Aneurysm neck diameter after endovascular repair of abdominal aortic aneurysms

Ultrasound elastography to quantify average percent pressure-normalized strain reduction associated with different aortic endografts in 3D-printed hydrogel phantoms

Objective

Strain has become a viable index for evaluating abdominal aortic aneurysm stability after endovascular aneurysm repair (EVAR). In addition, literature has shown that healthy aortic tissue requires a degree of strain to maintain homeostasis. This has led to the hypothesis that too much strain reduction conferred by a high degree of graft oversizing is detrimental to the aneurysm neck in the seal zone of abdominal aortic aneurysms after EVAR. We investigated this in a laboratory experiment by examining the effects that graft oversizing has on the pressure-normalized strain (ε ρ + ¯ /pulse pressure [PP]) reduction using four different infrarenal EVAR endografts and our ultrasound elastography technique. Approximate graft oversizing percentages were 20% (30 mm phantom-graft combinations), 30% (28 mm phantom-graft combinations), and 50% (24 mm phantom-graft combinations).

Methods

Axisymmetric, 10% by mass polyvinyl alcohol phantoms were connected to a flow simulator. Ultrasound elastography was performed before and after implantation with the four different endografts: (1) 36 mm polyester/stainless steel, (2) 36 mm polyester/electropolished nitinol, (3) 35 mm polytetrafluoroethylene (PTFE)/nitinol, and (4) 36 mm nitinol/polyester/platinum-iridium. Five ultrasound cine loops were taken of each phantom-graft combination. They were analyzed over two different cardiac cycles (end-diastole to end-diastole), yielding a total of 10 maximum mean principal strain (ε ρ + ¯ ) values.ε ρ + ¯ was divided by pulse pressure to yield pressure-normalized strain (ε ρ + ¯ /PP). An analysis of variance was performed for graft comparisons. We calculated the average percentε ρ + ¯ /PP reduction by manufacturer and percent oversizing. These values were used for linear regression analysis.

Results

Results from one-way analysis of variance showed a significant difference inε ρ + ¯ /PP between the empty phantom condition and all oversizing conditions for all graft manufacturers (F(3, 56) = 106.7 [graft A], 132.7 [graft B], 106.5 [graft C], 105.7 [graft D], P < .0001 for grafts A-D). There was a significant difference when comparing the 50% condition with the 30% and 20% conditions across all manufacturers by post hoc analysis (P < .0001). No significant difference was found when comparing the 20% and 30% oversizing conditions for any of the manufacturers or when comparingε ρ + ¯ /PP values across the manufacturers according to percent oversize. Linear regression demonstrated a significant positive correlation between the percent graft oversize and the all-graft average percentε ρ + ¯ /PP reduction (R 2  = 0.84, P < .0001).

Conclusions

This brief report suggests that a 10% increase in graft oversizing leads to an approximate 5.9% reduction inε ρ + ¯ /PP on average. Applied clinically, this increase may result in increased stiffness in axisymmetric vessels after EVAR. Further research is needed to determine if this is clinically significant.

A systematic review and meta-analysis of proximal aortic neck dilatation after endovascular abdominal aortic aneurysm repair

OBJECTIVE

To provide an updated systematic literature review summarizing current evidence on aortic neck dilatation (AND) after endovascular aortic aneurysm repair (EVAR) in patients with infrarenal abdominal aortic aneurysm.

METHODS

An extensive electronic search in major electronic databases was conducted between January 2000 and December 2021. Eligible for inclusion were observational studies that followed up with patients (n ≥ 20) undergoing EVAR with self-expanding endografts, for 12 or more months, evaluated AND with computed tomography angiography and provided data on relevant outcomes. The primary end point was the incidence of AND after EVAR, and the secondary end points were the occurrence of type Ia endoleak, stent graft migration, secondary rupture, and reintervention.

RESULTS

We included 34 studies with a total sample of 12,038 patients (10,413 men; median age, 71 years). AND was defined clearly in 18 studies, but significant differences in AND definition were evidenced. The pooled incidence of AND based on quantitative analysis of 16 studies with a total of 9201 patients (7961 men; median age, 72 years) was calculated at 22.9% (95% confidence interval [CI], 14.4-34.4) over a follow-up period ranging from 12 months to 14 years. The risk of a type Ia endoleak was significantly higher in AND patients compared with those without AND (odds ratio, 2.95; 95% CI, 1.10-7.93; P = .030). Similarly, endograft migration was more common in the AND group compared with the non-AND group (odds ratio, 5.95; 95% CI, 1.80-19.69; P = .004). The combined incidence of secondary rupture and reintervention did not differ significantly between the two groups, even though the combined effect was in favor of the non-AND group.

CONCLUSIONS

Proximal AND after EVAR is common and occurs in a large proportion of patients with infrarenal abdominal aortic aneurysm. AND can influence the long-term durability of proximal endograft fixation and is significantly related to adverse outcomes, often leading to reinterventions.

Fully automatic volume segmentation using deep learning approaches to assess aneurysmal sac evolution after infra-renal endovascular aortic repair

OBJECTIVE

Endovascular aortic repair (EVAR) surveillance relies on serial measurements of maximal diameter despite significant inter- and intra-observer variability. Volumetric measurements are more sensitive but general use is hampered by the time required for their implementation. An innovative fully automated software (PRAEVAorta® from Nurea), using artificial intelligence (AI), previously demonstrated fast and robust detection of infra-renal abdominal aortic aneurysm's (AAA) characteristics on pre-operative imaging. This study aimed to assess the robustness of these data on post-EVAR computed tomography (CT) scans.

METHODS

Comparison was made between fully automatic and semi-automatic segmentation manually corrected by a senior surgeon on a dataset of 48 patients (48 early post-EVAR CT scans with 6466 slices, and a total of 101 follow-up CT scans with 13708 slices).

RESULTS

The analyses confirmed an excellent correlation of post-EVAR volumes and surfaces, as well as, proximal neck and maximum aneurysm diameters measured with the fully automatic and manually corrected segmentation methods (Pearson's coefficient correlation >.99, p<.0001). Comparison between the fully automatic and manually corrected segmentation method revealed a mean Dice Similarity Coefficient of 0.950±0.015, Jaccard index of 0.906±0.028, Sensitivity of 0.929±0.028, Specificity of 0.965±0.016, Volumetric Similarity (VS) of 0.973±0.018 and mean Hausdorff Distance/slice of 8.7±10.8mm. The mean VS reached 0.873±0.100 for the lumen and 0.903±0.091 for the thrombus. The segmentation time was 9 times faster with the fully automatic method (2.5 vs 22 min/patient with the manually corrected method; p<.0001). Preliminary analysis also demonstrated that a diameter increase of 2mm can actually represent >5% volume increase.

CONCLUSION

PRAEVAorta® enables a fast, reproducible, and fully automated analysis of post-EVAR AAA sac and neck characteristics, with comparison between different time points. It could become a crucial adjunct for EVAR follow-up through early detection of sac evolution, which may reduce the risk of secondary rupture.

