Increased Wall Stress of Saccular Versus Fusiform Aneurysms of the Descending Thoracic Aorta

Three-dimensional characterization of sex differences in abdominal aortic aneurysm progression via vascular deformation mapping

Although abdominal aortic aneurysms (AAA) are more common in men, women are at greater risk for AAA growth/rupture. Vascular deformation mapping (VDM) utilizes deformable image registration to qualify and quantify 3D-AAA growth using computed tomography angiograms (CTA). In this study we leveraged VDM to investigate sex differences in AAA growth patterns. Patients with infra-renal AAA and ≥ 2 CTA were identified. Males and females were matched for age, hypertension, and smoking history. Patient characteristics, maximum diameter (Dmax), and AAA volume were obtained. CTA images were segmented, and VDM was conducted to quantify 3D AAA growth rate per year (GR, cm/year). Statistical shape modeling was utilized to compute mean aneurysm shapes and 3D GR. Average GR was evaluated at specific regions of the aortic surface for males and females. Seventeen males and 17 females were matched. At the individual level, there were no sex differences in changes in Dmax or AAA volume. However, females had larger GR across the anterior and right lateral AAA (1.33 vs 0.89 and 1.56 vs 0.74 cm/year, respectively), despite no difference in posterior or left lateral AAA GR. Despite comparable changes in Dmax, AAA volume, and GR magnitude, women demonstrated a more eccentric, anterior-predominant, AAA growth pattern.

Saccular and Fusiform Abdominal Aortic Aneurysms Treated With Endovascular Repair Differ in Presentation and Treatment Threshold: Analyses Using a National Clinical Database in Japan

BACKGROUND

Saccular abdominal aortic aneurysms (AAAs) are considered to be at higher risk of rupture than fusiform AAAs, but not much is known about the extent of this risk. Therefore, this study aimed to compare the rupture presentation between fusiform and saccular AAAs.

METHODS AND RESULTS

This is a retrospective cohort study on 27 290 patients who underwent primary endovascular repair for a degenerative AAA between 2016 and 2019, and who were registered in the National Clinical Database in Japan. At operation for nonruptured case, the aneurysm diameter was significantly smaller in saccular AAAs than in fusiform AAAs (median, 44.0 versus 51.0 mm; P<0.001). Similarly, aneurysm diameter at rupture was significantly smaller in saccular AAAs than in fusiform AAAs (median, 55.6 versus 68.0 mm; P<0.001). The likelihood of repair for rupture was significantly higher in saccular AAAs than in fusiform AAAs in the 40- to 54-mm diameter range, in which saccular morphology was found to be an independent risk factor for rupture against fusiform morphology by adjusting for sex and aneurysm diameter (odds ratio, 2.54 [95% CI, 1.75-3.69]). In addition, receiver-operating characteristic curve analysis revealed that the cutoff diameter to predict rupture was smaller in saccular AAAs than in fusiform AAAs (50.5 and 59.5 mm, respectively) based on the Youden index.

CONCLUSIONS

Saccular AAAs presented at smaller diameters than fusiform AAAs in patients with ruptured AAAs treated with endovascular aortic repair, which supports the idea that saccular AAAs should be treated at smaller diameters.

Significant thrombus in saccular aneurysm in a patient with polycythemia: a case report

BACKGROUND

Morphologically, the risk of aortic aneurysm rupture is mainly evaluated based on its type (e.g., fusiform or saccular) and diameter. Based on the finite element analysis, peak wall stress has been identified as a more sensitive and specific predictor of rupture in recent years. Moreover, in finite analysis, the neck of aneurysm is the highest peak wall stress and is associated with the rupture point.

CASE PRESENTATION

A saccular aortic aneurysm (84 mm) was incidentally detected during preoperative examination for chronic empyema in a 74-year-old male patient with a history of polycythemia. Aortic arch graft replacement using an open stent was performed.

CONCLUSIONS

Morphologically, this case was associated with a very high risk of rupture; nevertheless, it did not rupture. In this case, a mural thrombus (likely formed due to polycythemia) covered the neck of aneurysm that is experiencing the highest peak wall stress and is associated with the rupture point. The mural thrombus decreased peak wall stress and could reduce the risk of rupture even for huge saccular aneurysms. Furthermore, the mural thrombus was fully occupied in aneurysms, such as during coil embolization. Thus, polycythemia could decrease the risk of rupture of huge saccular aneurysms.

