Abdominal Aortic Aneurysm Neck Research Articles

PCSK9, a novel immune and ferroptosis related gene in abdominal aortic aneurysm neck

The gene expression profile of abdominal aortic aneurysm (AAA) neck is not fully understood. The etiology of AAA is considered to be related to atherosclerosis and the inflammatory response, involving congenital, genetic, metabolic, and other factors. The level of proprotein convertase subtilisin/kexin type 9 (PCSK9) is related to those of cholesterol, oxidized low-density lipoprotein, and triglycerides. PCSK9 inhibitors have significant effects on lowering LDL-cholesterol, reversing atherosclerotic plaques, and reducing the risk of cardiovascular events and have been approved by several lipid-lowering guidelines. This work was aimed to investigate the potential role of PCSK9 in the neck of AAA. We extracted the expression dataset (GSE47472) containing 14 AAA patients and 8 donors and single-cell RNAseq (scRNA-seq) data (GSE164678) of CaCl2-induced (AAA) samples from the Gene Expression Omnibus dataset. Through bioinformatics methods, we found that PCSK9 was up-regulated in the proximal neck of human AAA. In AAA, PCSK9 was mainly expressed in fibroblasts. Additionally, immune check-point PDCD1LG2 was also expressed higher in AAA neck than donor, while CTLA4, PDCD1, and SIGLEC15 were down-regulated in AAA neck. The expression of PCSK was correlated with PDCD1LG2, LAG3, and CTLA4 in AAA neck. Additionally, some ferroptosis-related genes were also down-regulated in AAA neck. PCSK9 was also correlated with ferroptosis-related genes in AAA neck. In conclusion, PCSK9 was highly expressed in AAA neck, and may exert its role through interacting with immune check-points and ferroptosis-related genes.

Technological Advances to Address the Challenging Abdominal Aortic Aneurysm Neck

There have been significant technologic advances in endovascular aortic therapies since the introduction of conventional infrarenal endovascular aortic aneurysm repair (EVAR). These advances have sought to address the weaknesses of conventional EVAR- particularly the difficult or “hostile” infrarenal aortic aneurysm neck. We review anatomical features that create a hostile neck and the most recent advancements to overcome these limitations. EndoAnchors replicate open suture fixation to seal endograft to aortic tissue and have been shown to be useful as a prophylactic measure in short, angulated necks as well as therapeutic for type Ia endoleaks. Fenestrated EVAR (FEVAR) devices such as the Z-fen (Cook Medical, Bloomington, IN, USA) raises the seal zone to the suprarenal segment while maintaining renal perfusion. Finally, multibranch aortic grafts such as the Thoracoabdominal Branch Endoprosthesis (Tambe; W. L. Gore & Associates, Flagstaff, AZ, USA) raise the seal zone above the visceral segment and can be used off the shelf with promising results.

One-year volume growth of abdominal aortic aneurysms measured by extended field-of-view ultrasound.

Measurement of volume has the potential to detect subtle growth not recognized in the current surveillance paradigm of abdominal aortic aneurysms (AAAs). Currently available three-dimensional ultrasound allows for estimation of AAA volume, but for most patients, the AAA extends beyond the ultrasound field-of-view and only allows visualization of a partial AAA volume. A new extended field-of-view three-dimensional ultrasound protocol (XFoV US) has been found to improve the proportion of patients with visualization of the full AAA volume. To investigate the applicability of the XFoV US protocol in estimating AAA volume growth in follow-up, 86 patients with AAAs were recruited from the surveillance program at a university hospital. All were imaged by XFoV US at baseline and at one-year follow-up. Assessment of full volume, based on visualization of the AAA neck and bifurcation at both baseline and one-year follow-up, was achieved in 67/86 (78%) of patients. One-year mean growth in maximum diameter was 2.8 mm (6%/year), in centerline length 2.9 mm (4%/year), and in volume 15.9 mL (19%/year). In 17/67 (25%) of patients, volume growth was detected in diameter-stable AAAs. Baseline XFoV US volume was associated with one-year AAA volume growth, while, conversely, maximum baseline diameter was not associated with one-year AAA diameter growth. This study concludes that the XFoV US protocol provides a safe and repeatable modality for assessing AAA volume growth, and that AAA volume is a promising predictive measure of AAA growth.

EndoSuture aneurysm repair versus fenestrated aneurysm repair in patients with short neck abdominal aortic aneurysm.

