Abdominal Aortic Aneurysm Rupture Research Articles

Precocious Rupture Of Abdominal Aortic Aneurysms Below Size Criteria For Repair: Risk Factors And Outcomes

Practice guidelines recommend elective repair for abdominal aortic aneurysms (AAA) ≥5.5 cm in men and ≥5 cm in women to prevent rupture. However, some rupture at smaller diameters. We identify risk factors for precocious rupture (rAAA) below this threshold and compare outcomes following rAAA repair above/below size criteria.

破裂性腹部大動脈瘤に対するdamage control surgeryの必要性が示唆された1例(Case of resuscitation from ruptured abdominal aortic aneurysm: necessity of damage control surgery)

要旨症例は87歳の男性。背部痛を主訴に前医へ救急搬送され，腹部大動脈瘤破裂の診断となった。当院への転院搬送中に心停止となったが，心肺蘇生を行い自己心拍再開して当院に到着した。直接手術室へ入室し，手術を開始した。入室時に再度心停止となったが，ステント拡張用のバルーンカテーテルで遮断を試みながら心肺蘇生を継続することで自己心拍再開した。前医で撮影された造影CT解析の結果，ステントグラフト内挿術の解剖学的条件を満たさず，開腹手術の方針とした。人工血管置換術は完遂したが，大量出血および低体温を原因とした凝固能破綻による静脈出血がコントロールできず，damage control surgery（DCS）に準じて早期の手術終了を図る方針としてガーゼパッキング後に閉腹した。術後2日目にガーゼ除去および閉腹術に臨んだが，開腹するとS状結腸から直腸にかけての壊死を認めたため，壊死腸管切除および横行結腸人工肛門造設術を施行した。その後の全身管理には難渋したが，術後294日で退院となった。近年，外傷外科領域ではDCSの考え方が重要視されているが，腹部大動脈瘤破裂を扱う心臓血管外科領域においてはその考え方が浸透しているとは言い難い。腹部大動脈瘤破裂を扱う心臓血管外科医もDCSを念頭においた計画を立てて手術を始めることが，救命率向上のためには重要である。

Uticaj perioperativnih faktora na ishod kod pacijenata sa rupturiranom aneurizmom abdominalne aorte

Introduction: An aneurysm is a permanent, localized extension of an artery diameter by at least 50% relative to its physiological diameter. Its most common localization is on the abdominal aorta. Rupture, the most common complication of an aneurysm, is clinically significant because of the high mortality rate. Patients with ruptured aneurysm of the abdominal aorta undergo urgent surgical treatment, where despite the efforts of surgeons and expansive progress in both medicine and technology, intraoperative and postoperative mortality is still present in a high percentage. Aim: To examine how different perioperative factors affect the outcome in patients with ruptured aneurysms of the abdominal aorta. Material and methods: A retrospective study based on medical records for a two-year period, in which descriptive statistical methods processed and analyzed perioperative clinical parameters and their impact on outcome in 57 patients operated on for rupture of abdominal aortic aneurysm. Results: Preoperative values of hemoglobin and components of the hemostasis system, intraoperative blood replenishment and intraoperative pH, and postoperative values of potassium, lactate, and the amount of diuresis in the first 24 hours after surgery showed a statistically significant effect on the outcome in patients operated at the Clinical Center of Vojvodina due to rupture of abdominal aortic aneurysm. Conclusion: The operative outcome in rAAA is still unpredictable despite many years of research into perioperative factors and attempts to find an ideal scoring system.

Survey of Food Intake in Patients with Abdominal Aortic Aneurysm.

