Factors Associated with Development of Large Abdominal Aortic Aneurysm in Middle-aged Men

Metabolic syndrome and the risk of abdominal aortic aneurysm: A nationwide cohort study

BACKGROUND AND AIMS

The association between metabolic syndrome (MetS) and abdominal aortic aneurysm (AAA) remains unclear. We investigated the potential association between AAA and MetS and its components in a large population-based cohort.

METHODS

We used the Korean National Health Insurance Service database including 4,162,640 participants aged ≥50 years who received a routine health examination in 2009. Cox proportional hazards models were used to analyze the association between MetS and its components (elevated waist circumference, blood pressure, glucose, triglycerides, and reduced high-density lipoprotein cholesterol [HDL-C]) with AAA incidence, with adjustment for confounders.

RESULTS

During a median 9.4 years of follow-up, 18,160 participants developed incident AAA. MetS was associated with an increased risk of AAA compared to the non-MetS group (adjusted hazard ratio [aHR], 1.38; 95% confidence interval [CI], 1.34-1.43). Among the individual components, elevated waist circumference, blood pressure, triglycerides, and reduced HDL-C were associated with increased AAA risk, while elevated glucose alone was associated with reduced AAA risk (aHR, 0.85; 95% CI, 0.82-0.87). AAA risk also increased linearly with the increasing number of MetS components, with the highest risk found in the presence of all 5 components (aHR, 1.98, 95% CI, 1.83-2.15).

CONCLUSIONS

MetS and its individual components, with the exclusion of elevated glucose, were associated with higher risk of AAA. Further studies are warranted to elucidate the association between MetS and AAA.

Prevalence of risk factors associated with rupture of abdominal aortic aneurysm (AAA): a single center retrospective study

BACKGROUND

Abdominal aortic aneurysm (AAA) is a severe cardiovascular disease. The mortality rate for an AAA rupture is very high. Understanding the risk factors for AAA rupture would help AAA management, but little is known about these risk factors in the Chinese population.

METHODS

This retrospective study included patients that were diagnosed with AAA during the last 5 years in a large national hospital in southern China. AAA patients were divided into a rupture and non-rupture group. Clinical data were extracted from the hospital medical record system. Clinical features were compared between the rupture and non-rupture groups. The associations between potential risk factors and rupture risk were evaluated using a multivariate logistic regression analysis.

RESULTS

A total of 337 AAA patients were included for analysis in the present study. AAA diameter was significantly larger, and high-sensitivity C-reactive protein (hs-CRP) and serum creatinine levels were both significantly higher in AAA rupture patients. High-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) levels were significantly lower in AAA rupture patients. After adjustment, the multivariate logistic analysis found that AAA diameter and hs-CRP were independently positively associated with AAA rupture, and HDL-C level was adversely associated with AAA rupture.

CONCLUSIONS

Our data suggests that larger AAA diameter and higher hs-CRP level are associated with a higher risk of AAA rupture, and higher HDL-C level is associated with a lower risk of AAA rupture. The results of this study may be helpful for the management of AAA patients in southern China.

Genetic and clinical determinants of abdominal aortic diameter: genome-wide association studies, exome array data and Mendelian randomization study

Progressive dilation of the infrarenal aortic diameter is a consequence of the ageing process and is considered the main determinant of abdominal aortic aneurysm (AAA). We aimed to investigate the genetic and clinical determinants of abdominal aortic diameter (AAD). We conducted a meta-analysis of genome-wide association studies in 10 cohorts (n = 13 542) imputed to the 1000 Genome Project reference panel including 12 815 subjects in the discovery phase and 727 subjects [Partners Biobank cohort 1 (PBIO)] as replication. Maximum anterior-posterior diameter of the infrarenal aorta was used as AAD. We also included exome array data (n = 14 480) from seven epidemiologic studies. Single-variant and gene-based associations were done using SeqMeta package. A Mendelian randomization analysis was applied to investigate the causal effect of a number of clinical risk factors on AAD. In genome-wide association study (GWAS) on AAD, rs74448815 in the intronic region of LDLRAD4 reached genome-wide significance (beta = -0.02, SE = 0.004, P-value = 2.10 × 10-8). The association replicated in the PBIO1 cohort (P-value = 8.19 × 10-4). In exome-array single-variant analysis (P-value threshold = 9 × 10-7), the lowest P-value was found for rs239259 located in SLC22A20 (beta = 0.007, P-value = 1.2 × 10-5). In the gene-based analysis (P-value threshold = 1.85 × 10-6), PCSK5 showed an association with AAD (P-value = 8.03 × 10-7). Furthermore, in Mendelian randomization analyses, we found evidence for genetic association of pulse pressure (beta = -0.003, P-value = 0.02), triglycerides (beta = -0.16, P-value = 0.008) and height (beta = 0.03, P-value < 0.0001), known risk factors for AAA, consistent with a causal association with AAD. Our findings point to new biology as well as highlighting gene regions in mechanisms that have previously been implicated in the genetics of other vascular diseases.

Prehabilitation for Vascular Surgery Patients: Challenges and Opportunities

Global demand for major surgery is rising as a consequence of a growing, ageing population and clinically applicable approaches to perioperative risk reduction have never been needed more. Prehabilitation aims to optimise aerobic capacity and address modifiable risk factors prior to surgery to improve postoperative outcomes. Given the inherently high-risk nature of vascular surgery and the frequently high-acuity, frail, vascular surgical population, the potential to introduce an intervention into the surgical pathway that may reduce postoperative complications cannot be overlooked. The aim of this article is to examine the current evidence base for prehabilitation in patients awaiting vascular surgery, and to summarise the potential benefits, pitfalls, and practicalities of this emerging perioperative intervention. There is a paucity of high-quality research specifically aimed at prehabilitation for patients undergoing vascular surgery, both peripheral and aortic, making it difficult to draw definitive conclusions upon which to base a change in practice. Currently, evidence is taken from small, often single-centre heterogenous studies that vary significantly from each other, meaning that the optimal exercise regimen for patients awaiting vascular surgery has yet to be defined. Establishing the impact of prehabilitation on outcomes for vascular patients is important as the effectiveness of preoperative exercise training is likely to vary between surgical interventions and patient populations. However, extrapolation from other cohorts is possible and indeed forms the basis of many current prehabilitation programmes. Given the success of prehabilitation in other surgical groups, it has potential to become an important future research target for patients awaiting vascular surgery.

