Stent-graft surface movement after endovascular aneurysm repair: baseline parameters for prediction, and association with migration and stent-graft-related endoleaks

A computed tomography angiography-based radiomics model for prognostic prediction of endovascular abdominal aortic repair

OBJECTIVE

This study aims to develop a radiomics machine learning (ML) model that uses preoperative computed tomography angiography (CTA) data to predict the prognosis of endovascular aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA) patients.

METHODS

In this retrospective study, 164 AAA patients underwent EVAR and were categorized into shrinkage (good prognosis) or stable (poor prognosis) groups based on post-EVAR sac regression. From preoperative AAA and perivascular adipose tissue (PVAT) image, radiomics features (RFs) were extracted for model creation. Patients were split into 80 % training and 20 % test sets. A support vector machine model was constructed for prediction. Accuracy is evaluated via the area under the receiver operating characteristic curve (AUC).

RESULTS

Demographics and comorbidities showed no significant differences between shrinkage and stable groups. The model containing 5 AAA RFs (which are original_firstorder_InterquartileRange, log-sigma-3-0-mm-3D_glrlm_GrayLevelNonUniformityNormalized, log-sigma-3-0-mm-3D_glrlm_RunPercentage, log-sigma-4-0-mm-3D_glrlm_ShortRunLowGrayLevelEmphasis, wavelet-LLH_glcm_SumEntropy) had AUCs of 0.86 (training) and 0.77 (test). The model containing 7 PVAT RFs (which are log-sigma-3-0-mm-3D_firstorder_InterquartileRange, log-sigma-3-0-mm-3D_glcm_Correlation, wavelet-LHL_firstorder_Energy, wavelet-LHL_firstorder_TotalEnergy, wavelet-LHH_firstorder_Mean, wavelet-LHH_glcm_Idmn, wavelet-LHH_glszm_GrayLevelNonUniformityNormalized) had AUCs of 0.76 (training) and 0.78 (test). Combining AAA and PVAT RFs yielded the highest accuracy: AUCs of 0.93 (training) and 0.87 (test).

CONCLUSIONS

Radiomics-based CTA model predicts aneurysm sac regression post-EVAR in AAA patients. PVAT RFs from preoperative CTA images were closely related to AAA prognosis after EVAR, enhancing accuracy when combined with AAA RFs. This preliminary study explores a predictive model designed to assist clinicians in optimizing therapeutic strategies during clinical decision-making processes.

Less Aortic Neck Dilatation of the ALTO Stent Graft compared to the Self-Expanding Stent Grafts after Endovascular Aortic Repair for Abdominal Aortic Aneurysms

PURPOSE

Proximal neck dilatation (PND) is a common issue after endovascular aneurysm repair (EVAR) for abdominal aortic aneurysms (AAAs), being a potential cause of stent graft migration or type Ia endoleak. The ALTO stent graft, featuring a unique polymer sealing mechanism, has been reported to exhibit less PND. This study aims to compare PND and clinical outcomes between the ALTO stent graft and alternative self-expanding stent grafts.

METHODS

The CustomSEAL study is a multi-center retrospective observational study involving 18 institutions in Japan. It compares EVAR outcomes using the ALTO stent graft and alternative self-expanding stent grafts for fusiform AAAs. The primary outcome measure was the difference in PND at 12 months post-EVAR. Secondary outcome measures included aneurysm sac diameter changes, reintervention rates, and mortality outcomes during the follow-up.

RESULTS

After propensity score matching, 111 patient pairs were extracted. Baseline characteristics, including proximal neck length/diameter and stent graft oversizing, were comparable between groups. The ALTO stent graft was associated with significantly less PND at 12 months (2.3% vs. 26.7%, P < 0.001). There were no significant differences in perioperative outcomes, aneurysm sac diameter changes, reintervention rates, or overall survival between the groups.

CONCLUSIONS

The ALTO stent graft demonstrated significantly less PND at 12 months post-EVAR compared to alternative self-expanding stent grafts, highlighting its potential advantage in exerting less chronic expanding force on the proximal aortic neck. Long-term follow-up is needed to validate the clinical benefits of the ALTO stent graft over the alternative self-expanding stent grafts.

