group C was 1% in the first 3 years, but accelerated to 8.0% in the fourth year. Incidence of unrelated death also was higher in groups C and B than in group A (76% and 82% freedom at 4 years vs 87%; P <.0001 for both comparisons). Ratio of aneurysm-related to unrelated death was 23%, 21%, and 50% in groups A, B, and C, respectively. Cox models demonstrated that the correlation between large aneurysms (group C) and all assessed outcome events was independent and highly significant. Older generation devices had an independent association with aneurysm-related and unrelated deaths (P =.02 and P =.04, respectively). However, this correlation was less strong than large aneurysm diameter (P =.0001 and P =.0009, respectively).

CONCLUSIONS

The midterm outcome of large aneurysms after EVAR was associated with increased rates of aneurysm-related death, unrelated death, and rupture. Reports of EVAR should stratify their outcomes according to the diameter of the aneurysm. Large aneurysms need a more rigorous post-EVAR surveillance schedule than do smaller aneurysms. In small aneurysms EVAR was associated with excellent outcome. This finding may justify reappraisal of currently accepted management strategies.

Factors Affecting the Displacement Force Exerted on a Stent Graft after AAA Repair—An In vitro Study

OBJECTIVES

To investigate the distraction forces affecting grafts used to treat abdominal aortic aneurysms in an in vitro model.

METHOD

Using a standard cardiac pump and a rigid plastic circulation system, distraction forces were measured with a gramometer attached to a PTFE graft while the pressure inside a rigid aortic sac was varied.

RESULTS

If the pressure in the 'aneurysm sac' is maintained at the same level as the systemic pressure, the displacement force is zero. The displacement force is affected adversely by the level of systemic pressure, as this rises the displacement forces rise in an almost linear fashion.

CONCLUSIONS

These observations may have important consequences for stent graft design and use in vivo pressurisation of a sealed sac may therefore not necessarily be an adverse event. Systemic hypertension is obviously important and its control may be necessary to prevent graft migration.

Should patients with challenging anatomy be offered endovascular aneurysm repair?

OBJECTIVES

Treatment of abdominal aortic aneurysm is controversial in patients at high physiologic risk for open repair and high anatomic risk for endovascular repair. We compared outcome in patients at high risk because of anatomy (short or angulated neck), severe occlusive disease, or bilateral iliac aneurysms (group A) with outcome in patients at low risk (group B).

MATERIAL AND METHODS

Patients at high anatomic risk who underwent treatment between October 1998 and March 2002 with the Zenith endovascular graft (group A) were compared with patients at low anatomic risk enrolled in a prospective multicenter trial (group B). Variables compared included overall mortality, need for secondary interventions, development of endoleak, and change in aneurysm sac diameter. The chi(2) test, Student t test, and proportions analysis were used to assess the data.

RESULTS

Data for 493 patients (group A, 141; group B, 352) were evaluated. Mean follow-up was 9 months (range, 1-24 months). Perioperative mortality was similar for groups A and B (0.7% vs 1%). Frequency of endoleak was higher in patients with high-risk anatomy (25% vs 11%), but not significantly so (P >.06). The rate of aneurysm shrinkage, even in the absence of endoleak, was slower in group A (P <.05).

CONCLUSIONS

In physiologically challenged patients at higher anatomic risk for endovascular aneurysm repair, initial mortality rate is similar to that in patients at lower risk. Short-term technical results are acceptable. Decreased long-term survival (largely unrelated to the procedure), slightly higher frequency of endoleak, and a lower rate of sac shrinkage may temper enthusiasm for endovascular repair in this subgroup. Risks of repairing aneurysms in this patient population must be viewed in the context of expected results of intervention or medical observation.

Does hostile neck anatomy preclude successful endovascular aortic aneurysm repair?

OBJECTIVES

Poor outcomes have been reported with endovascular aneurysm repair (EVAR) in patients with hostile neck anatomy. Unsupported endografts with active fixation may offer certain advantages in this situation. We compared EVAR results using the Ancure (Guidant) endograft in patients with and without hostile neck anatomy.