Genetically Predicted Insomnia in Relation to 14 Cardiovascular Conditions and 17 Cardiometabolic Risk Factors: A Mendelian Randomization Study

Background

This Mendelian randomization study aims to investigate causal associations between genetically predicted insomnia and 14 cardiovascular diseases (CVDs) as well as the potential mediator role of 17 cardiometabolic risk factors.

Methods and Results

Using genetic association estimates from large genome‐wide association studies and UK Biobank, we performed a 2‐sample Mendelian randomization analysis to estimate the associations of insomnia with 14 CVD conditions in the primary analysis. Then mediation analysis was conducted to explore the potential mediator role of 17 cardiometabolic risk factors using a network Mendelian randomization design. After correcting for multiple testing, genetically predicted insomnia was consistent significantly positively associated with 9 of 14 CVDs, those odds ratios ranged from 1.13 (95% CI, 1.08–1.18) for atrial fibrillation to 1.24 (95% CI, 1.16–1.32) for heart failure. Moreover, genetically predicted insomnia was consistently associated with higher body mass index, triglycerides, and lower high‐density lipoprotein cholesterol, each of which may act as a mediator in the causal pathway from insomnia to several CVD outcomes. Additionally, we found very little evidence to support a causal link between insomnia with abdominal aortic aneurysm, thoracic aortic aneurysm, total cholesterol, low‐density lipoprotein cholesterol, glycemic traits, renal function, and heart rate increase during exercise. Finally, we found no evidence of causal associations of genetically predicted body mass index, high‐density lipoprotein cholesterol, or triglycerides on insomnia.

Conclusions

This study provides evidence that insomnia is associated with 9 of 14 CVD outcomes, some of which may be partially mediated by 1 or more of higher body mass index, triglycerides, and lower high‐density lipoprotein cholesterol.

Relationships between metabolic syndrome and aspects of abdominal aortic aneurysm

BACKGROUND

Metabolic syndrome (MetS) is a cluster of metabolic abnormalities strongly associated with risks of cardiovascular diseases. However, a relationship between MetS and aneurysmal disease as compared with occlusive disease has not been confirmed. Therefore, correlations of MetS and abdominal aortic aneurysm (AAA) were evaluated.

METHODS

Between March 2011 and February 2020, 354 patients diagnosed with AAA were enrolled and divided into the MetS (n = 164) and the no-MetS (n = 190) groups. Individual components of MetS, characteristics of AAA, rupture rate, and survival rate were evaluated for both groups. Additionally, correlations between MetS and AAA were evaluated with focusing on effects of diabetes mellitus (DM).

RESULTS

The size of AAA was significantly larger in the MetS group compared with the no-MetS group (P < 0.05). The rupture rate was significantly higher in the MetS group compared with the no-MetS group (P < 0.05) and the survival rate was significantly higher in the no-MetS group (P < 0.05). In terms of DM, the size of AAA was significantly larger in the no-DM group compared with the DM group (P < 0.05). MetS was significantly more prevalent in the DM group compared with the no-DM group (P < 0.05). Finally, the rupture and survival rates were not statistically different between the DM and the no-DM groups (P > 0.05).

CONCLUSIONS

Although larger prospective studies are necessary, we suggest that MetS proportionally aggravates the status of AAA and survival rate. Therefore, surveillance for MetS and individual components may help to restrict the expansion of AAA.

Physical activity and the risk of abdominal aortic aneurysm: a systematic review and meta-analysis of prospective studies

The association between physical activity and risk of abdominal aortic aneurysm has been inconsistent with some studies reporting a reduced risk while others have found no association. We conducted a systematic review and meta-analysis of prospective studies to quantify the association. PubMed and Embase databases were searched up to 3 October 2020. Prospective studies were included if they reported adjusted relative risk (RR) estimates and 95% confidence intervals (CIs) of abdominal aortic aneurysm associated with physical activity. Summary RRs (95% CIs) were estimated using a random effects model. Nine prospective studies (2073 cases, 409,732 participants) were included. The summary RR for high vs. low physical activity was 0.70 (95% CI: 0.56-0.87, I² = 58%) and per 20 metabolic equivalent task (MET)-hours/week increase of activity was 0.84 (95% CI: 0.74-0.95, I² = 59%, n = 6). Although the test for nonlinearity was not significant (p = 0.09) the association appeared to be stronger when increasing the physical activity level from 0 to around 20-25 MET-hours/week than at higher levels. The current meta-analysis suggest that higher physical activity may reduce the risk of abdominal aortic aneurysm, however, further studies are needed to clarify the dose-response relationship between different subtypes and intensities of activity and abdominal aortic aneurysm risk.

Higher preprocedural fibrinogen levels are associated with aneurysm sac regression after EVAR