The aim of this study was to compare midterm results of EndoAnchors in EndoSuture aneurysm repair (ESAR) versus fenestrated endovascular aneurysm repair (FEVAR) in short neck abdominal aortic aneurysm (AAA). All patients who underwent an ESAR procedure for a short neck AAA at our center between September 2017 and May 2020 were considered for analysis. To form the control group, preoperative computed tomography angiography of patients who underwent FEVAR for juxtarenal AAA between April 2012 and May 2020 were reviewed and patients who met short neck criteria selected. A propensity-matched score on neck length and neck diameter was calculated, resulting in 18 matched pairs. AAA shrinkage, type Ia endoleaks (EL), AAA-related reinterventions, and AAA-related deaths were compared. The median AAA diameter was 54mm (interquartile range [IQR], 52-61mm) versus 58mm (IQR, 53-63mm) with a median neck length of 8mm (IQR, 6-12mm) vs 10mm (IQR, 6-13mm) in ESAR and FEVAR patients, respectively. Technical success was 100% in both groups. Procedural success was 94% in the ESAR group versus 100% in the FEVAR group. The median procedure duration was 138mm (IQR, 113-182mm) vs 240mm (IQR, 199-293mm) ( P< .001) and the median length of stay was 2days (IQR, 2-3days) vs 7days (IQR, 6-7days) (P< .001) in ESAR and FEVAR patients, respectively. No major hospital complications were observed in ESAR patients compared with two in FEVAR patients (11%) with one transient acute kidney injury and one transient paraplegia. The median follow-up was 23months (IQR, 19-33months) vs 36months (IQR, 22-57months) with 67% versus 61% AAA shrinkage in the ESAR and FEVAR groups, respectively (P= .73). No type Ia EL, proximal neck-related reinterventions, or AAA-related deaths were observed in either group. No AAA-related reintervention was observed in the ESAR group versus three reinterventions in the FEVAR group (P= .23). ESAR seems to be a safe technique with no major postoperative complications or reinterventions observed during follow-up. It seems to offer similar midterm results as FEVAR in terms of type Ia EL, aneurysm shrinkage, and aneurysm-related mortality. ESAR seems to be a good off-the-shelf alternative to FEVAR in case of technical constraints.

Comparative clinical study of short-term outcomes between table fenestrated and chimney endovascular aneurysm repair for hostile neck aneurysms.

Hostile neck abdominal aortic aneurysm (AAA) is challenging for standard endovascular aneurysm repair (EVAR). We sought to compare fenestrated endovascular aneurysm repair (fEVAR) and chimney endovascular aneurysm repair (chEVAR) for hostile neck AAA. Patients were identified retrospectively. Hostile neck anatomy was defined as a proximal neck length of <15mm or angulation >60°. The choice of fEVAR or chEVAR was based on neck anatomy and physician preference. Type I endoleak (T1EL) was the primary outcome. Other outcomes included type III endoleak (T3EL), visceral stent occlusion, renal insufficiency, reintervention, and mortality. A total of 84 patients were included from April 2012 to December 2021. fEVAR and chEVAR patients were 48 and 36 cases, respectively. Both groups showed similar rate of T1EL, T3EL, visceral stent occlusion, renal insufficiency, reintervention, and mortality. However, chEVAR patients had a more tortuous neck (61.1% vs. 16.7%, p < 0.001), while fEVAR patients had a greater neck size (29.5 ± 6.3mm vs. 24.5 ± 4.8mm, p < 0.001) and more reconstructing target arteries (2.2 ± 1.1 vs 1.3 ± 0.6, p < 0.001). fEVAR and chEVAR show similar safe and effective outcomes in well-selected hostile neck. fEVAR might be able to reconstruct multiple visceral arteries, and chEVAR seems justified in patients with poor anatomical suitability for fEVAR.

Endografts for the treatment of abdominal aortic aneurysms with a hostile neck anatomy: A systematic review.

