Increased Growth Rate of Abdominal Aortic Aneurysms in Women. The Tromsø Study

Evaluating growth patterns of abdominal aortic aneurysms among women

OBJECTIVE

Though initially protected from vessel dilation by estrogen, women may experience rapid abdominal aortic aneurysm (AAA) growth post-menopause. The rate of growth has been poorly defined in prior literature. Here, we describe aneurysm growth in a cohort of women found through an AAA screening program.

METHODS

Women with AAAs were retrospectively identified. Aortic imaging was reviewed, and measurements of maximum transverse and anterior-posterior diameters were completed. Growth was stratified by the type of aortic pathology (fusiform aneurysm, aortic ectasia, dissection with aneurysmal degeneration, saccular aneurysm) as well as size category (<3 cm, 3.0-3.9 cm, 4.0-4.9 cm, ≥5.0 cm) at diagnosis.

RESULTS

A cohort of 488 women was identified; 286 had multiple scans for review. The mean age of the entire cohort was 75 ± 9.9 years. Stratified by type of pathology, the mean age was 76 ± 8.9 years in patients with a fusiform AAA, 74 ± 9.8 years in ectasia, 65 ± 13.7 years in dissection, and 76 ± 5.6 years in saccular aneurysms. The maximum growth was highest in women with fusiform AAAs, followed by dissection, ectasia, and saccular pathology (9.7 mm, 7.0 mm, 3.0 mm, and 2.2 mm, respectively; P < .001). Comparing mean growth by year, the highest mean growth was in fusiform AAAs (3.6 mm vs 1.75 mm in dissection; P < .001). The Shapiro-Wilk test demonstrated that mean growth per year was non-normally distributed with a right skew. Stratified by aortic diameter at the time of diagnosis, mean growth/year increased with increasing size at diagnosis in fusiform AAAs and dissection (0.91 mm for <3 cm, 2.34 mm for 3.0-3.9 cm, 2.49 mm for 4.0-4.9 mm, and 6.16 mm for ≥5.0 cm in patients with fusiform AAAs vs 0.57 mm, 0.94 mm, 1.87 mm, and 2.66 mm, respectively, for patients with dissection). Smoking history was associated with a higher mean growth/year (2.6 mm vs 3.3 mm; P < .001). Conversely, patients with a family history of AAA had a lower mean growth/year (3.2 mm vs 1.5 mm; P < .001).

CONCLUSIONS

The rate of aneurysm growth in women varies based on pathology and aneurysm size, and women experience rapid aneurysm growth at sizes greater than 4.5 cm. Current screening guidelines are inadequate, and our results demonstrate that the rate of growth of fusiform aneurysms in women is faster than in men at a smaller size and may warrant more frequent surveillance than current Society for Vascular Surgery recommendations to prevent risk of increased morbidity.

Association of metformin use with abdominal aortic aneurysm: A systematic review and meta-analysis

BACKGROUND

Abdominal aortic aneurysm (AAA) is a cardiovascular disease characterized by a high mortality rate when ruptured. Some studies suggest a potential inverse correlation between AAA and diabetes patients, especially those undergoing metformin treatment. However, this relationship remains unclear. This paper offers a systematic review and meta-analysis with the objective of clarifying the influence of metformin on AAA.

METHODS

A search for relevant articles was performed across multiple databases including PubMed, ScienceDirect, Cochrane and Scopus. The focus was on studies that examined the comparative effects of metformin and non-metformin treatments on AAA patients. Data from appropriate studies were consolidated to estimate the effects. Our study encompassed 11 articles, comprising 13 cohorts that compared metformin (n = 32,250) with a control group (n = 116,339).

RESULTS

The random effects meta-analysis revealed that metformin was associated with a slower growth rate (weighted mean difference (WMD) -0.86 mm; 95% CI: -1.21 to -0.52; p < 0.01; I2: 81.4%) and fewer AAA-related events (OR: 0.54; 95% CI: 0.34 to 0.86; p = 0.01; I2: 60.9%). The findings suggest that metformin may be linked to a reduced risk of aortic aneurysm. A meta-regression analysis indicated that the association between metformin and AAA growth was significantly influenced by male gender (p = 0.027), but not by age (p = 0.801), hypertension (p = 0.256), DM (p = 0.689), smoking history (p = 0.786), use of lipid-lowering agents (p = 0.715), or baseline diameter (p = 0.291).

CONCLUSION

These results hint at a potential role for metformin in limiting annual AAA growth, AAA-related events, and the risk of AAA.

Racial and sex disparities in inpatient outcomes of patients with ruptured abdominal aortic aneurysms in the United States

BACKGROUND

Ruptured abdominal aortic aneurysm (AAA) is a medical emergency that requires immediate surgical intervention. The aim of this analysis was to identify the sex- and race-specific disparities that exist in outcomes of patients hospitalized with this condition in the United States using the National Inpatient Sample (NIS) to identify targets for improvement and support of specific patient populations.

METHODS

In this descriptive, retrospective study, we analyzed the patients admitted with a primary diagnosis of ruptured AAA between January 1, 2016, and December 31, 2020, using the NIS database. We compared demographics, comorbidities, and in-hospital outcomes in AAA patients, and compared these results between different racial groups and sexes.

RESULTS

A total of 22,395 patients with ruptured AAA were included for analysis. Of these, 16,125 patients (72.0%) were male, and 6270 were female (28.0%). The majority of patients (18,655 [83.3%]) identified as Caucasian, with the remaining patients identifying as African American (1555 [6.9%]), Hispanic (1095 [4.9%]), Asian or Pacific Islander (470 [2.1%]), or Native American (80 [0.5%]). Females had a higher risk of mortality than males (OR, 1.7; 95% confidence interval [CI], 1.45-1.96; P < .001) and were less likely to undergo endovascular aortic repair (OR, 0.70; 95% CI, 0.61-0.81; P < .001) or fenestrated endovascular aortic repair (OR, 0.71; 95% CI, 0.55-0.91; P = .007). Relative to Caucasian race, patients who identified as African American had a lower risk of inpatient mortality (OR, 0.50; 95% CI, 0.37-0.68; P < .001).

CONCLUSIONS

In this retrospective study of the NIS database from 2016 to 2020, females were less likely to undergo endovascular intervention and more likely to die during their initial hospitalization. African American patients had lower rates in-hospital mortality than Caucasian patients, despite a higher burden of comorbidities. Future studies are needed to elucidate the potential factors affecting racial and sex disparities in ruptured AAA outcomes, including screening practices, rupture risk stratification, and more personalized guidelines for both elective and emergent intervention.