Summary. Background: The aim of our study was to determine the diameter of the aneurysm sac 24 months after endovascular abdominal aortic aneurysm repair (EVAR); to identify factors associated with sac regression, and to determine the impact of sac regression on all-cause mortality during long-term follow-up. Patients and methods: We conducted a retrospective review of prospectively collected data from patients treated with EVAR between January, 2010 and July, 2016. Sac regression was defined as at least 5 mm decrease in aneurysm diameter in relation to the preprocedural diameter seen on computed tomography angiography. Sociodemographic information, comorbidities, treatment, laboratory parameters, selected anatomical and genetic factors were all analysed to determine their impact on sac regression. Results: During the study period, 124 patients with mean age of 71.2 ± 7.2 years met the inclusion criteria. Sac regression was found in 45.2% of patients. Higher preprocedural fibrinogen was found in patients with sac regression in comparison with patients with stable sac or sac expansion (3.84 g/l vs 3.47 g/l; p = 0.028). In multivariate analysis after adjustment for age, hypertension, sex, smoking, dyslipidaemia, volume and percentage of intraluminal thrombus higher fibrinogen was associated with an increased probability of sac regression (OR 2.47; 95% CI 1.29–4.72; p = 0.006). Persistent type II endoleak was associated with significantly lower probability of sac regression in univariate and multivariate analysis after adjustment for age, hypertension, sex, smoking and dyslipidaemia (OR 0.26; 95% CI 0.10–0.66; p = 0.004). Higher age was a significant predictor of sac regression in multivariate analysis after adjustment for hypertension, sex, smoking and dyslipidaemia (OR 1.07; 95% CI 1.02–1.14; p = 0.012). No difference was found between patient subgroups with and without sac regression in all-cause mortality during follow-up. Conclusions: Higher preprocedural fibrinogen, absence of persistent type II endoleak and higher age were predictive factors of aneurysm sac regression post-EVAR.

Blood pressure, hypertension and the risk of abdominal aortic aneurysms: a systematic review and meta-analysis of cohort studies

Abdominal aortic aneurysms (AAA) are fatal in 80% of the cases when ruptured. Hypertension has been considered a potential risk factor for AAA; but the findings from prospective cohort studies have not been entirely consistent, nor have they been summarised in a comprehensive meta-analysis. Our aim was to conduct a systematic review and meta-analysis of cohort studies of the association between blood pressure, hypertension and AAA to clarify the strength and shape of these associations. We searched PubMed and Embase databases for relevant cohort studies up to April 30th, 2018. Random-effects models were used to calculate summary relative risks (RRs) and 95% confidence intervals (CIs). The meta-analysis included 21 cohort studies (20 publications) with data on 28,162 cases and 5,440,588 participants. The findings indicate that the RR of AAA in hypertensive patients is 1.66 times (95% CI: 1.49–1.85, I² = 79.3%, n = 13) that of non-hypertensive patients. In addition, there was a 14% (95% CI: 6–23%, I² = 30.5%, n = 6) and a 28% (95% CI: 12–46%, I² = 80.1%, n = 6) increase in the RR of AAA for every 20 mmHg and 10 mmHg increase in systolic blood pressure (SBP) and diastolic blood pressure (DBP), respectively. The analysis of DBP showed evidence of a strong and highly significant nonlinear dose–response relationship (p < 0.001) with a steeper association from 80 mmHg and above. This meta-analysis suggests that hypertension increases the risk of developing AAA by 66%. Further studies are needed to clarify the underlying mechanism explaining the much stronger association between DBP and AAA than for SBP.

Tobacco smoking and the risk of abdominal aortic aneurysm: a systematic review and meta-analysis of prospective studies

Several studies have found that smoking increases the risk of abdominal aortic aneurysm, however, the strength of the association has differed between studies and data from cohort studies have not yet been summarized. A systematic review and meta-analysis was therefore conducted to clarify this association. We searched PubMed and Embase databases up to May 2nd 2018. A random effects model was used to estimate summary relative risks (RRs) and 95% confidence intervals (CIs). Twenty three prospective studies were included. Comparing current, former and ever smokers with never smokers the summary RRs were 4.87 (95% CI: 3.93-6.02, I2 = 92%, n = 20), 2.10 (95% CI: 1.76-2.50, I2 = 71%, n = 15) and 3.28 (95% CI: 2.60-4.15, I2 = 96%, n = 18), respectively. The summary RR was 1.87 (95% CI: 1.45-2.40, I2 = 97%) per 10 cigarettes per day, 1.78 (95% CI: 1.54-2.06, I2 = 83%) per 10 pack-years was and 0.45 (95% CI: 0.32-0.63, I2 = 92.3%) per 10 years of smoking cessation. There was evidence of nonlinearity for cigarettes per day and pack-years (pnonlinearity < 0.0001 and pnonlinearity = 0.02, respectively), but not for smoking cessation, pnonlinearity = 0.85. Among smokers who quit, the RR was similar to that of never smokers by 25 years of smoking cessation. These findings confirm a strong association between smoking and the risk of developing abdominal aortic aneurysms.

Analysis of the Correlation Between Central Obesity and Abdominal Aortic Diseases

BACKGROUND

Atherosclerosis and abdominal aortic aneurysms (AAAs) have several similar risk factors but different pathogenesis. Inflammation of the arteries is common to both. Central obesity can act as an endocrine organ through the secretion of inflammatory cytokines, and the perivascular fat has a local effect that could contribute to diseases of the abdominal aorta. Although the relation between central obesity and atherosclerosis occlusive arterial disease has been demonstrated, the correlation with AAA has conflicting results. The aim of this study was to analyze the correlation between central obesity and the presence of abdominal aortic diseases using computed tomography.

METHODS

Six hundred thirty-nine consecutive patients classified into 3 groups (AAA, aortic atherosclerotic occlusive disease (AAOD), and without aortic disease [control group]) who underwent computed tomography had the aorta diameter, the visceral fat area (VFA), and the subcutaneous fat area (SFA) measured at the level of third and fourth lumbar vertebrae.

RESULTS

VFA showed no difference between the groups. SFA was lower in atherosclerotic group (AAOD) than control (P < 0.01 in general and P < 0.04 in male). In AAA group, we found in men that the first tertile of aorta diameter had higher VFA than third tertile (P = 0.02).

CONCLUSIONS

There was no difference in VFA between patients in AAA, AAOD, and without aortic disease groups. In men with aneurysm, there was an inverse relationship between VFA and aortic diameter. In AAOD, visceral to subcutaneous ratio is higher due to lower SFA.