Abdominal aortic aneurysm (AAA) is a vascular disease that involves asymptomatic progressive expansion of the abdominal aorta. Aneurysm rupture is associated with a high mortality rate. Dietary conditions may be associated with the development and rupture of AAA. However, the relationship between nutrition and AAA is not completely understood. In this study, a nutrition survey was conducted using a brief self-administered diet history questionnaire (BDHQ) to evaluate the relationship between AAA and dietary habits. One-hundred and twenty-six Japanese people participated in the nutrition survey. Food intake status was analyzed in four groups: the analyzed group-1 (all men), analyzed group-2 (men with smoking history), analyzed group-3 (all women) and analyzed group-4 (women without smoking history). In group-2 and group-3, the intake of citrus fruits was significantly lower in the AAA group than in the non-AAA group. In group-2, the intake of soybean and soybean products was significantly lower in the AAA group than in the non-AAA group. In analyzed group-3, the intake of other vegetables (vegetables except for green and yellow vegetables and soybeans) and seafood was significantly lower in the AAA group than in the non-AAA group. This study suggests that AAA onset may be associated with low intake of fruits, soybeans, vegetables, and seafood.

Anticoagulants and reduced thrombus load in abdominal aortic aneurysms assessed with three-dimensional contrast-enhanced ultrasound examination.

The relationship between intraluminal thrombus (ILT) and abdominal aortic aneurysm (AAA) growth and rupture risk remains ambiguous. Studies have shown a limited effect of antiplatelet therapy on ILT size, whereas the impact of anticoagulant therapy on ILT is unresolved. This study aims to evaluate an association between antithrombotic therapy and ILT size assessed with three-dimensional contrast-enhanced ultrasound (3D-CEUS) examination in a cohort of patients with AAA. In a cross-sectional study, 309 patients with small AAAs were examined with 3D-CEUS. Patients were divided into three groups based on prescribed antithrombotic therapy: anticoagulant (n= 36), antiplatelet (n= 222), and no antithrombotic therapy (n= 51). Patient ILT size was calculated in volume and thickness and compared between the three groups. Patients on anticoagulants had a significantly lower estimated marginal mean ILT volume of 16mL (standard error [SE],±3.2) compared with 28mL (SE,±2.7) in the no antithrombotic group and 30mL (SE,±1.3) in the antiplatelet group when adjusting for AAA volume (P< .001) and comorbidities (P< .001). In addition, patients on anticoagulant therapy had significantly lower estimated marginal mean ILT thickness of 10mm (SE,±1.1) compared with 13mm (SE,±0.9) in the no antithrombotic group of and 13mm (SE,±0.4) in the antiplatelet group when adjusting for AAA diameter (P= .03) and comorbidities (P= .035). A 3D-CEUS examination is applicable for ILT assessment and demonstrates that patients with AAA on anticoagulant therapy have lower ILT thickness and volume than patients with AAA on antiplatelet therapy and those without antithrombotic therapy. Causality between anticoagulants and ILT size, and extrapolation to AAA growth and rupture risk, is unknown and merits further investigations, to further nuance US-based AAA surveillance strategy.

An abdominal aortic aneurysm rupture risk score: a pilot study for combining precise aortic measurements and clinical factors

ObjectiveCurrent screening and management for abdominal aortic aneurysms (AAAs) are based on maximal aortic diameter criteria. This study sought to compare anatomic and clinical factors between ruptured and intact AAAs to identify predictors of rupture. MethodsPatients treated for AAAs at Thomas Jefferson University Hospital from 2010 to 2021 were reviewed from intact AAAs (iAAAs), ruptured AAAs (rAAAs), and no aortic pathology (NP) groups. Preoperative computed tomography angiography (CTA) studies were retrospectively measured with Aquarius iNtuition (TeraRecon Inc). Maximal diameter, length, mural thrombus volume (MTV), and calcification volume were measured from the lowest renal artery to the femoral artery. A rupture risk score was calculated using AAA diameter (1 point), percent ≥MTV 50% (1 point), number of antihypertensive agents <2 (1 point), not on cholesterol-lowering medication (1 point), and active smoking (1 point) for a 5-point total score. ResultsCTAs from 48 patients (age, 69.5 ± 8.1 years; 87.5% male) were measured (23 iAAAs, 15 rAAAs, and 10 controls). When compared with iAAAs, the maximal AAA diameter (rAAA, 7.71 cm; iAAA, 6.02 cm; P = .005) and %MTV (rAAA, 66.1%; iAAA, 45.3%; P = .0001) were greater in patients with rAAAs. Mean AAA rupture risk score was greater in patients with rAAAs than those with iAAAs (rAAA, 3.40 ± 1.12; iAAA, 1.78 ± 1.44; P < .001) with 100% of rAAAs and 47.8% of iAAAs having a score 2 or greater. ConclusionsThis study demonstrates that AAA diameter, percent MTV, blood pressure control, and active smoking are significant risk factors for AAA rupture. Patients with multiple risk factors (risk score ≥2) were more likely to rupture and should be considered high risk.