METHODS

Records of EVAR patients from October 1999 to July 2002 at a tertiary care hospital were retrospectively reviewed from a division database. Patients with elective open abdominal aortic aneurysm (AAA) repair during the same period were reviewed to determine those unsuitable for EVAR. Hostile neck anatomy, assessed by computer tomography (CT) scans and angiograms, was defined as one or more of the following: (1) neck length </=10 mm, (2) focal bulge in the neck >3 mm, (3) >2-mm reverse taper within 1 cm below the renal arteries, (4) neck thrombus > or =50% of circumference, and (5) angulation > or =60 degrees within 3 cm below renals.

RESULTS

Three hundred and twenty-two patients underwent EVAR with an average follow-up of 18 months. Patients in Phase II trials (n = 41), repaired with other graft types (n = 48), or without complete anatomic records (n = 27) were excluded. Demographics and co-morbidities were similar in the 115 good-neck (GN) and 91 bad-neck (BN) patients except for age (mean, 72.9 years GN vs 75.7 BN; P = 0.13), gender (11% female GN vs 22% BN; P =.04); neck length (mean, 21.8 mm GN vs 14.4 mm BN: P <.001), and angulation (mean, 22 degrees GN vs 40 degrees BN; (P <.001). Perioperative mortality (0 GN vs 1.1% BN), late mortality (5.2% GN vs 4.4% BN), all endoleaks (19.1% GN vs 17.6% BN), proximal endoleaks (0.8% GN vs 2.1% BN), and graft migration (0 for both groups) did not reach statistical significance. Neck anatomy precluded EVAR in 106 of 165 (64%) patients with open AAA.

CONCLUSIONS

Unsupported endografts with active fixation can yield excellent results in treating many medically compromised patients with hostile neck anatomy. Nonetheless, an unsuitable neck remains the most frequent cause for open abdominal AAA.

Aortoiliac morphologic correlations in aneurysms undergoing endovascular repair

PURPOSE

The feasibility of endovascular aneurysm repair depends on morphologic characteristics of the aortoiliac segment. Knowledge of such characteristics is relevant to safe deployment of a particular device in a single patient and to development of new devices for use in patients with a broader spectrum of anatomic variations.

METHODS

We evaluated findings on computed tomography scans for 277 patients being considered for endovascular aneurysm repair. Aortic neck length and angulation estimates were generated with three-dimensional trigonometry. Specific centerline points were recorded, corresponding to the aorta at the celiac axis, lowest renal artery, cranial aspect of the aneurysm sac, aortic terminus, right hypogastric artery origin, and left hypogastric origin. Aortic neck thrombus and calcium content were recorded, and neck conicity was calculated in degrees. Statistical analysis was performed with the Spearman rank correlation. Data are expressed as median and interquartile range.

RESULTS

Median diameter of the aneurysms was 52 mm (interquartile range, 48-59 mm) in minor axis and 56 mm (interquartile range, 51-64 mm) in major axis, and median length was 88 mm (interquartile range, 74-103 mm). Median proximal aortic neck diameter was 26 mm (interquartile range, 22-29 mm), and median neck length was 30 mm (interquartile range, 18-45 mm). The common iliac arteries were similar in diameter (right artery, 16 mm [interquartile range, 13-20 mm]; left artery, 15 mm [interquartile range, 11-18 mm]) and length (right, 59 mm [interquartile range, 50-69 mm]; left, 60 mm [interquartile range, 49-70 mm]). Median angulation of the infrarenal aortic neck was 40 degrees (interquartile range, 29-51 degrees), and median angulation of the suprarenal segment was 45 degrees (interquartile range, 36-57 degrees). By gender, sac diameter, proximal neck diameter, and iliac artery diameter were significantly larger in men. Significant linear associations were identified between sac diameter and sac length, neck angulation, and iliac artery diameter. As the length of the aneurysm sac increased the proximal aortic neck length decreased. Conversely, as the sac length decreased sac eccentricity increased. Mural thrombus content within the neck increased with increasing neck diameter.

CONCLUSIONS

There is considerable variability in aortoiliac morphologic parameters. Significant associations were found between various morphologic variables, links that are presumably related to a shared pathogenesis for aberration in aortoiliac diameter, length, and angulation. Ultimately this information can be used to develop new endovascular devices with broader applicability and improved long-term results.