Polymer based endografts have improved rates of proximal aortic neck dilatation and migration

BACKGROUND

Proximal aortic neck dilatation (PND) affects a considerable proportion of patients undergoing endovascular aneurysm repair (EVAR) and is associated with increased rates of type I endoleak (EL1), migration, and reinterventions. Although there are numerous studies investigating PND following the placement of endografts that utilize self-expanding stent (SES) technology, there are few reports for patients treated with endografts that utilize polymer-filled rings. The purpose of this study is to examine PND and graft migration after EVAR with the Ovation stent graft.

METHODS

The study comprised patients who underwent EVAR as part of the prospective, international, multicenter Ovation stent graft trial. A clinical events committee adjudicated adverse events through 1 year, an independent imaging core laboratory analyzed imaging through 5 years, and a data safety and monitoring board provided study oversight. Neck diameter was measured at the level of the lowest renal artery. PND was defined as neck enlargement of 3 mm or more. Graft migration was defined as distal movement >10 mm or movement ≤10 mm when resulting in secondary intervention.

RESULTS

A total of 238 patients received this device during the study period. Patients were predominantly male (81%), with a mean age of 73 ± 8 years. Median follow-up was 58 months (IQR 36-60). Almost half the patients (110 patients, 46%) had challenging anatomy; defined as outside the instructions for use (IFU) with other commercially available stent grafts. 41 patients (17.2%) had a proximal neck length <10 mm and 93 (39%) had a minimum access vessel diameter <6 mm. The technical success rate was 100%. The 1-, 3- and 5-year overall survival rates were 96.6%, 86.2% and 74.9%, respectively. The immediate postoperative proximal neck diameter ranged from 16 mm to 31 mm with a mean of 22.4 ± 3 mm. During follow-up, ten patients (4.2%) developed PND. Freedom from PND estimates at 1, 3 and 5 years were 97.7%, 96%, and 93.6%, respectively. None of the patients developed endograft migration.

CONCLUSIONS

The use of the Ovation stent graft was associated with low rates of PND despite challenging neck anatomy in 17% of patients. No graft migration was observed. The design of this endograft may explain its superiority to SES in preventing neck dilatation and migration even in patients with challenging neck anatomy. This is important, as we continue to see significant late failures of EVAR due to proximal neck degeneration.

Risk Factors, Dynamics, and Clinical Consequences of Aortic Neck Dilatation after Standard Endovascular Aneurysm Repair

OBJECTIVE

Aortic neck dilatation (AND) occurs after endovascular aneurysm repair (EVAR) with self expanding stent grafts (SESs). Whether it continues, ultimately exceeding the endograft diameter leading to abdominal aortic aneurysm (AAA) rupture, remains uncertain. Dynamics, risk factors, and clinical relevance of AND were investigated after EVAR with standard SESs.

METHODS

All intact EVAR patients treated from 2000 to 2015 at a tertiary institution were included. Demographic, anatomical, and device related characteristics were investigated as risk factors for AND. Outer to outer diameters were measured at a single standardised aortic level on reconstructed computed tomography (CT) images.

RESULTS

A total of 460 patients were included (median follow up 5.2 years, interquartile range [IQR] 3.0, 7.7 years; CT imaging follow up 3.3 years, IQR 1.3, 5.4). Baseline neck diameter was 24 mm (IQR 22, 26) and increased 11.1% (IQR 1.5%, 21.9%) at last CT imaging. Endograft oversizing was 20.0% (IQR 13.6, 28.0). AND was greater during the first year (5.2% [IQR 0, 11.7]) decreasing subsequently (two to four years to 1.4%/year [IQR 0.0, 4.5%], p ≤ .001) and was associated with suprarenal fixation endografts (t value = 7.9, p < .001) and oversizing (t value = 4.4, p < .001). AND exceeding the endograft was 3.5% (95% CI 2.2% - 4.8%) and 14.4% (95% CI 11.0% - 17.8%) at five and eight years, respectively. Excessive AND was associated with baseline neck diameter (OR 1.2/mm, 95% CI 1.05 - 1.41) while the Excluder endograft had a protective effect (OR 0.15, 95% CI 0.04 - 0.58). Excessive AND was associated with type 1A endoleak (HR 3.3, 95% CI 1.1 - 9.7) and endograft migration > 5 mm (HR 3.1, 95% CI 1.4 - 6.9).

CONCLUSION

AND after EVAR with SES is associated with endograft oversizing and radial force but decelerates after the first post-operative year. Baseline aortic neck diameter and suprarenal stent bearing endografts were associated with an increased risk of AND beyond nominal stent graft diameter. However, it remains unclear whether patient selection, differences in endograft radial force or the suprarenal stent are accountable for this difference.

Large Diameter (≥29 mm) Proximal Aortic Necks Are Associated with Increased Complication Rates after Endovascular Repair for Abdominal Aortic Aneurysm

BACKGROUND

The aim of this study is to investigate the impact of proximal aortic diameter on outcome after endovascular aneurysm repair (EVAR) of infrarenal abdominal aortic aneurysms (AAAs).

METHODS

This is a case-control (1:1) retrospective analysis of prospectively collected data on 732 AAA patients treated with EVAR in 2 university centers. Patients with an infrarenal neck diameter of 29-32 mm (wide neck, WN group) were compared with patients with a neck diameter of 26-28.9 mm (control group) matched for age, gender, and maximum aneurysmal sac diameter. Any patients treated outside the instructions for use of each endograft or with no adequate follow-up were excluded. The primary end point was any neck-related adverse event (a composite of type Ia endoleak, neck-related secondary intervention, and endograft migration) during follow-up.

RESULTS

Sixty-four patients with a proximal neck diameter of 29-32 mm (WN group) were compared with a matched control group of 64 patients with a neck diameter of 26-28.9 mm (control group). Oversizing was significantly higher in the study group (17.9% vs. 15.5%, P = 0.001). Overall median available follow-up was 24 months (range 12-84) (WN group 24 months vs. control group 18.5 months, P = 0.943). Primary end point was recorded in 8 patients (12.5%) of the WN group and in 1 patient (1.6%) of the control group. Freedom from the primary end point at 36 months (standard error <10%) was 87.3% for the study versus 98.4% for the control group (log rank = 4.66, P = 0.03). On multiple regression analysis, the presence of a proximal aortic neck >29 mm was the only independent risk factor for neck-related adverse events (odds ratio 7.4, 95% confidence interval 1.2-47.1).

CONCLUSIONS

EVAR in the presence of a wide proximal aortic neck is likely to be associated with higher adverse neck-related event rates and thus, in such cases closer follow-up may be required.