Female-Specific Considerations in Aortic Health and Disease

The aorta plays a central role in the modulation of blood flow to supply end organs and to optimize the workload of the left ventricle. The constant interaction of the arterial wall with protective and deleterious circulating factors, and the cumulative exposure to ventriculoarterial pulsatile load, with its associated intimal-medial changes, are important players in the complex process of vascular aging. Vascular aging is also modulated by biomolecular processes such as oxidative stress, genomic instability, and cellular senescence. Concomitantly with well-established cardiometabolic and sex-specific risk factors and environmental stressors, arterial stiffness is associated with cardiovascular disease, which remains the leading cause of morbidity and mortality in women worldwide. Sexual dimorphisms in aortic health and disease are increasingly recognized and explain-at least in part-some of the observable sex differences in cardiovascular disease, which will be explored in this review. Specifically, we will discuss how biological sex affects arterial health and vascular aging and the implications this has for development of certain cardiovascular diseases uniquely or predominantly affecting women. We will then expand on sex differences in thoracic and abdominal aortic aneurysms, with special considerations for aortopathies in pregnancy.

Brazilian Society for Angiology and Vascular Surgery guidelines on abdominal aortic aneurysm

The Brazilian Society of Angiology and Vascular Surgery, through the Guidelines Project, presents new Abdominal Aortic Aneurysm Guidelines, on the subject of care for abdominal aortic aneurysm patients. Its development prioritized descriptive guidelines, using the EMBASE, LILACS, and PubMed databases. References include randomized controlled trials, systematic reviews, meta-analyses, and cohort studies. Quality of evidence was evaluated by a pair of coordinators, aided by the RoB 2 Cochrane tool and the Newcastle Ottawa Scale forms. The subjects include juxtarenal aneurysms, infected aneurysms, and new therapeutic techniques, especially endovascular procedures. The current version of the guidelines include important recommendations for the primary topics involving diagnosis, treatment, and follow-up for abdominal aortic aneurysm patients, providing an objective guide for medical practice, based on scientific evidence and widely available throughout Brazil.

Investigation of commonly used aortic aneurysm growth rate metrics: Comparing their suitability for clinical and research applications

An aneurysm is a pathological widening of a blood vessel. Aneurysms of the aorta are often asymptomatic until they rupture, killing approximately 10,000 Americans per year. Fortunately, rupture can be prevented through early detection and surgical repair. However, surgical risk outweighs rupture risk for small aortic aneurysms, necessitating a policy of surveillance. Understanding the growth rate of aneurysms is essential for determining appropriate surveillance windows. Further, identifying risk factors for fast growth can help identify potential interventions. However, studies in the literature have applied many different methods for defining the growth rate of abdominal aortic aneurysms. It is unclear which of these methods is most accurate and clinically meaningful, and whether these heterogeneous methodologies may have contributed to the varied results reported in the literature. To help future researchers best plan their studies and to help clinicians interpret existing studies, we compared five different models of aneurysmal growth rate. We examined their noise tolerance, temporal bias, predictive accuracy, and statistical power to detect risk factors. We found that hierarchical mixed effects models were more noise tolerant than traditional, unpooled models. We also found that linear models were sensitive to temporal bias, assigning lower growth rates to aneurysms that were detected earlier in their course. Our exponential mixed model was noise-tolerant, resistant to temporal bias, and detected the greatest number of clinical risk factors. We conclude that exponential mixed models may be optimal for large studies. Because our results suggest that choice of method can materially impact a study's findings, we recommend that future studies clearly state the method used and demonstrate its appropriateness.

Elective Endovascular Aneurysm Repair (EVAR) for the Treatment of Infrarenal Abdominal Aortic Aneurysms of 5.0-5.5 cm: Differences between Men and Women

BACKGROUND

There is significant debate regarding the existence of sex-related differences in the presentation, treatment, and outcomes of men versus women affected by abdominal aortic aneurysm (AAA). The purpose of this study is to compare endovascular aneurysm repair (EVAR) of infrarenal AAAs with the current sex-neutral 5.0-5.5 cm-diameter threshold for intervention between the two sexes.

METHODS

Retrospective review of consecutive cases from a single teaching institution over a period of five years of patients who had undergone elective EVAR for AAAs between 5.0 and 5.5 cm in diameter. Outcomes of interest were compared according to sex.

RESULTS

Ninety-four patients were included in the analysis, with a higher prevalence of men (53%). Females were older at the time of repair, 78 ± 5.1 years, versus 71.7 ± 7 years (p < 0.01), and had higher incidence of underlying comorbidities, namely, arrhythmia, chronic kidney disease, and previous carotid revascularization. Women had higher incidence of immediate systemic complications (p = 0.021), post-operative AMI (p = 0.001), arrhythmia (p = 0.006), pulmonary oedema (p < 0.001), and persistent renal dysfunction (p = 0.029). Multivariate analysis for post-operative factors associated to mortality and adjusted for sex confirmed that AMI (p = 0.015), arrhythmia (p = 0.049), pulmonary oedema (p = 0.015), persistent renal dysfunction (p < 0.001), cerebral ischemia (p < 0.001), arterial embolism of lower limbs (p < 0.001), and deep-vein thrombosis of lower limbs (p < 0.001) were associated to higher EVAR-related mortality; a higher incidence of post-operative AMI (p = 0.014), pulmonary edema (p = 0.034), and arterial embolism of lower limbs (p = 0.046) were associated to higher 30-days mortality. In females there was also a higher rate of suprarenal fixation (p = 0.026), insertion outside the instruction for use (p = 0.035), and a more hostile neck anatomy with different proximal aortic diameter (p < 0.001) and angle (p = 0.003).

CONCLUSIONS

A similar threshold of size of AAA for elective surgery for both males and females might not be appropriate for surgical intervention, as females tend to have worse outcomes. Further population-based studies are needed to guide on sex-related differences and intervention on AAA.

Exploring the expression and potential function of follicle stimulating hormone receptor in extragonadal cells related to abdominal aortic aneurysm

INTRODUCTION

Follicle stimulating hormone (FSH) is identified to play a role in postmenopausal disease and hypothesized to affect abdominal aortic aneurysm (AAA) onset/progression in postmenopausal women. We aimed to detect FSHR gene expression in AAA tissue and cell types involved in AAA formation.

METHODS

FSH stimulation of human umbilical cord endothelial cells (HUVECs), smooth muscle cells (HUCs) and PMA-differentiated macrophages to assess gene expression of FSHR and various markers. Human macrophages activated with various stimuli were assessed for FSHR gene expression. AAA dataset, AAA tissue samples and AAA-derived smooth muscle cells (SMC) obtained from elderly female donors were assessed for FSHR gene expression. AAA-SMCs were stimulated with FSH to assess its effect on gene expression. Lastly, oxidized low-density-lipoprotein (ox-LDL) uptake and abundance of cell surface protein markers were assessed by flow cytometry after FSH stimulation of human monocytes.

