Endovascular repair of abdominal aortic aneurysms: vascular anatomy, device selection, procedure, and procedure-specific complications

Abdominal aortic aneurysm histomorphology shows different inflammatory aspects among patients and is not associated with classic risk factors - the HistAAA study

AIMS

Abdominal aortic aneurysm (AAA) treatment is upon a diameter threshold. Attempts for medical growth abrogation have failed thus far. This study aims to elucidate the heterogeneity of AAA histomorphology in correlation to individual patient and aneurysm metrics.

METHODS AND RESULTS

Samples from the left anterior aneurysm wall underwent histologic analysis including angiogenesis, calcification, fibrosis, type and grade of inflammation in adventitia and media. Clinical information and state of aneurysm (intact, symptomatic, ruptured, inflammatory) were retrieved. Semi-automated geometric analysis (Endosize©, Therenva) and finite element methods (A4Clinics© Research Edition, Vascops GmbH) were included.364 patients' samples (85.4% male, median age 69 years) were scored for acute or chronic inflammation, both not associated with rupture (52x), symptomatic disease (37x) or diameter (57 [52-69] mm; p = 0.87). The degree of fibrosis and the presence of angiogenesis were significantly higher (both p < 0.001) with increasing inflammation, which in turn significantly decreased with patient age (est = - 0.015/year, p = 0.017). No significant differences were seen for acute (vs. elective), male (vs. female) or diabetic patients. Aneurysm geometry (n=252) or annual growth rate (n=142) were not associated with histologic characteristics. Yet, local luminal thrombus formation was significantly higher with increasing inflammation (p = 0.04).

CONCLUSION

Type and degree of inflammation are the most distinguishable histologic characteristics in the AAA wall between individual patients, yet are not associated with diameter or rupture. Local luminal thrombus formation is associated with inflammatory features and suggests a vivid bio-physical compartment with intra-individual age-dependent differences.

Endovascular Abdominal Aortic Aneurysm Repair

A great majority of abdominal aortic aneurysm are treated with endovascular aortic repair (EVAR) in current practice. EVAR has lower peri-procedural mortality and morbidity compared to open surgical repair. Anatomic factors such as aneurysm neck morphology, iliac anatomy, and access vessel anatomy need careful assessment for the successful performance of EVAR. Evolving technology and techniques are allowing more patients to be treated with EVAR with better long-term outcomes.

Atherosclerotic Abdominal Aortic Aneurysms on Computed Tomography Angiography: A Narrative Review on Spectrum of Findings, Structured Reporting, Treatment, Secondary Complications and Differential Diagnosis

Atherosclerotic abdominal aortic aneurysms (AAAs) are a common vascular pathology with significant morbidity and mortality risks. Timely diagnosis, accurate characterization, and standardized reporting are critical for effective management and monitoring of atherosclerotic AAAs. Imaging modalities, particularly computed tomography angiography (CTA), play a pivotal role in the detection, treatment planning, and identification of both primary and secondary complications, as well as distinguishing AAAs from other etiologies. This narrative review provides a comprehensive exploration of the spectrum of imaging findings in atherosclerotic AAAs on CTA, underscoring the importance of structured reporting. Additionally, it examines therapeutic approaches and complications, and it differentiates AAAs from inflammatory, mycotic, and traumatic variants, serving as a primer for radiologists in AAA evaluation.

Overcoming Anatomical Constraints: A Case of Successful Endovascular Repair in a High-Risk Patient With a Short, Angulated Abdominal Aortic Aneurysm

Endovascular aneurysm repair (EVAR) for abdominal aortic aneurysms (AAAs) is often limited by anatomical factors such as short necks (less than 15 mm) and significant angulation (over 60 degrees), making EVAR unsuitable. We present a case of a 60-year-old man with multiple comorbidities and a short, markedly angulated AAA neck. Despite being deemed unsuitable for EVAR, the patient underwent successful EVAR with the chimney technique. At the one-month follow-up, the patient had no complications, stable renal function, and no detected endoleak or other complications on routine CT scans. Cardiac tests were normal. This case challenges traditional contraindications and highlights the potential for EVAR in challenging anatomical situations. Incorporating the chimney technique and reinforcing the proximal neck can prevent complications, while future research should focus on tailored EVAR strategies addressing individual needs and anatomical challenges.

Deep Learning Based Automatic Segmentation of the Thoracic Aorta from Chest Computed Tomography in Healthy Korean Adults

OBJECTIVE

Segmenting the aorta into zones based on anatomical landmarks is a current trend to better understand interventions for aortic dissection or aneurysm. However, comprehensive reference values for aortic zones are lacking. The aim of this study was to establish reference values for aortic size using a fully automated deep learning based segmentation method.

METHODS

This retrospective study included 704 healthy adults (mean age 50.6 ± 7.5 years; 407;57.8%] males) who underwent contrast enhanced chest computed tomography (CT) for health screening. A convolutional neural network (CNN) was trained and applied on 3D CT images for automatic segmentation of the aorta based on the Society for Vascular Surgery and Society of Thoracic Surgeons classification. The CNN generated masks were reviewed and corrected by expert cardiac radiologists.

RESULTS

Aortic size was significantly larger in males than in females across all zones (zones 0 - 8, all p < .001). The aortic size in each zone increased with age, by approximately 1 mm per 10 years of age, e.g., 25.4, 26.7, 27.5, 28.8, and 29.8 mm at zone 2 in men in the age ranges of 30 - 39, 40 - 49, 50 - 59, 60 - 69, and ≥ 70 years, respectively (all p < .001).

CONCLUSION

The deep learning algorithm provided reliable values for aortic size in each zone, with automatic masks comparable to manually corrected ones. Aortic size was larger in males and increased with age. These findings have clinical implications for the detection of aortic aneurysms and other aortic diseases.

