Increased Peak Wall Stress, but Not Maximum Diameter, Is Associated with Symptomatic Abdominal Aortic Aneurysm

How to improve epidemiological trustworthiness concerning abdominal aortic aneurysms

BACKGROUND

Research on degenerative abdominal aortic aneurysms (AAA) is hampered by complex pathophysiology, sub-optimal pre-clinical models, and lack of effective medical therapies. In addition, trustworthiness of existing epidemiological data is impaired by elements of ambiguity, inaccuracy, and inconsistency. Our aim is to foster debate concerning the trustworthiness of AAA epidemiological data and to discuss potential solutions.

METHODS

We searched the literature from the last five decades for relevant epidemiological data concerning AAA development, rupture, and repair. We then discussed the main issues burdening existing AAA epidemiological figures and proposed suggestions potentially beneficial to AAA diagnosis, prognostication, and management.

RESULTS

Recent data suggest a heterogeneous scenario concerning AAA epidemiology with rates markedly varying by country and study cohorts. Overall, AAA prevalence seems to be decreasing worldwide while mortality is apparently increasing regardless of recent improvements in aortic-repair techniques. Prevalence and mortality are decreasing in high-income countries, whereas low-income countries show an increase in both. However, several pieces of information are missing or outdated, thus systematic renewal is necessary. Current AAA definition and surgical criteria do not consider inter-individual variability of baseline aortic size, further decreasing their reliability.

CONCLUSIONS

Switching from flat aortic-size thresholds to relative aortic indices would improve epidemiological trustworthiness regarding AAAs. Aortometry standardization focusing on simplicity, univocity, and accuracy is crucial. A patient-tailored approach integrating clinical data, multi-adjusted indices, and imaging parameters is desirable. Several novel imaging modalities boast promising profiles for investigating the aortic wall. New contrast agents, computational analyses, and artificial intelligence-powered software could provide further improvements.

Selection criterion for endovascular aortic repair in those with chronic kidney disease

OBJECTIVE

Endovascular aortic repair (EVAR) is the preferred method of repair for abdominal aortic aneurysms (AAAs). However, patients with advanced chronic kidney disease (CKD) are a high-risk group, and it is unknown which patients with CKD benefit from EVAR vs continued surveillance. The purpose of this study was to identify which patients with advanced CKD may benefit from EVAR.

METHODS

The Vascular Quality Initiative Database was utilized to identify elective EVARs for AAAs. Patients were excluded if they underwent urgent or emergent repairs. CKD stages were categorized based on preoperative estimated glomular filtration rate (eGFR) and dialysis status. Predicted 1-year mortality of untreated AAAs was calculated by modifying a validated comorbidity score that predicts 1-year mortality (Gagne Index) without repair. The primary outcome was actual 1-year mortality, which was compared with the predicted 1-year mortality without repair.

RESULTS

A total of 34,926 patient met study criteria. There were differences in Gagne Indices among the varying classes of CKD. Patients with CKD 4 and CKD 5 had the highest 1-year mortality rates, followed by CKD 3b, which was significantly higher than those with CKD 1 and CKD 2. Patients with CKD 4 had no differences between actual 1-year mortality with EVAR and predicted 1-year survival without EVAR across all AAA sizes. Those with CKD 5 had worse actual 1-year survival with EVAR than predicted 1-year survival without EVAR for AAAs <5.5 cm. Patients with CKD 5 only experienced an actual mortality benefit with EVAR compared with predicted 1-year mortality without EVAR for AAAs ≥7.0 cm.

CONCLUSION

The current data suggest that patients with CKD 3b, 4, and 5 represent a high-risk group who may not benefit from elective EVAR utilizing traditional size criteria. Patients with CKD 4 and 5 with AAAs <5.5 cm do not benefit from elective EVAR. In patients with CKD 5, elective EVAR may need to be reserved for AAAs ≥7.0 cm unless there are other concerning anatomic characteristics.