BackgroundEndovascular aortic repair (EVAR) of abdominal aortic aneurysms (AAAs) has emerged as a better alternative to conventional open surgery for AAAs. The purpose of the review is to define the improvement in the clinical management of the patient with hostile neck AAAs due to the introduction of new endografts while giving a thorough description of their instructions for use (IFUs), main characteristics and part sizing, reporting their outcomes from clinical studies and categorizing their usability.MethodsA MEDLINE search was conducted using keyword-specific combinations. Clinical studies were searched via the clinicaltrials.gov website. Relevant articles' references were also hand-searched.ResultsWe retrieved 640 records describing Alto, Ovation iX, Treovance, Aorfix, Anaconda, Conformable, and Endurant II/IIs endografts. Aortic necks >60° can be managed with Anaconda, Aorfix, and Conformable, which can treat up to 90° necks requiring ≥15 mm (Anaconda ≥20 mm), and Treovance, which is eligible for necks ≤75° with ≥15 mm length. Ovation's innovation of combining polymer-filled O-rings with integral anchors can treat conical necked AAAs giving Ovation iX and Alto an advantage. Short-necked AAAs can be treated with Alto, eligible for necks as short as 7 mm, and Endurant II, which can treat ≥10 mm necks or 4 mm if used in conjunction with the EndoAnchors system, respectively. Alto and Conformable report a 100% technical success rate, absence of AAA-related death, migration, ruptures, and limb occlusion during follow-up. Endurant II and Ovation iX report >99% technical success rate and are almost free from the AAA mortality rate, ruptures, migration, and limb occlusion, while Ovation iX has a high rate of sac dilation (15.5%) in a 5-year follow-up. Anaconda is slightly better than Aorfix and Treovance, which are related to the lowest technical success rates, 98.3%, 96.3%, and 96%, respectively. Aorfix has the highest AAA mortality rate, 4% in a 60 month follow-up.ConclusionMost new generation endografts described have comparable results. They broaden the eligibility of patients for EVAR due to their unique technical characteristics described. There is a lack of comparative studies for newer endografts and postmarket clinical studies with long-term results concerning the most recently approved devices described, Alto and Conformable.

Postendovascular Aneurysmal Repair Increase in Local Energy Loss for Fusiform Abdominal Aortic Aneurysm: Assessments With 4D flow MRI.

Although endovascular aneurysmal repair (EVAR) is a preferred treatment for abdominal aortic aneurysm (AAA) owing to its low invasiveness, its impact on the local hemodynamics has not been fully assessed. To elucidate how EVAR affects the local hemodynamics in terms of energy loss (EL). Prospective single-arm study. A 3.0 T/4D flow MRI using a phase-contrast three-dimensional cine-gradient-echo sequence. A total of 13 consecutive patients (median [interquartile range] age: 77.0 [73.0, 78.8] years, 11 male) scheduled for EVAR as an initial treatment for fusiform AAA. 4D flow MRI covering the abdominal aorta and bilateral common iliac arteries and the corresponding stent-graft (SG) lumen was performed before and after EVAR. Plasma brain natriuretic peptide (BNP) was measured within 1 week before and 1 month after EVAR. The hemodynamic data, including mean velocity and the local EL, were compared pre-/post-EVAR. EL was correlated with AAA neck angle and with BNP. Patients were subdivided into deformed (N=5) and undeformed SG subgroups (N=8) and pre-/post-EVAR BNP compared in each. Parametric or nonparametric methods. Spearman's rank correlation coefficients (r). The interobserver/intraobserver variabilities with Bland-Altman plots. A P value < 0.05 is considered significant. The mean velocity (cm/sec) at the AAA was five times greater after EVAR: 4.79 ± 0.32 vs. 0.91 ± 0.02. The total EL (mW) increased by 1.7 times after EVAR: 0.487 (0.420, 0.706) vs. 0.292 (0.192, 0.420). The total EL was proportional to the AAA neck angle pre-EVAR (r=0.691) and post-EVAR (r=0.718). BNP (pg/mL) was proportional to the total EL post-EVAR (r=0.773). In the deformed SG group, EL (0.349 [0.261, 0.416]) increased 2.4-fold to 0.848 (0.597, 1.13), and the BNP 90.3 (53.6, 105) to 100 (67.2, 123) post-EVAR. The local EL showed a 1.7-fold increase after EVAR. The larger increase in the EL in the deformed SG group might be a potential concern for frail patients. 1 TECHNICAL EFFICACY: Stage 2.

Endovascular Treatment of Infrarenal Aortic Aneurysm With Difficult Neck Anatomy

At present, endovascular treatment of infrarenal aortic aneurysms is the standard of care. However, worse aortic aneurysm anatomy is one of the main risk factors limiting the use of endovascular treatment of abdominal aortic aneurysms and leads to endoleak type I, endograft dislocation, and an increased risk of reintervention. The aim of our study was to demonstrate our single-center experience with the Gore conformable Excluder (GCE) endograft implantation in patients with difficult abdominal aortic aneurysm neck anatomy.