RESULTS

FSH stimulation showed similar levels of gene expression in HUVECs and HUCs. Only ACTA2 was downregulated in HUCs. In PMA-differentiated macrophages, gene expression of inflammation markers was unchanged after FSH stimulation. FSHR gene expression was found to be low in the AAA datasets. Female AAA-SMCs show occasional FSHR gene expression at a very low level, yet stimulation with FSH did not affect gene expression of SMC- or inflammation markers. FSH stimulation did not impact ox-LDL uptake or alter cell surface protein expression in monocytes. While FSHR gene expression was detected in human testis tissue, it was below quantification level in all other investigated cell types, even upon activation of macrophages with various stimuli.

CONCLUSION

Despite previous reports, we did not detect FSHR gene expression in various extragonadal cell types, except in occasional female AAA-SMCs. No clear effect on cell activation was observed upon FSH stimulation in any cell type. Our data suggest that a direct effect of FSH in AAA-related extragonadal cells is unlikely to influence AAA.

Sex Differences in Outcomes Following Ruptured Abdominal Aortic Aneurysm Repair

IMPORTANCE

Sex differences in aortic surgery outcomes are commonly reported. However, data on ruptured abdominal aortic aneurysm (rAAA) repair outcomes in women vs men are limited.

OBJECTIVE

To assess differences in perioperative and long-term mortality following rAAA repair in women vs men.

DESIGN, SETTING, AND PARTICIPANTS

A multicenter, retrospective cohort study was conducted using the Vascular Quality Initiative database, which prospectively captures information on patients who undergo vascular surgery across 796 academic and community hospitals in North America. All patients who underwent endovascular or open rAAA repair between January 1, 2003, and December 31, 2019, were included. Outcomes were assessed up to January 1, 2020.

EXPOSURES

Patient sex.

MAIN OUTCOMES AND MEASURES

Demographic, clinical, and procedural characteristics were recorded, and differences between women vs men were assessed using independent t test and χ2 test. The primary outcomes were in-hospital and 8-year mortality. Associations between sex and outcomes were analyzed using univariable and multivariable logistic regression and Cox proportional hazards regression analysis.

RESULTS

A total of 1160 (21.9%) women and 4148 (78.1%) men underwent rAAA repair during the study period. There was a similar proportion of endovascular repairs in women and men (654 [56.4%] vs 2386 [57.5%]). Women were older (mean [SD] age, 75.8 [9.3] vs 71.7 [9.6] years), more likely to have chronic kidney disease (718 [61.9%] vs 2184 [52.7%]), and presented with ruptured aneurysms of smaller diameters (mean [SD] 68 [18.2] vs 78 [30.2] mm). In-hospital mortality was higher in women (34.4% vs 26.6%; odds ratio, 1.44; 95% CI, 1.25-1.66), which persisted after adjusting for demographic, clinical, and procedural characteristics (adjusted odds ratio, 1.36; 95% CI, 1.12-1.66; P = .002). Eight-year survival was lower in women (36.7% vs 49.5%; hazard ratio, 1.25; 95% CI, 1.04-1.50; P = .02), which persisted when stratified by endovascular and open repair. This survival difference existed in both the US and Canada. Variables associated with long-term mortality in women included older age and chronic kidney disease.

CONCLUSIONS AND RELEVANCE

Women who underwent rAAA repair had higher perioperative and 8-year mortality rates following both endovascular and open repair compared with men. Older age and higher rates of chronic kidney disease in women were associated with higher mortality rates. These findings suggest that future studies should assess the reasons for these disparities and whether opportunities exist to improve AAA care for women.

Optimal timing of surveillance ultrasounds in small aortic aneurysms

OBJECTIVE

Small abdominal aortic aneurysms (AAA) surveillance intervals remain controversial and difficult to standardize. Current Society for Vascular Surgery guidelines lack quality evidence. The objective of this study is to examine patients followed in a high volume non-invasive vascular laboratory, determine if the current guidelines are fitting in clinical practice, and attempt to further identify risk factors for accelerated aneurysm growth.

METHODS

A retrospective analysis of patients who underwent at least two ultrasounds for AAA in the vascular laboratory during 2008-2018 with baseline diameter less than 5.0 cm was conducted. Patient demographics were collected. Groups were then created for comparison using the size criteria according to SVS guidelines. In addition, we compared overall growth rates specifically evaluating rapid growth (rate of at least 1.0 cm/year and size change of at least 0.5 cm from previous imaging), expected growth (any growth below 1.0 cm/year and of at least 0.5 cm from baseline) and no growth.

RESULTS

A total of 1581 patients (1232 male and 349 female) were identified with a total of 5945 ultrasound studies. The median age was 73 years and mean follow-up was 27.8 months. Baseline AAA size was 3.0-3.9 cm in 986 patients and 4.0-4.9 cm in 595 patients. The average maximum growth rate was 0.18 cm/year for AAAs 3.0-3.9 cm and 0.36 cm/year for AAAs 4.0-4.9 cm (p<0.001). Patients with AAA 4.0-4.9 cm at baseline were more likely to be white, male, hypertensive and have chronic kidney disease (p <0.05). 1078 patients (68.2%) demonstrated no growth over the observed time period with 342 patients (21.6%) demonstrating expected growth and 161 (10.2%) rapid growth. Male gender and baseline AAA size of 4.0-4.9 cm were more likely to demonstrate rapid growth (p=0.002) and eventual repair (p<0.001). Metformin use was more common in the AAA group with no growth (p <0.05). Freedom from rapid growth and repair indication at two years was significantly lower in those patients with baseline aneurysms 3.0-3.9 cm (p<0.001).

CONCLUSIONS

The overall low rate of events in small AAAs supports continued surveillance every 3 years for AAAs between 3.0 and 3.9 cm and yearly for male patients with AAAs 4.0-4.9 cm as recommended by the SVS Guidelines. Female gender may have less rapid growth than previously reported but likely merit more rigorous surveillance particularly as the AAAs approach 5.0 cm. Metformin use continues to demonstrate it may abrogate aneurysmal growth. Lastly, there is a subset of patients that exhibit more rapid growth of their small AAAs, and further study will be required to further classify these patients.

Sex Differences in Inflammation During Venous Remodeling of Arteriovenous Fistulae

Vascular disorders frequently have differing clinical presentations among women and men. Sex differences exist in vascular access for hemodialysis; women have reduced rates of arteriovenous fistula (AVF) maturation as well as fistula utilization compared with men. Inflammation is increasingly implicated in both clinical studies and animal models as a potent mechanism driving AVF maturation, especially in vessel dilation and wall thickening, that allows venous remodeling to the fistula environment to support hemodialysis. Sex differences have long been recognized in arterial remodeling and diseases, with men having increased cardiovascular events compared with pre-menopausal women. Many of these arterial diseases are driven by inflammation that is similar to the inflammation during AVF maturation. Improved understanding of sex differences in inflammation during vascular remodeling may suggest sex-specific vascular therapies to improve AVF success.