Early experience with patient-specific unibody bifurcated fenestrated-branched devices for complex endovascular aortic aneurysm repair

OBJECTIVE

Short distances between the lowest visceral/renal artery and the aortic bifurcation are technically challenging during complex endovascular aortic aneurysm repair (EVAR), particularly after previous infrarenal repair. Traditionally, inverted limb bifurcated devices have been used in addition to fenestrated-branched (FB) endografts, but short overlap, difficult cannulation, and potential crushing of bridging stents are limitations for their use. This study reviews the early experience of patient-specific company manufactured devices (PS-CMDs) with a unibody bifurcated FB design for complex EVAR.

METHODS

Consecutive complex EVAR procedures over a 34-month period with unibody bifurcated FB-devices as part of physician-sponsored investigational device exemption studies at two institutions were reviewed. Unibody bifurcated FB designs included FB bifurcated or fenestrated inverted limb devices. End points included technical success, survival, frequency of type I or III endoleaks, limb occlusion, and secondary interventions.

RESULTS

Among 168 patients undergoing complex EVAR, 33 patients (19.6%; 78.7% male; mean age, 77 years) received unibody bifurcated FB PS-CMDs. FB bifurcated and fenestrated inverted limb devices were used in 31 (93.9%) and 2 (6.06%) patients, respectively. The median maximum aneurysm diameter was 61 mm (interquartile range [IQR], 55-69 mm). Prior EVAR was reported by 29 patients (87.9%), of whom 2 (6.06%) had suprarenal stents. A short distance between the lowest renal artery and aortic bifurcation was demonstrated in 30 patients (90.9%), with median distance of 47 mm (IQR, 38-54 mm). Preloaded devices were used in 23 patients (69.7%). A total of 128 fenestrations were planned; 22 (17.2%) were preloaded with guidewires and 5 (3.9%) with catheters. The median operative time was 238 minutes (226-300 minutes), with a median fluoroscopy time of 65.5 minutes (IQR, 56.0-77.7 minutes) and a median dose area product of 147 mGy∗cm2 (IQR, 105-194 mGy∗cm2). Exclusive femoral access was used in 14 procedures (42.4%). Technical success was 100%. Target vessel primary patency was 100% at a median follow-up time of 11.7 months (IQR, 3.5-18.6 months). Two patients (6.06%) required reintervention for iliac occlusion; one patient required stenting and the other a femoral-femoral bypass. No aortic-related deaths occurred after the procedure. During follow-up, 11 type II endoleaks (33.3%) and 1 type Ib endoleak (3.03%) were detected; the latter was treated with leg extension. No type Ia or III endoleaks occurred.

CONCLUSIONS

Complex EVAR using unibody bifurcated FB-PS-CMDs is a simple, safe, and cost-effective alternative for the treatment of patients with short distances between the renal arteries and the aortic bifurcation. Further studies are required to assess benefits and durability of unibody bifurcated FB devices.

Outcomes and Imaging Surveillance Adherence in Juxta-Renal Aortic Aneurysms Repairs: A VASQIP Retrospective Study

OBJECTIVE

Fenestrated endovascular aortic repair (FEVAR) has demonstrated its value in the management of juxtarenal abdominal aortic aneurysms (JAAA), but data were largely derived from clinical trials and high-volume centers. Although routine imaging surveillance is recommended following endovascular interventions, little is known regarding follow-up compliance post-FEVAR. We examined the real-world treatment outcomes and adherence to the postoperative follow-up protocol after elective interventions for JAAA at Veteran Affairs (VA) health care facilities, the largest integrated health care system in the United State.

METHODS

This is a retrospective cohort study. We queried the Veteran Affairs Surgical Quality Improvement Program (VASQIP) database for elective FEVARs and juxtarenal open surgical repairs (j-OSR), then merged follow-up imaging and mortality information. Our primary endpoints were mortality following FEVAR and j-OSR, and adherence to surveillance guidelines. Secondary endpoints included short-term postoperative complications.

RESULTS

A total of 1110 veterans who underwent first-time JAAA repair between 2002 and 2019 (FEVAR, 26% [n=290]; j-OSR, 74% [n=820]) were included in the analysis. The number of j-OSR captured in the database gradually declined by 50%, from 62 interventions in 2002 to 28 in 2019, while FEVAR procedures quadrupled from 20 procedures in 2014 to 94 in 2019. The median follow-up was 3.99 years (95% confidence interval [CI]: 3.73-4.87) for FEVAR patients, and 12.80 (12.31-13.70) for those that underwent jOSR. A significantly lower risk of 30-day mortality was observed following FEVAR compared to j-OSR (1% vs 5%, odds ratio [OR]: 5.03 [1.54-16.38]; p=0.003). At 5 years, FEVAR was linked with significantly higher mortality (41.5% vs 21%, p<0.001) after adjusting for confounders (aHR=2.10 [1.56-2.82], p<0.001). Of surviving patients, the follow-up imaging rate was 66.3% by 1-year post-FEVAR. Follow-up rate at 5 years was 7% post-FEVAR compared to 32% post j-OSR.

CONCLUSION

Elective FEVAR is associated with lower perioperative mortality and morbidities compared to elective j-OSR for juxtarenal aortic aneurysms. However, the perioperative survival benefits of FEVAR diminish over time, with its mortality surpassing that of j-OSR at longer follow-up periods. The compliance with post-FEVAR imaging surveillance is also low. Further research is warranted to develop strategies to improve adherence to imaging surveillance protocols.

CLINICAL IMPACT

This study provides real-world evidence on the outcomes and follow-up adherence following fenestrated endovascular aortic repair (FEVAR) for juxtarenal abdominal aortic aneurysms (JAAA) in the Veterans Affairs health care system. With FEVAR's increasing use, the findings highlight the need for improved surveillance protocols, as adherence to postoperative imaging declines significantly after the first year. Clinicians should be aware of the risk of long-term mortality despite FEVAR's short-term benefits, urging better follow-up strategies that relay a survival benefit for patients.