TIMP‑3 suppresses the proliferation and migration of SMCs from the aortic neck of atherosclerotic AAA in rabbits, via decreased MMP‑2 and MMP‑9 activity, and reduced TNF‑α expression

The present study investigated the role of tissue inhibitor of matrix metalloproteinase‑3 (TIMP‑3) in regulating the proliferation, migration, apoptosis and activity of matrix metalloproteinase (MMP)‑2 and ‑9, during the development of an atherosclerotic abdominal artery aneurysm (AAA). Experiments were conducted using rabbit AAA neck (NA) smooth muscle cells (SMCs), to investigate the potential for TIMP‑3 to be used as a novel stent coating in preventing aortic dilation adjacent to the AAA. The atherosclerotic AAA model was induced in New Zealand white rabbits via a 6‑week high‑cholesterol diet, followed by incubation of the targeted aortic region with elastase. SMCs were isolated from the aorta adjacent to the aneurysm 30 days after AAA model induction, and stimulated with 3, 10, 30 or 100 ng/ml TIMP‑3. Cell proliferation was investigated using Cell Counting Kit‑8 reagent, migration was examined using a Boyden chamber assay and apoptotic rate was analyzed using the Annexin V‑fluorescein isothiocyanate Apoptosis Detection kit. Gelatin zymography and ELISA were used to measure the activity of MMP‑2 and MMP‑9, and the expression of tumor necrosis factor‑α (TNF‑α), respectively. Analysis of cell proliferation indicated that 10, 30 and 100 ng/ml TIMP‑3 reduced cell viability. Cell migration was decreased by 10, 30 and 100 ng/ml TIMP‑3. MMP‑2 activity was inhibited by 10, 30 and 100 ng/ml TIMP‑3, and MMP‑9 activity was suppressed by 30 and 100 ng/ml TIMP‑3. The protein levels of secreted TNF‑α were reduced by 10, 30 and 100 ng/ml TIMP‑3. The present study demonstrated the ability of 30 and 100 ng/ml TIMP‑3 to attenuate migration and proliferation, and to inhibit the activity of MMP‑2, MMP‑9 and TNF‑α secretion of NA SMCs. In conclusion, TIMP‑3 may be considered a potential therapeutic drug for use in a novel drug‑eluting stent, to attenuate the progressive dilation of the aortic NA.

Outcomes of using endovascular aneurysm repair with active fixation in complex aneurysm morphology

OBJECTIVE

The ideal treatment option for patients with complex aneurysm morphology remains highly debated. The aim of this study was to investigate the impact of endovascular aneurysm repair (EVAR) with active fixation on outcomes in patients with complex aneurysm morphology.

METHODS

There were 340 consecutive patients who underwent EVAR using active fixation devices, 234 with active infrarenal fixation (AIF; Gore Excluder; W. L. Gore & Associates, Flagstaff, Ariz) and 106 with active suprarenal fixation (ASF; 85 Medtronic Endurant [Medtronic, Santa Rosa, Calif] and 21 Cook Zenith [Cook Medical, Bloomington, Ind]). Demographics, comorbidities, anatomic features, and outcomes were analyzed for patients receiving devices with active fixation. Outcomes of using active fixation in necks with <15-mm neck lengths, >60-degree infrarenal neck angle (β), >30-mm infrarenal neck diameter, severe aortic neck calcification or thrombus, and nonstraight neck morphology were evaluated.

RESULTS

Of the 340 patients, 106 (78 men; mean age, 74.5 ± 9.3 years at the time of surgery) received implants with ASF and 234 (191 men; mean age, 74.6 ± 8.9 years at the time of surgery) received implants with AIF. In comparing AIF and ASF devices, patients in the suprarenal fixation group had significantly shorter follow-up time (25 ± 17 months vs 44.3 ± 32 months; P < .0001). Patients in the ASF group had shorter aortic neck lengths (25.5 ± 15.1 mm vs 28.6 ± 14.9 mm; P = NS) and significantly larger infrarenal neck diameters (25.9 ± 6.3 mm vs 23.4 ± 3.2 mm; P < .0001) and aneurysm diameters (59.9 ± 11.6 mm v. 55.9 ± 10.0 mm; P = .002). Outcomes were similar between groups, with no significant differences in reintervention, proximal endoleak, sac growth, abdominal aortic aneurysm-related death, or rupture. Of the complex anatomic neck features investigated, neck diameter >30 mm and nonstraight neck morphology had the highest rates of reintervention in ASF devices.

CONCLUSIONS

In cases of hostile infrarenal neck morphology, ASF appears to be used more frequently. Our data suggest that ASF may be useful for certain patients but may be unfavorable for others, such as those with wide necks or several difficult neck features. Nevertheless, further research is needed to evaluate more optimal treatment options, such as fenestrated EVAR, branched EVAR, and endovascular adjuncts such as EndoAnchors (Aptus Endosystems, Sunnyvale, Calif), in dealing with high-risk anatomic characteristics that may not be optimally managed with standard EVAR devices with active fixation.

Proximal Aortic Neck Progression: Before and After Abdominal Aortic Aneurysm Treatment

Several risk factors including short or highly angulated proximal aortic neck have been associated with long-term outcomes after endovascular or open abdominal aortic aneurysm (AAA) repair. However, research data have emerged recently concerning the behavior of proximal aortic neck, and several authors have tried to evaluate this behavior after endovascular or open repair. Additionally, computed tomography angiography (CTA) remains the golden standard for detecting and observing the morphology of an AAA, both before and after treatment. Moreover, the question of whether the proximal neck’s progression independently affects postoperative morbidity and reintervention risks still remains. Therefore, this focused review aims to present all relevant data on the behavior of an AAAs neck, based on CTA imaging before and after repair, in order to produce useful conclusions for future clinical practice.

A Systematic Review of Proximal Neck Dilatation After Endovascular Repair for Abdominal Aortic Aneurysm

Purpose: To provide an updated systematic literature review and summarize current evidence on proximal aortic neck dilatation (AND) after endovascular aneurysm repair (EVAR). Methods: A review of the English-language medical literature from 1991 to 2015 was conducted using MEDLINE and EMBASE to identify studies reporting AND after EVAR. Studies considered for inclusion and full-text review fulfilled the following criteria: (1) reported AND after EVAR, (2) included at least 5 patients, and (3) provided data on AND quantification. The search identified 26 articles published between 1998 and 2015 that encompassed 9721 patients (median age 71.8 years; 9439 men). Results: AND occurred in 24.6% of patients (95% CI 18.6% to 31.8%) over a period ranging from 15 months to 9 years after EVAR. No significant dilatation of the suprarenal part of the aorta was reported by most studies. The incidence of combined clinical events (endoleak type I, migration, reintervention during follow-up) was higher in the AND group (26%) when compared with 2% in the group without AND (OR 28.7, 95% CI 5.43 to 151.67, p<0.001). Conclusion: AND affects a considerable proportion of EVAR patients and was related to worse clinical outcome, as indicated by increased rates of type I endoleak, migration, and reinterventions. Future studies should focus on a better understanding of the pathophysiology, predictors, and risk factors of AND, which could identify patients who may warrant a different EVAR strategy and/or a closer post-EVAR surveillance strategy.

Is Neck Dilatation After Endovascular Aneurysm Repair Graft Dependent?