Influence of Sex on Outcomes After Thoracic Endovascular Repair for Type B Aortic Dissection

We aimed to investigate whether sex differences influence the clinical outcomes of patients who undergo thoracic endovascular aortic repair (TEVAR) for type B aortic dissection (TBAD). We retrospectively analyzed a prospectively maintained single-center cohort of patients with TBAD who underwent TEVAR between January 2010 and June 2017. We evaluated the in-hospital and long-term mortality and composite end point. Of the 913 patients, 793 (86.8%) were male and 120 (13.1%) were female. Compared to male patients, the female patients were older, more likely to have diabetes mellitus, but less likely to smoke or have hypertension. The proximal landing zone in 0 and 1 was higher in male patients (P = .023), who were more likely to require an aortic arch bypass. Endoleak, delirium, and ICU stay after stent-graft implantation were also more frequent in men. Sex factor was not associated with in-hospital or long-term mortality or the composite end point in the multivariable regression analyses and Cox regression model. The mean estimated survival time was similar between males and females (2462.9 ± 141.2 vs 2804.1 ± 117.4 days, P = .167) in the propensity score-matched cohort. Despite distinct characteristics between sex, there was no sex-related difference in long-term clinical outcomes after TEVAR for TBAD.

A Novel Hypothesis: A Role for Follicle Stimulating Hormone in Abdominal Aortic Aneurysm Development in Postmenopausal Women

An abdominal aortic aneurysm (AAA) is a dilatation of the abdominal aorta, which can potentially be fatal due to exsanguination following rupture. Although AAA is less prevalent in women, women with AAA have a more severe AAA progression compared to men as reflected by enhanced aneurysm growth rates and a higher rupture risk. Women are diagnosed with AAA at an older age than men, and in line with increased osteoporosis and cardiovascular events, the delayed AAA onset has been attributed to the reduction of the protective effect of oestrogens during the menopausal transition. However, new insights have shown that a high follicle stimulating hormone (FSH) level during menopause may also play a key role in those diseases. In this report we hypothesize that FSH may aggravate AAA development and progression in postmenopausal women via a direct and/or indirect role, promoting aorta pathology. Since FSH receptors (FSHR) are reported on many other cell types than granulosa cells in the ovaries, it is feasible that FSH stimulation of FSHR-bearing cells such as aortic endothelial cells or inflammatory cells, could promote AAA formation directly. Indirectly, AAA progression may be influenced by an FSH-mediated increase in osteoporosis, which is associated with aortic calcification. Also, an FSH-mediated decrease in cholesterol uptake by the liver and an increase in cholesterol biosynthesis will increase the cholesterol level in the circulation, and subsequently promote aortic atherosclerosis and inflammation. Lastly, FSH-induced adipogenesis may lead to obesity-mediated dysfunction of the microvasculature of the aorta and/or modulation of the periaortic adipose tissue. Thus the long term increased plasma FSH levels during the menopausal transition may contribute to enhanced AAA disease in menopausal women and could be a potential novel target for treatment to lower AAA-related events in women.

LUCY results show females have equivalent outcomes to males following endovascular abdominal aortic aneurysm repair despite more complex aortic morphology

OBJECTIVE

Females remain underrepresented in studies of endovascular aneurysm repair (EVAR) owing to anatomic ineligibility for EVAR devices. The aim of the LUCY study is to explore the comparative safety and effectiveness of EVAR using a low-profile stent graft (Ovation; Endologix, Inc, Irvine, Calif) in females as well as males.

METHODS

The LUCY registry was a prospective, nonrandomized, multicenter study where patient enrollment was stratified by sex in a two-to-one ratio (male-to-female). Main outcomes were procedural data, 30-day major adverse events, device-related adverse events confirmed with contrast-enhanced computed tomography scans, secondary interventions, and hospital readmissions. Adverse events were adjudicated by a clinical events committee. Patients were followed at their 1-month and 1-year follow-up visits.

RESULTS

A total of 225 patients (76 females, 149 males) were enrolled at 39 U.S. centers. No statistically significant sex differences were observed in demographics or medical history. Females presented with smaller access vessels (6.2 vs 7.7 mm; P < .001), statistically smaller neck diameter (22 mm vs 23 mm; P = .001), similar neck angulation (11% vs 9% angulation >45°; P = .81), and smaller maximum abdominal aortic aneurysm (AAA) diameter (50 mm vs 53 mm; P = .01), however, these factors do not seem to be clinically significant. Technical success was 99%, and the median hospital stay was 1 day. The incidence of MAE through 30 days was 1.3% in females and 2.0% in males. There were no differences between sexes observed among the 30-day perioperative outcomes. The 30-day secondary intervention rate was 0.4%. The all-cause readmission rate through 30 days was 5.3% in females and 6.7% in males. There were no reports of limb occlusion or deaths within the first 30 days. At 1 year, there were no deaths in the female arm but nine deaths (6.0%) were observed in males, two of which were AAA related (1.3%). Through 1 year, there were eight type IA endoleaks (one female, seven males; P = .27) and three cases with limb occlusion (one female, two males). There were no reports of migration, AAA rupture, or surgical conversion through the end of follow-up.

CONCLUSIONS

Despite more complex aortic morphology in females than males, EVAR with a low-profile stent graft was associated with comparable procedural and perioperative outcomes through 1 year between the sexes.

Peripheral Vascular Disease in Women: Therapeutic Options in 2019

PURPOSE OF REVIEW

In recent years, there have been advances in the prevention, management, and control of peripheral vascular disease (PVD). There is a trend towards aggressive risk factor modification, noninvasive screening, and endovascular revascularization with surgical approaches reserved only for select cases. This article reviews the different management strategies ranging from pharmacotherapy, revascularization, and rehabilitation with an emphasis on the response of women to these therapies.

RECENT FINDINGS

Overall, the representation of women in the majority of the published data in this arena remains poor. Studies examining medical therapy and endovascular and surgical revascularization were not designed to address sex disparities. Nevertheless, we dissect these therapies and their relevant randomized trials. The paucity of data investigating the response of women to the different management options makes it difficult to make any evidence-based recommendations. This not only applies to the type of intervention, but also the appropriate timing and risks entailed.

Risk Factor Analyses of Abdominal Aortic Aneurysms Growth in Japanese Patients

BACKGROUND

This study aimed to retrospectively demonstrate the growth rate (mm/year) of abdominal aortic aneurysm (AAA) diameters (ADs) and to analyze risk factors for AAA expansion.

METHODS

We retrospectively investigated the clinical data of 319 patients with AAAs who were followed up as outpatients for >2 years after their initial visit and who underwent computed tomography >4 times.