The correlation of aortic neck length to late outcomes following EVAR with the Ovation stent graft

ObjectiveEndovascular aneurysm repair (EVAR) performed outside manufacturers’ instructions for use due to short aortic neck for the treatment of abdominal aortic aneurysm (AAA) is associated with unfavorable outcomes. Newer endografts now have an indication for shorter neck aneurysms that previous endografts do not, but this cohort has yet to be evaluated individually. The aim of this study is to evaluate 5-year outcomes after EVAR in patients with short aortic necks (<10 mm) using the Ovation stent graft. MethodsThe study comprised 238 patients who underwent EVAR as part of the prospective international multicenter Ovation stent graft trials. The main inclusion criteria were AAA diameter ≥ 5 cm, proximal parallel neck length ≥7 mm, neck angulation ≤60°, and bilateral iliac fixation length ≥10 mm. 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. Patients were divided into short neck (<10 mm) and standard neck (≥10 mm) groups. End points included long-term survival, freedom from aneurysm-related mortality (ARM), freedom from type Ia endoleak, and freedom from reintervention. ResultsPatients were predominantly male (81%) with a mean age of 73 ± 8 years. Median follow-up time was 58 months (interquartile range, 36-60 months). Of 238 patients, 41 (17.2%) had a proximal neck length <10 mm and would be considered outside the instructions for use with other stent grafts. Baseline characteristics were relatively similar between the two groups. The 5-year overall survival estimates were 77.8% for the standard neck group compared with 59.5% for the short neck group (P = .03). There were no differences in the 5-year freedom from ARM (99.2% vs 100%; P = .7), freedom from type Ia endoleak (96.3% vs 96.3%; P = .8), and freedom from reintervention (77.9% vs 79.7%; P = .7) between the standard and short neck groups, respectively. After adjusting for age and other potential confounders, short proximal neck was associated with a two-fold increase in 5-year all-cause mortality (adjusted hazard ratio, 2; 95% confidence interval, 1.02-3.8; P = .04]. ConclusionsThe Ovation endograft performed well in short AAA neck with no difference in 5-year type Ia endoleak, reintervention, and ARM rates. However, short proximal neck was independently associated with a two-fold increase in the risk of all-cause mortality at 5 years. These findings confirm the prior literature on the association of hostile neck anatomy with late mortality following EVAR.

Abdominal aortic aneurysm neck dilatation and sac remodeling in fenestrated compared to standard endovascular aortic repair.

Contemporary commercially available endovascular devices for the treatment of abdominal aortic aneurysm (AAA) include standard endovascular aortic repair (sEVAR) or fenestrated EVAR (fEVAR) endografts. However, aortic neck dilatation (AND) can occur in nearly 25% of patients following EVAR, resulting in loss of proximal seal with risk of aortic rupture. AND has not been well characterized in fEVAR, and direct comparisons studying AND between fEVAR and sEVAR have not been performed. This study aims to analyze AND in the infrarenal and suprarenal aortic segments, including seal zone, and quantify sac regression following fEVAR implantation compared to sEVAR. A retrospective review of prospectively collected data on 20 consecutive fEVAR patients (Cook Zenith® Fenestrated) and 20 sEVAR (Cook Zenith®) patients was performed. Demographic data, anatomic characteristics, procedural details, and clinical outcome were analyzed. Pre-operative, post-operative (1month), and longest follow-up CT scan at an average of 29.3months for fEVAR and 29.8months for sEVAR were analyzed using a dedicated 3D workstation (iNtuition, TeraRecon Inc, Foster City, California). Abdominal aortic aneurysm neck diameter was measured in 5mm increments, ranging from 20mm above to 20mm below the lowest renal artery. Sub-analysis comparing the fEVAR to the sEVAR group at 12months and at greater than 30months was performed. Standard statistical analysis was done. Demographic characteristics did not differ significantly between the two cohorts. The fEVAR group had a larger mean aortic diameter at the lowest renal artery, shorter infrarenal aortic neck length, increased prevalence of nonparallel neck shape, and longer AAA length. On follow-up imaging, the suprarenal aortic segment dilated significantly more at all locations in the fEVAR cohort, whereas the infrarenal aortic neck segment dilated significantly less compared to the sEVAR group. Compared to the sEVAR cohort, the fEVAR patients demonstrated significantly greater positive sac remodeling as evident by more sac diameter regression, and elongation of distance measured from the celiac axis to the most cephalad margin of the sac. Device migration, endoleak occurrence, re-intervention rate, and mortalities were similar in both groups. Compared to sEVAR, patients undergoing fEVAR had greater extent of suprarenal AND, consistent with a more diseased native proximal aorta. However, the infrarenal neck, which is shorter and also more diseased in fEVAR patients, appears more stable in the post-operative period as compared to sEVAR. Moreover, the fEVAR cohort had significantly greater sac shrinkage and improved aortic remodeling. The suprarenal seal zone in fEVAR may result in a previously undescribed increased level of protection against infrarenal neck dilatation. We hypothesize that the resultant decreased endotension conferred by better seal zone may be responsible for a more dramatic sac shrinkage in fEVAR.