The Ratio of the Size of the Abdominal Aortic Aneurysm to That of the Unchanged Aorta as a Risk Factor for Its Rupture

Background: A ruptured abdominal aortic aneurysm is a severe condition associated with high mortality. Currently, the most important criterion used to estimate the risk of its rupture is the size of the aneurysm, but due to patients’ anatomical variability, many aneurysms have a high risk of rupture with a small aneurysm size. We asked ourselves whether individual differences in anatomy could be taken into account when assessing the risk of rupture. Methods: Based on the CT scan image, aneurysm and normal aorta diameters were collected from 186 individuals and compared in patients with ruptured and unruptured aneurysms. To take into account anatomical differences between patients, diameter ratios were calculated by dividing the aneurysm diameter by the diameter of the normal aorta at various heights, and then further comparisons were made. Results: It was found that the calculated ratios differ between patients with ruptured and unruptured aneurysms. This observation is also present in patients with small aneurysms, with its maximal size below the level that indicates the need for surgical treatment. For small aneurysms, the ratios help us to estimate the risk of rupture better than the maximum sac size (AUC: 0.783 vs. 0.650). Conclusions: The calculated ratios appear to be a valuable feature to indicate which of the small aneurysms have a high risk of rupture. The obtained results suggest the need for further confirmation of their usefulness in subsequent groups of patients.

Cohort Study Examining the Association of Optimal Blood Pressure Control at Entry With Infrarenal Abdominal Aortic Aneurysm Growth

Background and Aim

The benefit of controlling cardiovascular risk factors in slowing the progression of small abdominal aortic aneurysm (AAA) is controversial. This study investigated the association of optimal blood pressure control at entry with the growth of small AAA.

Methods and Results

A total of 1,293 patients with initial AAA diameter <50 mm were followed by a median 5 (inter-quartile range, IQR, 3–7) ultrasound scans for a median of 3.6 years (IQR 1.8, 5.3). Optimal blood pressure control was defined as blood pressure ≤140/90 mmHg at recruitment. The association of optimal blood pressure control at entry with AAA growth was assessed using linear mixed effects models adjusted for established risk factors of AAA growth and factors which were unequally distributed among the blood pressure groups. Optimal blood pressure control at entry was not significantly associated with AAA growth. In the risk factor adjusted model the mean difference in AAA growth between blood pressure groups was 0.04 mm/year (95% CI −0.20, 0.13; p = 0.65). The results were similar in sensitivity analyses excluding outliers or focused on systolic or diastolic blood pressure alone.

Conclusions

This observational study suggests that optimal blood pressure control at entry is not associated with slower AAA growth.

The Evaluation of Longitudinal Strain of Large and Small Abdominal Aortic Aneurysm by Two-Dimensional Speckle-Tracking Ultrasound

OBJECTIVES

Abdominal aortic aneurysm (AAA) is a dangerous and lethal vascular disease. Non-invasive two-dimensional speckle-tracking imaging (2D STI) plays an important role in assessing aortic biomechanical properties. Our study aimed to evaluate the alterations of biomechanical characteristics using 2D STI in 91 AAA patients with different size.

METHODS

Aneurysm strain, elastic modulus, stiffness index β, and aortic distensibility determined by M-Mode ultrasound (US), and longitudinal strain (LS) derived from 2D STI were compared in 40 large AAA patients (diameter ≥ 55 mm) and 51 small AAA patients (diameter < 55 mm).

RESULTS

Compared with small AAA group, anterior wall longitudinal strain (ALS) and posterior wall longitudinal strain (PLS) were significantly decreased in large AAA group (all P < .05) and not affected by age, symptom, hypertension, and thrombus. Meanwhile, ALS and PLS correlated negatively with maximal aneurysm diameters (r = -0.628 and -0.469, respectively, all P < .001). And only ALS was associated with M-Mode US parameters (all P < .05). Based on receiver operating characteristic (ROC) analysis, ALS and PLS had strong diagnostic values for large AAA with the area under the curve (AUC) of 0.82 and 0.72, and cut-off points of 1.71 and 1.64% with a sensitivity of 78 and 72%, and a specificity of 75 and 70%, respectively.

CONCLUSIONS

LS measured by 2D STI could evaluate the biomechanical properties of aneurysm wall with different size, and add additional diagnostic value in distinguishing between small and large AAA.

Neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio predict in-hospital mortality in symptomatic but unruptured abdominal aortic aneurysm patients

BACKGROUND

Symptomatic but unruptured abdominal aortic aneurysm (AAA) is a potentially fatal disease since its etiopathogenesis, involving acute changes in the aortic wall, including inflammation, increasing the probability of impending rupture. The objective of the present study was to assess the prognostic value of the neutrophil-to-lymphocyte ratio (NLR) and the plateletto-lymphocyte ratio (PLR) in patients undergoing urgent symptomatic AAA repair.

METHODS

This was a retrospective study including 29 patients with symptomatic AAA repaired between 2011 and 2020. Both NLR and PLR were calculated on hospital admission prior to the intervention. The primary endpoint was in-hospital mortality, and the secondary endpoint included length of hospital stay and postoperative complications.

RESULTS

In-hospital mortality rate was 10.3%. The discriminatory performance to predict the primary endpoint was very good both for PLR [area under the ROC curve (AUC): 0.92 (95% confidence interval (CI): 0.82-1.00; p=0.02] and NLR [AUC: 0.88 (95% CI: 0.75-1.00); p=0.04]. The best cutoff point to predict in-hospital mortality was 185 for PLR (100% sensitivity and 85% specificity) and 6.4 for NLR (100% sensitivity and 77% specificity). The most frequent postoperative complication was acute kidney failure (37.9%). Both elevated PLR as NLR were significantly associated with acute kidney failure and multiorgan failure in the immediate postoperative period (p <0.01). None of the two ratios was associated with length of hospital stay (p=NS).

CONCLUSIONS

Both PLR and NLR are low-cost inflammatory markers widely available in every emergency department, with excellent performance to predict in-hospital mortality in patients undergoing symptomatic AAA repair. Patients with a PLR ≥185 and/or an NLR ≥6.4 could benefit from a "surveyed waiting conduct" improving the preoperative clinical condition prior to the intervention, or even considering endovascular repair.

On stress in abdominal aortic aneurysm: Linear versus non-linear analysis and aneurysm rupture risk

We present comprehensive biomechanical analyses of abdominal aortic aneurysms (AAA) for 43 patients. We compare stress magnitudes and stress distributions within arterial walls of abdominal aortic aneurysms (AAA) obtained using two simulation and modelling methods: (a) Fully automated and computationally very efficient linear method embedded in the software platform Biomechanics based Prediction of Aneurysm Rupture Risk (BioPARR), freely available from https://bioparr.mech.uwa.edu.au/; (b) More complex and much more computationally demanding Non-Linear Iterative Stress Analysis (Non-LISA) that uses a non-linear inverse iterative approach and strongly non-linear material model. Both methods predicted localised high stress zones with over 90% of AAA model volume fraction subjected to stress below 20% of the 99th percentile maximum principal stress. However, for the non-linear iterative method, the peak maximum principal stress (and 99th percentile maximum principal stress) was higher and the stress magnitude in the low stress area lower than for the automated linear method embedded in BioPARR. Differences between the stress distributions obtained using the two methods tended to be particularly pronounced in the areas where the AAA curvature was large. Performance of the selected characteristic features of the stress fields (we used 99th percentile maximum principal stress) obtained using BioPARR and Non-LISA in distinguishing between the AAAs that would rupture and remain intact was for practical purposes the same for both methods.

Assessment of the Global and Regional Circumferential Strain of Abdominal Aortic Aneurysm with Different Size by Speckle-Tracking Echocardiography

OBJECTIVES

We aimed to use speckle-tracking echocardiography (STE) to quantify circumferential aortic strain of abdominal aortic aneurysms (AAA) with different size.

METHODS

A total of 87 AAA patients were included. The morphological variables, including aortic maximum diameter (MD), end systolic area (ESA), end diastolic area (EDA), and thickness and area of intraluminal thrombus (ILT), were measured by ultrasound. STE was applied to calculate circumferential strain (CS) at 6 equally divided segments of the aorta at MD. We evaluated the mean value of peak strain along the 6 segments as global circumferential strain (GCS).