Endoluminal AAA repair using intravascular ultrasound for graft planning and deployment: a 2-year community-based experience

PURPOSE

To examine the effectiveness of intravascular ultrasound (IVUS) and digital subtraction angiography (DSA) for preoperative planning and intraoperative deployment of stent-grafts to treat abdominal aortic aneurysms.

METHODS

One hundred seventy patients (143 men; mean age 73.6+/-7.2 years, range 51-89) underwent successful DSA and IVUS to determine suitability for stent-graft repair. Patients subsequently received the AneuRx (n=157) or Ancure (n=13) device; intraprocedural IVUS was used to survey the proximal endograft for proper apposition to the aortic wall.

RESULTS

Reliable preoperative IVUS measurements were obtained in all patients. Plaque morphology was assessed in 140 (82.3%) aortic necks; in 36 (25.7%), preoperative IVUS showed high-grade atherosclerotic plaque in the nonaneurysmal abdominal aortic neck. The procedure was successful in 168 (98.8%) cases (1 [0.6%] acute conversion and 1 access failure). There were 2 (1.2%) periprocedural deaths related to bowel ischemia. Four (2.3%) patients developed graft occlusion/kinking and 2 (1.2%) developed renal failure requiring dialysis within 30 days. Multivariate logistic regression analysis revealed that female gender (p=0.0247), a short nonaneurysmal aortic neck (p=0.0185), and presence of high-grade atherosclerotic plaque (p=0.0185) correlated with major acute complications. Over a mean 10.4-month follow-up (range 1-25), 11 patients died of unrelated causes; there was no known AAA rupture or device failure. The Kaplan-Meier estimate of survival at 1 year was 91.0%+/-2.8%. Sixteen (9.4%) patients underwent 17 secondary procedures for endoleak or graft limb occlusion at a mean 5.4 months after stent-graft repair (freedom from secondary intervention at 1 year 86.5%+/-3.2%).

CONCLUSIONS

Our findings suggest that IVUS may identify patients at increased risk of major adverse complications following endovascular repair. The combination of IVUS and DSA for endoluminal stent-graft planning and placement provides excellent short- and mid-term patient outcomes.

Long-term outcome after aortic endovascular repair: the Buenos Aires experience

Long-term (5 years) outcome of 30 patients whose aneurysm was excluded using the Parodi endograft (PE) was assessed. Thirty patients with a mean follow-up of 59 months were the basis of the analysis. Additionally, 100 consecutive patients treated with the Vanguard Endograft (VE) were followed up for 28 months (range, 7 to 56 months). Results were analyzed and both groups compared. There were no late failures related to the loss of the integrity of the device in the PE group. Aorto aortic systems showed distal neck dilatation in high proportion of patients (80%). Aorto-uni-iliac endograft was successful in 80% of the patients. Only one late type I endoleak developed in a patient in whom the proximal stent was placed far from the renal arteries and in contact with thrombus. Also, persistent type II endoleaks were the cause of failure. No neck dilatation was noted. In the VE group, most of the failures were device related.

Renal perfusion defects after endovascular repair of abdominal aortic aneurysms

PURPOSE

To determine the prevalence of new renal perfusion defects and the association of these events with aneurysm neck atheroma during endovascular stent-graft repair of abdominal aortic aneurysm (AAA).

MATERIALS AND METHODS

A retrospective review was performed of 50 patients who underwent AAA repair with bifurcated endovascular stent-grafts without suprarenal components between June 1998 and May 1999. Pre- and postprocedural computed tomographic (CT) angiograms were reviewed to determine the prevalence of new renal perfusion defects. The percent volume of atheroma of the aneurysm neck was determined by three-dimensional volumetric reformation and correlated with prevalence of new postprocedural renal perfusion defects. Follow-up CT angiography was performed between 6 months and 2 years after the procedure and used to evaluate the presence of residual defects and interval changes.

RESULTS

Of 50 subjects, 18% (n = 9) had new perfusion defects presumed to be embolic in origin. Follow-up was available for four patients: scarring and cortical thinning consistent with infarction developed in two, whereas the defects resolved in the other two. Analysis of aneurysm neck revealed an average percentage of atheroma of 32% and a range of 0%-73%. In subjects with >/=40% neck atheroma, the prevalence of new renal perfusion defects was 45.4% (five of 11), compared to 10.3% (four of 39) in subjects with <40% neck atheroma. This difference was significant (P =.0170).