Evaluation of the relationship between plasma lipids and abdominal aortic aneurysm: A Mendelian randomization study

Studies have reported that higher circulating levels of total cholesterol (TC), low-density lipoprotein (LDL) cholesterol and lower of high-density lipoprotein (HDL) cholesterol may be associated with increased risk of abdominal aortic aneurysm (AAA). Whether dyslipidemia causes AAA is still unclear and is potentially testable using a Mendelian randomization (MR) approach. We investigated the associations between blood lipids and AAA using two-sample MR analysis with SNP-lipids association estimates from a published genome-wide association study of blood lipids (n = 188,577) and SNP-AAA association estimates from European Americans (EAs) of the Atherosclerosis Risk in Communities (ARIC) study (n = 8,793). We used inverse variance weighted (IVW) MR as the primary method and MR-Egger regression and weighted median MR estimation as sensitivity analyses. Over a median of 22.7 years of follow-up, 338 of 8,793 ARIC participants experienced incident clinical AAA. Using the IVW method, we observed positive associations of plasma LDL cholesterol and TC with the risk of AAA (odds ratio (OR) = 1.55, P = 0.02 for LDL cholesterol and OR = 1.61, P = 0.01 for TC per 1 standard deviation of lipid increment). Using the MR-Egger regression and weighted median methods, we were able to validate the association of AAA risk with TC, although the associations were less consistent for LDL cholesterol due to wider confidence intervals. Triglycerides and HDL cholesterol were not associated with AAA in any of the MR methods. Assuming instrumental variable assumptions are satisfied, our finding suggests that higher plasma TC and LDL cholesterol are causally associated with the increased risk of AAA in EAs.

Redox proteomic analysis of serum from aortic anerurysm patients: insights on oxidation of specific protein target

Oxidative stress is undoubtedly one of the main players in abdominal aortic aneurysm (AAA) pathophysiology.

The Abdominal Aortic Aneurysm and Intraluminal Thrombus: Current Concepts of Development and Treatment

The pathogenesis of the abdominal aortic aneurysm (AAA) shows several hallmarks of atherosclerotic and atherothrombotic disease, but comprises an additional, predominant feature of proteolysis resulting in the degradation and destabilization of the aortic wall. This review aims to summarize the current knowledge on AAA development, involving the accumulation of neutrophils in the intraluminal thrombus and their central role in creating an oxidative and proteolytic environment. Particular focus is placed on the controversial role of heme oxygenase 1/carbon monoxide and nitric oxide synthase/peroxynitrite, which may exert both protective and damaging effects in the development of the aneurysm. Treatment indications as well as surgical and pharmacological options for AAA therapy are discussed in light of recent reports.

Preoperative hypofibrinogenemia is associated with increased intraoperative bleeding in ruptured abdominal aortic aneurysms

INTRODUCTION

Ruptured abdominal aortic aneurysm (rAAA) is associated with coagulopathy and intraabdominal hemorrhage. Fibrinogen acts as a key coagulation factor and has previously been suggested as a biomarker for increased perioperative bleeding in other surgical areas. The aim of the present study was to investigate fibrinogen and standard laboratory parameters and their association to preoperative hemodynamic status, intraoperative bleeding (IOB), and outcome in treatment of rAAA.

METHODS

This is a single university center retrospective cohort study of 91 consecutive patients with rAAA undergoing open surgery or endovascular aneurysm repair (EVAR) between 2008 and 2013. Patients were analyzed using the Swedish Vascular Registry (Swedvasc), and local hospital medical and laboratory records. Laboratory data analyzed included fibrinogen, hemoglobin, platelet count, prothrombin time ratio, activated partial thrombin time, and creatinine. Odds ratios (OR) with 95% confidence intervals (CI) were calculated in a logistical regression model.

RESULTS

In the study cohort (n = 91), median age was 74 (57-91) years; 80 % men; open surgical repair (n = 72; 77%); EVAR (n = 19; 23%). Median preoperative fibrinogen concentration was 1.8 g/L (IQR = 1.4) and varied significantly across bleeding groups: ≤1999 ml 2.3g/L, IQR = 1.4 (n = 35); 2000-4999 ml 1.6 g/L, IQR = 1.5 (n = 33); ≥5000 ml 1.4 g/L, IQR = 1.0 (n = 23) (P < 0.001). Preoperative fibrinogen concentration showed a linear relationship with preoperative blood pressure (r = .447, P = 0.01). When analyzing other preoperative laboratory values, only platelets showed a similar linear relationship with preoperative blood pressure (r = .247, P = 0.05). Patients with blood pressure <70 mmHg had an associated median fibrinogen concentration of less than 1.5 g/L (P = 0.001). In the multivariable logistic regression analysis, preoperative fibrinogen < 1.5 g/L [OR 10.0, CI (1.8-57.1), P = 0.009] was associated with IOB >2000 ml and preoperative blood pressure < 70 mmHg was associated with IOB >2 000 ml [OR 3.7, CI (1.1-12.6), P = 0.03] and >5000 ml [OR 5.2, CI (1.3-21.1), P = 0.02]. Low fibrinogen concentration (< 1.5 g/L) was associated with 30-day mortality in the univariate analysis but not in the multivariable logistic regression analysis.

CONCLUSION

Low preoperative fibrinogen concentration was significantly associated with preoperative hypotension and increased intraoperative bleeding in patients with rAAA. Patients in hemodynamic shock with blood pressure <70 mmHg had an associated fibrinogen concentration of less than 1.5 g/L. A fibrinogen concentration less than 1.5 g/L was associated with a ten-fold increased risk of intraoperative hemorrhage of more than 2000 ml.

Meta-analysis and meta-regression analysis of biomarkers for abdominal aortic aneurysm

Background

Many studies have investigated the systemic and local expression of biomarkers in patients with abdominal aortic aneurysm (AAA). The natural history of AAA varies between patients, and predictors of the presence and diameter of AAA have not been determined consistently. The aim of this study was to perform a systematic review, meta-analysis and meta-regression of studies comparing biomarkers in patients with and without AAA, with the aim of summarizing the association of identified markers with both AAA presence and size.

