Mid-term fixation stability of the EndoVascular Technologies endograft. EVT Investigators

Iliac fixation inhibits migration of both suprarenal and infrarenal aortic endografts

OBJECTIVE

To evaluate the role of iliac fixation in preventing migration of suprarenal and infrarenal aortic endografts.

METHODS

Quantitative image analysis was performed in 92 patients with infrarenal aortic aneurysms (76 men and 16 women) treated with suprarenal (n = 36) or infrarenal (n = 56) aortic endografts from 2000 to 2004. The longitudinal centerline distance from the superior mesenteric artery to the top of the stent graft was measured on preoperative, postimplantation, and 1-year three-dimensional computed tomographic scans, with movement more than 5 mm considered to be significant. Aortic diameters were measured perpendicular to the centerline axis. Proximal and distal fixation lengths were defined as the lengths of stent-graft apposition to the aortic neck and the common iliac arteries, respectively.

RESULTS

There were no significant differences in age, comorbidities, or preoperative aneurysm size (suprarenal, 6.0 cm; infrarenal, 5.7 cm) between the suprarenal and infrarenal groups. However, the suprarenal group had less favorable aortic necks with a shorter length (13 vs 25 mm; P < .0001), a larger diameter (27 vs 24 mm; P < .0001), and greater angulation (19 degrees vs 11 degrees ; P = .007) compared with the infrarenal group. The proximal aortic fixation length was greater in the suprarenal than in the infrarenal group (22 vs 16 mm; P < .0001), with the top of the device closer to the superior mesenteric artery (8 vs 21 mm; P < .0001) as a result of the 15-mm uncovered suprarenal stent. There was no difference in iliac fixation length between the suprarenal and infrarenal groups (26 vs 25 mm; P = .8). Longitudinal centerline stent graft movement at 1 year was similar in the suprarenal and infrarenal groups (4.3 +/- 4.4 mm vs 4.8 +/- 4.3 mm; P = .6). Patients with longitudinal centerline movement of more than 5 mm at 1 year or clinical evidence of migration at any time during the follow-up period comprised the respective migrator groups. Suprarenal migrators had a shorter iliac fixation length (17 vs 29 mm; P = .006) and a similar aortic fixation length (23 vs 22 mm; P > .999) compared with suprarenal nonmigrators. Infrarenal migrators had a shorter iliac fixation length (18 vs 30 mm; P < .0001) and a similar aortic fixation length (14 vs 17 mm; P = .1) compared with infrarenal nonmigrators. Nonmigrators had closer device proximity to the hypogastric arteries in both the suprarenal (7 vs 17 mm; P = .009) and infrarenal (8 vs 24 mm; P < .0001) groups. No migration occurred in either group in patients with good iliac fixation. Multivariate logistic regression analysis revealed that iliac fixation, as evidenced by iliac fixation length (P = .004) and the device to hypogastric artery distance (P = .002), was a significant independent predictor of migration, whereas suprarenal or infrarenal treatment was not a significant predictor of migration. During a clinical follow-up period of 45 +/- 22 months (range, 12-70 months), there have been no aneurysm ruptures, abdominal aortic aneurysm-related deaths, or surgical conversions in either group.

CONCLUSIONS

Distal iliac fixation is important in preventing migration of both suprarenal and infrarenal aortic endografts that have longitudinal columnar support. Secure iliac fixation minimizes the risk of migration despite suboptimal proximal aortic neck anatomy. Extension of both iliac limbs to cover the entire common iliac artery to the iliac bifurcation seems to prevent endograft migration.

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.

Effect of improved endograft design on outcome of endovascular aneurysm repair

OBJECTIVE

This study was undertaken to identify factors that lead to improvements in the results of endovascular aneurysm repair, with particular focus on new endograft design.

METHODS

We analyzed data for patients enrolled in the European Collaborators on Stent Graft Techniques for Abdominal Aortic Aneurysm Repair (EUROSTAR) registry, and compared those for endografts now withdrawn from the market with those for endografts currently in use. Patients in whom a variety of endograft types were used in small numbers were excluded. Postoperative and long-term outcomes were initially compared with univariate analyses, and subsequently multivariate tests were used to adjust for baseline differences between the 2 groups. The main outcome measures were freedom from a variety of secondary interventions, aneurysm rupture, and death.