LEVEL OF EVIDENCE

Non-randomized controlled cohort/follow-up study.

The Justification of Open Surgical Repair for an Abdominal Aortic Aneurysm: A Retrospective Comparison of Outcomes of Endovascular Aneurysm Repair and a Brief Review of the Literature

Background: Abdominal aortic aneurysms (AAAs) are life-threatening conditions that require timely intervention to prevent rupture. Endovascular aneurysm repair (EVAR) is preferred due to faster recovery and lower perioperative risk; however, intraoperative failure and long-term complications highlight the continued significance of open surgical repair (OSR) and the need for improved risk assessment. Methods: This retrospective study analyzed data from 210 patients who underwent EVAR (n = 163) or OSR (n = 47) at a single center. Clinical characteristics, complications, reintervention rates, and 30-day mortality were recorded. EVAR-to-OSR conversion and mortality predictors in AAA treatments were identified. Results: The overall mortality rate was 9.5% (20/210 patients), with 12 patients (7.3%) in the EVAR group and 8 patients (17%) in the OSR group (p = 0.085). Five patients required early and six required late conversion to open surgery. In follow-ups beyond 30 days, the reintervention rate for EVAR was higher (HR: 1.2, 95% CI: 0.4-3.6; p = 0.754). According to the multivariable analysis, rupture (p = 0.045), female sex (p = 0.018), body weight (p = 0.003), and aortic size index (p = 0.019) were significant predictors of mortality, whereas OSR was not (p = 0.212). Conclusions: Treatment optimization requires a balanced approach, integrating both EVAR and OSR based on patient-specific factors. Maintaining expertise in both techniques is essential to ensure the best possible outcomes, and OSR should remain a viable option when clinically indicated.

The Effect of EndoAnchors on Aneurysm Sac Regression for Patients Treated With Infrarenal Endovascular Repair With Hostile Neck Anatomies: A Propensity Scored Analysis

PURPOSE

To analyze sac evolution patterns in matched patients with hostile neck anatomy (HNA) treated with standard endovascular aneurysm repair (sEVAR) and endosutured aneurysm repair (ESAR).

METHODS

Observational retrospective study using prospectively collected data between June 2010 and December 2019. ESAR group data were extracted from the primary arm of the PERU registry with an assigned identifier (NCT04100499) at 8 centers and those from the sEVAR came from 4 centers. Suitability for inclusion required: no proximal endograft adjuncts (besides EndoAnchor use), ≤15 mm neck length and minimum of 12-months follow-up imaging. Bubble-shaped neck (noncylindrical short neck with discontinuous seal) aspect was analyzed. Both groups were analyzed using propensity score matching (PSM) for aortic neck length, width, angulation, and device fixation type. Main outcome assessed was sac evolution patterns (sac expansion and regression were defined as >5mm increase or decrease, of the maximum sac diameter respectively; all AAAs within this ±5 mm range in diameter change were considered stable) and secondary outcomes were type-Ia endoleaks; other endoleaks and mortality. A power analysis calculation >80% was confirmed for sac regression evaluation.

RESULTS

After exclusions, PSM resulted in 96 ESAR and 96 sEVAR patients. Mean imaging follow-up (months) was 44.4±21.3 versus 43.0±19.6 (p=0.643), respectively. The overall number of patients achieving sac regression was higher in the ESAR group (n=57, 59.4% vs n=31, 32.3%; p<0.001) and the cumulative sac regression achieved at 5 years was 65% versus 38% (p=0.003) in favor of the ESAR group. There were no statistically significant differences in type-Ia endoleak and/or other endoleaks. Univariate analysis for sac regression patients in the sEVAR and ESAR group individually showed the bubble-shape neck as a predictor of sac regression failure. There were no statistical differences in overall and aneurysm-related mortality.

CONCLUSION

Endosutured aneurysm repair provided improved rates of sac regression for patients with AAA and HNA when compared with sEVAR at midterm and up to 5 years, despite similar rates of type-Ia endoleaks, and the need to consider some important limitations. The presence of bubble-shaped neck was a predictor of sac regression failure for both groups equally.