Methods and results

Literature review identified 106 studies suitable for inclusion. Meta-analysis demonstrated a significant difference between matrix metalloproteinase (MMP) 9, tissue inhibitor of matrix metalloproteinase 1, interleukin (IL) 6, C-reactive protein (CRP), α1-antitrypsin, triglycerides, lipoprotein(a), apolipoprotein A and high-density lipoprotein in patients with and without AAA. Although meta-analysis was not possible for MMP-2 in aortic tissue, tumour necrosis factor α, osteoprotegerin, osteopontin, interferon γ, intercellular cell adhesion molecule 1 and vascular cell adhesion molecule 1, systematic review suggested an increase in these biomarkers in patients with AAA. Meta-regression analysis identified a significant positive linear correlation between aortic diameter and CRP level.

Conclusion

A wide variety of biomarkers are dysregulated in patients with AAA, but their clinical value is yet to be established. Future research should focus on the most relevant biomarkers of AAA, and how they could be used clinically.

Current status of medical treatment for abdominal aortic aneurysm

Although cardiovascular disease is widely recognized as the leading cause of death, a lesser known fact is that aortic aneurysm is the 15th leading cause of death over the age of 65 years in the USA. The golden standard of the treatments are invasive interventions either with open surgical repair (OS) or endovascular aneurysm repair (EVAR). The concept of medical treatment is to prevent abdominal aortic aneurysm (AAA) from rupture and avoid surgical treatment by preventing aneurysm enlargement or even reducing aneurysm size. Matrix metalloproteinases (MMP) are structurally related metalloendopeptidases that can degrade the extracellular matrix and is thought to play important roles in AAA. There are many proposed pharmacological treatments including: β-blockers, angiotensin-converting enzyme inhibitor (ACE inhibitors), angiotensin-receptor blocker (ARB), statins, macrolides and, doxycycline, an inhibitor of the MMP. The latter is a potential promising drug as medical treatment for AAA and the Non-invasive Treatment of Abdominal Aortic Aneurysm Clinical Trial (N-TA(3)CT) is currently ongoing in the USA. Here, the pathophysiology and potential medical therapy for AAA will be reviewed.

Effects of exercise training in patients with abdominal aortic aneurysm: preliminary results from a randomized trial

OBJECTIVE

No effective medical therapy exists for early abdominal aortic aneurysm (AAA) disease. Lower extremity exercise improves aortic hemodynamics and reduces inflammation, but the safety and efficacy of exercise training in AAA disease is unknown. As an interim analysis of our prospective, randomized, longitudinal trial of exercise for AAA suppression, we investigated whether subjects with early disease could safely achieve target metabolic and hemodynamic goals.

METHODS

One hundred eight participants were randomized to exercise training (EX) or usual care (UC). EX subjects participated in a combination of in-house and home exercise training, with efforts directed toward moderate daily exercise participation. Comparisons were made between EX and UC subjects who completed 1 year of follow-up (n = 26 and 31, respectively, mean age 72 ± 8 years). EX and UC groups were compared for safety, cardiopulmonary exercise test responses, weekly energy expenditure, and biometric indices.

RESULTS

No paradoxical increase in AAA growth rate or adverse clinical events occurred as a consequence of exercise training. EX participants expended an average of 2269 ± 1207 kcal/wk and increased exercise capacity (42% increase in treadmill time, 24% increase in estimated metabolic equivalents, P = .01 and .08 between groups, respectively). EX participants demonstrated a significant reduction in C-reactive protein and tended to reduce waist circumference and waist-to-hip ratio (P = .06 and .07, respectively).

CONCLUSIONS

Preliminary analyses suggest that exercise training is well tolerated and sustainable in small AAA subjects over 1 year. Despite age and comorbidities, exercising AAA subjects achieve meaningful exercise targets and significantly modify activity-dependent variables.

Experimental models of abdominal aortic aneurysms

Despite being a leading cause of death in the West, the pathophysiology of abdominal aortic aneurysms (AAA) is still incompletely understood. Pharmacotherapy to reduce the growth of small AAAs is limited and techniques for repairing aneurysms continue to evolve. Experimental models play a key role in AAA research, as they allow a detailed evaluation of the pathogenesis of disease progression. This review focuses on in vivo experimental models, which have improved our understanding of the potential mechanisms of AAA development and contributed to the advancement of new treatments.

Proteins associated with the size and expansion rate of the abdominal aortic aneurysm wall as identified by proteomic analysis

OBJECTIVES

Identification of biomarkers for the natural history of abdominal aortic aneurysms (AAA) holds the key to non-surgical intervention and improved selection for AAA repair. We aimed to associate the basic proteomic composition of AAA wall tissue with the expansion rate and size in patients with AAA.

METHODS

A proteomic approach was used, consisting of two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and mass spectrometry (MS) to identify differentially expressed proteins in AAA tissue. Relevant protein spots were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

Spearman's correlation analysis revealed 16 protein spots were strongly correlated with AAA expansion rate (ρ>±0.75). Nine protein spots were identified. Six protein spots showed correlation with AAA size (ρ>±0.5). Three protein spots were identified: vitronectin with traces of calreticulin, albumin and a spot containing two proteins: collagen α-3(VI) chain and vitamin D binding protein. Interestingly, in our previous study vitronectin was shown to be down-regulated in a ruptured AAA group compared with non-ruptured AAA. Western blot analysis in the present study confirmed a correlation of vitronectin bands with AAA size in aortic aneurysm tissue.

CONCLUSION

A proteomic approach seems valuable, and identified several candidates not previously associated with AAA. Larger studies are required to confirm the potential and clinical role of the identified proteins.