Analyzing the contribution of vasa vasorum in oxygenation of the aneurysmal wall: A computational study

The mechanisms of abdominal aortic aneurysm (AAA) formation and rupture are controversial in the literature. While the intraluminal thrombus (ILT) plays a crucial role in reducing oxygen flux to the tissue and therefore decreasing the aortic wall strength, other physiological parameters such as the vasa vasorum (VV) oxygen flow and its consumption contribute to altered oxygenation responses of the arterial tissue as well. The goal of this research is to analyse the importance of the aforementioned parameters on oxygen delivery to the aneurysmal wall in a patient-specific AAA. Numerical simulations of coupled blood flow and mass transport with varying levels of VV concentration and oxygen reaction rate coefficient are performed. The hypoperfusion of the adventitial VV and high oxygen consumption are observed to have critical effects on reducing aneurysmal tissue oxygen supply and can therefore exacerbate localized oxygen deprivation.

Spatiotemporal Registration of 3-D Multi-perspective Ultrasound Images of Abdominal Aortic Aneurysms.

Methods for patient-specific abdominal aortic aneurysm (AAA) progression monitoring and rupture risk assessment are widely investigated. Three-dimensional ultrasound can visualize the AAA's complex geometry and displacement fields. However, ultrasound has a limited field of view and low frame rate (i.e., 3-8 Hz). This article describes an approach to enhance the temporal resolution and the field of view. First, the frame rate was increased for each data set by sequencing multiple blood pulse cycles into one cycle. The sequencing method uses the original frame rate and the estimated pulse wave rate obtained from AAA distension curves. Second, the temporal registration was applied to multi-perspective acquisitions of the same AAA. Third, the field of view was increased through spatial registration and fusion using an image feature-based phase-only correlation method and a wavelet transform, respectively. Temporal sequencing was fully correct in aortic phantoms and was successful in 51 of 62 AAA patients, yielding a factor 5 frame rate increase. Spatial registration of proximal and distal ultrasound acquisitions was successful in 32 of 37 different AAA patients, based on the comparison between the fused ultrasound and computed tomography segmentation (95th percentile Haussdorf distances and similarity indices of 4.2 ± 1.7 mm and 0.92 ± 0.02 mm, respectively). Furthermore, the field of view was enlarged by 9%-49%.

Surgical Treatment of Small Intestinal Bleeding Caused by Arterial Gastrointestinal Fistula: A 2-Case Report

Background: This study aims to better understand diagnosing and treating arterial gastrointestinal fistulas. Methods: The diagnosis and treatment of two patients with arterial gastrointestinal fistulas were reported, and the experience with diagnosis and treatment was summarized. Results: In these two cases, both patients were admitted with bleeding as the primary complaint, both underwent emergency laparotomies, and both patients were diagnosed with small intestinal bleeding before surgery. the first patient died as a result of an abdominal aortic aneurysm rupture caused by chronic vascular repair and postoperative implant infection; the second patient underwent vascular repair on time, we treated him with third-generation cephalosporin, and after he was stabilized, we performed left total iliac stent placement and left internal iliac artery embolization; he had no fever after surgery, his incision was healed, and he was successfully discharged from the hospital. Conclusion: Aortic gastrointestinal fistula is rare and has a high mortality rate, attention should be paid to distinguishing it from small intestinal bleeding. Timely diagnosis and rapid surgical treatment are keys to improving survival.

Biomechanical Rupture Risk Assessment in Management of Patients with Abdominal Aortic Aneurysm in COVID-19 Pandemic.