RESULTS

Large AAA (≥5.5 cm) patients had higher MD, ESA, EDA, AAA length, ILT thickness, and area, but lower fractional area change, GCS, and segmental CSs than small AAA (<5.5 cm) subjects (all P < .05). Compared with AAA <4.5 cm group, AAA patients ≥4.5 cm possessed increased MD, ESA, EDA, AAA length, ILT thickness, and area, which results were also reflected in the comparison between AAA <6.5 and ≥6.5 cm group. In small AAA patients, GCS and regional strains in CS1, CS3, and CS5 segments were lower in AAA subjects ≥4.5 cm than those <4.5 cm (all P<.05). However, no significant differences in the GCS and regional CS between ≥6.5 and <6.5 cm group were found. Correlation analysis revealed a significant negative association of GCS with MD, ESA, and EDA, even after adjusting the potential confounding factors (all P < .05).

CONCLUSIONS

Our findings may yield insight into the structural strain characteristics of AAA wall with different size, which adds the benefit of using simple echocardiography-derived biomechanics to stratify AAA patients.

Endovascular Aortic Repair in Patients of Advanced Age

PURPOSE

Treatment decisions for the elderly with abdominal aortic aneurysms (AAAs) are challenging. With advancing age, the risk of endovascular aneurysm repair (EVAR) increases while life expectancy decreases, which may nullify the benefit of EVAR. The purpose of this study was to quantify the impact of EVAR on 1-year mortality in patients of advanced age.

MATERIALS AND METHODS

The 2003-2020 Vascular Quality Initiative Database was utilized to identify patients who underwent EVAR for AAAs. Patients were included if they were 80 years of age or older. Exclusions included non-elective surgery or missing aortic diameter data. Predicted 1-year mortality of untreated AAAs was calculated based on a validated comorbidity score that predicts 1-year mortality (Gagne Index, excluding the component associated with AAAs) plus the 1-year aneurysm-related mortality without repair. The primary outcome for the study was 1-year mortality.

RESULTS

A total of 11 829 patients met study criteria. The median age was 84 years [81, 86] with 9014 (76.2%) being male. Maximal AAA diameters were apportioned as follows: 39.6% were <5.5 cm, 28.6% were 5.5-5.9 cm, 21.3% were 6.0-6.9 cm, and 10.6% were ≥7.0 cm. The predicted 1-year mortality rate without EVAR was 11.9%, which was significantly higher than the actual 1-year mortality rate with EVAR (8.2%; p<0.001). The overall rate of perioperative MACE was 4.4% (n = 516). Patients with an aneurysm diameter <5.5cm had worse actual 1-year mortality rates with EVAR compared to predicted 1-year mortality rates without EVAR. In contrast, those with larger aneurysms (≥5.5cm) had better actual 1-year mortality rates with EVAR. The benefit from EVAR for those with Gagne Indices 2-5 was largely restricted to those with AAAs ≥ 7.0cm; whereas those with Gagne Indices 0-1 experience a survival benefit for AAAs larger than 5.5 cm.

CONCLUSION

The current data suggest that EVAR decreases 1-year mortality rates for patients of advanced age compared to non-operative management in the elderly. However, the survival benefit is largely limited to those with Gagne Indices 0-1 with AAAs ≥ 5.5 cm and Gagne Indices 2-5 with AAAs ≥ 7.0 cm. Those of advanced age may benefit from EVAR, but realizing this benefit requires careful patient selection.

Systematic Review and Meta-Analysis of Peak Wall Stress and Peak Wall Rupture Index in Ruptured and Asymptomatic Intact Abdominal Aortic Aneurysms