Computed Tomography Angiography for Aortic Diseases

Aortic pathologies encompass a heterogeneous group of disorders, including acute aortic syndrome, traumatic aortic injury , aneurysm, aortitis, and atherosclerosis. The clinical manifestations of these disorders can be varied and non-specific, ranging from acute presentations in the emergency department to chronic incidental findings in an outpatient setting. Given the non-specific nature of their clinical presentations, the reliance on non-invasive imaging for screening, definitive diagnosis, therapeutic strategy planning, and post-intervention surveillance has become paramount. Commonly used imaging modalities include ultrasound, computed tomography (CT), and MR imaging. Among these modalities, computed tomography angiography (CTA) has emerged as a first-line imaging modality owing to its excellent anatomic detail, widespread availability, established imaging protocols, evidence-proven indications, and rapid acquisition time.

Computational Comparison of the Mechanical Behavior of Aortic Stent-Grafts Derived from Auxetic Unit Cells

PURPOSE

Inappropriate stent-graft (SG) flexibility has been frequently associated with endovascular aortic repair (EVAR) complications such as endoleaks, kinks, and SG migration, especially in tortuous arteries. Stents derived from auxetic unit cells have shown some potential to address these issues as they offer an optimum trade-off between radial stiffness and bending flexibility.

METHODS

In this study, we utilized an established finite element (FE)-based approach to replicate the mechanical response of a SG iliac limb derived from auxetic unit cells in a virtual tortuous iliac aneurysm using a combination of a 180° U-bend and intraluminal pressurization. This study aimed to compare the mechanical performance (flexibility and durability) of SG limbs derived from auxetic unit cells and two commercial SG limbs (Z-stented SG and circular-stented SG models) in a virtual tortuous iliac aneurysm. Maximal graft strain and maximum stress in stents were employed as criteria to estimate the durability of SGs, whereas the maximal luminal reduction rate and the bending stiffness were used to assess the flexibility of the SGs.

RESULTS

SG limbs derived from auxetic unit cells demonstrated low luminal reduction (range 4-12%) with no kink, in contrast to Z-stented SG, which had a kink in its central area alongside a high luminal reduction (44%).

CONCLUSIONS

SG limbs derived from auxetic unit cells show great promise for EVAR applications even at high angulations such as 180°, with acceptable levels of durability and flexibility.

Editor's Choice -- Type IIIb Endoleaks: Fabric Perforations of Explanted New Generation Endoprostheses

OBJECTIVE

To analyse explanted endografts (EGs) and describe fabric degradation responsible for type IIIb endoleaks.

METHODS

As part of the European collaborative retrieval programme, 32 EGs with fabric defects on macroscopic evaluation were selected. The explanted EGs were processed and studied based on the ISO 9001 certified standard protocol. It includes instructions on the collection, transportation, cleaning, and examination of explanted material. The precise analysis was performed with a digital microscope of 20 - 200 times magnification. Possible perforation mechanisms were assessed in stress tests.

RESULTS

The median time to explantation of the 32 EGs was 54 months. The explants included 65 separate EG modules, with 46 (70.8%) having a combined 388 fabric perforations. Each EG had a median of 4.79 mm2 (interquartile range [IQR] 9.86 mm2) of cumulated hole area (an average of 0.13% of an EG's area). There were 239 (61.6%) expanded polytetrafluoroethylene (ePTFE; 11 EGs) and 149 (38.4%) polyethylene terephthalate (PET; 21 EGs) fabric ruptures, with no difference in hole distribution between these types of material. Overall, 126 (32.5%) stent related and 262 (67.5%) non-stent related fabric perforations were identified. Perforations caused by fabric fatigue in ePTFE (151, 63.2%) and material kinking in PET (41, 27.5%) were the most common. The stent related perforations were larger in size (0.80 mm2) than non-stent related perforations (0.19 mm2); p < .001. Wider interstent spaces and prolonged implantation duration were associated with an increased risk of stent related perforation development; p < .001 and p = .004, respectively. Large stent related perforations were also detected in the short term, suggesting mechanical issues as underlying causes.

CONCLUSION

The fabric of EGs may degrade and lead to the development of perforations. The largest perforations are stent related. Their occurrence and size depend on the implantation time and the EG shape affected by arterial tortuosity. The conclusions are limited to the samples from a select explant group.

The Challenge of Endoleaks in Endovascular Aneurysm Repair (EVAR): A Review of Their Types and Management

An abdominal aortic aneurysm (AAA) is a dilatation of the abdominal aorta above 3 cm or 50% greater than the segment above. It is a dangerous condition accounting for a substantial number of deaths per year and increasing at an alarming rate. Various factors come into play in the development of AAAs, which this study has elaborated on, including smoking and old age, demographics, and comorbid conditions. Endovascular aneurysm repair (EVAR) is a newer treatment modality used for AAAs in which an endograft device is placed into the aorta, thereby creating a bypass tract from the aneurysm and generating flow mimicking that of the natural aorta. It is minimally invasive and associated with less postoperative mortality and reduced hospital stay. However, EVAR is also associated with significant postoperative complications, including endoleaks, which were reviewed in depth. Endoleaks are postprocedural leaks into the aneurysm sac that are usually identified immediately after graft placement and indicate treatment failure. They are of five subtypes, categorized according to their mechanism of development. The most common type is type II endoleaks, and the most dangerous is type I endoleaks. Each subtype has multiple management options with varying rates of success. Prompt identification along with appropriate treatment of endoleaks can lead to better postoperative outcomes and improved quality of life for patients.

Atypical patterns of spinal segment degeneration in patients with abdominal aortic aneurysms

PURPOSE

Abdominal aortic aneurysms (AAAs) affect the vascular perfusion of the lumbar spine. The treatment of AAAs with endovascular aortic aneurysm repair (EVAR) completely occludes the direct vascular supply to the lumbar spine. We hypothesized that patients with AAA who undergo EVAR show a different pattern of spinal degeneration than individuals without AAA.