Background: The acute phase of the COVID-19 pandemic requires a redefinition of healthcare system to increase the number of available intensive care units for COVID-19 patients. This leads to the postponement of elective surgeries including the treatment of abdominal aortic aneurysm (AAA). The probabilistic rupture risk index (PRRI) recently showed its advantage over the diameter criterion in AAA rupture risk assessment. Its major improvement is in increased specificity and yet has the same sensitivity as the maximal diameter criterion. The objective of this study was to test the clinical applicability of the PRRI method in a quasi-prospective patient cohort study. Methods: Nineteen patients (fourteen males, five females) with intact AAA who were postponed due to COVID-19 pandemic were included in this study. The PRRI was calculated at the baseline via finite element method models. If a case was diagnosed as high risk (PRRI > 3%), the patient was offered priority in AAA intervention. Cases were followed until 10 September 2021 and a number of false positive and false negative cases were recorded. Results: Each case was assessed within 3 days. Priority in intervention was offered to two patients with high PRRI. There were four false positive cases and no false negative cases classified by PRRI. In three cases, the follow-up was very short to reach any conclusion. Conclusions: Integrating PRRI into clinical workflow is possible. Longitudinal validation of PRRI did not fail and may significantly decrease the false positive rate in AAA treatment.

Double-edged sword of diabetes mellitus for abdominal aortic aneurysm.

Diabetes mellitus (DM) has been proved to contribute to multiple comorbidities that are risk factors for abdominal aortic aneurysm (AAA). Remarkably, evidences from epidemiologic studies have demonstrated a negative association between the two disease states. On the other hand, hyperglycemic state was linked to post-operative morbidities following AAA repair. This review aims to provide a thorough picture on the double-edged nature of DM and major hypoglycemic medications on prevalence, growth rate and rupture of AAA, as well as DM-associated prognosis post AAA repair. We performed a comprehensive search in electronic databases to look for literatures demonstrating the association between DM and AAA. The primary focus of the literature search was on the impact of DM on the morbidity, enlargement and rupture rate, as well as post-operative complications of AAA. The role of antidiabetic medications was also explored. Retrospective epidemiological studies and large database researches associated the presence of DM with decreased prevalence, slower expansion and limited rupture rate of AAA. Major hypoglycemic drugs exert similar protective effect as DM against AAA by targeting pathological hallmarks involved in AAA formation and progression, which were demonstrated predominantly by animal studies. Nevertheless, presence of DM or postoperative hyperglycemia was linked to poorer short-term and long-term prognosis, primarily due to greater risk of infection, longer duration of hospital stays and death. While DM is a positive factor in the formation and progression of AAA, it is also associated with higher risk of negative outcomes following AAA repair. Concomitant use of antidiabetic medications may contribute to the protective mechanism of DM in AAA, but further studies are still warranted to explore their role following AAA repair.

CXCR4 - a possible serum marker for risk stratification of abdominal aortic aneurysms.

Background: Abdominal aortic aneurysm (AAA) rupture is still associated with a mortality rate of 80-90%. Imaging techniques or molecular fingerprinting for patient-specific risk stratification to identify pending rupture are still lacking. The chemokine (C-X-C motif) receptor (CXCR4) activation by CXCL12 ligand has been identified as a marker of inflammation and atherosclerosis, associated with AAA. Both are highly expressed in the aortic aneurysm wall. However, it is still unclear whether different expression levels of CXCR4 and CXCL12 can distinguish ruptured AAAs (rAAA) from intact AAAs (iAAA). Patients and methods: Abdominal aortic tissue samples (rAAA: n=29; iAAA: n=54) were excised during open aortic repair. Corresponding serum samples from these patients (n=9 from rAAAs; n=47 from iAAA) were drawn pre-surgery. Healthy aortic tissue samples (n=8) obtained from adult kidney donors during transplantation and serum samples from healthy adult volunteers were used as controls (n=5 each). Results: CXCR4 was mainly expressed in the media of the aneurysmatic tissue. Focal positive staining was also observed in areas of inflammatory infiltrates within the adventitia. In tissue lysates, no significant differences between iAAA, rAAA, and healthy controls were observed upon ELISA analysis. In serum samples, the level of CXCR4 was significantly increased in rAAA by 4-fold compared to healthy controls (p=0.011) and 3.0-fold for rAAA compared to iAAA (p<0.001). Furthermore a significant positive correlation between aortic diameter and serum CXCR4 concentration was found for both, iAAA and rAAA (p=0.042). Univariate logistic regression analysis showed that increased CXCR4 serum concentrations were associated with AAA rupture (OR: 4.28, 95% CI: 1.95-12.1, p=0.001). Conclusions: CXCR4 concentration was significantly increased in serum of rAAA patients and showed a significant correlation with an increased aortic diameter. The level of CXCR4 in serum was associated with a more than 4-fold risk increase for rAAA and thus could possibly serve as a biomarker in the future. However, further validation in larger studies is required.