Long-term success of endovascular aneurysm repair (EVAR) relies on a stable proximal neck. The authors' goal was to determine whether neck dilatation after EVAR varies among 4 different endografts and whether it is related to complications of the proximal neck. Core laboratory data from 4 phase II trials of aortic endografts were analyzed for neck diameter changes over time. Patients who had at least 24 months' follow-up were included in the analysis. Neck measurement methodology varied among the 3 core labs used. Values are reported within the parameters used by each lab. Short-axis neck diameter close to 5 mm below the renal arteries, when available, was used for longitudinal comparisons. Dilation was defined as an enlargement of 3 mm or more from the first postoperative scan to the last available follow-up for each patient. Graft migration and late proximal endoleaks were determined by the individual core labs. A limited number of Lifepath grafts had most recent follow-up measurements performed by the authors. Results were compared by using Student's t test, chi-square analysis, and the Pearson correlation coefficient. Postoperative measurements from 729 EVAR patients were examined. Follow-up ranged from 24 to 60 months for 229 Ancure (Guidant) and 258 AneuRx (Medtronic) patients, and from 24 to 36 months for 211 Excluder (Gore) and 31 first-generation Lifepath (Edwards) patients. Neck dilation was noted in 124 patients (17.0%) and did not differ significantly among graft types. The incidences of late proximal endoleaks were similar among graft types, but rates of migration differed (p= 0.01). Dilation was associated with migration in Ancure (p=0.03) and Excluder (p=0.02) grafts. Late proximal endoleaks were seen in 4.1% of patients with and in 0.7% of patients without dilation (p=0.001). Patients with initial neck diameter >25 mm had significantly less dilatation than those with smaller necks (p<0.001). The incidence of neck dilation approached 20% in all EVAR patients after 24 months and was not significantly different among graft types. Neck dilation of 3 mm or more appears to be one risk factor for migration and late proximal endoleak.

Influence of Pulmonary Status and Diabetes Mellitus on Aortic Neck Dilatation following Endovascular Repair of Abdominal Aortic Aneurysms: A EUROSTAR Report

Purpose:

To elucidate the association of impaired pulmonary status (IPS) and diabetes mellitus (DM) with clinical outcome and the incidences of aortic neck dilatation and type I endoleak after elective endovascular infrarenal aortic aneurysm repair (EVAR).

Methods:

In 164 European institutions participating in the EUROSTAR registry, 6383 patients (5985 men; mean age 72.4±7.6 years) underwent EVAR. Patients were divided into patients without versus with IPS or with/without DM. Clinical assessment and contrast-enhanced computed tomography (CT) were performed at 1, 3, 6, 12, 18, and 24 months and annually thereafter. Cumulative endpoint analysis comprised death, aortic rupture, type I endoleak, endovascular reintervention, and surgical conversion.

Results:

Prevalence of IPS was 2733/6383 (43%) and prevalence of DM was 810/6383 (13%). Mean follow-up was 21.1±18.4 months. Thirty-day mortality, AAA rupture, and conversion rates did not differ between patients with versus without IPS and between patients with versus without DM. All-cause and AAA-related mortality, respectively, were significantly higher in patients with IPS compared to patients with normal pulmonary status (31.0% versus 19.0%, p<0.0001 and 6.8% versus 3.3%, p=0.0057) throughout follow-up. In multivariate analysis adjusted for smoking, age, gender, comorbidities, fitness for open repair, co-existing common iliac aneurysm, neck and aneurysm size, arterial angulations, aneurysm classification, endograft oversizing >15%, and type of stent-graft, the presence of IPS was not associated with significantly higher rates of aortic neck dilatation (30.6% versus 38.0%, p>0.05) and did not influence cumulative rates of type I endoleak, endovascular reintervention, or conversion to open surgery (p>0.05). Similarly, the presence of DM did not influence the above-mentioned study endpoints.

Conclusion:

In contrast to observations regarding the natural course of AAAs, impaired pulmonary status does not negatively influence aortic neck dilatation, while the presence of diabetes does not protect from these dismal events after EVAR.

Follow-up after Endovascular Aortic Aneurysm Repair: The Plain Radiograph Has an Essential Role in Surveillance

Periodic follow-up is mandatory for patients with aortic stent-grafts. Central to surveillance is the establishment of a baseline against which changes can be detected. Computed tomography (CT) has been the benchmark of follow-up imaging for endografts, but comparison of serial AP and lateral plain radiographs will detect structural alterations that can be missed on CT scans. In this review, we illustrate these common endograft complications and the value of plain radiographs in their detection. We believe that the plain radiograph should be the cornerstone of aortic endograft surveillance. However, a standardized protocol should be used to avoid parallax and positioning errors that affect interpretation.

Aortic neck enlargement after endovascular aneurysm repair using balloon-expandable versus self-expanding endografts

OBJECTIVE

This study evaluated changes in aortic neck diameter after endovascular aneurysm repair (EVAR) using a balloon-expandable stent (BES) endograft compared with a commercially available self-expanding stent (SES) endograft. We hypothesized that forces applied to the aortic neck by SES endografts may induce aortic neck enlargement over time and that such enlargement may not occur in aneurysm patients treated with a device that does not use a proximal SES.

METHODS

This was a retrospective quantitative computed tomography (CT) image analysis of patients treated with the Nellix (Endologix, Irvine, Calif) BES (n = 49) or the Endurant II (Medtronic, Minneapolis, Minn) SES (n = 56) endograft from 2008 to 2010. Patients with preimplant, postimplant, and at least 1-year serial CT scans underwent quantitative morphometric assessment by two independent vascular radiologists blinded to the outcome results. Changes in the infrarenal neck over time were compared with the suprarenal aorta for each patient.

RESULTS

Follow-up extended to 4.8 years for the BES and to 4.6 years for the SES, with no significant difference in median follow-up time (34 months for BESs and 24 months for SESs; P = .06). There were no differences in preimplant neck diameter (25.2 ± 0.9 mm vs 25.7 ± 1.1 mm; P = .54) or length (27.7 ± 3.7 mm vs 23.6 ± 3.7 mm; P = .12) between BESs and SESs at baseline. After implantation, neck diameter increased by 1.1 ± 0.5 mm in BES patients and 2.6 ± 0.5 mm in SES patients (P = .07) compared with the preoperative diameter. At 3 years, neck diameter increased by 0.5 ± 0.9 mm in BES patients and by 3.8 ± 1.0 mm in SES patients (P = .0002) compared with the first postoperative CT scan. The annual postimplant rate of increase in the infrarenal neck diameter was fivefold greater in SES patients (1.1 ± 0.1 mm/y) than in BES patients (0.22 ± 0.04 mm/y; P < .0001). There were no significant differences in the diameter of the suprarenal aorta at baseline or at 3 years and no differences in the annual rate of change in suprarenal aortic diameter between BES and SES endografts.

CONCLUSIONS

EVAR using SES endografts resulted in progressive infrarenal aortic neck enlargement, whereas EVAR using BES endografts resulted in no neck enlargement over time. These data suggest that infrarenal neck enlargement after EVAR with SES endografts is likely related to the force exerted by SES elements rather than disease progression in the infrarenal neck.

The fate of untreated concomitant suprarenal aortic aneurysms after endovascular aneurysm repair of infrarenal aortic aneurysms

OBJECTIVE

Many patients treated with endovascular aortic repair (EVAR) have a concomitant suprarenal abdominal aortic aneurysm (sAAA). The natural history of these sAAAs and whether they require intervention after EVAR is unknown.

METHODS

We identified 470 patients from the M2S database (M2S Inc, West Lebanon, NH) as having an infrarenal AAA (iAAA) with a concomitant sAAA (diameter, 2.9-4.7 cm). The analysis included 217 patients with preoperative computed tomography angiography and follow-up imaging of ≥12 months. Patients who did not undergo EVAR (n = 65) served as a control. Patients with EVAR were subdivided into 90 with suprarenal fixation (SR) and 62 with infrarenal fixation (IR). Standard measurements from the M2S images were extracted, and growth rates were calculated for different abdominal aortic segments.

