The impact of stent-graft development on outcome of AAA repair--a 7-year experience

Adverse Events at the Aneurysmal Neck Identified at Follow-Up after Endovascular Abdominal Aortic Aneursym Repair: How Do They Correlate?

The objective of this study was to assess the prevalence of and the correlation between dilatation of the infrarenal neck and proximal device migration after endovascular abdominal aortic aneurysm repair (EVAR). The analysis made use of the EUROSTAR registry.

Between 1994 and 2004, 4,233 patients with an abdominal aortic aneurysm larger than 4 cm underwent EVAR. Only patients with available follow-up data regarding neck size and device position were included in this assessment. Chi-square and t-tests or Wilcoxon rank sum tests were used for comparison of discrete and continuous variables, respectively. Time-dependent variables were evaluated by log-rank tests. In addition, multivariate analysis was performed to determine anatomic and operative variables with an independent correlation with neck growth and device migration, respectively. In addition, the association with proximal endoleak was assessed.

Neck dilatation and proximal migration were found in 1,342 (32%) and 192 (4.5%) of the 4,233 patients, respectively. One hundred twelve patients (2.5%) had neck dilatation and migration of the proximal device extremity. The correlation between proximal migration and neck dilatation was statistically significant ( p < .0001). Other independent variables for migration were a wider neck and aneurysmal diameter, shorter necks, proximal endoleak, and absence of suprarenal fixation. Neck dilatation was predicted by narrow necks, use of devices with suprarenal fixation, and larger device diameters. Proximal endoleak occurred in 136 (3.2%) patients and was significantly associated with shorter, angulated necks and proximal migration.

The present study documented that migration may be caused by neck dilatation. However, neck dilatation was not significantly promoted by proximal migration. Other factors, such as dimensions of the neck, the device fixation system, and perhaps progressive wall degeneration, are also likely to play a role in the pathogenesis of neck dilatation. To obtain good results from EVAR, accepted criteria of neck dimensions should be adhered to.

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.

Is there a benefit of frequent CT follow-up after EVAR?

OBJECTIVE

Imaging follow-up (FU) after endovascular aneurysm repair (EVAR) is usually performed by periodic contrast-enhanced computed tomography (CT) scans. This study aims to evaluate the effectiveness of CT-FU after EVAR.

METHODS

In this study, 279 of 304 consecutive patients (261 male, aged 74 years (interquartile range (IQR): 70-79 years) with a median abdominal aortic aneurysm (AAA) diameter of 58 mm (IQR: 53-67 mm)) underwent at least one of the yearly CT scans and plain abdominal films after EVAR. All patients received Zenith stent-grafts for non-ruptured AAAs at a single institution. Patients were considered asymptomatic when a re-intervention was done solely due to an imaging FU finding. The data were prospectively entered in a computer database and retrospectively analysed.

RESULTS

As a follow-up, 1167 CT scans were performed at a median of 54 months (IQR: 34-74 months) after EVAR. Twenty-seven patients exhibited postoperative AAA expansion (a 5-year expansion-free rate of 88+/-2%), and 57 patients underwent 78 postoperative re-interventions with a 5-year secondary success rate of 91+/-2%. Of the 279 patients, 26 (9.3%) undergoing imaging FU benefitted from the yearly CT scans, since they had re-interventions based on asymptomatic imaging findings: AAA diameter expansion with or without endoleaks (n=18), kink in the stent-graft limbs (n=4), endoleak type III due to stent-graft limb separation without simultaneous AAA expansion (n=2), isolated common iliac artery expansion (n=1) and superior mesenteric artery malperfusion due to partial coverage by the stent-graft fabric (n=1).

CONCLUSIONS

Less than 10% of the patients benefit from the yearly CT-FU after EVAR. Only one re-intervention due to partial coverage of a branch by the stent-graft would have been delayed if routine FU had been based on simple diameter measurements and plain abdominal radiograph. This suggests that less-frequent CT is sufficient in the majority of patients, which may simplify the FU protocol, reduce radiation exposure and the total costs of EVAR. Contrast-enhanced CT scans continue, nevertheless, to be critical when re-interventions are planned.