Clinical presentation, outcomes, and threshold for repair by sex in degenerative saccular vs fusiform aneurysms in the descending thoracic aorta

OBJECTIVE

Saccular-shaped thoracic aortic aneurysms (TAAs) are often treated at smaller diameters compared with fusiform TAAs, despite a lack of strong clinical evidence to support this practice. The aim of this study was to examine differences in presentation, treatment, and outcomes between saccular TAAs and fusiform TAAs in the descending thoracic aorta. We also examined the need for sex-specific treatment thresholds for TAAs.

METHODS

All Vascular Quality Initiative (VQI) patients undergoing thoracic endovascular aneurysm repair (TEVAR) for degenerative TAAs in the descending thoracic aorta from 2012 through 2022 were reviewed. Patients were stratified by urgency: emergent/urgent vs elective repairs (ruptured/symptomatic). Demographics, comorbidities, anatomical/procedural characteristics, and outcomes for fusiform TAAs and saccular TAAs were compared. Cumulative distribution curves were used to plot the proportion of patients who underwent emergent/urgent repair according to sex-stratified aortic diameter.

RESULTS

Among 655 emergent/urgent TEVARs, 37% were performed for saccular TAAs, whereas among 1352 elective TEVARs, 35% had saccular TAA morphology. Compared with fusiform TAAs, saccular TAAs more frequently underwent emergent/urgent (ruptured/symptomatic) TEVAR below the repair threshold in both females (<50 mm: 38% vs 10%; relative risk, 3.39; 95% confidence interval [CI], 2.04-5.70; P < .001), and males (<55 mm: 47% vs 21%; relative risk, 2.26; 95% CI, 1.60-3.18; P < .001). Moreover, among patients with emergent/urgent fusiform TAAs, females presented at smaller diameters compared with males, whereas there was no difference in preoperative aneurysm diameter among patients with saccular TAAs. Regarding outcomes, emergent/urgent treated saccular TAAs had similar postoperative outcomes and 5-year mortality compared with fusiform TAAs. Nevertheless, in the elective cohort, patients with saccular TAAs had similar postoperative mortality compared with those with fusiform TAAs, but a lower rate of postoperative spinal cord ischemia (0.7% vs 3.2%; P = .010). Furthermore, patients with saccular TAAs had a higher rate of 5-year mortality compared with their fusiform counterparts (23% vs 17%; hazard ratio, 1.53; 95% CI, 1.12-2.10; P = .010).

CONCLUSIONS

Patients with saccular TAAs underwent emergent/urgent TEVAR at smaller diameters than those with fusiform TAAs, supporting current clinical practice guideline recommendations that saccular TAAs warrant treatment at smaller diameters. Furthermore, these data support a sex-specific treatment threshold for patients with fusiform TAAs, but not for those with saccular TAAs. Although there were no differences in outcomes following TEVAR between morphologies in the emergent/urgent cohort, patients with saccular TAAs who were treated electively were associated with higher 5-year mortality compared with those with fusiform TAAs.

2022 ACC/AHA guideline for the diagnosis and management of aortic disease: A report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate.

STRUCTURE

Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

Fatal ascending aortic aneurysm in a patient with systemic lupus erythematosus: A case report

Aortic aneurysm is a potentially life-threatening condition with higher incidence in patients with systemic lupus erythematosus(SLE). Patients usually present with nonspecific symptoms and diagnosis is typically made incidentally through imaging studies. Management strategies include medical therapy to control inflammation and hypertension, surgical intervention for large or symptomatic aneursyms, and close monitoring for early detection of complications. We present a case of a 49-year female with multiple joint pain and other nonspecific symptoms for 7 years. Anti-ds DNA and ANA titre were significantly high and CT angiogram showed ascending aortic aneurysm measuring 5.5 cm. Conservative management was started with steroids, hydroxychloroquine, and antihypertensives, while awaiting surgery. However she suddenly collapsed, probably due to aneurysm rupture and could not be revived. Our case report therefore emphasizes the importance of close surveillance and timely intervention to minimize the morbidity and mortality in these patients.