CONCLUSIONS

In this series, the frequency of renal embolic events associated with AAA endovascular repair was 18%. Prevalence of renal embolic perfusion defects was shown to correlate with volume of aneurysm neck atheroma.

Aneurysm neck diameter after endovascular repair of abdominal aortic aneurysms

PURPOSE

To determine aneurysm neck diameter change after endovascular repair (EVR) of abdominal aortic aneurysm (AAA) and its relationship to stent-graft diameter.

MATERIALS AND METHODS

The cases of 73 patients with AAAs who underwent EVR were reviewed retrospectively: 68 had preoperative imaging available. Neck diameter was reviewed by a single observer (M.F.B.) on preoperative, immediate postoperative, annual, and most recent contrast-enhanced computed tomographic scans. Baseline and follow-up neck diameters were compared with the manufacturers' values for unconstrained stent-graft diameters.

RESULTS

Intraobserver error was 2 mm. Aneurysm neck diameter increased from 21.8 mm (range, 17-28 mm) at baseline to 22.8 mm (range, 19-30 mm) postoperatively and 25.8 mm (range, 19-31 mm; P <.001) at a mean follow-up of 25.5 months (range, 6.2-60.8 mo). Neck diameter increase was more than 2 mm in 24 patients (33%). Mean change in the first, second, third, and fourth years was +1.63 mm, +0.52 mm, +0.25 mm, and +0.33 mm, respectively. Baseline mean stent-graft oversizing was 2.9 mm (13.7%; range, -1 to +8 mm), which decreased to 0.7 mm (range, -4 to +6 mm) at latest follow-up. Neck diameter exceeded stent-graft diameter (mean, 1.8 mm; range, 1-4 mm) in 21 cases (28%) and by more than 2 mm in five cases (6.8%). When neck diameter change was correlated with change in sac diameter, it was found to be insignificant (P =.24); however, it was significantly correlated with baseline oversizing (P =.01).

CONCLUSIONS

After EVR, the aneurysm neck dilates, mostly in the first 2 years, by greater than 2 mm in one third of patients. This is possibly related to the presence of the endograft. The associated reduction of stent-graft oversizing warrants continued vigilance for proximal endoleak.

Eligibility rates of ruptured and symptomatic AAA for endovascular repair

PURPOSE

To determine the anatomical eligibility rate for endovascular repair of ruptured and symptomatic abdominal aortic aneurysms (AAA) using commercially available endografts.

METHODS

In a retrospective review, 28 preoperative computed tomographic (CT) scans were examined from among 83 patients who underwent surgical repair of a ruptured or acutely symptomatic AAA at a university-based tertiary care center during the past 10 years. The proximal aortic neck, aneurysm, and iliac dimensions were compared to corresponding measurements from 100 preoperative CT scans from patients who underwent elective repair of asymptomatic AAA. Based on expanded selection criteria for the 2 FDA-approved endografts (AneuRx and Ancure), eligibility rates for endovascular repair were compared between patients with ruptured/symptomatic and asymptomatic AAAs.

RESULTS

The proximal neck of the ruptured/symptomatic AAAs was on the average 2 mm larger in diameter (25 +/- 4 versus 23 +/- 3 mm, p=0.04) and 7 mm shorter (16 +/- 10 versus 23 +/- 14, p=0.017) than asymptomatic AAAs. The maximum AAA diameter was significantly larger in the ruptured/symptomatic group (64 +/- 16 mm) than in the asymptomatic group (58 +/- 11 mm, p=0.033). Of the 28 ruptured/symptomatic AAAs assessed morphologically, 13 (46%) were anatomically eligible for endovascular repair compared to 74 of the 100 asymptomatic AAAs (p=0.006). The main cause for exclusion was an unfavorable proximal neck, which was present in 15 (54%) of the 28 ruptured/symptomatic AAAs and in 24 (24%) of the 100 asymptomatic AAAs (p=0.003).