Thirty-day Results from the ZEPHYR Registry: Outcomes of EVAR Using the Zenith Alpha™ Abdominal Endovascular Graft for the Treatment of AAA in 347 Patients

To report technical and clinical 30-day results following treatment with the Zenith Alpha™ abdominal stent graft from the ZEnith alPHa for aneurYsm Repair Registry (ZEPHYR). Multicenter, nonrandomized, single arm, core laboratory-controlled, prospective registry collecting data on the Zenith Alpha Abdominal Endovascular Graft being used in subjects with abdominal aortic aneurysms (AAA) from sites in Germany, Belgium, and The Netherlands between December 2016 and December 2019. Inclusion criteria were non-ruptured AAAs with a maximum diameter ≥50 mm or enlargement >5 mm over 6 months with an AAA neck length ≥10 mm (site reported). Primary outcome measure was treatment success at 30 days. Treatment success was defined as a combined endpoint consisting of technical and clinical success. Technical success was defined as successful stent graft delivery and deployment as well as successful removal of the delivery system. Clinical success at 30 days was defined as freedom from type I and III endoleak, aneurysm rupture, conversion to open surgery and stent graft occlusion. Three hundred forty-seven subjects were included from 14 sites with a median age of 73.0 years (IQR 68.0-79.0). Thirty-four patients were female (9.8%). The median AAA diameter was 58.3 mm (IQR 55.0-63.5). The median proximal neck diameter was 23.6 mm (IQR 22.0-25.2) with a median proximal neck length of 24.4 mm (IQR 15.0-34.8) and a median infrarenal neck angulation of 24.5° (IQR 15.0-35.0). The right and left common iliac diameter were 16.1 mm (IQR 14.1-19.4) and 16.2 mm (IQR 14.1-19.1), respectively. The treatment success rate at 30 days was 94.8% (N=329). Technical success was achieved in 333 patients (96.0%). The clinical success rate at 30 days was 98.8% (N=343). Three patients had limb occlusions at 30 day follow up (0.9%). One patient had a type Ib endoleak (0.3%). Seventy percent of vascular access approaches were percutaneous. The reintervention rate was 1.7% (N=6) within 30 days. Indications for reinterventions were a false aneurysm at puncture site (N=1), limb complications (N=2), stentgraft-associated renal artery occlusions (N=2), and an external iliac artery thrombosis (N=1). Endovascular aneurysm repair using the Zenith Alpha Abdominal Endovascular Graft is effective in the short term. Long term results will be reported in the future.

Wide necks, worse outcomes: Is this still a debate?

Many aspects of abdominal aortic aneurysm (AAA) anatomy must be considered when planning and performing endovascular abdominal aortic aneurysm repair (EVAR), with proximal AAA neck morphology and diameter being critical. Given the broad availability of multiple devices with varying designs, device selection is often complex and depends on the individual physician's experience, knowledge of various devices, graft availability, and urgency of presentation. Necessary knowledge of each device's instructions for use (IFU) is intensely important; even within the IFU, certain aortic characteristics can leave some patients at risk for future reintervention and failure.

Anatomic eligibility for endovascular aneurysm repair preserved over 2 years of surveillance

ObjectiveEndovascular aneurysm repair (EVAR) is a widely used option for patients with suitable vascular anatomy who have a large infrarenal abdominal aortic aneurysm (AAA). Patients with small AAAs are managed with careful surveillance and it is a common concern that their anatomy may change with AAA growth, and their option for EVAR may become limited. Device innovation has resulted in expanded ranges of anatomy that may be eligible for EVAR. This study sought to identify changes in anatomic eligibility for repair with contemporary endovascular devices in AAA patients, monitored by computed tomography scan over the course of 2 years. MethodsPatients from the Non-Invasive Treatment of Abdominal Aortic Aneurysm Clinical Trial (N-TA3CT, NCT01756833) were included in this analysis. Females had baseline AAA maximum transverse diameter between 3.5 and 4.5 cm, and males had baseline maximum transverse diameter between 3.5 and 5.0 cm. Patients were included in this analysis if they completed pre-enrollment and 2-year follow-up computed tomography imaging. Pertinent anatomic measurements were performed on a postprocessing workstation in a centralized imaging core laboratory. EVAR candidacy was determined by measuring proximal aortic neck diameter, AAA length, and infrarenal neck angulation. Patients were considered to be eligible for EVAR if they qualified for at least one of the seven studied devicesʼ instructions for use at baseline and at 2 years. A paired t test analysis was used to detect differences in aortic measurements over 2 years, and the McNemar test was used to compare eligibility over 2 years. ResultsWe included 192 patients in this analysis—168 male and 24 female. Of these patients, 85% were eligible for EVAR at baseline and 85% after 2 years of follow-up (P = 1.00; 95% confidence interval –0.034 to 0.034). Of the 164 EVAR candidates at baseline, 160 (98%) remained eligible over 2 years of surveillance. Insufficient neck length was the most common reason for both ineligibility at baseline (18 of 28 patients) as well as loss of candidacy over 2 years (3 of 4 patients). ConclusionsThe majority of patients eligible for EVAR when entering a surveillance program for small AAA remain eligible after 2 years. Substantial changes in AAA neck anatomy resulting in loss of EVAR treatment options are infrequent. Patients with anatomic AAA progression beyond EVAR eligibility remain candidates for complex EVAR and open repair.