Background Prior studies have suggested aortic peak wall stress (PWS) and peak wall rupture index (PWRI) can estimate the rupture risk of an abdominal aortic aneurysm (AAA), but whether these measurements have independent predictive ability over assessing AAA diameter alone is unclear. The aim of this systematic review was to compare PWS and PWRI in participants with ruptured and asymptomatic intact AAAs of similar diameter. Methods and Results Web of Science, Scopus, Medline, and The Cochrane Library were systematically searched to identify studies assessing PWS and PWRI in ruptured and asymptomatic intact AAAs of similar diameter. Random-effects meta-analyses were performed using inverse variance-weighted methods. Leave-one-out sensitivity analyses were conducted to assess the robustness of findings. Risk of bias was assessed using a modification of the Newcastle-Ottawa scale and standard quality assessment criteria for evaluating primary research papers. Seven case-control studies involving 309 participants were included. Meta-analyses suggested that PWRI (standardized mean difference, 0.42; 95% CI, 0.14-0.70; P=0.004) but not PWS (standardized mean difference, 0.13; 95% CI, -0.18 to 0.44; P=0.418) was greater in ruptured than intact AAAs. Sensitivity analyses suggested that the findings were not dependent on the inclusion of any single study. The included studies were assessed to have a medium to high risk of bias. Conclusions Based on limited evidence, this study suggested that PWRI, but not PWS, is greater in ruptured than asymptomatic intact AAAs of similar maximum aortic diameter.

Oxidative Stress and Inflammatory Markers in Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is increasing due to aging of the population and is a major cause of death among the elderly. Ultrasound screening programs are useful in early diagnosis, but aneurysm size is not always a good predictor of rupture. Our aim was to analyze the value of circulating molecules related to oxidative stress and inflammation as new biomarkers to assist the management of AAA. The markers were quantified by ELISA, and their expression in the aneurysmal wall was studied by real-time PCR and by immunostaining. Correlation analysis of the studied markers with aneurysm diameter and peak wall stress (PWS), obtained by finite element analysis, and multivariate regression analysis to assess potential confounding factors were performed. Our study shows an extensive inflammatory infiltration in the aneurysmal wall, mainly composed by T-cells, macrophages and B-cells and altered levels of reactive oxygen species (ROS), IgM, IgG, CD38, GDF15, S100A4 and CD36 in plasma and in the aneurysmal tissue of AAA patients compared with controls. Circulating levels of IgG, CD38 and GDF15 positively correlated with abdominal aortic diameter, and CD38 was correlated with PWS. Our data show that altered levels of IgG, CD38 and GDF15 have potential diagnostic value in the assessment of AAA.

Neutrophil-lymphocyte ratio predicts disease severity and outcome after lower extremity procedures

OBJECTIVE

Neutrophil-lymphocyte ratio (NLR) has been associated with inferior outcomes after lower extremity interventions. NLR has been associated with systemic inflammation and atherosclerotic burden. We examined NLR, severity of peripheral artery disease (PAD), and outcomes after endovascular or open surgical procedures.

METHODS

Inpatients undergoing lower extremity procedures (2008-2016) were selected from Cerner Health Facts database (Cerner Corporation, North Kansas City, Mo) using International Classification of Diseases, Ninth Revision procedure codes. Disease severity was grouped into claudication, rest pain, and tissue loss. Outcomes were identified using International Classification of Diseases, Ninth Revision codes. NLR was calculated preoperatively and postoperatively. A χ² analysis and multivariable logistic regression were performed. A receiver operating characteristic curve analysis was used to determine the cutoff for preoperative (low, <3.65; high, ≥3.65) and postoperative (low, <5.96; high, ≥5.96) NLR values.

RESULTS

There were 3687 patients evaluated; 2183 (59%) underwent endovascular procedures and 1504 (41%) had open procedures. Compared with black patients, claudication was more frequent in white patients (81.7% vs 72.7%; P < .0001), and tissue loss was less common (12.9% vs 20.9%; P < .0001). NLR values were higher for patients with tissue loss than for patients with rest pain or claudication (4.89, 4.33, and 3.11, respectively; P < .0001). Open procedures were associated with higher postoperative NLR values than endovascular procedures (6.8 vs 5.2; P < .0001). Mean preoperative and postoperative NLR values were greater in patients with more severe PAD. Multivariable analysis demonstrated that preoperative high NLR was strongly associated with in-hospital death (odds ratio [OR], 5.4; 95% confidence interval [CI], 1.68-17.07), cardiac complications (OR, 2.9; 95% CI, 1.57-5.40), amputation (OR, 2.5; 95% CI, 1.65-3.87), renal failure (OR, 1.9; 95% CI, 1.18-2.93), respiratory complications (OR, 1.7; 95% CI, 1.09-2.76), and prolonged length of stay (OR, 1.9; 95% CI, 1.89-3.71).