CLINICAL IMPACT

The use of EndoAnchors aids and improves EVAR treatment in hostile neck anatomies by an increased rate of sac regression when compared to EVAR treatment alone in up to 5 year analysis. Moreover, a trend to reduced number of type Ia endoleaks is also achieved, although not significant in the present study. This data, adds to current and growing evidence on the usefulness of EndoAnchors for AAA endovascular treatment.

Stent-induced new entry and device migration associated with hemodynamic stress after thoracic endovascular aortic repair for type B chronic aortic dissection using computational fluid dynamics analysis: a case report

BACKGROUND

Stent graft-induced new entry (SINE) after thoracic endovascular aortic repair (TEVAR) is a serious adverse event which leads to stent graft migration and rupture. SINE is known to be more frequent in cases of chronic dissection and oversizing. However, few studies have evaluated the influence of hemodynamic stress on SINE in patients with chronic dissection. Here, we report a rare case of TEVAR for chronic dissection with a dissection stent, inducing SINE 6 years after the first surgery. In addition, we analyze the hemodynamic stress for the aortic event using computational fluid dynamics (CFD) analysis.

CASE PRESENTATION

A 69-year-old male underwent TEVAR with left subclavian artery debranching for chronic type B aortic dissection, using a stent graft and dissection stent. The postoperative course was uneventful, but follow-up computed tomography (CT) showed that the stent graft and bare-metal stent had dislodged 4 years after surgery. The gap between the bare-metal stent and the stent graft increased over time, and the proximal edge of the bare-metal stent led to SINE at the descending aorta 6 years after surgery. We performed reintervention to cover the SINE. The patient recovered well and was discharged at 6 days postoperatively. He is currently in good condition 6 months after reintervention. CFD analysis of the patient's CT image suggested that the local change in wall shear stress at the stent graft and dissection stent might be related to the aortic event.

CONCLUSION

Hemodynamic stress is a factor affecting SINE and device migration. CFD may be useful for evaluating patient-specific risk of aortic events.

Ex vivo biaxial load testing analysis of aortic biomechanics demonstrates variation in elastic energy distribution across the aortic zone zero

OBJECTIVES

We hypothesized that tissue characteristics vary significantly along zone zero, which may be reflected by regional differences in stored elastic energy. Our objectives were to (1) characterize the regional variation in stored elastic energy within tissues of the aortic zone zero and (2) identify the association between this variation and patient characteristics.

METHODS

From February 2018 to January 2021, 123 aortic tissue samples were obtained from the aortic root and proximal and distal ascending aortas of 65 adults undergoing elective ascending aorta replacement. Biaxial biomechanics testing was performed to obtain tissue elastic energy at the inflection point and compared with patient demographics and preoperative computed tomography imaging. Coefficient models were fit using B-spline to interrogate the relationship among elastic energy, region, and patient characteristics.

RESULTS

Mean elastic energy at inflection point was 24.3 ± 15.6 kJ/m3. Elastic energy increased significantly between the root and proximal, and root and distal ascending aorta and decreased with increasing age. Differences due to history of connective tissue disorder and bicuspid aortic valve were significant but diminished when controlled for other patient characteristics. Among covariates, age and region were found to be the most important predictors for elastic energy.

CONCLUSIONS

Aortic tissue biomechanical metrics varied across regions and with patient characteristics within the aortic zone zero. Assessment of endovascular outcomes in the ascending aorta must closely consider the region of deployment and variable tissue qualities along the length of the landing zone. Regional variation in tissue characteristics should be incorporated into existing patient-specific models of aortic mechanics.

Conical Aortic Neck as a Predictor of Outcome after Endovascular Aneurysm Exclusion: Midterm Results

BACKGROUND

Conical neck may affect endovascular aneurysm repair (EVAR) outcomes. The aim of this study was to present EVAR neck adverse events [endoleak type Ia (ET Ia) and graft migration], in patients with conical neck morphology compared to patients with non-conical necks. An additional analysis of the factors that may affect neck adverse events in patients with conical necks, during the first postoperative year, was executed.