Association between serum lipoproteins and abdominal aortic aneurysm

The importance of dyslipidemia in the etiology of abdominal aortic aneurysm (AAA) is poorly defined, in part because previous association analyses have often not considered the use of current lipid-modifying medications. Medications targeted at altering the concentrations of circulating lipids have an established role in occlusive atherosclerosis but are of unknown value in the primary prevention of AAA. We examined the association between fasting serum levels of triglycerides low- and high-density lipoprotein and the presence of an AAA in a cohort of 3,327 men aged 65 to 83 years. The analyses were adjusted for established risk factors of AAA and the prescription of lipid-modifying agents using multiple logistic regression analysis. Of the 3,327 men, 1,043 (31%) were receiving lipid-modifying therapy at the fasting lipid measurement. The lipid-modifying therapy was statins in most cases (n = 1,023). The serum high-density lipoprotein concentrations were lower in patients with AAAs. The serum high-density lipoprotein concentration was independently associated with a reduced risk of having an AAA in men not receiving current lipid-modifying therapy (odds ratio 0.72, 95% confidence interval 0.56 to 0.93 per 0.4-mM increase) and in the total cohort (odds ratio 0.76, 95% confidence interval 0.63 to 0.91 per 0.4-mM increase, adjusted for lipid-modifying therapy). The concentrations of low-density lipoprotein and triglycerides were not associated with the presence of AAAs. In conclusion, high-density lipoprotein appeared to be the most important lipid in predicting the risk of AAA development, with potential value as a therapeutic target. Current cardiovascular strategies aimed at lowering low-density lipoprotein might not have any effect on the prevention of AAAs.

Plasma concentrations of apolipoproteins A-I, B and M in patients with abdominal aortic aneurysms

OBJECTIVES

Apolipoproteins play important roles in the development of atherosclerosis but their involvement in the pathogenesis of abdominal aortic aneurysm (AAA) is poorly understood. The aim was to investigate whether apoA-I, apoB and apoM are independently associated with AAA.

DESIGN AND METHODS

Plasma apoA-I, apoB and apoM were measured in 343 patients with AAA and in 214 elderly apparently healthy control individuals from the background population.

RESULTS

AAA patients had lower apolipoprotein levels, as compared to healthy individuals: apoA-I, 1.62 vs. 2.08 g/L; apoB, 0.91 vs. 1.04 g/L; apoM, 0.72 vs. 0.91 mumol/L (p<0.0001 for all three). In multivariate analyses, apoA-I and apoB were associated with AAA, odds ratios (95% confidence intervals) being 0.53 (0.43-0.64) and 0.86 (0.75-0.998), respectively.

CONCLUSIONS

ApoA-I, apoB and apoM levels were significantly lower in patients with AAA than in the control individuals, but only apoA-I and apoB were independently associated to AAA.

A unique plasma proteomic profiling with imbalanced fibrinogen cascade in patients with Kawasaki disease

Kawasaki disease (KD) is the leading cause of acquired heart disease during childhood in the developed countries. The mechanism and biomarkers of KD remain to be determined. In this study, we sought to elucidate potential plasma proteomic markers in KD patients in comparison to that in febrile controls. Plasma samples from KD patients and febrile controls were subjected to two-dimensional polyacrylamide gel electrophoresis analysis. Differential protein displays between KD patients and febrile controls were determined. Fibrinogen beta and gamma chains, alpha-1-antitrypsin (A1AT), CD5 antigen-like precursor (CD5L), and clusterin were increased in KD patients, whereas immunoglobulin free light chains were decreased, as compared with controls. The differential protein displays were validated with enzyme-linked immunosorbent assay tests. We found higher fibrinogen-related proteins (fibrinogen, A1AT, clusterin, and CD5L), along with a lower level of the immunoglobulin free light chains that involve fibrin degradation in KD. Results from this study showing a unique proteomic profiling with abnormal fibrinogen cascade may afford a good biomarker of KD and a better strategy to prevent cardiovascular complications of KD by correcting abnormal fibrin deposition or degradation.

High Levels of Endothelin (ET)-1 and Aneurysm Diameter Independently Predict Growth of Stable Abdominal Aortic Aneurysms

The etiology of abdominal aortic aneurysm (AAA) includes inflammation and endothelial dysfunction. To evaluate relations between these mechanisms and AAA growth, endothelin (ET)-1, tumor necrosis factor (TNF)-α, interleukin (IL)-6, and CD40 ligand were related to yearly AAA growth for 2.9 ± 1.6 years (mean ± SD) in 178 patients with conservatively followed AAA. Total number of follow-up years was 491. Abdominal aortic aneurysm diameter increased by 3.3 ± 4.0 mm during the first year and by 4.9 ± 4.4 mm during the first 2 years. Median (range) growth was 2.5 (—1.0 to 30.6) mm/year. When patients with AAA growth above or below median were compared, initial AAA diameter (46.1 ± 5.8 vs 42.0 ± 8.3 mm; P < .0001), age (75 ± 7 vs 72 ± 8 years; P < .029), and initial ET-1 levels (1.31 ± 0.50 vs 1.13 ± 0.49 pg/mL; P < .0177) were higher in patients with growth above median. Endothelin 1 (P = .0230) and initial AAA diameter (P = .0019) predicted AAA growth above median in logistic regression. In conclusion, higher initial levels of ET-1 and initial AAA diameter independently predict AAA growth.

Is Increased Thrombin Activation in Patients With Abdominal Aortic Aneurysms Dependent on Area or Volume of Aneurysm Thrombus Mass?

Objectives: Does thrombin activation seen in patients with abdominal aortic aneurysms (AAA) relate to the thrombus surface area or volume within the aneurysm? Patients and methods: A total of 130 patients with AAA were analyzed regarding levels of the complex between activated protein C—protein C inhibitor (APC-PCI) and AAA morphology. Analysis of APC-PCI complex was made using a sandwich immunofluorometric method. Results: Increased APC-PCI concentrations were seen in patients with AAA (0.44 μg/L; P < .001 compared with controls). The correlations of APC-PCI values were r = .13, P = .13 for aneurysm size, r = .08, P = .35 for thrombus surface area, and r = .13, P = .14 for thrombus volume. APC-PCI values elevated to 0.45 μg/L in 10 patients with AAA having no or very little thrombus mass. Conclusion: Disappointingly, no correlation was found between thrombus surface area or volume and levels of the APC-PCI complex. Mechanisms other than the AAA-sac thrombus must be evaluated as cause of thrombin activation in patients with AAA.