CONCLUSIONS

Preoperative and postoperative NLR significantly increases with disease severity for PAD, providing further evidence of NLR as a biomarker of a patient's systemic inflammatory state. After adjustment for confounders, NLR still remained strongly associated with death and other adverse outcomes after intervention for PAD. Further study of the clinical association of NLR with other vascular disorders, such as symptomatic carotid stenosis and symptomatic and ruptured aortic aneurysmal disease, is planned to guide individualized treatment to prevent stroke or aneurysm rupture.

Risk Factors for Preoperative Anxiety and Depression in Patients Scheduled for Abdominal Aortic Aneurysm Repair

Background

Perioperative emotional disorders of patients underwent abdominal aortic aneurysm (AAA) repair is an emerging area of study, and preoperative mental distress of those patients remains poorly understood. The aim of this study was to investigate the prevalence and identify the risk factors of preoperative anxiety and depression in patients scheduled for AAA repair.

Methods

A total of 189 patients who underwent elective AAA repair between 2015 and 2016 were included in this study. These patients were preoperatively evaluated by Hospital Anxiety and Depression Scale (HADS). Demographics and anxiety and depression scores of the patients were documented. Logistic regression was used to identify the independent risk factors of preoperative anxiety and depression.

Results

A total of 150 AAA patients were included in final analysis. Of these 150 patients, 44 patients (29.3%) had borderline anxiety or clinical anxiety, and 42 patients (28.0%) were found to have borderline or clinical depression. Female (odds ratio [OR]: 2.81, 95% confidence interval [CI]: 1.08-7.26), the American Society of Anesthesiologists (ASA) Grade 3/4 (OR: 4.34, 95% CI: 1.13-16.68), higher education (OR: 1.44, 95% CI: 1.02-2.04), and abdominal or back pain (OR: 3.08, 95% CI: 1.20-7.87) were identified as significant independent risk factors of abnormal HADS-anxiety in overall patients; and higher level of education (OR: 1.87, 95% CI: 1.16-3.01) was predictive of anxiety in patients planned for endovascular aortic repair. Besides, higher body mass index (BMI) (OR: 1.18, 95% CI: 1.04-1.33) and abdominal or back pain (OR: 3.93, 95% CI: 1.70-9.11) were predictive of abnormal preoperative HADS-depression in overall patients.

Conclusion

As for patients scheduled for AAA repair, female, higher ASA, higher level of education, and symptom may be independent risk factors for preoperative anxiety, and symptom and higher BMI may predict preoperative depression.

Finite element analysis in symptomatic and asymptomatic abdominal aortic aneurysms for aortic disease risk stratification

BACKGROUND

Advanced biomechanical models can provide additional information concerning rupture risk in abdominal aortic aneurysms (AAA). Here we evaluated the predictive value of finite element analysis (FEA) to assess AAA rupture risk.

METHODS

In a case-control study, we compared FEA parameters in a group of symptomatic AAA (sAAA) patients, considered as a high risk of rupture group, with FEA parameters in asymptomatic AAA patients (aAAA).

RESULTS

We included 15 sAAA and 28 aAAA patients matched for age- and maximum diameter diagnosed with infrarenal non-ruptured AAA at our center between 2009 and 2013. Mean age was 75±69 years and mean maximum diameter was 77±17 mm. Peak wall stress (PWS) was significantly higher in sAAA patients than in aAAA patients (354.3±139.6 kPa vs. 248.6±81.9 kPa; P=0.001). The C statistic for the ROC curve based on PWS was 0.748 (95% CI: 0.592-0.903; P=0.008). CART analysis classified patients into high and low PWS groups. The high-PWS group (>305.15 kPa; N.=15) had a higher incidence of sAAA (33.3% aAAA, 66.7% sAAA) than the low-PWS-group (≤305.15 kPa; N.=28. 82.1% aAAA, 17.9% sAAA).

CONCLUSIONS

In conclusion, PWS was significantly higher in sAAA patients. Measuring PWS may help estimate the individual rupture risk in patients with AAA, but larger studies are needed to confirm our results.