METHODS

In this retrospective institutional review board-approved study, 100 randomly selected patients with AAA who underwent EVAR with computed tomography (CT) scans between 2005 and 2017 were compared with age- and gender-matched controls without AAA. In addition, long-term follow-up CT images (> 6 months before EVAR, at the time of EVAR, and > 12 months after EVAR) of the patients were analysed to compare the progression of degeneration from before to after EVAR. Degeneration scores, lumbar levels with the most severe degeneration, and lumbar levels with progressive degeneration were analysed in all CT images. Fisher's exact test, Wilcoxon signed-rank test, and Mann-Whitney U test were performed for statistical analyses.

RESULTS

Compared with the control group (n = 94), the most severe degeneration was more commonly detected in the mid-lumbar area in the patient group (n = 100, p = 0.016), with significantly more endplate erosions being detected in the lumbar spine (p = 0.015). However, EVAR did not result in significant additional acceleration of the degenerative process in the long-term follow-up analysis (n = 51).

CONCLUSION

AAA is associated with atypical, more cranially located spinal degradation, particularly in the mid-lumbar segments; however, EVAR does not seem to additionally accelerate the degenerative process. This observation underlines the importance of disc and endplate vascularization in the pathomechanism of spinal degeneration.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Rupture risk parameters upon biomechanical analysis independently change from vessel geometry during abdominal aortic aneurysm growth

Objective

The indication for abdominal aortic aneurysm (AAA) repair is based on a diameter threshold. However, mechanical properties, such as peak wall stress (PWS) and peak wall rupture index (PWRI), influence the individual rupture risk. This study aims to correlate biomechanical and geometrical AAA characteristics during aneurysm growth applying a new linear transformation-based comparison of sequential imaging.

Methods

Patients with AAA with two sequential computed tomography angiographies (CTA) were identified from a single-center aortic database. Patient characteristics included age, gender, and comorbidities. Semiautomated segmentation of CTAs was performed using Endosize (Therenva) for geometric variables (diameter, neck configuration, α/β angle, and vessel tortuosity) and for finite element method A4 Clinics Research Edition (Vascops) for additional variables (intraluminal thrombus [ILT]), vessel volume, PWS, PWRI). Maximum point coordinates from at least one CTA 6 to 24 months before their final were predicted for the final preoperative CTA using linear transformation along fix and validation points to estimate spatial motion. Pearson's correlation and the t test were used for comparison.

Results

Thirty-two eligible patients (median age, 70 years) were included. The annual AAA growth rate was 3.7 mm (interquartile range [IQR], 2.25-5.44; P < .001) between CTs. AAA (+17%; P < .001) and ILT (+43%; P < .001) volume, maximum ILT thickness (+35%; P < .001), β angle (+1.96°; P = .017) and iliac tortuosity (+0.009; P = .012) increased significantly. PWS (+12%; P = .0029) and PWRI (+16%; P < .001) differed significantly between both CTAs. Both mechanical parameters correlated most significantly with the AAA volume increase (r = 0.68 [P < .001] and r = 0.6 [P < .001]). Changes in PWS correlated best with the aneurysm neck configuration. The spatial motion of maximum ILT thickness was 14.4 mm (IQR, 7.3-37.2), for PWS 8.4 mm (IQR, 3.8-17.3), and 11.5 mm (IQR, 5.9-31.9) for PWRI. Here, no significant correlation with any of the aforementioned parameters, patient age, or time interval between CTs were observed.

Conclusions

PWS correlates highly significant with vessel volume and aneurysm neck configuration. Spatial motion of maximum ILT thickness, PWS, and PWRI is detectable and predictable and might expose different aneurysm wall segments to maximum stress throughout aneurysm growth. Linear transformation could thus add to patient-specific rupture risk analysis.

Clinical Relevance

Abdominal aortic aneurysm rupture risk assessment is a key feature in future individualized therapy approaches for patients, since more and more data are obtained concluding a heterogeneous disease entity that might not be addressed ideally looking only at diameter enlargement. The approach presented in this pilot study demonstrates the feasibility and importance of measuring peak wall stress and rupture risk indices based on predicted and actual position of maximum stress points including intraluminal thrombus.

Contrast-enhanced US Evaluation of Endoleaks after Endovascular Stent Repair of Abdominal Aortic Aneurysm

Ruptured abdominal aortic aneurysm (AAA) carries high morbidity and mortality. Elective repair of AAA with endovascular stent-grafts requires lifetime imaging surveillance for potential complications, most commonly endoleaks. Because endoleaks result in antegrade or retrograde systemic arterialized flow into the excluded aneurysm sac, patients are at risk for recurrent aneurysm sac growth with the potential to rupture. Multiphasic CT has been the main imaging modality for surveillance and symptom evaluation, but contrast-enhanced US (CEUS) offers a useful alternative that avoids radiation and iodinated contrast material. CEUS is at least equivalent to CT for detecting endoleak and may be more sensitive. The authors provide a general protocol and technical considerations needed to perform CEUS of the abdominal aorta after endovascular stent repair. When there are no complications, the stent-graft lumen has homogeneous enhancement, and no contrast material is present in the aneurysm sac outside the stented lumen. In patients with an antegrade endoleak, contrast material is seen simultaneously in the aneurysm sac and stent-graft lumen, while delayed enhancement in the sac is due to retrograde leak. Recognition of artifacts and other potential pitfalls for CEUS studies is important for examination performance and interpretation. Online supplemental material is available for this article. ^©RSNA, 2022.

Can We Still Teach Open Repair of Abdominal Aortic Aneurysm in The Endovascular Era? Single-Center Analysis on The Evolution of Procedural Characteristics Over 15 Years

OBJECTIVE

In many vascular centers an endovascular first policy for the treatment of abdominal aortic aneurysms (AAA) has resulted in endovascular aortic repair (EVAR) outnumbering open aortic repair (OAR). The declining routine in OAR raises the question whether this might influence procedural outcomes and diminish surgical expertise for current and future vascular surgeons. We aimed to analyze OAR outcomes, AAA morphology and procedural details over the past 15 years while an endovascular first approach was successively implemented.