Trends in Incidence of Abdominal Aortic Aneurysm Rupture, Repair, and Mortality in Nova Scotia

The purpose of this study was to examine sex-based trends in incidence of elective abdominal aortic aneurysm (AAA), ruptured AAA, ruptured AAA repair, and AAA-related mortality. A retrospective analysis of patients presenting with AAA from 2005 to 2015 was conducted. Rates of elective AAA repair, ruptured AAA, ruptured AAA repair, and mortality were obtained from linking provincial administrative data using medical services insurance billing number. The age-adjusted incidence of elective AAA repair, overall rate of ruptured AAA, ruptured AAA repair, and AAA-related mortality was calculated for each sex based on Canadian census estimates, adjusted to the Canadian standard population. Weighted linear regression was performed to analyze trends in incidence over time. One thousand nine hundred eighty-six elective AAA repairs were identified, of which 1,098 were repaired open and 898 underwent endovascular abdominal aneurysm repair (EVAR). Five hundred and seventy ruptured AAAs were identified, of which 295 (52%) were repaired: 259 open and 36 EVAR. The proportion of ruptured AAA that was repaired did not change over time (P=0.54). The proportion repairs performed using EVAR increased significantly in both elective (P<0.001) and rupture repairs (P<0.001). During the study period, 662 patients died of AAA-associated mortality. The average incidence of elective AAA repair in men was 29.3 (95% confidence interval (CI): 27.8 to 30.8) per 100,000 and decreased over time (P=0.04), whereas the average incidence in women was 9.2 [8.3 to 10.0] and stable (P=0.07). The incidence of open elective AAA repair was 10.5 [9.9-11.1] with a decreasing trend over time (P<0.001) and EVAR was 9.0 (8.5-9.6) with an increasing trend over time (P<0.001). A decreasing trend of overall ruptured AAA (5.4 [5.0-5.9], P<0.001), ruptured AAA repair (2.9 [2.5-3.2], P=0.02), and of AAA-related mortality (6.2 [5.8-6.8], P<0.001) was found, with consistent trends in both sexes. The incidence of open ruptured AAA repair decreased over time (P=0.001) whereas the incidence of ruptured EVAR remained stable (P=0.23). The incidence of elective AAA repair is decreasing in males but not females, whereas the incidence of rupture has decreased in both sexes. This has translated into reduced incidence of AAA-related mortality. Increased adoption of EVAR for ruptured AAA should continue these trends.

Dying to Get There: Patients Who Reside at Increased Distance from Tertiary Center Experience Increased Mortality Following Abdominal Aortic Aneurysm Rupture