2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate. Structure: Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate.

STRUCTURE

Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

Thoracic and Thoracoabdominal Aneurysms: Etiology, Epidemiology, and Natural History

Thoracic aortic aneurysms and thoracoabdominal aneurysms are often found incidentally. Complications include dissection or rupture. Most of the thoracic aortic aneurysms and thoracoabdominal aneurysms develop in patients with risk factors for atherosclerosis. Younger patients without significant cardiovascular risk factors may have a genetic basis and include syndromes such as Marfan, Ehlers-Danlos, and Loeys-Dietz and bicuspid aortic valve. Most thoracic aneurysms grow slowly over time and factors that accelerate growth rate include dissection, aneurysm size, bicuspid valve disease, and Marfan syndrome. Size cutoffs where complications occur determine when surgery or intervention should be considered.

The hemodynamic effect of eccentricity in visceral branched aneurysms with multilayer stents

It is preliminarily acknowledged that multilayer stent (MS) is a promising alternative technology in the treatment of visceral branched aneurysms, but hemodynamic consequences of eccentricity in such aneurysms with MS are less examined. In this work, we performed a time-dependent simulation of branched aneurysms of various eccentricities with different stent layers, and thrombosis-related parameters, such as time-averaged wall shear stress (TAWSS), oscillating shear index (OSI), and relative residence time (RRT), were also analyzed. Our results revealed that MS can generally restore laminar flow inside the stent, and allow proper perfusion to vital organs while also fostering a relatively secluded hemodynamic environment for thrombosis formation. Particularly, a flow in the aneurysm sac communicating between the main artery and side branch forms at early systole. However, MS fails to completely eliminate detrimental flow impingement after peak systole, which may hinder aneurysm recovery, especially in the cases of eccentric aneurysms. Therefore, saccular aneurysms should be treated with more caution than fusiform aneurysms. And further therapeutic attempts to keep both perfusion in the proximal region of the aneurysm and isolation in the distal region of the aneurysm should be considered.

Treatment strategies for inferior vena cava aneurysms

OBJECTIVE

An inferior vena cava (IVC) aneurysm is a rare but potentially life-threatening entity. We successfully embolized an IVC aneurysm in a patient with history of blue rubber bleb nevus syndrome, a rare syndrome with multiple venous malformations. This new case was added to a literature review of previously reported cases, to analyze the management algorithm.

METHODS

A PubMed search for all English-language articles and abstracts of IVC aneurysm were conducted. A comprehensive descriptive analysis, including etiology, presentation, classification, comorbidities, and treatment options of our case joining all previously published cases, is presented and discussed.

RESULTS

Including our new case, a total of 74 (44 males) IVC aneurysms were analyzed. The average age was 39.0 ± 21.1 years (range, 0.4-89 years). Forty-nine (66.2%) were symptomatic; common symptoms include abdominal or back pain (24/74, 32.4%) and leg swelling or heaviness (20/74, 27.0%). Nineteen (19/59, 33.2%) were complicated with vena cava thrombosis, and 14 (14/59, 23.7%) were complicated with deep venous thrombosis of lower extremities. Thirty-two (43.2%) accepted surgical or endovascular intervention. There were 26 type I, 13 type II, 31 type III, and 4 type IV aneurysms. In type I group, 25 of 26 were treated conservatively, 2 deaths were reported. In type II group, 5 of 13 accepted conservative treatment. In type III group, 9 of 31 accepted conservative treatment, and 1 death was reported. In type IV group, 3 of 4 accepted conservative treatment, and 1 death was reported.

CONCLUSIONS

Conservative management can be conducted in type I and type IV groups with close surveillance. For type II and III groups, considering the high incidence of vena cava thrombosis and risk of rupture, more active treatment should be considered.

A comparison of subjective clinical and objective judgement of abdominal aortic aneurysm morphology

BACKGROUND

We compared the subjective, clinical judgement of "saccular" morphology with the objective judgement of mechanical structural analysis.