RESULTS

The mean follow-up period was 3.7 ± 1.5 years. The annual average growth rates according to varying ADs were as follows: 1.9 ± 0.8 (AD 30-34 mm), 2.6 ± 1.2 (AD 35-39 mm), 2.8 ± 1.1 (AD 40-44 mm), 3.1 ± 1.3 (AD 45-49 mm), 3.4 ± 1.6 (AD 50-54 mm), and 3.5 ± 1.4 mm (AD ≥55 mm). Factors associated with AAA expansion were smoking (P = 0.017), hypertension (P < 0.001), and ADs (P < 0.001). In the subgroup analysis, data regarding growth rates of ≥3 mm were extracted, and a statistically significant difference between smoking status and ADs of ≥40 mm was observed.

CONCLUSIONS

Factors associated with AAA expansion in Japanese patients included smoking, hypertension, and ADs, and a statistically significant difference was observed between smoking status and ADs of ≥40 mm.

Epidemiology and contemporary management of abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is most commonly defined as a maximal diameter of the abdominal aorta in excess of 3 cm in either anterior-posterior or transverse planes or, alternatively, as a focal dilation ≥ 1.5 times the diameter of the normal adjacent arterial segment. Risk factors for the development of AAA include age > 60, tobacco use, male gender, Caucasian race, and family history of AAA. Aneurysm growth and rupture risk appear to be associated with persistent tobacco use, female gender, and chronic pulmonary disease. The majority of AAAs are asymptomatic and detected incidentally on various imaging studies, including abdominal ultrasound, and computed tomographic angiography. Symptoms associated with AAA may include abdominal or back pain, thromboembolization, atheroembolization, aortic rupture, or development of an arteriovenous or aortoenteric fistula. The Screening Abdominal Aortic Aneurysms Efficiently (SAAAVE) Act provides coverage for a one-time screening abdominal ultrasound at age 65 for men who have smoked at least 100 cigarettes and women who have family history of AAA disease. Medical management is recommended for asymptomatic patients with AAAs < 5 cm in diameter and focuses on modifiable risk factors, including smoking cessation and blood pressure control. Primary indications for intervention in patients with AAA include development of symptoms, rupture, rapid aneurysm growth (> 5 mm/6 months), or presence of a fusiform aneurysm with maximum diameter of 5.5 cm or greater. Intervention for AAA includes conventional open surgical repair and endovascular aortic stent graft repair.

Sex Chromosome Complement Defines Diffuse Versus Focal Angiotensin II-Induced Aortic Pathology

OBJECTIVE

Aortic pathologies exhibit sexual dimorphism, with aneurysms in both the thoracic and abdominal aorta (ie, abdominal aortic aneurysm [AAA]) exhibiting higher male prevalence. Women have lower prevalence of aneurysms, but when they occur, aneurysms progress rapidly. To define mechanisms for these sex differences, we determined the role of sex chromosome complement and testosterone on the location and progression of angiotensin II (AngII)-induced aortic pathologies.

APPROACH AND RESULTS

We used transgenic male mice expressing Sry (sex-determining region Y) on an autosome to create Ldlr (low-density lipoprotein receptor)-deficient male mice with an XY or XX sex chromosome complement. Transcriptional profiling was performed on abdominal aortas from XY or XX males, demonstrating 1746 genes influenced by sex chromosomes or sex hormones. Males (XY or XX) were either sham-operated or orchiectomized before AngII infusions. Diffuse aortic aneurysm pathology developed in XY AngII-infused males, whereas XX males developed focal AAAs. Castration reduced all AngII-induced aortic pathologies in XY and XX males. Thoracic aortas from AngII-infused XY males exhibited adventitial thickening that was not present in XX males. We infused male XY and XX mice with either saline or AngII and quantified mRNA abundance of key genes in both thoracic and abdominal aortas. Regional differences in mRNA abundance existed before AngII infusions, which were differentially influenced by AngII between genotypes. Prolonged AngII infusions resulted in aortic wall thickening of AAAs from XY males, whereas XX males had dilated focal AAAs.

CONCLUSIONS

An XY sex chromosome complement mediates diffuse aortic pathology, whereas an XX sex chromosome complement contributes to focal AngII-induced AAAs.

Thoracic Aortic Aneurysm Growth: Role of Sex and Aneurysm Etiology

BACKGROUND

Thoracic aortic aneurysm (TAA) outcomes are worse in women than men, although reasons for sex differences are unknown. Because faster TAA growth is a risk factor for acute aortic syndromes, we sought to determine the role of sex and aneurysm etiology on TAA growth.

METHODS AND RESULTS

Eighty-two consecutive unoperated subjects with TAA who had serial aneurysm measurements were recruited. In multivariable linear regression the association of female sex with aneurysm growth rate was assessed after adjustment for potential confounders. We also tested the interaction term sex×aneurysm etiology in the prediction of TAA growth. Seventy-four percent of subjects were men; mean±SD age was 62.4±11.9 years in men and 67.7±10.7 years in women (P=0.06). Forty-seven (57%) subjects had degenerative TAAs, and the remainder had heritable TAAs. Absolute baseline aneurysm size and follow-up time were not different between men and women. Aneurysm growth rate was 1.19±1.15 mm/y in women and 0.59±0.66 mm/y in men (P=0.02). Female sex remained significantly associated with greater aneurysm growth in multivariable analyses (β±SE: 0.35±0.12, P=0.005). In addition, female sex was associated with faster TAA growth only among those with degenerative TAA (β±SE: 0.33±0.08, P=0.0002) and not among those with heritable TAA (P=0.79), with a significant sex×etiology interaction (P=0.001).

CONCLUSIONS

TAA growth rates are greater in women than men, and this difference is specific to women with degenerative TAAs. Our findings may explain sex differences in TAA outcomes and provide a foundation for future investigations of this topic.

Abdominal Aortic Aneurysms and Risk Factors for Adverse Events

An abdominal aortic aneurysm (AAA) is a focal full thickness dilatation of the abdominal aorta, greater than 1.5 times its normal diameter. Although some patients with AAA experience back or abdominal pain, most remain asymptomatic until rupture. The prognosis after AAA rupture is poor. Management strategies for patients with asymptomatic AAAs include risk factor reduction, such as smoking cessation, optimizing antihypertensive treatment, and treating dyslipidemia, as well as surveillance by ultrasound. Currently, aneurysm diameter alone is often used to assess risk of rupture. Once the aneurysm diameter reaches 5.5 cm, the risk of rupture is considered greater than the risk of intervention and elective aneurysm repair is undertaken. There is increasing interest in detecting AAAs early, and national screening programs are now in place. Furthermore, there is increasing research interest in biomarkers, genetics, and functional imaging to improve detection of AAAs at risk of progression and rupture. In this review, we discuss risk factors for AAA rupture, which should be considered during the management process, to advance current deficiencies in management pathways.