RESULTS

The average follow-up was 33.0 ± 18.8 months. The average sAAA initial size and growth rate were 34.6 ± 3.0 and 0.6 ± 1.1 mm/y for SR, 34.0 ± 3.3 and 0.6 ± 1.3 mm/y for IR, and 36.6 ± 3.4 and 1.2 ± 1.5 mm/y for controls (SR vs IR, P > .05; SR or IR vs control, P < .05). After EVAR, two of 152 (1.3%) sAAAs grew to ≥ 50 mm, which was not statistically different from four of 65 (6.2%) in the control group (P = .07). At 48 months, the Kaplan-Meier freedom from sAAA growth to ≥ 50 mm was 99.3% for patients undergoing EVAR and 95.2% for controls (P = .061). Patients with starting sAAAs sized ≥ 40 mm had a higher growth rate (1.4 ± 2.1 mm/y) and frequency of growth to ≥50 mm (14.3%) than patients with starting sAAAs sized <40 mm (0.7 ± 1.2 mm/y and 1.5%; P < .05).

CONCLUSIONS

Isolated treatment of iAAAs via EVAR with a concomitant sAAA is acceptable because endografts with or without SR do not affect sAAA growth rates. Routine EVAR follow-up is sufficient for sAAAs of <40 mm, and more intensive follow-up should be considered for sAAAs of 40 to 50 mm. For sAAAs approaching 50 mm, an endograft with IR should be considered in case sAAA repair is required in the future.

Long-term follow-up of neck expansion after endovascular aortic aneurysm repair

OBJECTIVE

This study determined the rate, extent, and clinical significance of neck dilatation after endovascular aneurysm repair (EVAR).

METHODS

The study included 46 patients who underwent elective EVAR using bifurcated Zenith stent grafts (Cook, Bloomington, Ind) and had at least 48 months of clinical and radiographic follow-up. Computed tomography images were analyzed on a 3-dimensional workstation (TeraRecon, San Mateo, Calif). Neck diameter was measured 10 mm below the most inferior renal artery in planes orthogonal to the aorta. Nominal stent graft diameter was obtained from implantation records.

RESULTS

Median follow-up was 59 months (range, 48-120 months). Neck dilation occurred in all 46 patients. The rate of neck dilation was greatest at early follow-up intervals. At 48 months, median neck dilation was 5.3 mm (range, 2.3-9.8 mm). The extent of neck dilation at 48 months correlated with percentage of stent graft oversizing (Spearman rho = 0.61, P < .001). No type I endoleak or migration >5 mm occurred.

CONCLUSIONS

After EVAR with the Zenith stent graft, the neck dilates until its diameter approximates the diameter of the stent graft. Neck dilation was not associated with type I endoleak or migration of the stent graft.

Size of the proximal neck in AAAs treated with balloon-expandable stent-grafts: CTA findings in mid- to long-term follow-up

PURPOSE

To determine the evolution of the proximal aortic neck diameter in mid- to long-term follow-up after endovascular aneurysm repair of abdominal aortic aneurysm (AAA) with a balloon-expandable stent-graft.

METHODS

Thirty patients (27 men; average age 71 years, range 56-87) with infrarenal AAAs were treated with the SETA-Latecba balloon-expandable stent-graft (6 aortomonoiliac and 24 bifurcated configurations). Follow-up ranged from 4 to 8 years (mean 73.4 months). Computed tomography was done systematically before the procedure, after implantation (1-3 months), at 1 year, and annually thereafter. The last follow-up scan was utilized to measure the proximal neck for purposes of comparison with baseline and the initial post-implant scans.

RESULTS

Five patients died during follow-up of causes unrelated to the procedure. No endoleaks or graft migrations were observed. The pre-deployment proximal neck diameter (a) averaged 23.4 mm (range 18-32), the diameter after deployment of the stent-graft (b) averaged 24.9 mm (range 18-34), and the most recent follow-up proximal neck measurement (c) averaged 23.8 mm (range 18-31). Comparing the last follow-up to the post-implant measurements (c-b), the neck diameter decreased in 15 (50%) patients [7 with short necks (i.e., <15 mm)] and remained unchanged (no variation) in 15 (50%) patients (4 with short necks). All patients treated with the SETA-Latecba balloon-expandable stent-graft showed stability of the proximal aortic neck diameter in mid- to long-term follow-up.

CONCLUSION

The study showed that the diameter reached at initial deployment did not increase further in the long term, which supports the safety and reliability of this modular balloon-expandable stent-graft and illustrates that this device does not produce dilatation of the proximal neck after deployment. Future dilatation of the aortic neck is unlikely, and consequently, migration or delayed type I endoleak are also unlikely.

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

The first commercially available stent grafts were unable to withstand the hemodynamic forces of the vascular environment. The past 15 years have seen a gradual improvement in long-term stent graft performance as designs evolved through the elimination of features associated with late failure and the replication of features associated with durable success. Clinical experience provides the following principles on which to base device design and implantation techniques. Few patients have an adequate length of non-dilated aorta distal to the aneurysm to allow implantation of an aorto-aortic stent graft; bifurcated stent grafts are usually required for AAA repair. Friction, column strength and tissue ingrowth do not prevent migration of the stent graft from its attachment within the neck into the aneurysm; some form of active fixation is required, usually in the form of barbs. Any movement between the apex of a stent and the overlying graft material will erode the fabric; stents and grafts need to move as a single unit. Nitinol is versatile, but fragile; Nitinol components must be polished to eliminate all surface irregularities and they cannot be subjected to compression loading, or excessive pulsatile movement. The neck of an aneurysm is unstable; it will dilate unless protected by a securely fixed, non-compliant stent graft. The aneurysm does not heal; freedom from risk of rupture depends on durable depressurization of the sac. The sole objective of image-based follow-up is the early detection, and catheter-based correction, of device failure. Once any given design has been in use long enough to identify its failure modes, the frequency of follow-up studies can be adjusted accordingly. However, it takes a long time to identify all the potential forms of late failure, and pre-clinical testing remains an imprecise science. New, or recently modified, devices cannot necessarily be assumed to be as durable as their predecessors.

Thoracic CT Findings Following Endovascular Stent-Graft Treatment for Thoracic Aortic Aneurysm

PURPOSE

To investigate the transient computed tomographic (CT) findings and morphological characteristics of the descending thoracic aorta following endovascular repair of thoracic aortic aneurysm (TAA).

METHODS

Of 50 TAAs repaired using custom-made endoprostheses between May 1997 and September 2005, 35 (25 men; mean age 67 years) were successfully treated and followed for >3 months by thoracic CT. The TAA etiologies were 22 degenerative/atherosclerotic, 7 dissection-related from intramural hematoma, 2 traumatic, 2 anastomotic, and 2 penetrating ulcers. The CT findings following stent-graft placement were retrospectively studied.

RESULTS

Over a mean follow-up of 27.0+/-25 months (range 3-92), periaortic changes were observed in 17 (48.6%) patients, and the amount of pleural effusion increased in 13 (37.1%). In all cases, these findings disappeared without specific treatment during the follow-up period. Late secondary endoleak was observed in 1 (2.9%) patient, and there was 1 (2.9%) caudal migration of the proximal end of the stent-graft. Five (14.3%) aneurysms increased in size. Two patients, both with dissection, showed aortic neck dilatation. There was a positive relationship between neck dilatation and dissection-related TAA etiology (p = 0.035).