Mid-Term Results of Endovascular Aneurysm Sealing in the Treatment of Abdominal Aortic Aneurysm With Unfavorable Morphology.

To report mid-term results of endovascular aneurysm sealing (EVAS) of abdominal aortic aneurysms (AAA) deemed unsuitable for a standard endovascular aneurysm repair (EVAR). A prospectively maintained database of 42 patients with EVAR-unfavorable anatomy treated by EVAS combined with chimney grafts in case of the proximal AAA neck shorter than 5 mm was analyzed. Early outcomes included final angiographic result, intra- and early post-operative deaths, and complications. Mid-term outcomes included all-cause mortality (ACM), aneurysm-related mortality (ARM), patency of the stents, occurrence of endoleaks, serious complications and graft failures defined as the AAA growth of more than 5 mm, type I endoleak, occlusion of the stent-graft or chimney graft, aorto-duodenal fistula, or aneurysm rupture. The procedure was completed in all patients. Twenty-eight chimney grafts were implanted in 19 patients. Patients were followed for a median of 24 months (range 12-34 months). There were 2 intraoperative ruptures and 1 patient died in an early postoperative period. The cumulative ACM was 15, 21, and 36% at 12, 24, and 36 months, respectively, and the cumulative ARM was 8, 11, and 27% at 12, 24, and 36 months, respectively. Three out of 5 aneurysm-related deaths were due to a secondary aorto-duodenal fistula. The cumulative incidence of graft failure was 20, 27, and 42% at 12, 24, and 36 months, respectively. The cumulative incidence of an endoleak was 5, 9, and 23% at 12, 24, and 36 months, respectively. The graft failure increased significantly both ACM (p = .012) and ARM (p = .00003). The implantation of chimney grafts at the initial procedure increased ARM significantly (p = .008). The presence of an endoleak did not have any significant influence on ACM and ARM. Patients treated with EVAS for AAAs with EVAR-unfavorable anatomy, especially those with chimney grafts, exhibit a high risk of graft failure and subsequent death.

Computational Analysis of EndoAnchor Effectiveness in Dilating Abdominal Aortic Aneurysm Neck

Endovascular surgery is standard of care for nearly all aortic aneurysm repairs. A paradigm shift is under way concerning endoleaks, especially in the population of patients with persistent sac pressurization or growth. Focus is shifting from type II endoleaks to the most vulnerable part of the aorta-endograft interface leading to stable or expanding sacs—the proximal seal zone (type IA). Clinically, fixation and seal are often thought of as a single entity and considered in selecting an appropriately sized endograft based on patient-specific parameters, such as neck diameter and geometry. However, mechanistically, seal and fixation are two different problems. Active graft fixation with EndoAnchors (EAs; Medtronic, Santa Rosa, Calif) is showing improved rates of sac regression and seal zone stabilization. Whereas there is growing clinical understanding of the effectiveness of EAs in endovascular surgery, a biophysical understanding of the role of EAs under different mechanisms of seal zone failure is lacking. We build on our prior work using finite element analysis with cohesive zone modeling of the seal zone to study the role of EAs on interfacial stability under hypertensive conditions. In the current work, we study the role of EAs in preventing seal zone failure as a function of continued aortic neck dilation. Aortic dilation is modeled by a morphoelasticity approach (Fig). We study radial, circumferential, longitudinal, and isotropic dilation. Our simulations show that seal zone loss is sensitive to neck dilation. As the neck dilates, the seal zone is lost, similar to cases in which the supra-device aorta is overpressurized. EA placement prevents seal zone failure with neck dilation. The pattern of seal zone failure is sensitive to the mode and degree of aortic neck dilation. Isotropic dilation leads to the fastest failure because mode 1, 2, and 3 fracture is activated. Circumferential and radial dilation lead to different modes of interfacial fracture dominating. Our work provides the first biophysical mechanism for the effectiveness of EA fixation in a dilating aortic neck (disease progression). We show that EAs do stabilize the seal zone under these conditions. However, this effectiveness is sensitive to the mode of dilation.