Mid-Term Comparison of Bifurcated Modular Endograft Versus Aorto-Uni-Iliac Endograft in Patients with Abdominal Aortic Aneurysm

The aim of this prospective study was to compare the outcome of the Talent bifurcated endograft versus the Endofit aorto-uni-iliac endograft in the short-term and mid-term. Between March 2000 and December 2003, 86 patients were treated with the Talent bifurcated endograft (group A) and 21 with the Endofit aorto-uni-iliac endograft (group B) in the same institute by the same surgical team. All patients followed a prospective protocol of preoperative evaluation and postoperative follow-up. We compared groups A and B in terms of perioperative mortality and morbidity, mid-term endoleak rate, mid-term success rate, and mid-term survival. The perioperative mortality for group A was 1.63%, while that for group B was 0% (P = 0.62). The endoleak rate for group A was 4.65%, and that for group B was 14.29% (P = 0.135). The mid-term success rate was 96.5% for group A and 100% for group B (P = 0.386). There was no significant difference in outcome between the patients treated with the Talent and those treated with the Endofit endoprosthesis. Treating abdominal aortic aneurysms with aorto-uni-iliac endoprosthesis is as safe and effective as treating them with bifurcated endografts.

Systematic Review and Meta-analysis of 12 Years of Endovascular Abdominal Aortic Aneurysm Repair

BACKGROUND

Endovascular repair (ER) of abdominal aortic aneurysm (AAA) is a new technique, and reported rates of endoleak, conversion to open repair, rupture and mortality vary widely. The aim of this study was to estimate these rates from the published data, and examine how this has changed as more patients have undergone ER.

METHODS

A systematic review and meta-analysis of publications identified through searches of the electronic databases EMBASE and Medline. All publications quoting endoleak, conversion to open repair, rupture and mortality rates for a series of patients undergoing ER were included.

RESULTS

163 studies pertaining to 28,862 patients undergoing ER were identified as relevant for the review and meta-analysis. The pooled estimate for operative mortality was 3.3% (95% confidence interval 2.9 to 3.6%). The pooled estimate for type 1 endoleaks was 10.5% (95% confidence interval 9.0 to 12.1%), with an annual rate of 8.4% (95% confidence interval 5.7% to 12.2%). The pooled estimate of type 2,3 and 4 endoleaks was 13.7% (95% confidence interval 12.3 to 15.3%), with an annual rate of 10.2% (95% confidence interval 7.4% to 14.1%). The pooled estimate for primary conversion to open repair was 3.8% (95% confidence interval 3.2 to 4.4%), and for secondary conversion to open repair 3.4% (95% confidence interval 2.8 to 4.2%). The pooled estimate for post-operative rupture was 1.3% (95% confidence interval 1.1 to 1.7%), with an annual rupture rate of 0.6% (95% confidence interval 0.5% to 0.8%). Multivariate meta-regression analysis showed that rates of operative mortality, post-operative rupture and total number of endoleaks all fell significantly (p<0.05) over time.

CONCLUSIONS

This study demonstrates a low mortality and a gradual reduction in vascular morbidity and mortality associated with endovascular repair since it was first introduced.

Combined Staged Procedures for the Treatment of Thoracoabdominal Aneurysms

PURPOSE

To examine the efficacy of a staged approach for the treatment of thoracoabdominal aneurysms, with open visceral revascularization followed by aortic endografting, in selected patients not considered candidates for conventional surgical repair.

METHODS

A retrospective review was conducted of 13 consecutive patients (8 women; mean age 64 years, range 33-77) who underwent visceral bypass followed by endovascular thoracoabdominal stent-graft implantation since 1999. Three patients presented with symptomatic aneurysms and 2 with rupture. Two patients had connective tissue disorders. All patients were deemed unfit for conventional thoracoabdominal repair due to comorbid conditions. The procedures were tailored to the pathology and specific patient anatomical situation: 5 aortic dissections with aneurysmal degeneration and 8 aneurysms (5 Crawford type II, 2 type III, and 1 type IV).

RESULTS

The patients underwent retrograde visceral bypass (11 iliovisceral and 2 infrarenal aortic to visceral artery) followed by endovascular aortic relining with Zenith TX2 devices (n=7), homemade endografts (n=5), or a Talent thoracic endograft (n=1). Six patients required either a proximal or distal direct aortic repair (2 infrarenal reconstructions, 3 arch elephant trunk grafts, and 1 ascending aortic repair), while 3 patients also underwent left carotid-subclavian bypass grafting. Two patients developed paraplegia (1 following a ruptured aneurysm), and 2 patients had transient paraparetic events. Two patients had acute renal failure requiring short-term dialysis. Three patients died within 30 days; 2 late aneurysm-related deaths were noted. Three patients developed endoleaks during follow-up. Mean lengths of stay were 13 days (7-30) for the visceral bypass and 12 (3-25) for the endovascular stent-graft. In addition, remaining procedures in 8 patients required a mean of 7 days (0-14) in hospital.