CONCLUSION

Although aortic neck dilatation is less common after endovascular TAA repair than after abdominal repairs, patients with dissection-related TAA may be a subgroup prone to aneurysm neck dilatation.

Intraobserver and interobserver variability of 64-row computed tomography abdominal aortic aneurysm neck measurements

BACKGROUND

Integrity of the abdominal aortic aneurysm (AAA) neck is crucial for the long-term success of endovascular AAA repair (EVAR). However, suitable tools for reliable assessment of changes in small aortic volumes are lacking. The purpose of this study was to assess the intraobserver and interobserver variability of software-enhanced 64-row computed tomographic angiography (CTA) AAA neck volume measurements in patients after EVAR.

METHODS

A total of 25 consecutive patients successfully treated by EVAR underwent 64-row follow-up CTA in 1.5-mm collimation. Manual CTA measurements were performed twice by three blinded and independent readers in random order with at least a 4-week interval between readings. Maximum and minimum transverse aortic neck diameters were measured twice on two different levels within the proximal neck. Volumetry of the proximal aortic neck was performed by using dedicated software. Variability was calculated as 1.96 SD of the mean arithmetic difference according to Bland and Altman. Two-sided and paired t tests were used to compare measurements. P values <.05 were considered to indicate statistical significance.

RESULTS

Intraobserver agreement was excellent for dedicated aneurysmal neck volumetry, with mean differences of less than 1 mL (P > .05), whereas it was poor for transverse aortic neck diameter measurements (P < .05). However, interobserver variability was statistically significant for both neck volumetry (P < .005) and neck diameter measurements (P < .015).

CONCLUSIONS

The reliability of dedicated AAA neck volumetry by using 64-row CTA is excellent for serial measurements by individual readers, but not between different readers. Therefore, studies should be performed with aortic neck volumetry by a single experienced reader.

Aortic necks of ruptured abdominal aneurysms dilate more than asymptomatic aneurysms after endovascular repair

BACKGROUND

Endovascular repair of abdominal aortic aneurysm (AAA) is increasingly used. We evaluated if a difference exists in the rate of change of the aortic neck diameter between non-ruptured and ruptured AAAs after endovascular aneurysm repair (EVAR).

METHODS

Details of patients undergoing elective (group I) and emergency (group II) EVAR using Talent stents between October 1999 and September 2005 were reviewed. Top neck diameters were prospectively recorded on the hospital database from computed tomography scans preoperatively and at 1, 3, 12, and 24 months postoperatively. The aortic neck diameter rate of change was calculated for each group.

RESULTS

Endovascular repair was performed on 110 elective and 41 emergency patients, of which 100 (80 male) elective and 29 (26 male) emergency patients were included in this analysis. Mean age was similar in each group. Stents were oversized by 20.9% +/- 13.6% in group I and by 24.7% +/- 16.3% in group II (P = .37). The preoperative mean proximal aortic neck was larger in group II (25.0 +/- 3.3 mm vs 23.5 +/- 2.8 mm; P = .029). The growth rate of the top neck diameter was significantly greater at 12 months (1.48 +/- 2.4 mm/year vs 3.89 +/- 6.24 mm/year; P = .04) and 24 months (.99 +/- 1.1 mm/year vs 2.61 +/- 3.3 mm/year; P = .04) in group II than in group I. A decreasing sac size was found in 68.2% of patients whose neck dilated. The complication rate was similar in each group.

CONCLUSION

Aneurysm necks in patients with ruptured aneurysms are larger and dilate at a greater rate than those with nonruptured aneurysms. The accelerated rate of expansion in some patients must be borne in mind during follow-up and in secondary endovascular interventions and conversion to open surgery.

Correlation between the Measurement of Transverse Diameter in the Proximal Neck on Computed Tomography and on Aortography before Endovascular Treatment of Infrarenal Aortic Aneurysm

The aim of this study was to determine the correlation between the measurement of transverse diameter of the proximal neck on computed tomographic angiography (CTA) and graduated catheter aortography in patients who are candidates for endovascular graft placement in order to replace, if both measurements are equivalent, aortography for CTA alone. Preoperative dual-slice CTA and graduated catheter aortography were performed in 35 consecutive patients with infrarenal aortic aneurysm within 10 days. Transverse proximal neck diameters were measured on a true axial section on CTA reconstructions and on aortographic images, always 6 mm distal from the most inferior main renal artery. Mean, median, and standard deviation were obtained and the measurements correlated for each patient using Pearson's correlation and linear regression analysis. A significant difference in proximal neck transverse diameter measurements was found between graduated catheter aortography and CTA in all cases. CTA values were a mean of 1.74 mm higher than aortography values. Pearson's correlation indicates a strong correlation between both techniques, and a regression equation determines the predictive value of aortography on the basis of CTA values. Estimation of the transverse diameter of the proximal neck on aortography on the basis of that obtained on CTA allows us to affirm that CTA could be used as the sole method for the preoperative selection of appropriate endograft size in patients with infrarenal aortic aneurysm.

Aortic Neck Dilation after Endovascular Abdominal Aortic Aneurysm Repair: Should Oversizing Be Blamed?

Long-term durability after endovascular abdominal aortic aneurysm repair (EVAR) is dependent upon the maintenance of an effective seal between the endograft and the proximal landing zone. Continuous neck dilation might lead to the loss of such a seal. This study aims at evaluating the incidence, risk factors, and clinical consequences of post-EVAR aneurysm neck dilation in patients treated with two types of endografts: AneuRx and Ancure. We reviewed data concerning all consecutive patients submitted to primary EVAR using the AneuRx and Ancure devices. Preoperative neck anatomic characteristics (diameter, calcification, and thrombus load) were evaluated, and device oversize percentage was calculated. Postoperative same-level neck diameter was measured on all postoperative computed tomographic (CT) scans. Probabilities of neck dilation (> or = 10% and > or = 15%) relative to preoperative diameter and first postoperative diameter were estimated with the Kaplan-Meier method and compared between patients using both types of endograft. The impact of anatomic characteristics on neck dilation incidence was evaluated using Cox proportional hazards models. Mean neck dilation was compared between patients with and without device migration and proximal type I endoleak. Both groups had similar probabilities of dilating > 10% relative to preoperative diameter and to first postoperative diameter. Proximal necks in AneuRx-treated patients had higher probabilities of dilating > or = 15% relative to preoperative diameter than Ancure-treated patients (45.5% vs. 18.7% at 1.5 years, p = 0.025), but the probability of such dilation relative to the first postoperative diameter was not different between the two groups (12.4% vs. 9.1% at 1.5 years, p = 0.832). None of the preoperative neck characteristics was associated with neck dilation risk. Device oversize percentage was correlated with the percentage of neck dilation at first postoperative CT scan relative to preoperative diameter in both the AneuRx (correlation coefficient = 0.469, p < 0.0001) and the Ancure (correlation coefficient = 0.464, p < 0.011) groups, but it was not correlated with the percentage of neck dilation at 1 or 1.5 years relative to first postoperative CT scan in either group. Patients with and without caudad device migration (> or = 5 mm) had similar percentages of neck dilation at 1.5 years relative to preoperative diameter, but migrators had higher mean percentages of dilation at 1.5 years relative to first postoperative neck diameter (11.4% vs. 5.6, p = 0.012). Two phenomena may be differentiated: an immediate postimplant dilation, strongly correlated with the percentage of oversize and more likely to reach values > or = 15% with an AneuRx device than with an Ancure graft, and a subsequent dilation, relative to the first postoperatively measured diameter, equally probable with either type of device, not correlated with the percentage of oversizing but associated with caudad device migration. Our study does not support any adverse role for the degree of oversize.