PARTICICPANTS AND DESIGN

All patients operated for (i)ntact infra-/juxtarenal AAA between January 1, 2005 and December 31, 2019 were identified. Outcome parameters were length of stay (hospital/ICU), in-hospital mortality and medical/surgical complications. Operative details were clamping zone, access and graft configuration. AAA anatomy including neck and iliac parameters was analyzed with Endosize©. Logistic regression, uni- and multivariate analysis were applied.

RESULTS

293 patients received elective OAR for iAAA. Baseline characteristics (age, sex, hypertension, smoking, occlusive disease, coronary disease, hyperlipidemia, diabetes, renal insufficiency and obesity) did not change over time. The number of OAR dropped significantly (-0.5 cases/year p = 0.02). The procedure time (2005-2007: 192.2 ± 87.5min to 2017-2019: 235.6 ± 88.2min; p = 0.0001) and the length of stay (2005-2007: 12.0 ± 7.9 to 2017-2019: 17.0 ± 23.1; p = 0.03) increased significantly, whereas the in-hospital mortality, length of ICU stay and complication rates didn't, nor did AAA anatomy. Upon multivariate analysis, annual number of OAR and any additional anastomosis significantly influenced procedure time, trainee involvement, for example, did not. Hospital length-of-stay depended on patient age (p = 0.002), complication rates (p < 0.0001) and procedure time (p = 0.006).

CONCLUSION

Mortality and complication rates for OAR have remained low and constant. With the increase of EVAR, the absolute number of OARs has decreased significantly. However, the total procedure time has increased and depends significantly on the annual number of OARs in total and per surgeon. This might influence outcome parameters and should be implanted in future surgical education.

The Technological Advancement to Engineer Next-Generation Stent-Grafts: Design, Material, and Fabrication Techniques

Endovascular treatment of aortic disorders has gained wide acceptance due to reduced physiological burden to the patient compared to open surgery, and ongoing stent-graft evolution has made aortic repair an option for patients with more complex anatomies. To date, commercial stent-grafts are typically developed from established production techniques with simple design structures and limited material ranges. Despite the numerous updated versions of stent-grafts by manufacturers, the reoccurrence of device-related complications raises questions about whether the current manfacturing methods are technically able to eliminate these problems. The technology trend to produce efficient medical devices, including stent-grafts and all similar implants, should eventually change direction to advanced manufacturing techniques. It is expected that through recent advancements, especially the emergence of 4D-printing and smart materials, unprecedented features can be defined for cardiovascular medical implants, like shape change and remote battery-free self-monitoring. 4D-printing technology promises adaptive functionality, a highly desirable feature enabling printed cardiovascular implants to physically transform with time to perform a programmed task. This review provides a thorough assessment of the established technologies for existing stent-grafts and provides technical commentaries on known failure modes. They then discuss the future of advanced technologies and the efforts needed to produce next-generation endovascular implants.

Evaluando la experiencia local: primeros 50 casos de reparo endovascular de aneurismas aórticos en Manizales, Colombia

Introducción. En las últimas décadas, la terapia endovascular en aneurismas aórticos abdominales ha ganado un papel representativo en los escenarios quirúrgicos, lo que nos motivó a conocer los resultados de este procedimiento en nuestra población. Métodos. Estudio analítico retrospectivo en el cual se incluyeron los primeros 50 casos de aneurismas aórticos abdominales con terapia endovascular, en la ciudad de Manizales, Colombia, entre los años 2015 y 2021. Se describió la población estudiada, la relación de los antecedentes prequirúrgicos con las complicaciones posoperatorias, la estancia hospitalaria y la mortalidad. Resultados. La edad promedio fue de 73 años, el sexo predominante fue el femenino (72 %), el aneurisma fusiforme fue el tipo más frecuente (63,3 %), con un diámetro promedio de 70 mm (+/- 17,3 mm). En relación con los antecedentes, el más frecuente fue hipertensión arterial (86 %), encontrándose una asociación entre la presencia de enfermedad pulmonar obstructiva crónica e hipertensión arterial con las complicaciones. Se encontró también relación entre el valor de creatinina con las complicaciones. Las complicaciones tempranas fueron de carácter leve en la mayoría de los casos (30,6 %), a diferencia de las tardías, que fueron principalmente graves (12,5 %), asociadas a una mortalidad del 10,2 % y una estancia hospitalaria promedio de 10,8 días (mediana de 5 días). Conclusiones. La población analizada tiene una alta carga de morbilidad, en la cual factores como los antecedentes médicos prequirúrgicos y la función renal, se asocian con una mayor morbilidad postquirúrgica y mortalidad.

CT angiography for the assessment of EVAR complications: a pictorial review

Endovascular aneurysm repair (EVAR) is a minimally invasive treatment proposed as an alternative to open repair in patients with abdominal aortic aneurysms. EVAR consists in a stent-graft placement within the aorta in order to exclude the aneurysm from arterial circulation and reduce the risk of rupture. Knowledge of the various types of devices is mandatory because some stents/grafts are more frequently associated with complications. CT angiography is the gold standard diagnostic technique for preprocedural planning and postprocedural surveillance. EVAR needs long-term follow-up due to the high rate of complications. Complications can be divided in endograft device-related and systemic complications. The purpose of this article is to review the CT imaging findings of EVAR complications and the key features for the diagnosis.

Endovascular Aortic Aneurysm Repair: A Narrative Review

Endovascular aortic aneurysm repair (EVAR) has evolved as minimally invasive method of treating infrarenal abdominal aortic aneurysms (AAA) with perioperatively mortality of less than 1% compared with 5% with open AAA repair as suggested by many randomized control trials. Computed tomography angiography is the imaging of choice for appropriate selection of a patient with EVAR. For patients with unsuitable anatomy, advanced EVARs techniques, such as fenestrated, branch, and chimney EVARs, are also increasingly being offered to patients with equal success. Patients with ruptured AAA are treated with this minimally invasive procedure. Percutaneous EVAR emerged with less of wound-related complications. Endoleaks are the most common complications peculiar to this procedure, and most are preventable by preoperative planning. They are detected on completion angiogram or on the surveillance imaging. This review discusses indications of EVAR, its selection criteria, procedural steps, and common complications associated with this procedure and advanced EVARs.