METHODS

A retrospective analysis of prospective data was conducted, including patients that underwent elective EVAR, between 2017 and 2019. All patients completed the clinical and imaging follow-up of the initial 12 months. Regarding imaging, all cases underwent computed tomography angiography (CTA), preoperatively, at the 1st and 12th month of follow-up. Preoperative and postoperative aneurysm anatomic characteristics (supra-renal and infra-renal aortic diameters, aneurysm diameter, neck angle, thrombus, and calcification) were recorded. Proximal neck was defined as the infrarenal aortic segment, with a diameter less than 30 mm. Conical neck was any neck with a diameter increase ≥2 mm per cm of length (from outer-to-outer aortic wall). The proximal 15 mm of the neck length were considered the zone of endograft sealing. Migration was any ≥10 mm caudal movement of the endograft, relative to its position detected at the CTA of the first month. Neck adverse events were defined as the composite event of ET Ia and migration.

RESULTS

The cohort included 150 patients; 66 (44%) presented conical neck morphology. No significant difference was detected regarding the preoperative anatomic characteristics between the conical and non-conical groups. Only distal (15 mm) neck diameter was wider in the conical group (P < 0.001). Supra-renal active fixation was used in 63.3% of the total cohort; 59.5% in patients with non-conical necks and 68.2% in patients with conical morphology (P = 0.275). Graft oversizing was 18.2% and 18.7% in the non-conical and conical group, respectively (P = 0.248). Oversizing >20% was equal between groups [37.8% vs. 33.3%% (P = 0.608) while oversizing ≥30% was more common among patients with conical necks (3.5% vs. 10.6%, P < 0.001, 3.2 odds ratio, 95% confidence interval: 0.79, 12.91). Regarding ET Ia and migration, no difference was recorded between the groups. In a subanalysis among patients with conical necks, a lower graft migration rate was detected among patients with higher oversizing rate (P = 0.037).

CONCLUSIONS

EVAR may offer similarly good midterm outcomes in patients with conical and non-conical neck anatomy. An oversizing to the higher suggested rate may be preventive of graft migration during the first postoperative year in necks with conical morphology. Aggressive oversizing (>20%) do not offer any benefit regarding the prevention of adverse events among patients with conical necks.

Fast and Accurate Computation of the Displacement Force of Stent Grafts after Endovascular Aneurysm Repair

Purpose: Currently, the displacement force of stent grafts is generally obtained using computational fluid dynamics (CFD), which requires professional CFD knowledge to perform the correct simulation. This study proposes a fast, simple, and clinician-friendly approach to calculating the patient-specific displacement force after endovascular aneurysm repair (EVAR). Methods: Twenty patient-specific post-EVAR computed tomography angiography images were used to reconstruct the patient-specific three-dimensional models, then the displacement forces were calculated using CFD and the proposed approaches, respectively, and their numerical differences were compared and analyzed. Results: Based on the derivation and simplification of the momentum theorem, the patient-specific displacement forces were obtained using the information of the patient-specific pressure, cross-sectional area, and angulation of the two stent graft ends, and the average relative error was no greater than 1.37% when compared to the displacement forces calculated by CFD. In addition, the linear regression analysis also showed good agreement between the displacement force values calculated by the new approach and CFD (R = 0.999). Conclusions: The proposed approach can quickly and accurately calculate the patient-specific displacement force on a stent graft and can therefore help clinicians quickly evaluate the post-EVAR displacement force.

Stent-Graft Migration Post-Endovascular Repair of Thoracic Aorta: A Retrospective Cohort Study

Background Migration of the stent-graft post-thoracic endovascular aortic repair (TEVAR) is not uncommon; however, it is sparsely reported. The objective of this study was to assess the incidence, risk factors, and complications of stent-graft migration post-TEVAR.

Materials and Methods Thirty-one patients who underwent TEVAR were retrospectively analyzed. The demographic, anatomical, and procedure-related factors were assessed. The measurements were done along the greater curvature of aorta around two fixed anatomic landmarks, that is, left common carotid artery or neoinnominate artery (hybrid repair) proximally and celiac artery distally. Aortic elongation and migration at proximal, distal, as well as at overlapping zone were measured. More than 10 mm of migration was considered significant.