Cardiovascular risk factors and acute-phase response in idiopathic ascending aortitis: a case control study

Introduction

Idiopathic aortitis is a rare condition characterized by giant cell or lymphoplasmacytic inflammation of the aorta. The purpose of this study was to describe risk factors for the development of idiopathic aortitis.

Methods

We conducted a case control study of 50 patients who were age-matched with two control subjects with non-inflammatory ascending aortic aneurysms. We examined whether the prevalences of gender, hypertension, hyperlipidemia, diabetes mellitus, smoking, family history of any aortic aneurysms, and elevated inflammatory markers differed between cases and controls.

Results

The mean age of cases was 71.6 ± 8.9 years and that of controls was 71.1 ± 8.9 years. We found female gender (odds ratio [OR] 2.41, 95% confidence interval [CI] 1.20 to 4.85; P = 0.014) and active smoking (OR 3.37, 95% CI 1.12 to 10.08; P = 0.03) to be associated with idiopathic aortitis. The association with smoking persisted after adjustment for gender (OR 3.24, 95% CI 1.05 to 9.96; P = 0.04). There was a trend toward lower prevalence of diabetes mellitus in cases (OR 0.39, 95% CI 0.11 to 1.43; P = 0.16) but no difference in prevalences of other risk factors. The median pre-operative erythrocyte sedimentation rate (ESR) was 20 mm/hour in cases (n = 13) and 9 mm/hour in controls (n = 22). The median pre-operative C-reactive protein (CRP) levels were 12 mg/L in cases (n = 8) and 3 mg/L in controls (n = 6) (normal: <8 mg/L). A higher proportion of cases versus controls had elevations in ESR (38% versus 9%; P = 0.075) and CRP (62% versus 0%; P = 0.031).

Conclusions

Gender and smoking may interact in complex mechanisms with immune and proteolytic pathways in older, less distensible thoracic aortas. Elevated acute-phase reactants as a marker of systemic inflammation may be present in some patients.

Gene expression profiling of peripheral blood in patients with abdominal aortic aneurysm

OBJECT

Abdominal aortic aneurysm (AAA) pathogenesis remains poorly understood. This study investigated the gene expression profile of peripheral blood from patients with AAA using microarray technology.

METHODS AND RESULTS

We determined gene expression profiles in pooled RNA from 10 AAA patients and 10 matched controls with arrays representing 14,000 transcripts. Microarray data for selected genes were confirmed by real-time PCR in two different AAA (n=36) and control (n=36) populations and integrated with biochemical data. We identified 91 genes which were differentially expressed in AAA patients. Gene Ontology analysis indicated a significant alteration of oxygen transport (increased hemoglobin gene expression) and lipid metabolism [including monoglyceride lipase and low density lipoprotein receptor-related protein 5 (LRP5) gene]. LRP5 expression was associated inversely with serum lipoprotein(a) [Lp(a)] concentration.

CONCLUSIONS

Increased expression of hemoglobin chain genes as well as of genes involved in erythrocyte mechanical stability were observed in the AAA RNA pools. The association between low levels of LRP5 gene expression and increased levels of Lp(a) in AAA patients suggests a potential role of LRP5 in Lp(a) catabolism. Our data underline the power of microarrays in identifying further molecular perturbations associated with AAA.

Epidemiology and Long-Term Prognostic Factors in Acute Type B Aortic Dissection

The epidemiological data and reports on long-term predictors of mortality after medically or endovascularly and medically treated patients with acute type B aortic dissection (AD) are scarce. Patients with type B AD between 2000 and 2004 were identified through the inpatient endovascular or autopsy registry at Malmö-Lund University Hospital, Sweden. Seventy-two patients had acute type B AD, of whom eight were found at autopsy. Shock due to ruptured type B AD was associated with in-hospital mortality (P = 0.006) in the 64 eligible patients. Renal insufficiency (odds ratio [OR] = 4.7, 95% confidence interval [CI] 1.1-19.4) and coexistent aortic disease (OR = 4.1, 95% CI 1.0-16.9) remained as independent predictors for long-term mortality after multivariate logistic regression analysis. Endovascular intervention (n = 32) was associated with neither short- nor long-term mortality. The estimated overall incidence of acute type B AD was 2.1/100,000 person-years, and the highest incidence rates were found in men aged 65-74 years (14.6/100,000 person-years) and women aged 75-84 years (19.0/100,000 person-years). Survival in patients with complicated acute type B AD managed with the endovascular technique was the same as in uncomplicated medically treated patients. Renal insufficiency and coexistent aortic disease were strong predictors for long-term mortality.

Cigarette smoking increases aortic dilatation without affecting matrix metalloproteinase-9 and -12 expression in a modified mouse model of aneurysm formation

OBJECTIVE

The development of abdominal aortic aneurysms (AAA) is presumed to result from multiple genetic and environmental factors, with exposure to tobacco smoke the single largest known factor predisposing to aneurysm growth. We have attempted to adapt the elastase-perfused animal model to determine whether tobacco exposure can lower the threshold of aortic injury necessary for AAA development.

METHODS

Adult C57BL/6 mice underwent transient perfusion of the infrarenal aorta with an active solution of elastase: high-dose (HDE, 0.19 U/mL, n=9), standard-dose (SDE, 0.16 U/mL, n=21) or low-dose (LDE, 0.07 U/mL, n=24). Control animals (n=24) were treated with heat inactivated elastase (HIE). Twenty LDE perfused mice were exposed to cigarette smoke (LDE-S) beginning 2 weeks before perfusion and continuing until aortic harvest. Aortic diameter (AD) was measured preperfusion, postperfusion, and at harvest on day 14. AAA was defined as %DeltaAD>or=100% between preperfusion and harvest. Aortas from each group (except HDE) were analyzed for matrix metalloproteinase-9 (MMP-9) and MMP-12 expression by real-time polymerase chain reaction normalized to glyceraldehyde-3-phosphate dehydrogenase.