A contemporary review of non-invasive methods in diagnosing abdominal aortic aneurysms

Background: Currently, the impact of abdominal aortic aneurysm may be changing despite the aging population, but may be ambiguous given the decline in smoking, the use of screening methods, and integration of non-surgical treatment. Objective: This review aimed to assess the most common currently used non-invasive methods to identify abdominal aortic aneurysm, namely ultrasound and computed tomography. Methods: PRISMA guidelines were utilized to retrieve original articles from the past five years. All retrospective and prospective studies/trials were included, but limited to US and CT abdominal aortic aneurysm diagnostic imaging methods. Qualitative assessment of study quality is described. Results: Three of the six studies reported abdominal aortic aneurysm screening data. The estimated prevalence of abdominal aortic aneurysm for the three studies ranged from 4.5% to 6.2%. CT had slightly higher sensitivity and US had higher specificity for abdominal aortic aneurysm diagnosis. Two of the described studies assessed technical issues and problems with contemporary imaging of abdominal aortic aneurysm. The final article described measuring abdominal aortic aneurysm function of aortic distensibility and its pulse wave velocity for a comprehensive assessment of the abdominal aortic aneurysm via standard CT imaging. Conclusions: Both US and CT are useful diagnostic imaging modalities for abdominal aortic aneurysm, but remain with unique pitfalls and propensity for errors, notwithstanding patient-related errors. Technical issues in imaging with both ultrasound and CT are not straightforward. The potential value of an integrated CT protocol with CT-US fusion and/or assessment of aortic function rather than solely aortic anatomy may further diminish diagnostic complexities.

A Simple Target Will Save the Day and the Kidney: This Is How We Perform Our Endovascular Fenestrated Graft Procedure

With the advent of state-of-the-art imaging modalities, increasing population age, and advanced preventive medical treatments, medical device design attempts to keep up with procedural demand. An abdominal aortic aneurysm (AAA) is a recognized, potentially fatal disease process where strides have been made in screening, detection, and treatment since its discovery. With the introduction of percutaneous endograft procedures in 1991, open surgical treatment is nearly a lost art. Endovascular aortic repair is now the gold standard. However, short landing zone necks, hostile angulation, and markedly dilated seal zones present challenges for one size fits all endovascular aortic devices. Suprarenal and juxtarenal fenestrated aortic grafts are the most advanced individually customized grafts invented to date. Subsequently, proper placement of these complex devices still presents challenges. We present a method for preoperative renal stent placement for target purposes. This article includes a pictorial guide and describes the tips and pitfalls for easy proper AAA exclusion with a fenestrated aortic graft. We were successful in the deployment of the fenestrated graft device and the exclusion of an aortic aneurysm while preserving the patency of the renal arteries. The patient had no postoperative complications. During 18-month postoperative surveillance, imaging demonstrated proper graft positioning without evidence of an endoleak. In fenestrated endovascular aortic repair, preoperative renal stenting is paramount for targeting purposes. This allows for the precise and timely deployment of the renal limbs through the fenestrations while minimizing the risk of postoperative complications, including renal artery occlusion.

Comparative Outcome Analysis of N-Butyl Cyanoacrylate Embolization of the False Lumen Versus Thoracic Endovascular Aortic Repair in Aortic Dissection

PURPOSE

To evaluate the feasibility, safety, and effectiveness of N-butyl cyanoacrylate (NBCA) embolization for the treatment of aortic dissection.

MATERIALS AND METHODS

In this single-center retrospective study conducted from February 2003 to June 2019, NBCA embolization of an aortic false lumen was attempted in 12 patients (median age, 59 y; range, 41-68 y) and thoracic endovascular aortic repair (TEVAR) was performed in 53 patients (median age, 59 y; range, 37-70 y) for aortic dissection with one or more indications of persisting pain, malperfusion, rupture or impending rupture, maximal aortic diameter ≥ 55 mm, and/or rapid aortic enlargement. The main exclusion criterion for embolization was the presence of fast blood flow in the aortic false lumen on aortography. The efficacy of NBCA embolization and TEVAR was compared by evaluating technical and clinical outcomes, repeat intervention-free survival (RFS), and overall survival (OS).

RESULTS

Technical success was achieved in 11 of the 12 patients treated with NBCA embolization (91.7%), and clinical success was achieved in 9 of these 11 (81.8%). No significant difference was found between embolization and TEVAR in clinical success rates (embolization, 81.8%; TEVAR, 84.9%; P = .409) or procedure-related complications (embolization, 1 patient [8.3%]; TEVAR, 4 patients [7.5%]; P = .701). In addition, embolization showed comparable 5-y RFS (embolization, 82.5% ± 9.3; TEVAR, 85.5% ± 4.8; P = .641) and 5-y OS (embolization, 100%; TEVAR, 95.4% ± 3.2; P = .744) rates to TEVAR.

CONCLUSIONS

NBCA embolization of the false lumen in aortic dissection seems to be a safe and effective treatment modality for the closure of false lumen in selected patients.

Endovascular Aneurysm Repair for Abdominal Aortic Aneurysm: A Comprehensive Review

Abdominal aortic aneurysm (AAA) can be defined as an abnormal, progressive dilatation of the abdominal aorta, carrying a substantial risk for fatal aneurysmal rupture. Endovascular aneurysmal repair (EVAR) for AAA is a minimally invasive endovascular procedure that involves the placement of a bifurcated or tubular stent-graft over the AAA to exclude the aneurysm from arterial circulation. In contrast to open surgical repair, EVAR only requires a stab incision, shorter procedure time, and early recovery. Although EVAR seems to be an attractive solution with many advantages for AAA repair, there are detailed requirements and many important aspects should be understood before the procedure. In this comprehensive review, fundamental information regarding AAA and EVAR is presented.