Results Significant migration was observed in six (19%) patients. No significant migration was observed in the overlapping zone. The proximal landing zone 3 (odds ratio [OR] 12.78, p 0.01) was a significant risk factor, whereas landing zone 2 was a protective factor against the migration (OR 0.08, p 0.02). The odds for migration were more in segments I/3 and II/3 compared with I/2 and II/2, respectively, as per Modified Arch Landing Areas Nomenclature. A single complication was seen in the migration group which was treated by an overlapping stent graft.

Conclusion The stent-graft migration after TEVAR is not uncommon. Type 3 proximal landing zone was a significant risk factor for migration with an increased risk toward I/3 and II/3. Proximal landing zone 2 as well as adequate overlapping distance in multiple stent grafts can prevent migration.

Ethical Approval No IECPG-227/24.06.2020

Single centre experience with Excluder® stent graft; 17-year outcome

BACKGROUND

Endovascular abdominal aortic aneurysm repair (EVAR) has become a mainstay of abdominal aorta aneurysm treatment. Long term follow-up on specific stent grafts is needed.

PATIENTS AND METHODS

This study included 123 patients (104 men; mean age 73.0 years, range 51-89) with abdominal aorta aneurysm, treated with Excluder^® stent graft between October 2002 and June 2008. Periprocedural and follow-up data were retrieved by reviewing the records of our institution, while time and cause of death were retrieved from the National Institute of Public Health. If an abdominal aortic aneurysm rupture was listed as the cause of death, records were retrieved from the institution that issued the death certificate. Our primary goal was to assess the primary technical success rate, type 1 and type 2 endoleak, reintervention free survival, 30-day mortality, the overall survival and aneurysm rupture-free survival.

RESULTS

The median follow-up was 9.7 years (interquartile range, 4.6-13.8). The primary technical success was 98.4% and the 30-day mortality accounted for 0.8%. Secondary procedures were performed in 29 (23.6%) patients during the follow-up period. The one-, five-, ten-, fifteen- and seventeen-year overall survival accounted for 94.3%, 74.0%, 47.2%, 35.8% and 35.8%, while the aneurysm-related survival was 98.4%, 96.3%, 92.6%, 92.6%, 92.6%. In seven (5.7%) patients, abdominal aortic rupture was found as the primary cause of death during follow-up.

CONCLUSIONS

Our data showed that EVAR with Excluder^® stent graft offers good long-term results. More than 75% of patients can be treated completely percutaneously. Late ruptures do occur in the first ten years, raising awareness about regular medical controls.

Structural failure in bridging stentgrafts for branched endovascular aneurysm repair: a case–control study

Objective

To present a case series of spontaneous structural failure of bridging stentgrafts (BSGs) after branched endovascular aortic repair (bEVAR), as well as their failure types and their detection. While bEVAR is a safe and effective procedure, one main limitation is the reintervention rate associated with the BSGs. Structural failure of BSGs, defined as fabric disruption, stent fracture with leak or complete separation is a major cause for reinterventions and difficult to detect in computed tomography angiography (CTA).

Methods

From a multicenter bEVAR complication database, structural BSG failures were identified. Patient and BSG characteristics, detection mode, failure type, treatment and outcome were recorded and compared with bEVAR patients with intact BSGs.

Results

Twenty-three BSG failures were detected in 12 patients with only 43% directly identified in CTA, after a mean of 21.4 months after implantation. The BSGs were Advanta (n = 4), E-Ventus (n = 16) and BeGraft (n = 3) in 10 renal, 9 superior mesenteric, and 4 celiac branches. Religning with another BSG was successful in 20/22 cases, one BSG failure necessitated renal branch embolization (organ loss), and one mesenteric bypass surgery. Two reintervention-related mortalities occurred.

Conclusion

Structural failure of BSGs is a serious limitation for bEVAR, which can result in high reintervention rates and serious complications. BSG failure typically occurs in single-layer types and events are clustered in patients. The necessary reinterventions carry serious morbidity and mortality. Since the use as BSG in bEVAR is off-label with all current BSG manufacturers, caution is advised regarding patient-informed consent.

Computational analysis of endovascular aortic repair proximal seal zone preservation with endoanchors: A case study in cylindrical neck anatomy

BACKGROUND

Endovascular aortic repair is the common approach for abdominal aortic aneurysms, but endoleaks remain a significant problem with long-term success. Endoanchors have been found to reduce the incidence of type 1A endoleaks and can treat intraoperative type 1a endoleaks. However, little is known about the optimal number and position of endoanchors to achieve the best outcome.