CONCLUSIONS

A significantly smaller proportion of patients presenting with ruptured/symptomatic AAA are anatomically eligible for endovascular AAA repair compared to patients with asymptomatic AAA due to unfavorable proximal neck anatomy.

Device migration after endoluminal abdominal aortic aneurysm repair: analysis of 113 cases with a minimum follow-up period of 2 years

PURPOSE

Device migration (DM) has been shown to cause late failure after endoluminal abdominal aortic aneurysm (AAA) repair. To establish the incidence rate and the predictive factors of distal migration of the proximal portion of the endograft, computed tomographic (CT) scans performed at different time intervals during follow-up examination of 113 patients were reviewed.

PATIENTS AND METHODS

Between April 1997 and March 1999, 148 patients underwent endoluminal AAA repair with a modular endograft with infrarenal fixation (Medtronic-AVE AneuRx, Santa Rosa, Calif) at our unit. CT scans performed at 1, 6, and 12 months after surgery and yearly thereafter were prospectively stored in a computer imaging database. Patient demographics, risk factors, operative details, and follow-up events were prospectively collected. No patients were lost to follow-up examination. Twelve patients died within 2 years of surgery, four patients underwent immediate conversion to open repair, and adequate CT measurements were not feasible in 19 cases, which left 113 patients available for a minimum 2-year assessment and 418 CT scan results reviewed. Two vascular surgeons, blinded to patient identity and history with tested interobserver agreement (kappa = 0.64), separately reviewed axial reconstructions of CT scans. DM was defined as changes of 10 mm or more in the distance between the lower renal artery and the first visible portion of the endograft at follow-up examination. Ten possible independent predictors of DM were analyzed with multivariate Cox proportional hazards regression model.

RESULTS

One AAA rupture, which was successfully treated, occurred at a mean follow-up period of 28 months (range, 24 to 46 months). Seventeen patients (15%) showed DM. Eight patients (47%) with DM underwent reintervention: a proximal cuff was positioned in six patients and late conversion to open repair was performed in two patients. Of the 10 variables analyzed with Cox proportional hazards regression model, AAA neck enlargement of more than 10% after endoluminal repair (hazard ratio, 7.3; confidence interval, 1.8 to 29.2; P =.004) and preoperative AAA diameter of 55 mm or more (hazard ratio, 4.5; confidence interval, 1.2 to 16.7; P =.02) were positive independent predictors of DM. The probability of DM at 36 months was 27% according to life table analysis.

CONCLUSION

DM occurred in a significant portion of our patients, yet aggressive follow-up examination and a high reintervention rate prevented aneurysm-related death. According to our data, dilatation of the infrarenal aortic neck is an important factor that contributes to the distal migration of stent grafts, and patients with large aneurysms are at high risk for DM.

An in situ adjustable endovascular graft for the treatment of abdominal aortic aneurysms

Twenty-nine patients underwent placement of the Teramed Ariba Endovascular Graft System (Maple Grove, Minn) as part of a European Feasibility study (14 patients) and a US phase I trial (15 patients). Salient features of this modular endograft system include a crimped seamless polyester bifurcation graft supplied in three diameters and three iliac limb lengths, three types of nitinol stents including a suprarenal stent with aortic barbs, a flexible delivery system capable of controlled incremental sheath retraction, a flexible tapered lead balloon, and a telescoping technique for adjusting the length of graft coverage during surgery over a range of 3 cm. Twenty-eight of the 29 patients met the primary objective of this evaluation, which was to confirm the safety of the system, defined as the absence of major device-related adverse events and type I, III, or IV endoleaks within 1 month of implantation. Three major adverse events occurred within 1 month of discharge: renal failure, which was related to deployment of the device close to the renal arteries; pulmonary edema, which was related to the procedure but not the device; and peripheral ischemia, which was related to the patient's pre-existing condition. Seven patients had type II endoleaks noted by means of computed tomography scanning at 1 month; the endoleaks were identified by means of angiography and classified at the time of surgery. There were no deaths, aneurysm ruptures, stent-graft migrations, stent fractures, graft ruptures, graft thromboses, or surgical conversions at 1 month. This early clinical experience indicates that the Ariba Bifurcated Endovascular System can be safely implanted.