METHODS

Using structural analysis with the finite element method, we previously created a simple model of abdominal aortic aneurysm (AAA) that visualized the distribution of the maximum principal stress (MPS) in the aortic wall and identified the area of prominent stress. AAA "saccular" morphology was determined according to the area showing MPS>0.03 MPa. AAAs with low aspect ratio (horizontally long AAA sac) and small fillet radius were defined as "saccular." Twelve vascular surgeons were recruited. First, they judged the AAA as saccular or fusiform with 3-dimensional images at their clinical impression (subjective "eyeball" judgement). Second, they applied the deformable figure tools on the simple AAA-shaped sagittal view in the application model for 30 AAA cases. From the data of the tools applied, the mechanical structural analysis was performed semi-automatically and the morphology was judged with the objective "simple application."

RESULTS

The structural analysis revealed that only one case was judged as saccular by 11 out of 12 surgeons and the other 29 AAAs were judged as fusiform by two-thirds or more of the surgeons. In contrast, 5 cases were subjectively judged as saccular by eight and more of the surgeons.

CONCLUSIONS

The clinical judgement of AAA saccular morphology by the vascular surgeons was different from the judgement derived from the mechanical structural analysis using the application model. The saccular morphology may be theoretically rare in AAAs.

An infected aneurysm of the vertebral artery following cervical pyogenic spondylitis: a case report and literature review

BACKGROUND

An important complication of pyogenic spondylitis is aneurysms in the adjacent arteries. There are reports of abdominal aortic or iliac aneurysms, but there are few reports describing infected aneurysms of the vertebral artery. Furthermore, there are no reports describing infected aneurysms of the vertebral arteries following cervical pyogenic spondylitis. We report a rare case of an infected aneurysm of the vertebral artery as a complication of cervical pyogenic spondylitis, which was successfully treated by endovascular treatment.

CASE PRESENTATION

Cervical magnetic resonance imaging (MRI) of a 59-year-old man who complained of severe neck pain showed pyogenic spondylitis. Although he was treated extensively by antibiotic therapy, his neck pain did not improve. Follow-up MRI showed the presence of a cyst, which was initially considered an abscess, and therefore, treatment initially included guided tapping and suction under ultrasonography. However, under ultrasonographic examination an aneurysm was detected. The contrast-enhanced computed tomography (CT) scan showed an aneurysm of the vertebral artery. Following endovascular treatment (parent artery occlusion: PAO), the patient's neck pain disappeared completely.

CONCLUSION

Although there are several reports of infected aneurysms of the vertebral arteries, this is the first report describing an infected aneurysm of the vertebral artery as a result of cervical pyogenic spondylitis. Whenever a paraspinal cyst exist at the site of infection, we recommend that clinicians use not only X-ray, conventional CT, and MRI to examine the cyst, but ultrasonography and contrast-enhanced CT as well because of the possibility of an aneurysms in neighboring blood vessels. It is necessary to evaluate the morphology of the aneurysm to determine the treatment required.

Persistence of Intraluminal Thrombus Makes Saccular Aneurysm More Biologically Active than Fusiform in an Experimental Rat Model

INTRODUCTION

Saccular aneurysms are thought to have a worse prognosis than fusiform aneurysms in humans, due to hemodynamic reasons. However, data comparing hemodynamic and biology in saccular and fusiform aneurysms are lacking. The main objective was to evaluate the impact of aneurysm morphology on intra-luminal thrombus (ILT) formation and activity.

METHODS

Forty Lewis rats were ran-domly divided into 2 groups of 20: "saccular" (Group A) and "fusiform" (Group B) aneurysms. Decellularized thoracic aortas from guinea pigs were xenografted to create saccular or fusiform aneurysms. Final imaging evaluation of the aneurysms was carried out during the third week, by quantitative Doppler ultrasound and magnetic resonance imaging. Assays of myeloperoxidase (MPO), platelet factor 4 (PF4), advanced oxidation protein products (AOPPs) iron and matrix metallopeptidase-9 (MMP-9) were performed as biological criteria.