Abdominal Aortic Aneurysm Repair in Octogenarians versus Younger Patients in a Tertiary Referral Center

Operative survival is as high as 96% for elective abdominal aortic aneursym (AAA) repair but as low as 10% for emergency repair. Our primary aim was to compare elective AAA repair in octogenarians with nonoperative management. Our secondary aim was to compare octogenarians with their younger counterparts.

From 1998 to 2003, 180 patients with AAA were treated operatively or nonoperatively. Factors determining treatment included American Society of Anesthesiologists grade ≥ 4, inoperable malignancy, New York Heart Association class III, forced expiratory volume in 1 second < 35%, creatinine > 6.0 mg/dL, and patient and family choice. A parallel-group observational study was performed to assess age and treatment effects on outcome.

Seventy (39%) patients were repaired electively, 68 (38%) were managed nonoperatively, and 42 (23%) underwent emergency repair. Fifty-nine (33%) were octogenarians.

The octogenarian 5-year survival rate was 20% following emergency repair, 42% if treated nonoperatively, and 83% following elective repair. Younger cohort rates were 55% (emergency), 44% (nonoperative), and 76% (elective).

The octogenarian mean expansion rate was 0.26 cm/yr in those treated nonoperatively and 1.04 cm/yr in confirmed rupture. Rupture rate was related to expansion rate (95% confidence interval [CI] 0.06–0.59, r = .35, p = .01). The rates in the younger subgroup were 0.32 cm/yr and 1.14 cm/yr (95% CI −0.021–0.672}, r = .37, p = .03).

The octogenarian survival rate was highest following elective repair. Rupture was closely correlated with aneurysm expansion. Screening should reduce the incidence of octogenarian rupture of AAA and identify those patients most suitable for nonoperative management.

Association of diabetes mellitus with presence, expansion, and rupture of abdominal aortic aneurysm: "Curiouser and curiouser!" cried ALICE

Both coronary artery and peripheral artery disease are representative atherosclerotic diseases that are positively associated with presence of abdominal aortic aneurysm (AAA). Diabetes mellitus, which is one of major risk factors of coronary artery and peripheral artery diseases, however, has been curiously suggested to be negatively associated with AAA, despite the positive associations of coronary artery and peripheral artery diseases with presence of AAA. In the present article, we overviewed epidemiologic evidence (meta-analyses) regarding the associations of diabetes mellitus with presence, expansion, and rupture of AAA through a systematic literature search. Our exhaustive search identified seven meta-analyses. Main results of almost all meta-analyses (except for the two earliest ones) apparently found that diabetes mellitus is negatively associated with presence, expansion, and rupture of AAA.

Influence of Selective Biochemical and Morphological Agents on Natural History of Aneurysm of Abdominal Aorta Development

BACKGROUND The development of abdominal aortic aneurysm (AAA) is probably influenced by many factors. The role of some of these factors, such as intraluminal thrombus (ILT) or cystatin C serum levels, remains controversial. Proving their influence could have therapeutic implications for some patients with AAA. Associations between the rate of increase in diameter of an aneurysm and ILT, as well as other factors, including biochemical factors (C-Reactive Protein - CRP, cystatin C), age, sex, and comorbidities, could predict disease progression in individual patients. MATERIAL AND METHODS Seventy patients with small AAA were included into the study. The patients were followed using ultrasound and CT imaging. We evaluated aneurysm dimensions and aneurysm wall thickness, as well as ILT and its dimensions, aneurysm wall morphology, CRP, and cystatin C. RESULTS We observed significant growth of AAA and thinning of aneurysmal wall. Aneurysms over 4 cm grew significantly faster in the second year of observation. ILT grew together with AAA size. Age, sex, smoking, dyslipidemias, or controlled arterial hypertension had no influence on aneurysm progression rate. Changes in serum of CRP concentration did not reach statistical significance, but cystatin C levels did. CONCLUSIONS Presence and size of ILT, wall thickness, and cystatin C levels may be considered in prediction of AAA progression. ILT might exert a protective influence on the risk of aneurysm rupture. However, larger aneurysms containing larger thrombi grow faster and their walls undergo more rapid degradation, which in turn increases the risk of rupture. This matter requires further studies.

Diabetes and Abdominal Aortic Aneurysm Growth

We performed a systematic literature search and a meta-analysis to assess the association between diabetes mellitus (DM) and abdominal aortic aneurysm (AAA) growth. Databases including MEDLINE and EMBASE were searched through June 2015 using PubMed and OVID. For each study, data regarding AAA growth rates in both the DM and the non-DM groups were used to generate standardized mean differences (SMDs) and 95% confidence intervals (CIs). Our search identified 19 relevant studies including data on 9777 patients with AAA. Pooled analyses demonstrated a statistically significant slower growth rates in DM patients than in non-DM patients (unadjusted SMD, −0.32; 95% CI, −0.40 to −0.24; P < .00001; adjusted SMD, −0.29; 95% CI, −0.417 to −0.18; P < .00001). Despite possible publication bias in favor of DM based on funnel plot asymmetry, even adjustment of the asymmetry did not alter the beneficial effect of DM. In conclusion, on the basis of a meta-analysis of data on a total of 9777 patients (19 studies) identified through a systematic literature search, we confirmed the association of DM with slower growth rates of AAA.

Exogenous 17-β estradiol administration blunts progression of established angiotensin II-induced abdominal aortic aneurysms in female ovariectomized mice

Background

Abdominal aortic aneurysms (AAAs) occur predominately in males. However, AAAs in females have rapid growth rates and rupture at smaller sizes. Mechanisms contributing to AAA progression in females are undefined. We defined effects of ovariectomy, with and without 17-β estradiol (E2), on progression of established angiotensin II (AngII)-induced AAAs in female mice.

Methods

We used neonatal testosterone exposures at 1 day of age to promote susceptibility to AngII-induced AAAs in adult female Ldlr^−/− mice. Females were infused with AngII for 28 days to induce AAAs, and then stratified into groups that were sham, ovariectomized (Ovx, vehicle), or Ovx with E2 administration for 2 months of continued AngII infusions. Aortic lumen diameters were quantified by ultrasound and analyzed by linear mixed model, and maximal AAA diameters were analyzed by one-way ANOVA. Atherosclerosis was quantified en face in the aortic arch. AAA tissue sections were analyzed for cellular composition. We quantified effects of E2 on abdominal aortic smooth muscle cell (SMC) growth, α-actin and transforming growth factor-beta (TGF-β) production, and wound healing.