RESULTS

All SDE mice developed large AAA by %DeltaAD (189.3%+/-16.9%, mean+/-standard error of the mean), but control mice had only a small dilatation (69.7%+/-3.7%, P<.01). Higher doses of elastase did not produce larger aneurysms in HDE mice. In contrast, only 63% of LDE mice showed aneurysmal dilatation, and these were significantly smaller (104.3%+/-4.2%, P<.01). When exposed to cigarette smoke, LDE animals developed significantly larger aneurysms (%DeltaAD, 134.5%+/-7.9%, P=.0021). There was no difference in normalized aortic MMP-9 and MMP-12 expression between elastase doses or between smoke-exposed and unexposed animals. Histologic analysis revealed that smoking increased the extent of aortic elastin degradation when compared with LDE-S animals.

CONCLUSION

Aneurysm development in the elastase model is dependent on the quantity of active elastase infused. Exposure of animals to tobacco smoke after a relatively minor aortic elastase injury produces increases in elastin degradation and aneurysm size without affecting MMP-9 or MMP-12 expression. To our knowledge, this is the first demonstration in an animal model that smoking can act as a synergistic factor in AAA development. Further understanding of the relationship between smoking and AAA in this model may help unveil the pathophysiologic pathways involved between cigarette smoke and AAAs.

Traditional and novel risk factors for clinically diagnosed abdominal aortic aneurysm: the Kaiser multiphasic health checkup cohort study

BACKGROUND

Identification of risk factors for and early diagnosis of clinically significant abdominal aortic aneurysm (AAA) before rupture is vital to optimize outcomes in these patients. Our aim was to examine traditional and three novel potential risk factors (abdominal obesity, white blood cell count, and kidney function) for abdominal aortic aneurysm (AAA, comprising discharge diagnosis or surgical repair) in a large multiethnic population.

METHODS

Cohort study (N =104,813) conducted at an integrated health care delivery system in northern California.

RESULTS

After a median of 13 years, 605 AAA events (490 in men and 115 in women; 91 [15%] fatal) were observed. In multivariable analysis, factors significantly associated with risk of clinically detected AAA included male gender, older age, black race (inversely), low educational attainment, cigarette smoking (with dose-response relation), height, treated and untreated hypertension, high total serum cholesterol, elevated white blood cell count, known coronary artery disease, history of intermittent claudication, and reduced kidney function. A significant Asian race by gender interaction was found such that Asian race had a (borderline significant) protective association with AAA in men but not in women.

CONCLUSIONS

Our findings confirm that major atherosclerotic risk factors, except for diabetes and obesity, are also prospectively related to AAA and suggest that elevated white blood cell count and reduced kidney function may improve risk stratification for clinically relevant AAA.

The Genetic Basis of Abdominal Aortic Aneurysms: A Review

INTRODUCTION

The pathogenesis of abdominal aortic aneurysm (AAA) remains poorly understood, however significant evidence has emerged in recent years to suggest a chronic inflammatory process. Observational studies have highlighted a familial trend towards AAA development among relatives of affected individuals and it is thought that inflammatory genes may influence an individual's susceptibility. Conflicting reports exist over single gene versus multiple gene inheritance patterns in addition to a collection of studies examining individual inflammatory genes. This paper reviews the evidence for a genetic predisposition to aneurysm formation including familial and segregation studies in addition to experimental evidence investigating specific candidate genes.

METHOD

Medline and Pubmed database searches were conducted using the search terms abdominal aortic aneurysm and gene. Papers were reviewed and references manually searched for further relevant publications which were added to the data. Papers were categorised under the headings familial, segregation and candidate gene studies.

RESULTS

A review of 58 papers is presented under sub-headings as above. In the case of the candidate gene section, a brief report of the functional relevance of each gene is included.

CONCLUSION

A summary of the evidence presented is given and the direction of future work in this field is briefly considered.

Smoking and Aortic Diseases

Cigarette smoking is a major vascular risk factor and in this context, it is an independent risk factor for the development of aortic disease, especially the formation and growth of abdominal aortic aneurysms (AAA). Medline was searched up to January 31, 2007 for the relevant literature for this review of the mechanisms by which smoking causes aortic wall damage and its subsequent impact on the clinical manifestation of this process. Idiopathic AAAs and aortic dissection are considered, as well as other aortic diseases (eg, Takayasu, Kawasaki, Behcet and Buerger). There is evidence suggesting an abnormal homeostasis between proteolytic and antiproteolytic activity in the vascular wall during the development of AAAs, and these mechanisms can be influenced by smoking. Smoking cessation plays an important role in the management of aortic disease.

Raised plasma fibrinogen concentration in patients with abdominal aortic aneurysm

A feature associated with abdominal aortic aneurysms (AAA) is the presence of intraluminal thrombi (ILT). Elevated plasma fibrinogen concentrations predict a greater risk of thrombosis. Therefore, the authors assessed the relationship between fibrinogen levels, AAA size, and ILT. An age- and sex-matched case-control study was conducted. Demographic data and plasma samples were obtained from 110 patients with AAA and 110 controls. All subjects had an abdominal ultrasound scan to determine the size of the aneurysm and the percentage of the ILT occupying the lumen. Plasma fibrinogen concentrations were measured by the Clauss method. Fibrinogen concentrations were significantly higher in patients with AAA than in controls (median: 2.89 vs 2.53 g/L; p<0.01). Patients with AAA who were current smokers had a larger median AAA size (4.50 vs 4.30 cm; p<0.04) and greater percentage of the ILT (40% vs 30%) than those who did not smoke. Fibrinogen was positively correlated with AAA size (r =0.323; p<0.01) and the percentage of ILT occupying the lumen (r =0.358; p<0.05). Fibrinogen levels were higher in the AAA group. The authors also demonstrated positive correlations between the AAA size, ILT, and fibrinogen concentration. Smoking was associated with larger aneurysms and ILT. Fibrinogen may be a useful marker to monitor the progression of AAA.