RESULTS

Quantitatively, saccular aneurysms are characterized by a more thicker ILT, lower inflow velocities and more important relative backflow velocities as compared to fusiform aneurysms. Compared to fusiform, saccular aneurysms released significantly more MPO (p = 0.004), PF4 (p = 0.02), AOPPs (p < 0.002), iron (p < 0.0001) and MMP-9 (p < 0.04).

CONCLUSION

Experimental saccular and fusiform aneurysms show differential specific hemodynamics, which seem to impact the histology and the biology of the ILT in each type of aneurysm.

Visceral Artery Aneurysms: Diagnosis, Surveillance, and Treatment

Visceral artery aneurysms (VAAs) are a rare, but serious clinical entity as rupture confers a high rate of mortality. Data regarding the prevalence, treatment, and prognosis of VAAs is largely from case series, as true randomized trials are lacking. The incidence of VAAs has risen over the decades with advances in imaging technology, availability, and utilization. Even in the presence of symptoms, the prompt diagnosis of VAAs may be challenging as symptoms are often nonspecific and varied. Although there are no definitive treatment guidelines, asymptomatic VAAs require treatment in the following scenarios: when the aneurysm diameter is greater than 2 cm, when identified during pregnancy, when multiple aneurysms are present, and in the case of hepatic transplant. Similar to therapeutic trends in other vascular beds, advances in endovascular devices and techniques have driven an "endovascular first" approach for the treatment of VAAs. However, although the success rates of endovascular repair are impressive, surgical intervention is still necessary in treating centers. This paper reviews the pathophysiology, clinical features, anatomic characteristics, and management strategies required for the effective diagnosis and treatment of VAAs.

Open repair management of a patient with aortic arch saccular aneurysm, penetrating atherosclerotic ulcer, one vessel coronary artery disease and an isolated dissection of the abdominal aorta

Isolated saccular compared to fusiform aneurysm is considered to be a rare entity with challenges of its own. A 62-year-old female was diagnosed with a case of saccular aneurysm and penetrating atherosclerotic ulcer of the aortic arch. Additionally, she also had one vessel coronary artery disease and type B abdominal aortic dissection. She was then managed with open aortic arch repair and coronary artery bypass grafting. If required, elective endovascular repair will be done for the abdominal aorta on a later date.

Characterizing saccular aortic arch aneurysms from the geometry-flow dynamics relationship

OBJECTIVE

Low wall shear stress (WSS) has been reported to be associated with accelerated atherosclerosis, aneurysm growth, or rupture. We evaluated the geometry of aortic arch aneurysms and their relationship with WSS by using the 4-dimensional flow magnetic resonance imaging to better characterize the saccular aneurysms.

METHODS

We analyzed the geometry in 100 patients using multiplanar reconstruction of computed tomography. We evaluated WSS and vortex flow using 4-dimensional flow magnetic resonance imaging in 16 of them, which were compared with 8 age-matched control subjects and eight healthy young volunteers.

RESULTS

Eighty-two patients had a saccular aneurysm, and 18 had a fusiform aneurysm. External diameter/aneurysm length ratio and sac depth/neck width ratio of the fusiform aneurysms were constant at 0.76 ± 0.18 and 0.23 ± 0.09, whereas those of saccular aneurysms, especially those involving the outer curvature, were higher and more variable. Vortex flow was always present in the aneurysms, resulting in low WSS. When the sac depth/neck width ratio was less than 0.8, peak WSS correlated inversely with luminal diameter even in the saccular aneurysms. When this ratio exceeded 0.8, which was the case only with the saccular aneurysms, such correlation no longer existed and WSS was invariably low.

CONCLUSIONS

Fusiform aneurysms elongate as they dilate, and WSS is lower as the diameter is larger. Saccular aneurysms dilate without proportionate elongation, and they, especially those occupying the inner curvature, have higher and variable sac depth/neck width ratio. When this ratio exceeds 0.8, WSS is low regardless of diameter, which may explain their malignant clinical behavior.

Morphology of Small Abdominal Aortic Aneurysms Should be Considered before Continued Ultrasound Surveillance

BACKGROUND

To evaluate abdominal aortic aneurysm (AAA) morphology in a cohort of patients presenting with ruptured AAA (rAAA) and to explore if aneurysms with diameters below the recommended threshold for elective repair (<55 mm) have some distinctive morphological characteristics.