Absence of proximal neck dilatation and graft migration after endovascular aneurysm repair with balloon-expandable stent-based endografts

OBJECTIVE

Proximal neck dilatation (PND) and/or endograft migration with the subsequent development of type I endoleak is a significant cause of late endograft failure after endovascular abdominal aortic aneurysm repair (EVAR). Although there are numerous reports examining PND in patients receiving endografts that use self-expanding stents (SES) for proximal fixation, there are no such reports for patients treated with endografts that use balloon-expanding stents (BES). The purpose of this study was to investigate PND and endograft migration after EVAR with BES endografts.

METHODS

We retrospectively reviewed all charts and all serial computed tomographic scans available for patients who underwent EVAR with a BES endograft (surgeon-made, aortounifemoral polytetrafluoroethylene graft with a proximal Palmaz stent) between August 1997 and October 2002. Only patients with longer than a 12-month follow-up were analyzed. Neck diameter was measured at the level of the lowest renal artery and at 5 mm below it. PND was defined as neck enlargement of 2.5 mm or more. To assess endograft migration, the distance between the superior mesenteric artery and the cranial end of the BES was measured. Stent migration was defined as a change of 5 mm or more.

RESULTS

A total of 77 patients received this device during the study period. The technical success rate was 99%. The 1-, 3-, and 5-year survival was 66%, 48%, and 29.5%, respectively. Complete serial computed tomographic scans were available in 41 of the 48 patients who survived 12 months or longer after the operation. The mean follow-up period for these patients was 31 months (range, 12-66 months). The maximum aneurysm diameter was either unchanged or decreased in 35 patients (85%). The immediate postoperative proximal neck diameter was 19 to 29 mm (median, 24 mm). This was unchanged at the latest follow-up. None of the patients had significant PND. The cranial end of the BES was located in the area between 14 mm proximal and 36 mm distal to the superior mesenteric artery (median, 6 mm). None of the patients developed significant endograft migration.

CONCLUSIONS

Neither PND nor endograft migration was observed with the BES endograft. The nature of the SES may be responsible for the observed neck dilatation and device migration after EVAR with SES endografts. This study suggests that BES may be a better fixation method for EVAR.

Mid- and long-term device migration after endovascular abdominal aortic aneurysm repair: A comparison of AneuRx and Zenith endografts

BACKGROUND

Freedom from migration is key to the durability of endovascular aneurysm repair (EVAR). This study evaluates the mid- and long-term incidence of migration with two different endografts.

METHODS

Between September 1997 and June 2004, 235 patients were scheduled for EVAR with an AneuRx (Medtronic/AVE Inc.) or Zenith (Cook) endograft. Patients with fusiform, infrarenal aneurysms and a minimum 12 months of follow-up were analyzed, for a final cohort of 130 patients. Migration was assessed on axial computed tomography (CT) (2.5 to 3 mm cuts) as the distance from the most caudal renal artery to the first slice containing endograft (AneuRx) or to the top of the bare suprarenal stent (Zenith). Aortic neck diameters were measured at the most caudal renal artery. The initial postoperative CT scan was the baseline. Migration was defined by caudal movement of the endograft at two thresholds, > or =5 mm and > or =10 mm, or any migration with a related clinical event.

RESULTS

Life-table analysis demonstrated AneuRx freedom from migration (> or =10 mm or clinical event) was 96.1%, 89.5%, 78.0%, and 72.0% at 1, 2, 3, and 4 years, respectively. Zenith freedom from migration was 100%, 97.6%, 97.6%, and 97.6% at 1, 2, 3, and 4 years, respectively (P = .01, log-rank test). The stricter 5-mm migration threshold found 67.4% of AneuRx and 90.1% of Zenith patients free from migration at 4 years of follow-up. Twelve out of 14 (85.7%) AneuRx patients (12/14) with migration (> or =10 mm or clinical event) underwent 14 related secondary procedures (13 endovascular, 1 open conversion). The single Zenith patient with migration (> or =10 mm) has not required adjuvant treatment. Mean follow-up was 39.0 +/- 2.3 months (AneuRx) and 30.8 +/- 1.9 months (Zenith, P = .01). Patients with and without migration did not differ in age, gender ratio, aneurysm diameter, and neck diameter. However, initial neck length was shorter in patients with migration (22.1 +/- 2.1 mm vs 31.2 +/- 1.2 mm, P = .02). A subset of patients (21.6%) experienced significant (defined as > or =3 mm) maximum aortic neck dilation. Of the AneuRx patients, > or =3 mm aortic neck dilation affected 30.8% of migrators vs 13.0% of nonmigrators (P = .20).

CONCLUSIONS

Endograft migration is a time-dependent phenomenon affected by both device choice and aortic neck length. A great majority of patients (85.7%) with migration of the AneuRx device ultimately required treatment. A minority of patients experienced aortic neck dilation that could be considered clinically significant. Careful surveillance for migration is an essential component of long-term follow-up after EVAR.

Real-time magnetic resonance-guided endovascular repair of experimental abdominal aortic aneurysm in swine

OBJECTIVES

This study tested the hypotheses that endografts can be visualized and navigated in vivo solely under real-time magnetic resonance imaging (rtMRI) guidance to repair experimental abdominal aortic aneurysms (AAA) in swine, and that MRI can provide immediate assessment of endograft apposition and aneurysm exclusion.

BACKGROUND

Endovascular repair for AAA is limited by endoleak caused by inflow or outflow malapposition. The ability of rtMRI to image soft tissue and flow may improve on X-ray guidance of this procedure.

METHODS

Infrarenal AAA was created in swine by balloon overstretch. We used one passive commercial endograft, imaged based on metal-induced MRI artifacts, and several types of homemade active endografts, incorporating MRI receiver coils (antennae). Custom interactive rtMRI features included color coding the catheter-antenna signals individually, simultaneous multislice imaging, and real-time three-dimensional rendering.

RESULTS

Eleven repairs were performed solely using rtMRI, simultaneously depicting the device and soft-tissue pathology during endograft deployment. Active devices proved most useful. Intraprocedural MRI provided anatomic confirmation of stent strut apposition and functional corroboration of aneurysm exclusion and restoration of laminar flow in successful cases. In two cases, there was clear evidence of contrast accumulation in the aneurysm sac, denoting endoleak.

CONCLUSIONS

Endovascular AAA repair is feasible under rtMRI guidance. Active endografts facilitate device visualization and complement the soft tissue contrast afforded by MRI for precise positioning and deployment. Magnetic resonance imaging also permits immediate post-procedural anatomic and functional evaluation of successful aneurysm exclusion.