RESULTS

Some 1224 patients received "withdrawn" endografts, and 2768 patients received "current" endografts. The 2 groups were generally similar, but patients with current devices were more often men, significantly older, more frequently unfit for open surgery, and had larger aneurysms with wider necks. Of no surprise, current endografts were also more often used by experienced (>60 previous cases) surgical teams (44% vs 20%; P <.0001). Thirty-day clinical outcomes were comparable in the 2 groups, although patients with withdrawn devices were less likely to have type II endoleak (9.2% vs 5.5%; P <.0001), and those with current devices had a shorter mean hospital stay (5.4 vs 6.8 days; P <.0001). At 3 years more patients with current devices were free from secondary transfemoral intervention (88.4% vs 76%; P <.0001) and conversion to open repair (95.4% vs 93.4%; P =.007). Aneurysm-related mortality at 3 years, defined as death due to aneurysm rupture or within 30 days of a secondary intervention, was also less frequent with current endografts (2.7% vs 4.4%; P =.02). Aneurysm rupture at 3 years was infrequent (0.8% vs 1.8%; P =.07). At multivariate analysis the use of current devices was a protective factor against late conversion to open repair (hazard ratio, 0.49; 95% confidence interval, 0.28-0.86; P =.014) and aneurysm-related death (hazard ratio, 0.51, 95% confidence interval, 0.34-0.75; P =.0008). Larger aneurysm or neck diameter and shorter neck length were also associated with late conversion to open repair; larger aneurysm diameter, older age, and unfitness for open surgery were predictive of aneurysm-related death.

CONCLUSION

Modern endograft design has improved the results of endovascular aneurysm repair.

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.

Stent-graft migration after endovascular repair of abdominal aortic aneurysm

PURPOSE

To report the incidence of graft migration in patients after endovascular repair of abdominal aortic aneurysms (AAA) and assess the significance of neck diameter changes in patients with and without suprarenal stent implantation.

METHODS

The medical records and imaging studies of 176 consecutive patients (175 men; median age 71 years, range 48-88) who had endovascular AAA repair with the Nottingham aortomonoiliac system were reviewed. The following parameters were recorded: preoperative neck diameter and length, presence of intraoperative and late graft migrations, time to onset of late migration, length of late migration, and neck diameter changes in patients with documented late graft migration. The patients were divided into 2 groups based on the placement of an endograft with or without suprarenal bare stent fixation. Median follow-up was 15 months (range 1-48).

RESULTS

There were 15 (8.5%) graft migrations (6 intraoperative and 9 late). Of those, 14 (10.9%) were in the 128-patient infrarenal fixation group and 1 (2.1%) in the 48-patient suprarenal stent group. Median neck diameters on preoperative and postoperative computed tomography scans in patients with late migration were 22.2 mm and 23.0 mm, respectively (p>0.05). The median time to graft migration was 14 months after the original operation (range 6-36).

CONCLUSIONS

Distal device migration occurred frequently with the Nottingham system. Late graft migration was not associated with neck enlargement. Endografts with a suprarenal stent may have a decreased incidence of graft migration.

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.

Histological changes in canine aorta 1 year after stent-graft implantation: implications for the long-term stability of device anchoring zones

PURPOSE

To examine aortic histology 1 year after stent-graft implantation in a canine model as a means of assessing the durability of endograft fixation.

METHODS

Fourteen mongrel dogs each received 1 stent-graft and 1 bare stent placed endoluminally in the abdominal aorta. Eight animals were followed for 1 year, 3 for 4 to 8 weeks, and the remaining 3 for 24 to 48 hours. Aortic specimens were stained with hematoxylin-eosin, elastica-van Gieson, and Masson's trichrome and examined with light and electron microscopy and immunohistochemistry to identify smooth muscle cells (SMC), endothelialization, aortic wall ultrastructure, and changes at the device anchoring sites.