CONCLUSION

Staged endovascular and open procedures are feasible for thoracoabdominal aneurysms in patients at prohibitive risk for open thoracoabdominal reconstruction. However, this approach still carries a significant risk of perioperative mortality and morbidity. The potential for less invasive alternatives should be investigated.

Risk-Adjusted Outcome Analysis of Endovascular Abdominal Aortic Aneurysm Repair in a Large Population:How Do Stent-Grafts Compare?

PURPOSE

To compare differences in the applicability and incidence of postoperative adverse events among stent-grafts used for repair of infrarenal aortic aneurysms.

METHODS

An analysis of 6787 patients from the EUROSTAR Registry database was conducted to compare aneurysm morphological features, patient characteristics, and postoperative events for the AneuRx, EVT/Ancure, Excluder, Stentor, Talent, and Zenith devices versus the Vanguard device (control) and each other. Annual incidence rates of complications were determined, and risks were compared using the Cox proportional hazards analysis.

RESULTS

The annual incidence rates were: device-related endoleak (types I and III) 6% (range 4%-10%), type II endoleak 5% (range 0.3%-11%), migration 3% (range 0.5%-5%), kinking 2% (range 1%-5%), occlusion 3% (range 1%-5%), rupture 0.5% (range 0%-1%), and all-cause mortality 7% (range 5%-8%). After adjustment for factors influencing outcome, AneuRx, Excluder, Talent, and Zenith devices were associated with a lower risk of migration, kinking, occlusion, and secondary intervention compared to the Vanguard device. Significant increased risk for conversion (EVT/Ancure) and reduced risk of aneurysm rupture (AneuRx and Zenith) and all-cause mortality (Excluder) were found compared to the Vanguard device.

CONCLUSIONS

Significant differences exist between stent-grafts of different labels in terms of applicability and complications during intermediate to long-term follow-up. Since each stent-graft has its drawbacks, no single label can be identified as the best. It is reassuring that developments in stent-grafts indeed result in better performance than the early stent-grafts. However, a single device incorporating all the perceived improvements should still be pursued.

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.

A mathematical model to predict the in vivo pulsatile drag forces acting on bifurcated stent grafts used in endovascular treatment of abdominal aortic aneurysms (AAA)

Endovascular treatment of abdominal aortic aneurysms (AAA) is a promising new alternative to the traditional surgical repair. However, the endovascular approach suffers problems such as stent graft migration, endoleaks and stent mechanism breakage. Fatigue failure is believed to be the major cause of stent graft migration and device breakage. Knowledge of the in vivo forces acting on such devices is a basic requirement for the design of a successful endovascular device. Using a Fourier series trigonometric fit of a typical pressure and flow relationship, a mathematical model, using the control volume method, was developed to predict the pulsatile drag forces acting on various bifurcated stent graft geometries. It was found that for an iliac angle of 30 degrees, a proximal diameter of 24 mm and an iliac diameter of 12 mm, the drag force varied, over the cardiac cycle, between 3.9 and 5.5 N in the axial direction. It was noted that for a specific iliac angle the drag force variation with proximal diameter approximates a quadratic fit, with an increase in proximal diameter producing an increase in drag force. The more compliant the aorta the higher the drag force. Previously published results demonstrated the axial loads (axial drag forces) required for stent graft migration for certain stents types are lower than the drag forces calculated in this study. It is believed that the results of this study can provide guidelines for the quantitative analyses of the in vivo drag forces experienced by stent grafts and could therefore be used as design criteria for such devices.

Cumulative sum failure analysis of the learning curve with endovascular abdominal aortic aneurysm repair

PURPOSE

The purpose of this study was to evaluate the importance of experience and the learning curve with endovascular abdominal aortic aneurysm (AAA) repair.

METHODS

A retrospective analysis was performed of all elective endovascular AAA repairs attempted by an individual surgeon and radiologist over a 4-year period. The primary outcome variable was achievement and 30-day maintenance of initial clinical success as defined by the Society for Vascular Surgery/American Association of Vascular Surgery reporting standards. Following standard statistical analysis, the cumulative sum (CUSUM) method was used to analyze the learning curve, with a predetermined acceptable failure rate of 10% and calculated 80% alert and 95% alarm lines.