Creation of individual ideally shaped stents using multi-slice CT: in vitro results from the semi-automatic virtual stent (SAVS) designer

To plan stent-grafting for thoracic aortic aneurysm with complicated morphology, we created a virtual stent-grafting program [Semi Automatic Virtual Stent (SAVS) designer] using three-dimensional CT data. The usefulness of the SAVS designer was evaluated by measurement of transformed anatomical and straight stents. Curved model images (source, multi-planer reconstruction and volume rendering) were created, and a hollow virtual stent was produced by the SAVS designer. A straight Nitinol stent was transformed to match the curved configuration of the virtual stent. The accuracy of the anatomical stent was evaluated by experimental strain phantom studies in comparison with the straight stent. Mean separation length was 0 mm in the anatomical stent [22 mm outer diameter (OD)] and 5 mm in the straight stent (22 mm OD). The straight stent strain voltage was four times that of the anatomical stent at the stent end. The anatomical stent is useful because it fits the curved structure of the aorta and reduces the strain force compared to the straight stent. The SAVS designer can help to design and produce the anatomical stent.

AneuRx Device Migration: Incidence, Risk Factors, and Consequences

Success after endovascular abdominal aortic aneurysm repair (EVAR) is dependent on device positional stability. The quest for such stability has motivated different endograft designs, and the risk factors entailed remain the subject of debate. This study aims at defining the incidence, risk factors, and clinical implications of device migration after EVAR with the AneuRx endograft. In this study we included all consecutive 109 patients submitted to primary AneuRx placement for infrarenal aortic or aortoiliac aneurysms. Preoperative computed tomography (CT) scans were reviewed for the following anatomic characteristics: neck length, diameter, angulation, calcification, and thrombus load; and sac diameter and thrombus load. Percentage of device oversizing relative to the proximal neck diameter was determined. All postoperative CT scans were reviewed, and the distance between the lowest renal artery and the craniad end of the device was measured. A >/=5-mm increase in such distance was considered indicative of device migration. Migration cumulative incidence was estimated by the Kaplan-Meier method, and its association with any of the preoperative anatomical characteristics was tested using Cox proportional hazards models. Median follow-up time was 9 (range, 1-31) months. Migration occurred in nine patients, corresponding to a 15.6% estimated probability of migration at 30 months (SE = 5.1%). Migration was associated with the risk of proximal type I endoleak (hazard ratio = 3.39, 95% confidence interval = 1.46-7.87; p = 0.007). This type of endoleak occurred in three of the migration-affected patients (33.3%); all of them were resolved by additional cuff placement at the proximal landing zone. No other migration-related reinterventions were performed. The only significant associations between anatomic factors and device migration probability were the protective effects of longer necks (odds ratio [OR] = 0.71 for each additional 5 mm, p = 0.045) and longer overlapped portions of neck and device (OR = 0.56 for each additional 5 mm, p = 0.003). There was a trend toward higher probability of migration among reverse-tapered necks (OR = 1.75, p = 0.109). Percentage of device oversizing correlated with early neck dilation (between preoperative and first postoperative diameters, correlation coefficient = 0.4, p < 0.0001), but not with late neck dilatation (between first postoperative and 1.5-year scan diameters, correlation coefficient = 0.29, p = 0.112). There was a trend toward higher mean percentage of late dilation among migrators (11.4%, standard error of the mean [SEM] 2.6) than nonmigrators (5.7%, SEM = 1) (p = 0.08), but both groups had similar mean percentages of early dilation (3%, SEM = 1.6%, vs. 5.5%, SEM = 0.6%; p = 0.365). This result indicates that device migration is not a rare event after AneuRx implantation. This phenomenon is associated with proximal type I endoleaks. Deployment of the endograft immediately below the renal arteries might help to prevent migration, since use of greater lengths of overlapped device relative to the proximal neck has a protective effect. Migration seems to be independent of the degree of device oversizing.

Late problems at the proximal aortic neck: Migration and dilation

Migration is a late-term complication of endovascular aneurysm repair (EVAR) evidenced by downward slippage of the endograft. The etiology of migration may be inherent to problems with endograft fixation, although aortic neck dilation may also play a role. Devices with active fixation (ie, hooks and barbs) possess an additional mechanism of fixation and may better resist migration. Aortic neck dilation after EVAR is significant in a subset of patients and may be related to neck degeneration. Excessive oversizing of endografts may contribute to dilation and migration and is, therefore, not recommended. Migration should be treated when the overlap between the endograft and aortic neck is less than 10 mm or when associated with clinically significant events such as type I endoleak or aneurysm expansion. Failure to treat migration could lead to repressurization and subsequent rupture of the aneurysm.

Proximal Type I Endoleak After Endovascular Abdominal Aortic Aneurysm Repair: Predictive Factors

Proximal type I endoleaks after endovascular abdominal aortic aneurysm repair (EVAR) are associated with a high risk of rupture. Risk factors for developing this complication are not fully elucidated. We aimed to define preoperative predictors for proximal type I endoleak and describe its clinical outcome. From a consecutive series of 257 patients who underwent EVAR, we selected 202 who had available pre- and postoperative CT scan studies. Proximal neck diameter, length, angulation, calcification, thrombus load (thickness, percentage of neck circumference coverage, percentage of neck area occupancy), and maximum aneurysm diameter were evaluated on preoperative CT scans. All postoperative CT and duplex ultrasound scans, supplemented with angiograms in selected cases, were reviewed for the presence or absence of endoleak. Device overlap and oversizing (relative to the proximal neck) were also determined. Type I proximal endoleak rates were estimated using the Kaplan-Meier method. The associations between the variables listed above and proximal type I endoleak were evaluated by use of Cox proportional hazards models. Proximal type I endoleak occurred in eight patients, corresponding to a 3-year incidence rate of 4% (SE = 1.5%). The median follow-up was 340 days (range, 22-1954). Univariate analyses found significant associations between proximal type I endoleak and the following variables: percentage of calcified neck circumference (hazards ratio = 2.19 for a 25% increase, p = 0.019), aneurysm maximum diameter (hazards ratio = 1.98 for a 1-cm increase, p = 0.006) and proximal neck and device overlap (hazards ratio = 0.53 for a 5-mm increase, p = 0.007). The mean overlap among cases with and without type I proximal endoleak was 15.6 mm and 29.3 mm, respectively. When these variables were included in a multivariate model, all remained statistically significant. No significant association could be documented for neck thrombus-related variables. Thirty-nine (19.3%) patients had a beta neck angle inferior to 120 degrees . There was a trend toward a higher incidence of proximal type I endoleaks in these patients (p = 0.057). Device oversize relative to proximal neck diameter did not affect the probability of this type of endoleak. One patient survived an emergency open repair of a ruptured aneurysm after significant expansion. Six patients underwent endovascular reinterventions (4 additional proximal cuff placements, 2 proximal angioplasties). The mean interval for reintervention was 389 days. Distal migration (>or=5 mm) was identified in four cases (50%). Proximal type I endoleak is a rare complication after EVAR, but it is associated with a high number of reinterventions and potentially serious consequences. Patients with short and heavily calcified aneurysmal necks and large aneurysms are at increased risk of proximal type I endoleaks.