Centralization of vascular surgery care for Ruptured Abdominal Aortic Aneurysms (RAAAs) to high-volume tertiary centers may hinder access to timely surgical intervention for patients in remote areas. The objective of this study was to determine the association between distance from vascular care and mortality from RAAAs in the province of Nova Scotia, Canada. A retrospective cohort study of all RAAAs in Nova Scotia between 2005 and 2015 was performed through linkage of administrative databases. Patients were divided into groups by estimated travel time from their place of residence to the tertiary center (<1hr and ≥1hr) using geographic information software. Baseline and operative characteristics were identified for all patients through available databases and completed through chart review. Mortality at home, during transfer to the vascular center, and overall 30-day mortality were compared between groups using t-test and chi-squared test, as appropriate. Multivariable logistic regression analysis was used to calculate the independent effect of travel time on survival outcomes. A total of 567 patients with RAAA were identified from 2005-2015, of which 250 (44%) resided <1hr travel time to the tertiary center and 317 (56%) resided ≥1hr. On multivariable analysis, travel time ≥1hr from vascular care was an independent predictor of mortality at home (odds ratio [OR] 1.68, 95% confidence interval [CI] 1.07-2.63, P=0.02), mortality prior to operation (OR 2.64, 95% CI 1.81-3.83, P<0.001), and overall 30-day mortality (OR 1.61, 95% CI 1.10-2.37, P=0.02). In patients who received an operation (n=294), there was no association between increased travel time and mortality (OR 1.02, 95% CI 0.60-1.73, P=0.94). Travel time ≥1hr to the tertiary center is associated with significantly higher mortality from ruptured abdominal aortic aneurysm (AAA). However, there was no difference in overall chance of survival between groups for patients that underwent AAA repair. Therefore, strategies to facilitate early detection, and timely transfer to a vascular surgery center may improve outcomes for patients with RAAA.

Characterization of immediate and early mortality after repair of ruptured abdominal aortic aneurysm.

We sought to compare immediate and early mortality among patients undergoing ruptured abdominal aortic aneurysm (RAAA) repair. Evaluation of RAAA has focused on 30-day postoperative mortality. Other emergency conditions such as trauma have demonstrated a multimodal mortality distribution within the 30-day window, expanding the pathophysiologic understanding and allowing for intervention investigations with practice changing and lifesaving results. However, the temporal distribution and risk factors of postoperative morbidity and mortality in RAAA have yet to be investigated. We evaluated factors associated with RAAA postoperative mortality in immediate (<1day) and early (1-30days) postoperative periods in a landmarked retrospective cohort study using data from the Vascular Quality Initiative (2010-2020). We identified 5157 RAAA repairs (mean age, 72 ± 10years; 77% male; 88% White; 61% endovascular). The mortality rate in the immediate period was 10.2% (528/5157) and the early mortality rate was 22.1% (918/4163). In multivariable regression analyses, signs of hemorrhagic shock (ie, hemoglobin<7g/dL: adjusted odds ratio [aOR], 1.87 [95% confidence interval [CI], 1.14-3.06]; any preoperative systolic blood pressure<70mm Hg: aOR, 1.40 [95% CI, 1.04-1.89]; and estimated blood loss >40%: aOR, 3.65 [95% CI, 2.29-5.83]) were associated with an increased risk of immediate mortality. Comorbid conditions (heart failure: aOR, 1.38 [95% CI, 1.00-1.92]; pulmonary disease: aOR, 1.29 [95% CI, 1.05-1.58]; elevated creatinine: aOR 1.26 [95% CI, 1.31-1.41]) were associated with increased risk of early mortality. Immediate deaths were associated predominantly with shock from massive hemorrhage, whereas early deaths were associated with comorbid conditions predisposing patients to multisystem organ failure despite successful repair. These temporal distinctions should guide future mechanistic and intervention evaluations to improve RAAA mortality.

Computed Tomography Angiography Markers and Intraluminal Thrombus Morphology as Predictors of Abdominal Aortic Aneurysm Rupture.