Results

Serum E2 concentrations were increased significantly by E2. Aortic lumen diameters increased over time in sham-operated and Ovx (vehicle) females, but not in Ovx females administered E2. At day 70, E2 administration decreased significantly aortic lumen diameters compared to Ovx vehicle and sham-operated females. Compared to Ovx females (vehicle), maximal AAA diameters were reduced significantly by E2. AAA tissue sections from Ovx females administered E2 exhibited significant increases in α-actin and decreases in neutrophils compared to Ovx females administered vehicle. In abdominal aortic SMCs, E2 resulted in a concentration-dependent increase in α-actin, elevated TGF-β, and more rapid wound healing. E2 administration to Ovx females also significantly reduced atherosclerotic lesions compared to sham-operated females. This effect was accompanied by significant reductions in serum cholesterol concentrations.

Conclusions

E2 administration to Ovx females abolished progressive growth and decreased severity of AngII-induced AAAs. These effects were accompanied by increased SMC α-actin, elevated TGF-β, and reduced neutrophils. Similarly, E2 administration reduced AngII-induced atherosclerosis. These results suggest that loss of E2 in post-menopausal females may contribute to progressive growth of AAAs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13293-015-0030-1) contains supplementary material, which is available to authorized users.

Population risk factor estimates for abdominal aortic aneurysm from electronic medical records: a case control study

BACKGROUND

Using abdominal aortic aneurysm (AAA) as a model, this case-control study used electronic medical record (EMR) data to assess known risk factors and identify new associations.

METHODS

The study population consisted of cases with AAA (n =888) and controls (n =10,523) from the Geisinger Health System EMR in Central and Northeastern Pennsylvania. We extracted all clinical and diagnostic data for these patients from January 2004 to December 2009 from the EMR. From this sample set, bootstrap replication procedures were used to randomly generate 2,500 iterations of data sets, each with 500 cases and 2000 controls. Estimates of risk factor effect sizes were obtained by stepwise logistic regression followed by bootstrap aggregation. Variables were ranked using the number of inclusions in iterations and P values.

RESULTS

The benign neoplasm diagnosis was negatively associated with AAA, a novel finding. Similarly, type 2 diabetes, diastolic blood pressure, weight and myelogenous neoplasms were negatively associated with AAA. Peripheral artery disease, smoking, age, coronary stenosis, systolic blood pressure, age, height, male sex, pulmonary disease and hypertension were associated with an increased risk for AAA.

CONCLUSIONS

This study utilized EMR data, retrospectively, for risk factor assessment of a complex disease. Known risk factors for AAA were replicated in magnitude and direction. A novel negative association of benign neoplasms was identified. EMRs allow researchers to rapidly and inexpensively use clinical data to expand cohort size and derive better risk estimates for AAA as well as other complex diseases.

Impact of gender and body surface area on outcome after abdominal aortic aneurysm repair

BACKGROUND

A gender-neutral threshold aneurysm diameter (AD) of more than 5.5 cm for surgical intervention in abdominal aortic aneurysms (AAA) ignores the fact that women have a smaller baseline AD. We hypothesized that women have a greater AD relative to body surface area (BSA) at the time of surgery and that this worsens outcome.

METHODS

The Vascular Study Group of New England database was queried for elective AAA repairs performed from 2003 to 2011 to compare BSA-indexed AD, ie, aortic size index (ASI), between men and women at the time of surgery and the impact of ASI on outcome.

RESULTS

Women were older and had higher ASI among both open-repair (n = 1,566) and endovascular repair (n = 2,172) patients (P < .001). Among open-repair patients, mean ASI for men undergoing repair at AD of 5.5 cm (2.75 cm/m²) was used to subdivide women into 2 categories: women with ASI of 2.75 or more were older (P < .001), had a larger aneurysm size (P < .001), and had a higher 1-year mortality (P = .042) than women with ASI less than 2.75.

CONCLUSIONS

When indexed to BSA, women have a larger aneurysm size than men at the time of AAA repair.

Family history of aortic aneurysm is an independent risk factor for more rapid growth of small abdominal aortic aneurysms in Japan

OBJECTIVE

We aimed to investigate risk factors associated with more rapid growth of abdominal aortic aneurysms (AAA) <50 mm (small AAAs) in Japan.

METHODS

We retrospectively investigated the clinical data of 374 patients with small AAAs (maximum diameter, ≤50 mm) who were referred to The University of Tokyo Hospital, Tokyo Medical University Hospital, or Saitama Medical Center, between 1995 and 2008.

RESULTS

A total of 374 patients (321 men and 53 women) were followed up for a median of 66 months. The median diameter on initial examination was 40 mm, and the median growth rate of the AAAs was 2.1 mm/y. The growth rate of AAAs with an initial diameter ≥45 mm was significantly greater than those with an initial diameter <45 mm (3.3 mm/y vs 2.0 mm/y, respectively; P = .007). The growth rate of AAAs was significantly greater in patients with hypertension than in those without (2.3 mm/y vs 1.7 mm/y, respectively; P = .006) and in patients with a family history of aortic aneurysm than in those without (4.2 mm/y vs 2.0 mm/y, respectively; P = .009). Logistic regression analysis revealed that a large initial diameter and family history of aortic aneurysm were independent predictors of accelerated growth rate of small AAAs in Japan.

CONCLUSIONS

In the present study, a large initial diameter and family history of aortic aneurysm were independent risk factors for more rapid growth of small AAAs. Although few studies have reported similar findings thus far, family history of aortic aneurysm should be carefully considered during follow-up of patients with small AAAs.

Castration of male mice prevents the progression of established angiotensin II-induced abdominal aortic aneurysms

OBJECTIVE

Male sex is a nonmodifiable risk factor for abdominal aortic aneurysm (AAA) development. Similar to humans, male mice are more susceptible to angiotensin II (AngII)-induced AAAs than female mice. Previous studies demonstrated that castration of males markedly reduced the formation of AngII-induced AAAs. Progression of AAA size is associated with increased risk of aneurysm rupture. In this study, we hypothesized that castration of male mice would reduce the progression of established AngII-induced AAAs.

METHODS

Male apolipoprotein E-deficient mice were infused with AngII for 1 month to induce AAA formation. Aortic diameters were measured by ultrasound imaging, and mice were stratified into two groups that underwent a sham operation or castration. AngII infusions were continued for a further 2 months. Ultrasound imaging was used to quantify lumen diameters, and excised aortas were processed for quantification of AAA size, volume, and tissue characteristics.

RESULTS

Sham-operated mice exhibited progressive dilation of suprarenal aortic lumen diameters during the continued AngII infusion. Aortic lumen diameters were significantly decreased in castrated mice (n = 17) compared with sham-operated mice (n = 15) at study end point (1.63 ± 0.04 vs 1.88 ± 0.05 mm; P < .05). However, maximal external AAA diameters were not significantly different between sham-operated and castrated mice. The vascular volume/lumen volume ratio of excised AAAs imaged by ultrasound was significantly increased by castration (9.5% ± 2.0%) vs sham operation (4.8% ± 0.9%; n = 11 per group; P < .05). Moreover, compared with the thin-walled AAAs of sham-operated mice, aneurysm sections from castrated mice exhibited increased smooth muscle α-actin and collagen.