Analysing The Cross-Section of The Abdominal Aortic Aneurysm Neck and Its Effects on Stent Deployment

Stent graft devices for the treatment of abdominal aortic aneurysms (AAAs) are being increasingly used worldwide. Yet, during modelling and optimization of these devices, as well as in clinical practice, vascular sections are idealized, possibly compromising the effectiveness of the intervention. In this study, we challenge the commonly used approximation of the circular cross-section of the aorta and identify the implications of this approximation to the mechanical assessment of stent grafts. Using computed tomography angiography (CTA) data from 258 AAA patients, the lumen of the aneurysmal neck was analysed. The cross-section of the aortic neck was found to be an independent variable, uncorrelated to other geometrical aspects of the region, and its shape was non-circular reaching elliptical ratios as low as 0.77. These results were used to design a finite element analysis (FEA) study for the assessment of a ring stent bundle deployed under a variety of aortic cross-sections. Results showed that the most common clinical approximations of the vascular cross-section can be a source of significant error when calculating the maximum stent strains (underestimated by up to 69%) and radial forces (overestimated by up to 13%). Nevertheless, a less frequently used average approximation was shown to yield satisfactory results (5% and 2% of divergence respectively).

Long-term Results of Endovascular Aneurysm Sealing in Treatment of Infrarenal Abdominal Aortic Aneurysm With Unfavourable Morphology

Introduction: Endovascular aneurysm repair (EVAR) is a less invasive alternative of treatment of patients with abdominal aortic aneurysm (AAA). Its applicability however is limited by the AAA anatomy. Endovascular aneurysm sealing originally emerged as an endovascular solution for AAA repair with very promising early results. The purpose of this study was to report long-term results of EVAS of AAAs with unfavourable anatomy for EVAR. Methods: A prospectively maintained database of 42 patients with EVAR-unfavourable anatomy treated by EVAS was analysed. The median age of the patients was 74 (IQR 67-80) years. The median diameter of AAA was 61 (IQR 56-71) mm. The EVAS consisted of implantation of two balloon expandable aorto-iliac stent-grafts surrounded by polymer filled endobags. In case of proximal AAA neck shorter than 5 mm chimney grafts were implanted. The final angiographic result, intra- and early post-operative complications were noted. A follow-up included a clinical assessment angio-CT 4-6 weeks and 12 months after the procedure and duplex Doppler at 12 months intervals thereafter. In case of any abnormalities detected in either clinical or duplex Doppler examination an angio-CT was performed. Patency of the aorto-iliac stents and chimney grafts, occurrence of graft failure and all additional interventions and/or events were noted in the database. The graft failure was defined as AAA growth of more than 5mm, type I endoleak, occlusion of the stent-graft or chimney graft or aneurysm rupture. All-cause mortality (ACM) and aneurysm related mortality (ARM) were analysed with Kaplan-Meier estimates. Results: The procedure was completed in all patients. Twenty-eight chimney grafts were implanted in 19 patients. There were two intraoperative ruptures, one of an aortic neck that required conversion to an open repair and one of an external iliac artery that was successfully treated with implantation of a self-expandible covered stent. One patient died in an early postoperative period. The median follow-up period was 24 (IQR 12-34) months. The cumulative ACM was 15, 21 and 35% at 12, 24 and 36 months respectively and the cumulative ARM was 8, 11 and 27% at 12, 24 and 36 months respectively. Three out of five aneurysm related deaths were due to a secondary aorto-duodenal fistula. The cumulative incidence of graft failure was 20, 27 and 42% at 12, 24 and 36 months, respectively. Cumulative incidence of endoleak was 5, 9 and 23% at 12, 24 and 36 months, respectively.The graft failure increased significantly both ACM (p = 0,012) and ARM (p = 0,00003). The implantation of chimney grafts at the initial procedure increased significantly ARM (p=0,008). The presence of endoleak did not have any significant influence on ACM and ARM. Conclusion: Patients treated with EVAS for AAA with EVAR-unfavourable anatomy, especially those with chimney grafts, have a high risk of graft failure and subsequent death. These patients require more rigorous monitoring than patient after standard EVAR. Disclosure: Nothing to disclose

Computational study on hemodynamic changes in patient-specific proximal neck angulation of abdominal aortic aneurysm with time-varying velocity.