Endovascular Abdominal Aortic Aneurysm Repair

Most abdominal aortic aneurysms are treated with endovascular repair (EVAR) in current practice. EVAR has lower periprocedural mortality and morbidity than open surgical repair. Aneurysm neck morphology, iliac anatomy, and access vessel anatomy need careful assessment for the successful performance of EVAR. Regular and long-term follow-up with imaging is mandatory after EVAR, and patients who are less likely to comply are less favorable EVAR candidates. Endoleaks are the most frequent complication of EVAR. Most can be managed with transcatheter or endovascular means. Evolving technology and techniques are allowing more patients to be treated with EVAR with better long-term outcomes.

Multidetector Computed Tomography in Traumatic and Nontraumatic Aortic Emergencies: Emphasis on Acute Aortic Syndromes

Aortic emergencies comprise of a list of conditions which are uncommon but are potentially fatal. Prognosis is usually determined by emergent diagnosis and treatment and hence radiology plays a key role in patient management. In this article, we aim to review the various causes of aortic emergencies and the relevant imaging findings placing special emphasis on acute aortic syndromes.

The Impact of Epidural Analgesia on Perioperative Morbidity or Mortality after Open Abdominal Aortic Aneurysm Repair

BACKGROUND

Epidural analgesia (EA) is frequently used as an adjuvant to general anesthesia (GA) for improved postoperative analgesia and reduced rates of cardiac, pulmonary, and renal complications. However, only a few studies have examined EA-GA specifically during open abdominal aortic aneurysm (AAA) repair. The effects of EA-GA specifically during open AAA repair regarding postoperative outcomes are unknown. This study was performed to evaluate postoperative outcomes in patients undergoing open AAA repair with EA-GA versus GA alone.

METHODS

We performed a retrospective analysis for patients undergoing surgery between January 1, 2014 and December 31, 2016 using the National Surgical Quality Improvement Program (NSQIP) database. Propensity score matching was used to establish cohorts for analysis. Multivariable logistic regression was performed to determine significant perioperative outcomes for each anesthesia type. A total of 2,171 patients underwent open AAA repair in our date range; we excluded emergent and ruptured AAA. A total of 2,145 patients were included in our analysis, of whom 653 patients received EA-GA and 1,492 patients received GA only.

RESULTS

Major postoperative outcomes included mortality, pulmonary cardiac and renal complications, infections, thrombosis, and blood transfusion requirement (including Cell-Saver usage). Additional overall outcomes included hospital length of stay, return to the operating room, and readmission. Patients in EA + GA and GA alone groups were comparable regarding demographics, functional status, and comorbidities. Decreased odds of readmission was observed in EA + GA compared with GA (0.49, 95% CI [0.28-0.86]; P = 0.014); and increased odds of receiving a blood transfusion was observed in those who underwent EA + GA (1.63, 95% CI [1.23-2.14]; P = 0.001). No difference was observed between patients who had an AAA repair with EA + GA versus GA alone with regard to mortality, return to operating room, major pulmonary, cardiac, renal, or infectious complications.

CONCLUSIONS

EA + GA was not associated with decreased mortality or decreased rates of major postoperative pulmonary, cardiac, or renal complications. EA + GA was associated with increased transfusion requirements and decreased rates of hospital readmission.

Meta-analysis of fenestrated endovascular aneurysm repair versus open surgical repair of juxtarenal abdominal aortic aneurysms over the last 10 years

Background

Juxtarenal abdominal aortic aneurysms pose a significant challenge whether managed endovascularly or by open surgery. Fenestrated endovascular aneurysm repair (FEVAR) is now well established, but few studies have compared it with open surgical repair (OSR). The aim of this systematic review was to compare short- and long-term outcomes of FEVAR and OSR for the management of juxtarenal aortic aneurysms.

Methods

A literature search was conducted of the Ovid Medline, EMBASE and PubMed databases. Reasons for exclusion were series with fewer than 20 patients, studies published before 2007 and those concerning ruptured aneurysms. Owing to variance in definitions, the terms 'juxta/para/suprarenal' were used; thoracoabdominal aortic aneurysms were excluded. Primary outcomes were 30-day/in-hospital mortality and renal insufficiency. Secondary outcomes included major complication rates, rate of reintervention and rates of endoleak.

Results

Twenty-seven studies were identified, involving 2974 patients. Study designs included 11 case series, 14 series within retrospective cohort studies, one case-control study and a single prospective non-randomized trial. The pooled early postoperative mortality rate following FEVAR was 3·3 (95 per cent c.i. 2·0 to 5·0) per cent, compared with 4·2 (2·9 to 5·7) per cent after OSR. After FEVAR, the rate of postoperative renal insufficiency was 16·2 (10·4 to 23·0) per cent, compared with 23·8 (15·2 to 33·6) per cent after OSR. The major early complication rate following FEVAR was 23·1 (16·8 to 30·1) per cent versus 43·5 (34·4 to 52·8) per cent after OSR. The rate of late reintervention after FEVAR was higher than that after OSR: 11·1 (6·7 to 16·4) versus 2·0 (0·6 to 4·3) per cent respectively.

Conclusion

No significant difference was noted in 30-day mortality; however, FEVAR was associated with significantly lower morbidity than OSR. Long-term durability is a concern, with far higher reintervention rates after FEVAR.