Background: Abdominal aortic aneurysm (AAA) is a complex vascular disease characterized by progressive and irreversible local dilatation of the aortic wall. Currently, the indication for repair is linked to the transverse diameter of the abdominal aorta, using computed tomography angiography imagery, which is one of the most used markers for aneurysmal growth. This study aims to verify the predictive role of imaging markers and underlying risk factors in AAA rupture. Methods: The present study was designed as an observational, analytical, retrospective cohort study and included 220 patients over 18 years of age with a diagnosis of AAA, confirmed by computed tomography angiography (CTA), admitted to Vascular Surgery Clinic of Mures County Emergency Hospital in Targu Mures, Romania, between January 2018 and September 2022. Results: Patients with a ruptured AAA had higher incidences of AH (p = 0.006), IHD (p = 0.001), AF (p < 0.0001), and MI (p < 0.0001), and higher incidences of all risk factors (tobacco (p = 0.001), obesity (p = 0.02), and dyslipidemia (p < 0.0001)). Multivariate analysis showed that a high baseline value of all imaging ratios markers was a strong independent predictor of AAA rupture (for all p < 0.0001). Moreover, a higher baseline value of DAmax (OR:3.91; p = 0.001), SAmax (OR:7.21; p < 0.001), and SLumenmax (OR:34.61; p < 0.001), as well as lower baseline values of DArenal (OR:7.09; p < 0.001), DACT (OR:12.71; p < 0.001), DAfemoral (OR:2.56; p = 0.005), SArenal (OR:4.56; p < 0.001), SACT (OR:3.81; p < 0.001), and SThrombusmax (OR:5.27; p < 0.001) were independent predictors of AAA rupture. In addition, AH (OR:3.33; p = 0.02), MI (OR:3.06; p = 0.002), and PAD (OR:2.71; p = 0.004) were all independent predictors of AAA rupture. In contrast, higher baseline values of SAmax/Lumenmax (OR:0.13; p < 0.001) and ezetimibe (OR:0.45; p = 0.03) were protective factors against AAA rupture. Conclusions: According to our findings, a higher baseline value of all imaging markers ratios at CTA strongly predicts AAA rupture and AH, MI, and PAD highly predicted the risk of rupture in AAA patients. Furthermore, the diameter of the abdominal aorta at different levels has better accuracy and a higher predictive role of rupture than the maximal diameter of AAA.

Gut microbiome sheds light on the development and treatment of abdominal aortic aneurysm.

Abdominal aortic aneurysm (AAA) is an inflammatory vascular disease with high disability and mortality. Its susceptible risk factors include old age, being male, smoking, hypertension, and aortic atherosclerosis. With the improvement of screening techniques, AAA incidence and number of deaths caused by aneurysm rupture increase annually, attracting much clinical attention. Due to the lack of non-invasive treatment, early detection and development of novel treatment of AAA is an urgent clinical concern. The pathophysiology and progression of AAA are characterized by inflammatory destruction. The gut microbiota is an "invisible organ" that directly or indirectly affects the vascular wall inflammatory cell infiltration manifested with enhanced arterial wall gut microbiota and metabolites, which plays an important role in the formation and progression of AAA. As such, the gut microbiome may become an important risk factor for AAA. This review summarizes the direct and indirect effects of the gut microbiome on the pathogenesis of AAA and highlights the gut microbiome-mediated inflammatory responses and discoveries of relevant therapeutic targets that may help manage the development and rupture of AAA.

Abstract 14293: Sex Differences in Cytokine and Chemokine Expression in an Experimental AAA Rodent Model

Introduction: Abdominal aortic aneurysms (AAAs) are a multifactorial disease process that results from a series of biomolecular processes. AAAs are more prevalent in men; however, women are at greater risk of rupture. Despite continued investigation, the mechanisms of sex disparities in AAA remain unknown. Hypothesis We hypothesize that male and female rats will have different inflammatory cytokine and chemokine expression in AAA tissue. Methods: Male and female Sprague-Dawley rats underwent intraluminal infrarenal abdominal aortic exposure to elastase to induce AAA. Rats were administered daily β-aminopropionitrile to promote AAA rupture. In vivo aortic diameters were evaluated using ultrasound (12MHz) at day 7 and 14 post-AAA induction. PET imaging with 64 Cu-DOTA-ECL1i (a selective radio-marker for C-C chemokine receptor type 2; CCR2), AAA tissue zymography and cytokine array were performed at day 6 and 14 to evaluate CCR2, matrix metalloproteinases (MMP), chemokine, and cytokine content. Results: Male rats developed larger AAAs at day 7 and 14 compared to female rats (p&lt;0.0001; Figure 1A), but AAA rupture rate was similar between sexes. At day 6, AAA cytokine arrays demonstrated Rantes, IFN-y, and IL-17A were higher in males (p&lt;0.01; Figure 1B-D). However, MCP-1, IL-6, IL-10, IL-18, IL-1B, and TNF-α were similar between groups (Figure 1E-J). Interestingly, at day 14, females showed significantly higher MCP-1, IL-6, and IL-10 (p&lt;0.05; Figure 1E-G). PET imaging demonstrated that males had higher CCR2 uptake at day 14 (p&lt;0.05; Figure 1K). AAA zymography demonstrated equivalent levels of total MMP-9, pro-MMP 9, and active MMP-9 between groups (Figure 1L-O). Conclusion Our findings demonstrated that inflammatory cytokines and chemokines are differentially expressed in AAA tissue - particularly CCR2 which is higher in males. This provides sex-specific AAA tissue targets for diagnostic molecular imaging and potential future immune-modulation strategies.