RESULTS

No dilatation or dissection was noted at any of the device anchoring sites. The aortic media at 1 year was remarkably decreased in thickness: 891 +/- 196 microm in the control tissue versus 388 +/- 70 microm for the proximal stent-grafted aorta and 457 +/- 148 microm for the bare-stented aortic segment. Other important histological features were reduced elastic lamellae in the stent-grafted aorta versus control (p<0.0001), increased SMC density in the stent-grafted aortic region (p<0.0001 versus control), and absence of inflammatory infiltrate. Complete neointimal covering and endothelialization of the luminal endograft surface were found. SMCs generally showed no ultrastructural features of necrosis.

CONCLUSIONS

Aortic stent-grafts induce distinctive histological changes in the aortic wall at 1 year, even when implanted in a healthy aorta. Although there is considerable medial elastin loss, an increased medial SMC density, an exuberant neointima, and a general absence of perigraft inflammation suggest an ongoing process of structural restoration at the device anchoring sites.

Three year single centre experience with the AneuRx aortic stent graft

OBJECTIVES

To report the mid-term single-centre experience with the AneuRx self-expandable nitinol stentgraft for endovascular aneurysm repair.

PATIENTS AND METHODS

Between December 1996 and January 2000 a total of 128 patients were treated with an AneuRx bifurcated stentgraft. Of these, 77 patients had a minimum follow-up of 12 months. Patient operative and follow-up data were prospectively gathered.

RESULTS

Two (3%) conversions were necessary. Median hospital stay was 3 days. One superficial wound infection occurred. Periprocedural (30 days) mortality was 5% (four patients). Three graft occlusions were noted of which two required treatment. Fifteen patients developed 18 endoleaks (six type 1, eight type 2 and four type 3). Type 1 and type 3 endoleaks were treated by extension cuffs. Four type 2 endoleaks were treated with embolisation or direct lumbar puncture. Two-year freedom from endoleak was 76%. Graft migration occurred in six cases, resulting in a 2-year freedom from migration of 90%, kinking only once.

CONCLUSIONS

endovascular AAA treatment is feasible and so far mid-term results are without major problems. Extensive follow-up is essential as secondary problems may occur later. Long-term results are to be awaited.

Endoluminal stent grafts in the management of infrarenal abdominal aortic aneurysms: a realistic assessment

OBJECTIVES

transfemoral endoluminal aortic management (TEAM) is technically feasible in the treatment of infrarenal abdominal aortic aneurysms but its advantage over conventional repair is unproved. We report our initial experience, learning curve and technical difficulties encountered during the process of establishing this novel technique in our institute.

MATERIAL AND METHODS

over a 3-year period 400 cases of abdominal aortic aneurysms were reviewed; only 58 cases (15%) were suitable for endovascular repair under our TEAM protocol and 36 (9%) were offered endovascular intervention. They were mainly high-risk patients (85% ASA III and IV) with a mean age of 72 years. Thirty-three bifurcated grafts, two straight tube grafts and one aorto mono-iliac graft were deployed. We oversized the graft by 15-20% to the diameter of the aortic neck and both common iliac arteries.

RESULTS

two cases (6%-95% CI: 1-19%) had on-table conversion because of ruptured common iliac arteries. Peri-operatively there were two deaths from multi-organ failure. Transient renal failure occurred in two patients and three patients (9%) suffered a non-fatal myocardial infarction. Sixteen percent of patients had a groin wound problem. The mean hospital stay was 7 days. Five minor endoleaks (15%) were identified and sealed at 30 days. One secondary endoleak was identified at 18 months because of a patent juxta-renal lumbar artery. No secondary cuffs or extensions were used. Mean follow-up was 29 months and all grafts remained patent. The technical, clinical, continuous and secondary success rates were 78%, 91%, 89% and 91% respectively with TEAM.

CONCLUSION

endovascular training, patient selection and learning curve impose an impact on the final outcome. Until a reliable hard point is reached so that endovascular repair could be exercised in routine practice, the use of TEAM must be questioned in high-risk patients, and should be performed under clinical trial conditions using strict selection criteria.