METHODS

All patients diagnosed with rAAA using computed tomography (CT) scans between January 2006 and June 2013 were eligible for this study. Where CT scans of acceptable quality were available, images were reconstructed in a dedicated three-dimensional vascular workstation for evaluation of aneurysm diameters and morphology. All morphological characteristics were defined according to the reporting standards for endovascular aortic aneurysm repair. Additionally, fusiform AAAs were defined as aneurysms involving the whole circumference of the aortic wall and saccular AAAs as spherical aneurysms involving only a portion of the aortic circumference.

RESULTS

A total of 248 patients were identified. Of those, 83% (n = 206) had high-quality CT scans available and were included in the study. Patients were on average 75 years old and 85% were men. Mean aneurysm diameter was 76 ± 14 mm and 95% (n = 197) had fusiform morphology. Six percent (n = 12) were <55 mm and those included all saccular aneurysms in women (n = 3) and 22% of saccular aneurysms in men (n = 2). The remaining saccular aneurysms (n = 4) were small with a maximal diameter of 56 mm. Aneurysms <55 mm had less angulated proximal necks than their larger counterparts (P < 0.01). No other morphological differences were found between the groups.

CONCLUSIONS

Ruptured aneurysms are often large and the ≥55 mm threshold for elective repair is probably appropriate. However, approximately 6% of rAAAs are <55 mm, with a significant portion being saccular, especially in women. Morphological assessment of AAAs with CT scans should be considered in small aneurysms (40-55 mm), particularly in women, to exclude saccular morphology before continued ultrasound surveillance.

Is There a Role for Biomechanical Engineering in Helping to Elucidate the Risk Profile of the Thoracic Aorta?

Clinical estimates of rupture and dissection risk of thoracic aortic aneurysms are based on nonsophisticated measurements of maximum diameter and growth rate. The use of aortic size alone may overlook the role that vessel heterogeneity plays in assessing the risk of catastrophic complications. Biomechanics may help provide a more nuanced approach to predict the behavior of thoracic aortic aneurysms. In this report, we review modeling studies with an emphasis on mechanical and fluid dynamics analyses. We identify open problems and highlight the future possibility of a multidisciplinary approach that includes biomechanics and imaging to evaluate the likelihood of rupture or dissection.

Biomechanical analysis of an aortic aneurysm model and its clinical application to thoracic aortic aneurysms for defining "saccular" aneurysms

Background

We aimed to develop a simple structural model of aortic aneurysms using computer‐assisted drafting (CAD) in order to create a basis of definition for saccular aortic aneurysms.

Methods and Results

We constructed a simple aortic aneurysm model with 2 components: a tube similar to an aorta and an ellipse analogous to a bulging aneurysm. Three parameters, including the vertical and horizontal diameters of the ellipse and the fillet radius, were altered in the model. Using structural analysis with the finite element method, we visualized the distribution of the maximum principal stress (MPS) in the aortic wall and identified the area(s) of prominent stress. We then selected patients with thoracic aortic aneurysms in whom the aneurysm expansion rates were followed up and applied the theoretical results to the raw imaging data. The maximum MPS drastically increased at areas where the aspect ratio (vertical/horizontal) was <1, indicating that “horizontally long” hypothetical ellipses should be defined as “saccular” aneurysms. The aneurysm expansion rate for the patients with thoracic aneurysms conforming to these parameters was significantly high. Further, “vertically long” ellipses with a small fillet might be candidates for saccular aneurysms; however, the clinical data did not support this.

Conclusions

Based on the biomechanical analysis of a simple aneurysm model and the clinical data of the thoracic aortic aneurysms, we defined “horizontally long” aortic aneurysms with an aspect ratio of <1 as “saccular” aneurysms.

New-generation stent grafts for endovascular management of thoracic pseudoaneurysms after aortic coarctation repair

OBJECTIVE

Late thoracic aneurysms develop in 5% to 12% of patients having undergone open repair for coarctation of the aorta (CoA). We report our early results for thoracic endovascular aortic repair for pseudoaneurysms after CoA repair.