Aneurysms are considered as a critical cardiovascular disease worldwide when they rupture. The clinical understanding of geometrical impact on the flow behaviour and biomechanics of abdominal aortic aneurysm (AAA) is progressively developing. Proximal neck angulations of AAAs are believed to influence the hemodynamic changes and wall shear stress (WSS) within AAAs. Our aim was to perform pulsatile simulations using computational fluid dynamics (CFD) for patient-specific geometry to investigate the influence of severe angular (≥ 60°) neck on AAA's hemodynamic and wall shear stress. The patient's geometrical characteristics were obtained from a computed tomography images database of AAA patients. The AAA geometry was reconstructed using Mimics software. In computational method, blood was assumed Newtonian fluid and an inlet varying velocity waveform in a cardiac cycle was assigned. The CFD study was performed with ANSYS software. The results of flow behaviours indicated that the blood flow through severe bending of angular neck leads to high turbulence and asymmetry of flows within the aneurysm sac resulting in blood recirculation. The high wall shear stress (WSS) occurred near the AAA neck and on surface of aneurysm sac. This study explained and showed flow behaviours and WSS progression within high angular neck AAA and risk prediction of abdominal aorta rupture. We expect that the visualization of blood flow and hemodynamic changes resulted from CFD simulation could be as an extra tool to assist clinicians during a decision making when estimation the risks of interventional procedures.

Follow-up after endovascular aortic aneurysm repair can be stratified based on first postoperative imaging.

Lifelong postoperative surveillance is recommended following endovascular aneurysm repair (EVAR). Although the purpose is to prevent and/or identify complications early, it also results in increased cost and workload. This study was designed to examine whether it may be possible to identify patients at low risk of complications based on their first postoperative CT angiogram (CTA). All patients undergoing EVAR in two Swedish centres between 2001 and 2012 were identified retrospectively and categorized based on the first postoperative CTA as at low risk (proximal and distal sealing zone at least 10 mm and no endoleak) or high risk (sealing zone less than 10 mm and/or presence of any endoleak) of complications. Some 326 patients (273 men) with a CTA performed less than 1 year after EVAR were included (low risk 212, 65·0 per cent; high risk 114, 35·0 per cent). There was no difference between the groups in terms of sex, age, co-morbidities, abdominal aortic aneurysm (AAA) diameter, preoperative AAA neck anatomy, stent-graft type or duration of follow-up (mean(s.d.) 4·8(3·2) years). Five-year freedom from AAA-related adverse events was 97·1 and 47·7 per cent in the low- and high-risk groups respectively (P < 0·001). The corresponding freedom from AAA-related reintervention was 96·2 and 54·1 per cent (P < 0·001). The method had a sensitivity of 88·3 per cent, specificity of 77·0 per cent and negative predictive value of 96·6 per cent to detect AAA-related adverse events. The number of surveillance imaging per AAA-related adverse event was 168 versus 11 for the low-risk versus high-risk group. Two-thirds of patients undergoing EVAR have an adequate seal and no endoleak on the first postoperative CTA, and a very low risk of AAA-related events up to 5 years. Less vigilant follow-up after EVAR may be considered for these patients.

Clinical Outcomes of Endovascular Aneurysm Repair with the Kilt Technique for Abdominal Aortic Aneurysms with Hostile Aneurysm Neck Anatomy: A Korean Multicenter Retrospective Study.

We aimed to evaluate the clinical efficacy and short-term clinical outcomes of Kilt technique-based endovascular aneurysm repair (EVAR) with Seal® stent-grafts for abdominal aortic aneurysms (AAAs) with hostile neck anatomy (angle>60°). We retrospectively evaluated the pre-EVAR and follow-up computed tomography angiography findings of 24 patients (mean age 71±11years; age range 32-87years; mean follow-up 50±12months) with hostile neck AAAs treated between 2010 and 2015. Serial change in aneurysmal neck angle was calculated using a standardized protocol. Relationships between clinical variables and outcomes were evaluated using univariate and multivariate Cox analyses and mixed-model regression. In addition, the Kaplan-Meier method was used to assess the cumulative rates of survival, endoleak, and reintervention. The primary technical success rate (success within 24h after EVAR) was 100% (24/24). The survival rate was 96±8% at 1month, 6months, 1year, and 3years, and 87±18% at 5years. Endoleaks occurred in three patients. Four reinterventions were performed in three patients; no surgical revisions were required. Causes of post-EVAR mortality included intracerebral hemorrhage at 14days and rhabdomyolysis at 32months. The most remarkable change after Kilt-based EVAR was an acute decrease in the neck angle, which was observed between the pre-EVAR and first follow-up visits (at 1month) (P=0.001). Kilt-based EVAR with Seal® stent-grafts for AAAs with a severely angulated neck (angle>60°) provided high technical success, low mortality, and low complication rates during short-term follow-up.