RESULTS

Ninety-six elective endovascular AAA repairs were attempted by this team between 1998 and 2002 (mean age 74 +/- 0.8 years; mean aneurysm diameter 5.98 +/- 0.8 cm). Initial clinical success was achieved and maintained in 85 of 96 patients (88.5%). Although results were acceptable throughout the study period, improved results with respect to the target failure rate (10%) were not achieved until 60 patients were treated. The learning or CUSUM curves did not differ for different device manufacturers, with improved results being achieved following 20 implantations of each device. The results did differ when comparing aortouniiliac grafts (n = 27) and bifurcated grafts (n = 64). Results with bifurcated grafts remained consistent throughout the study period, whereas with aortouniiliac grafts, results improved after only a few procedures in comparison with the target failure rate.

CONCLUSION

Success rates with endovascular aneurysm repair will improve with an individual's experience. The CUSUM method is a valuable tool in the evaluation of this learning curve, which has credentialing and training implications. Although acceptable results were obtained throughout the study period, this analysis indicates that 60 endovascular aneurysm repairs, or 20 with an individual device, are necessary before optimal rates of initial clinical success can be achieved. These results can be achieved more readily with aortouniiliac grafts than with bifurcated grafts.

Does the wide application of endovascular AAA repair affect the results of open surgery?

PURPOSE

to examine the effect of the adoption of endovascular aneurysm repair (EVAR) on the outcome of open repair (OR).

METHODS

between May 1998 and December 2001, EVAR (Zenith) was performed in 117 patients, and OR was performed because of anatomic restrictions in 40 (group A), and because of young age in 11 patients (group B).

RESULTS

EVAR patients had higher ASA classifications (p < 0.0001). EVAR was associated with a 98.3% (115 patients) technical success rate, one conversion to OR and one fatal cardiac arrest. Thirty-day mortality was 2.6% (3 patients) in EVAR, 15% (6 patients) in group A and none in group B. There was no difference in late survival between the three groups. Late reinterventions, mainly endovascular, were more frequent in EVAR. At a median follow-up of 17 months one stent-graft had migrated 5 mm distally and five stents had fractured, but without clinical consequence.

CONCLUSIONS

EVAR provides good results even with inclusion of high-risk patients. The adoption of EVAR may adversely affect the results of OR offered to patients because of anatomic considerations. However, OR continues to be the first option for low-risk young patients.

The Zenith aortic stent-graft: a 5-year single-center experience

PURPOSE

To evaluate the efficacy and midterm results of the Zenith stent-graft in the treatment of abdominal aortic aneurysms (AAA).

METHODS

Since March 1994, 364 patients have undergone endovascular repair of infrarenal AAA. Of the 94 who were treated with the Zenith stent-graft from 1996 to 2002, 88 patients (82 men; mean age 72.6 +/- 6.5 years, range 47-88) with at least 6-month follow-up were analyzed. Sixty-one (69.3%) patients were considered at high risk for intervention; 7 ruptured AAAs were treated emergently. In all, 68 (77.3%) bifurcated stent-grafts (including 18 TriFab systems) and 20 aortomonoiliac configurations were used. Cumulative data on endoleak, migration, secondary procedures, and survival were evaluated with Kaplan-Meier analyses.

RESULTS

Implantation success was 97.7%; 2 (2.3%) access-related failures were converted to open repair (1 immediate, 1 at 3 months). There were 3 (3.4%) graft limb thromboses (2 immediate, 1 late), 3 (3.4%) cases of colon ischemia due to embolization in 1 and hypogastric artery occlusion in 2, and 1 (1.1%) renal infarction due to embolism. Three (3.4%) patients died within 30 days. Eleven (12.5%) endoleaks and 1 (1.1%) late endograft migration were recorded. The 5-year cumulative endoleak and migration rates were 15% and 7%, respectively. Sixty-three (71.6%) patients did not present any complication related to the repair during a mean follow-up of 20.6 +/- 14.9 months (range 6-68); notably, no complications were associated with the 18 TriFab systems. Six (6.8%) secondary procedures were performed (31% 5-year cumulative secondary procedural rate). All 6 (6.8%) aneurysm-related deaths (the 3 perioperative, 2 from late AAA rupture, and 1 during a secondary procedure) and 14 of 18 (20.4%) non-aneurysm-related deaths occurred in high-risk patients; the 5-year cumulative survival rates were 57% for any death and 92% for aneurysm-related deaths.

CONCLUSIONS

The Zenith stent-graft appears both safe and effective in terms of midterm outcome of endovascular aortic aneurysm repair.