METHODS

From 2008 to 2013, data regarding demographics, aneurysm morphology, procedure, and follow-up were collected prospectively on all patients treated for pseudoaneurysms after CoA repair. Retrospective analysis of identified patients was then performed.

RESULTS

Thirteen patients (six men, seven women) were treated. Patients were a median age, 45 years (interquartile range (IQR), 39-56; range, 27-66 years, and the median time after CoA repair to aneurysm treatment was 34 years (IQR, 24-40 years). All patients had saccular pseudoaneurysms of the aortic arch, with a median aneurysm size of 4.1 cm (IQR, 3.4-5.1 cm). The left subclavian artery (LSCA) was involved in 10 patients and was occluded at presentation in three. Four patients had concurrent LSCA revascularization with carotid-subclavian bypass, one had aortic arch hybrid repair, and the LSCA was intentionally covered in two patients. Patients underwent thoracic endovascular aortic repair using the conformable TAG (6 of 13; W. L. Gore & Associates, Flagstaff, Ariz), Valiant device (4 of 13; Medtronic, Minneapolis, Minn), and a custom-made Relay endograft with LSCA scallop (4 of 13; Bolton Medical, Barcelona, Spain). Technical success was 100%, with satisfactory deployment of the stent grafts in all patients. There was no 30-day mortality, stroke, or paraplegia. Median follow-up was 15 months (IQR, 9-19 months; range, 1-67 months). Two type II endoleaks from an intercostal artery were managed conservatively, and one type Ib endoleak was treated successfully with distal stent extension.

CONCLUSIONS

In this cohort, new-generation stent grafts have good early clinical and radiologic outcomes, avoiding the need for redo open surgery. Management of the LSCA can be tailored to individual patients with new stent graft technology. Long-term follow-up of these patients is crucial to understanding whether endovascular management of this cohort is acceptable.

A modern experience with saccular aortic aneurysms

OBJECTIVE

Repair of saccular aortic aneurysms (SAAs) is frequently recommended based on a perceived predisposition to rupture, despite little evidence that these aneurysms have a more malignant natural history than fusiform aortic aneurysms.

METHODS

The radiology database at a single university hospital was searched for the computed tomographic (CT) diagnosis of SAA between 2003 and 2011. Patient characteristics and clinical course, including the need for surgical intervention, were recorded. SAA evolution was assessed by follow-up CT, where available. Multivariate analysis was used to examine potential predictors of aneurysm growth rate.

RESULTS

Three hundred twenty-two saccular aortic aneurysms were identified in 284 patients. There were 153 (53.7%) men and 131 women with a mean age of 73.5±10.0 years. SAAs were located in the ascending aorta in two (0.6%) cases, the aortic arch in 23 (7.1%), the descending thoracic aorta in 219 (68.1%), and the abdominal aorta in 78 (24.2%). One hundred thirteen (39.8%) patients underwent surgical repair of SAA. Sixty-two patients (54.9%) underwent thoracic endovascular aortic repair, 22 underwent endovascular aneurysm repair (19.5%), and 29 (25.6%) required open surgery. The average maximum diameter of SAA was 5.0±1.6 cm. In repaired aneurysms, the mean diameter was 5.4±1.4 cm; in unrepaired aneurysms, it was 4.4±1.1 cm (P<.001). Eleven patients (3.9%) had ruptured SAAs on initial scan. Of the initial 284 patients, 50 patients (with 54 SAA) had CT follow-up after at least 3 months (23.2±19.0 months). Fifteen patients (30.0%) ultimately underwent surgical intervention. Aneurysm growth rate was 2.8±2.9 mm/yr, and was only weakly related to initial aortic diameter (R2=.19 by linear regression, P=.09 by multivariate regression). Decreased calcium burden (P=.03) and increased patient age (P=.05) predicted increased aneurysm growth by multivariate analysis.

CONCLUSIONS

While SAA were not found to have a higher growth rate than their fusiform counterparts, both clinical and radiologic follow-up is necessary, as a significant number ultimately require surgical intervention. Further clinical research is necessary to determine the optimal management of SAA.