Association Between Blood Flow Pattern and Rupture Risk of Abdominal Aortic Aneurysm Based on Computational Fluid Dynamics

This study aimed to derive a novel classification of blood flow pattern in abdominal aortic aneurysms (AAA) based on computational fluid dynamics (CFDs), and to determine the predictive value of flow patterns in AAA rupture. This was an age and sex matched case control study. Cases were identified as patients who underwent emergency endovascular or open repair due to ruptured or AAA at risk of impending rupture. Controls were age and sex matched with patients with an AAA who were asymptomatic and had a confirmed unruptured AAA from computed tomography angiography images from the same period. Classification of blood flow pattern (type I: non-helical main flow channel with multiple vortices; type II: non-helical main flow channel with single vortices; and type III, helical main flow channel with helical vortices) and haemodynamic parameters (areas of low wall shear stress [AlowWSS], aneurysm pressure drop [Δ pressure], etc) were derived from CFD analyses. Multivariable regression was used to determine independent AAA rupture risk factors. The incremental discriminant and reclassification abilities for AAA rupture were compared among different models. Fifty-three ruptured and 53 intact AAA patients were included. Ruptured AAA showed a higher prevalence of type III flow pattern than intact AAA (60.4% vs. 15.1%; p < .001). Type III flow pattern was associated with a significantly increased risk of aneurysm rupture (odds ratio 10.22, 95% confidence interval 3.43 – 30.49). Among all predicting models, the combination of AAA diameter, haemodynamic parameters (AlowWSS or Δ pressure), and flow pattern showed highest discriminant abilities in both the overall population (c-index = 0.862) and subgroup patients with AAAs < 55 mm (c-index = 0.972). Compared with AAA diameter, adding the flow pattern could significantly improve the reclassification abilities in both the overall population (net reclassification index [NRI] = 0.321; p < .001) and the subgroup of AAAs < 55 mm (NRI = 0.732; p < .001). Type III flow pattern was associated with a significantly increased risk of AAA rupture. The integration of blood flow pattern may improve the identification of high risk aneurysms in both overall population and in those with AAAs < 55 mm.

Evaluation of aortic tortuosity as a negative predictor of abdominal aortic aneurysm rupture.

The maximal aortic diameter has been used as a key indication for whether to repair abdominal aortic aneurysms (AAAs). Aortic tortuosity has been proposed as another factor to consider. In the present study, we compared the degree of aortic tortuosity in ruptured AAAs with that of unruptured AAAs using computed tomography. We performed a retrospective review of a prospectively maintained database of patients who had undergone AAA repair from December 2014 to December 2019. Patients with a ruptured aneurysm (rAAA) were matched with patients with a nonruptured AAA (nrAAA) with the same maximal aneurysm diameter and age. The degree of aortic tortuosity, defined as the maximum lateral deviation from the aortic centerline, was measured on preoperative coronal computed tomography scans. During a 5-year period, 572 AAA cases were identified. The aortic tortuosity of the 25 rAAA cases was compared with that of a matched control group of 31 nrAAAs, selected by the same mean maximum diameter of 8.4cm and similar patient age. In the rAAA group, the mean age was 74.8years (84% men). In the nrAAA group, the mean age was 76.3years (88% men). The mean aortic tortuosity for the rAAA and nrAAA groups was 9.3± 7.9mm and 18.0± 11.2mm, respectively (P< .01). Greater aortic tortuosity was seen in the nrAAA cases compared with the rAAA cases at the same matched aneurysm size. Thus, aortic tortuosity might confer a reduced rupture risk. Further studies with larger cohorts are needed to verify this observation.