METHODS

Using image segmentation and a computational model derived from a reconstructed native patient abdominal aortic aneurysm geometry, the stability of the proximal seal zone was examined through finite element analysis in Abaqus (Dassault Systèmes, Providence, RI). The biomechanical parameter of contact area was compared for varying numbers (0, 2, 4, 8) and positions (proximal, medial, distal) of endoanchors under different adhesion strengths and physiologic pressure conditions.

RESULTS

In every simulation, an increase in adhesion strength is associated with maintenance of proximal seal. For biologically plausible adhesion strengths, under conditions of normal blood pressure (120 mm Hg), the addition of any number of endoanchors increases the stability of the endograft-wall interface at the proximal seal zone by approximately 10% compared with no endoanchors. At hypertensive pressures (200 mm Hg), endoanchors increase the stability of the interface by 20% to 60% compared with no endoanchors. The positioning of endoanchors within the proximal seal zone has a greater effect at hypertensive pressures, with proximal positioning increasing stability by 15% compared with medial and distal positioning and 30% compared with no endoanchors.

CONCLUSIONS

Endoanchors improve fixation within the proximal seal zone particularly under conditions of high peak systolic pressure. Seal zone stabilization provides a mechanism through which endoanchor addition may translate into lower rates of type 1a endoleaks for patients.

Endograft platform does not influence aortic neck dilatation after infrarenal endovascular aneurysm repair with primary endostapling

OBJECTIVES

Aortic endografts used for endovascular aneurysm repair (EVAR) are based on varying skeletal platforms such as stainless steel or nitinol stents, using radial force applied to seal at the aneurysm neck, and varying proximal fixation methods, applying either suprarenal or infrarenal fixation. This study assesses whether varying skeleton/fixation platforms affect neck-related outcomes after primary endostapling with Heli-FX EndoAnchors at EVAR.

METHODS

Retrospective analysis of a prospective database of infrarenal EVAR undertaken at a single centre. Chimney-EVAR, secondary cases were excluded. Primary outcomes analysed included neck diameter evolution from pre-EVAR to latest imaging follow-up, including a comparison of stent platforms to see if there was any outcome difference between those using stainless steel or nitinol, as also freedom from type I endoleakage and migration. Secondary outcomes assessed included average number of EndoAnchors, and sac size patterns before and after EVAR.

RESULTS

A total of 101 patients underwent endostapled infrarenal EVAR between September 2013 and March 2020. After exclusion of ineligible patients, 84 patients (76 male, 8 female, age 73.7 ± 7.8 years) were available for analysis. 57/27 endografts used suprarenal/infrarenal fixation, whilst 16/68 devices were based on stainless steel/nitinol platforms, respectively. Mean oversizing was higher for stainless steel/suprarenal fixation endografts (p = 0.02). A total of 582 EndoAnchors were deployed, averaging 7 ± 2 per patient. Median neck diameter was 25 mm (IQR 22-31) with 22 necks having non-parallel morphology (conical, tapered or bubble). Median follow-up period was 28.5 (IQR 12-43) months. Neck evolution studies suggested aortic neck dilatation of 5 ± 4 mm (p <0.001, paired T-test), independent of platforms employed (p = NS, ANOVA). There was no endograft migration; one immediate post-EVAR endoleak settled by eight weeks. There was a mean 5.7 ± 8.2 mm sac size reduction (p < 0.001, paired T-test).

CONCLUSION

Aortic neck dilatation occurs after EVAR with primary endostapling, but the process may be independent of stainless steel/nitinol platforms, possibly due to the attenuating effect of EndoAnchors. Adjunct aneurysm neck fixation by primary endostapling prevents migration regardless of whether suprarenal/infrarenal fixation is the primary fixative method. Device platform choice therefore may be left to the operator discretion if primary endostapling is applied at EVAR. Freedom from complications such as migration and endoleakage in the intermediate term suggests a higher level of 'tolerance' to aortic neck dilatation with primary endostapling. We would therefore suggest routine usage of EndoAnchors at EVAR when not otherwise contraindicated.