Type 2 endoleaks in endovascular aortic repair: cone beam CT and automatic vessel detection to guide the embolization

Background Dual-phase cone beam computed tomography (DP-CBCT) and automatic vessel detection (AVD) software are helpful tools for detecting arteries before planned endovascular interventions. Purpose To evaluate the usefulness of DP-CBCT and AVD software in guiding the trans-arterial embolization (TAE) of challenging T2 lumbar endoleaks (T2-L-EL). Material and Methods Ten patients with T2-L-EL were included in this study. The accuracy of DP-CBCT and the AVD software was defined by the ability to detect the endoleak and arterial feeding vessel, respectively. Technical success was defined as the correct positioning of the microcatheter using AVD software and the successful embolization of the endoleak. Clinical success was defined as the absence of recurrent endoleaks during follow-up and the stability of the sac diameter for persistent endoleaks. The total volume of iodinated contrast medium, overall procedure time, mean procedural radiation dose, and mean fluoroscopy time were recorded. Results The EL was detected by DP-CBCT in all patients. The AVD software identified the feeding arterial branch in all cases. In one patient, the nidus of the endoleak was not reached due to the small caliber of the feeding artery, even though the software had clearly identified the vessel route. The mean contrast volume was 109 mL, the mean overall procedural time was 74.3 min. The mean procedural radiation dose was 140.97 Gy cm², and the mean fluoroscopy time was 29.8 min. Conclusion The use of DP-CBCT and the AVD software is feasible and may facilitate successful embolization in challenging occult T2-L-EL with complex vasculature.

Postoperative imaging of the aorta

Considerable progress has been made in the management of diseases of the thoracic and abdominal aorta over the past decades, ranging from advances in open repair to the advent of minimally invasive endovascular techniques. Along with this comes an equivalent rise in imaging necessity for these patients, both in preoperative planning and postoperative surveillance. With the growing complexity and diversity of vascular procedures and techniques, it is essential to have a solid understanding of the imaging features and postoperative complications of these procedures to avoid imaging pitfalls. This review is an attempt to define the normal postoperative appearance and important complications of various open and endovascular surgical techniques of the thoracic and abdominal aorta.

A computational assessment of the hemodynamic effects of crossed and non-crossed bifurcated stent-graft devices for the treatment of abdominal aortic aneurysms

There are several issues attributed with abdominal aortic aneurysm endovascular repair. The positioning of bifurcated stent-grafts (SG) may affect SG hemodynamics. The hemodynamics and geometrical parameters of crossing or non-crossing graft limbs have not being totally accessed. Eight patient-specific SG devices and four pre-operative cases were computationally simulated, assessing the hemodynamic and geometrical effects for crossed (n= 4) and non-crossed (n= 4) configurations. SGs eliminated the occurrence of significant recirculations within the sac prior treatment. Dean's number predicted secondary flow locations with the greatest recirculations occurring at the outlets especially during the deceleration phase. Peak drag force varied from 3.9 to 8.7N, with greatest contribution occurring along the axial and anterior/posterior directions. Average resultant drag force was 20% smaller for the crossed configurations. Maximum drag force orientation varied from 1.4° to 51°. Drag force angle varied from 1° to 5° during one cardiac cycle. 44% to 62% of the resultant force acted along the proximal centerline where SG migration is most likely to occur. The clinician's decision for SG positioning may be a critical parameter, and should be considered prior to surgery. All crossed SG devices had an increased spiral flow effect along the distal legs with reductions in drag forces.

The emergency medicine approach to abdominal vascular graft complications

INTRODUCTION

Abdominal aortic aneurysm (AAA) is a deadly condition, particularly with rupture. Emergency physicians provide vital frontline care to the diagnosis and treatment of this disease. Endovascular aortic repair (EVAR) has become the gold standard for treatment of AAA, but the management of EVAR complications is not well discussed in the emergency medicine literature.

OBJECTIVE OF THIS REVIEW

The purpose of this article is to provide an emergency medicine-focused review of the complications of EVAR.

DISCUSSION

Although many complications may arise after AAA repair, the most common include aortoenteric fistula, endoleak, limb ischemia, and graft infection. All potential complications should receive vascular surgery consultation and hemodynamic resuscitation. Aortoenteric fistula often presents nonspecifically with gastrointestinal (GI) bleeding, abdominal pain, and vomiting. Computed tomography with intravenous contrast is required for diagnosis. An endoleak is defined by vascular flow outside of the graft. The optimal diagnostic modality includes triple phase computed tomographic scan (noncontrast, arterial, delayed phase). Limb ischemia may occur before 2 months, or in a later period, with symptoms ranging from claudication to complete neurovascular compromise. Graft infection is most commonly due to Staphylococcus aureus, and imaging can suggest the diagnosis. Definitive diagnosis requires tissue or fluid sampling. Through an understanding of these complications, emergency physicians may improve patient outcomes.

CONCLUSIONS

With the growing use of EVAR, emergency physician exposure to complications of this procedure is increasing. Knowledge of the complication presentations, diagnoses, and management can play an integral role patient care.

Unstable abdominal aortic aneurysms: a review of MDCT imaging features

Abdominal aortic aneurysms are commonly encountered during abdominal CT imaging, and size-based parameters for surgical or endovascular repair are well established. Aneurysms greater than 5 cm in diameter are recognized as representing an increased rupture risk and meriting intervention. Increasingly, additional interest has been generated in recognizing imaging features which may herald instability and portend a higher chance for potentially catastrophic rupture. This article will review and illustrate such signs, including hyperattenuation of mural thrombus, rapid expansion, low thrombus to lumen ratio, intimal calcification disruption, posterior mural draping, and saccular outpouching. Other features of complicated abdominal aneurysms including perianeurysmal inflammation, aortocaval and aortoenteric fistula formation will also be addressed. Heightened awareness of these features and their prognostic implications, as well as timely communication with the clinical service, is critical for the interpreting radiologist.

Detecting Aortic Graft Complications: A Spectrum of Computed Tomography Findings

Endovascular aneurysm repair (EVAR) is a successful technique as well as an excellent alternative to the surgical management of abdominal aortic aneurysms. EVAR has improved the mortality and morbidity of many patients who would have otherwise suffered greatly from the consequences of abdominal aortic aneurysms. However, EVAR is not without complications. Some complications require lifelong surveillance, whereas others may necessitate immediate surgical intervention. We discuss the various modalities available for the surveillance as well as the common complications that can be seen on computed tomography.