CONCLUSIONS

Removal of endogenous male hormones by castration selectively reduces aortic lumen expansion while not altering the external AAA dimensions.

CLINICAL RELEVANCE

There are no therapeutics that slow the progression of abdominal aortic aneurysms (AAAs), and as the size of an AAA increases, so does the risk of rupture and death. Male sex is a nonmodifiable risk factor for AAA development, but whether male sex hormones have a similar effect on AAA progression is unclear. Removal of male sex hormones in an established mouse model of angiotensin II-induced AAAs resulted in reduced progressive lumen dilation while not altering external AAA dimensions. Therapies that limit androgen action may provide benefit against AAA progression. Alternatively, supplemental testosterone may be contraindicated in men diagnosed with an AAA.

Multidimensional growth measurements of abdominal aortic aneurysms

BACKGROUND

Monitoring the expansion of abdominal aortic aneurysms (AAAs) is critical to avoid aneurysm rupture in surveillance programs, for instance. However, measuring the change of the maximum diameter over time can only provide limited information about AAA expansion. Specifically, regions of fast diameter growth may be missed, axial growth cannot be quantified, and shape changes of potential interest for decisions related to endovascular aneurysm repair cannot be captured.

METHODS

This study used multiple centerline-based diameter measurements between the renal arteries and the aortic bifurcation to quantify AAA growth in 51 patients from computed tomography angiography (CTA) data. Criteria for inclusion were at least 1 year of patient follow-up and the availability of at least two sufficiently high-resolution CTA scans that allowed an accurate three-dimensional reconstruction. Consequently, 124 CTA scans were systematically analyzed by using A4clinics diagnostic software (VASCOPS GmbH, Graz, Austria), and aneurysm growth was monitored at 100 cross-sections perpendicular to the centerline.

RESULTS

Monitoring diameter development over the entire aneurysm revealed the sites of the fastest diameter growth, quantified the axial growth, and showed the evolution of the neck morphology over time. Monitoring the development of an aneurysm's maximum diameter or its volume over time can assess the mean diameter growth (r = 0.69, r = 0.77) but not the maximum diameter growth (r = 0.43, r = 0.34). The diameter growth measured at the site of maximum expansion was ~16%/y, almost four times larger than the mean diameter expansion of 4.4%/y. The sites at which the maximum diameter growth was recorded did not coincide with the position of the maximum baseline diameter (ρ = 0 .12; P = .31). The overall aneurysm sac length increased from 84 to 89 mm during the follow-up (P < .001), which relates to the median longitudinal growth of 3.5%/y. The neck length shortened, on average, by 6.2% per year and was accompanied by a slight increase in neck angulation.

CONCLUSIONS

Neither maximum diameter nor volume measurements over time are able to measure the fastest diameter growth of the aneurysm sac. Consequently, expansion-related wall weakening might be inappropriately reflected by this type of surveillance data. In contrast, localized spots of fast diameter growth can be detected through multiple centerline-based diameter measurements over the entire aneurysm sac. This information might further reinforce the quality of aneurysm surveillance programs.

Standardization of outcome measures in clinical trials of pharmacological treatment for abdominal aortic aneurysm

An abdominal aortic aneurysm (AAA) is a common aortic wall disease with an increased prevalence in the elderly population (4-8% for those aged >65 years). Many AAAs are slow growing and remain insidious. Current standard of care for patients with small AAAs (<49 mm) is surveillance, with interventional therapy (open surgical repair or endovascular aneurysm repair) recommended for large (>50-55 mm), rapidly growing (>10 mm/year) or symptomatic AAAs. Although open surgical repair or endovascular aneurysm repair are effective, significant short- and long-term postoperative morbidity and mortality occurs. Currently, there is no pharmacological treatment specific for AAA; the need for the development of targeted pharmacological therapies based on clinically relevant and feasible outcomes acceptable to the medical community, regulatory agencies and third-party payers is high. A consensus on such end points will be critical to accelerating the development of pharmacological agents to prevent formation, arrest the expansion and reduce the rupture risk of AAA.

Meta-analysis of individual patient data to examine factors affecting growth and rupture of small abdominal aortic aneurysms

Background

Surveillance is a common management strategy for small abdominal aortic aneurysm (AAA) (3·0–5·4 cm in diameter). Individual characteristics, other than diameter, may influence aneurysm growth or rupture rates.

Methods

Individual data were collated from 15 475 people under follow-up for a small aneurysm in 18 studies. The influence of co-variables (including demographics, medical and drug history) on aneurysm growth and rupture rates (analysed using longitudinal random-effects modelling and survival analysis with adjustment for aneurysm diameter) were summarized in an individual patient meta-analysis.

Results

The mean aneurysm growth rate of 2·21 mm/year was independent of age and sex. Growth rate was increased in smokers (by 0·35 mm/year) and decreased in patients with diabetes (by 0·51 mm/year). Mean arterial pressure had no effect and antihypertensive or other cardioprotective medications had only small, non-significant effects on aneurysm growth, consistent with the observation that calendar year of enrolment was not associated with growth rate. Rupture rates were almost fourfold higher in women than men (P &lt; 0·001), were double in current smokers (P = 0·001) and increased with higher blood pressure (P = 0·001).

Conclusion

Follow-up schedules for individuals with a small AAA may need to consider diabetes and smoking, in addition to aneurysm diameter. The differing risk factors for growth and rupture suggest that a lower threshold for surgical intervention in women may be justified. No single drug used for cardiovascular risk reduction had a major effect on the growth or rupture of small aneurysms.

Diagnosis and monitoring of abdominal aortic aneurysm: current status and future prospects

Abdominal aortic aneurysm (AAA) remains an important cause of morbidity and mortality in elderly men, and prevalence is predicted to increase in parallel with a global aging population. AAA is commonly asymptomatic, and in the absence of routine screening, diagnosis is usually incidental when imaging to assess unrelated medical complaints. In the absence of approved diagnostic and prognostic markers, AAAs are monitored conservatively via medical imaging until aortic diameter approaches 50-55 mm and surgical repair is performed. There is currently significant interest in identifying molecular markers of diagnostic and prognostic value for AAA. Here we outline the current guidelines for AAA management and discuss modern scientific techniques currently employed to identify improved diagnostic and prognostic markers.

Systematic review and meta-analysis of growth rates of small abdominal aortic aneurysms

BACKGROUND

Small abdominal aortic aneurysms are usually asymptomatic and managed safely in ultrasound surveillance programmes until they grow to a diameter threshold where intervention is considered. The aim of this study was to synthesize systematically the published data on growth rates for small aneurysms to investigate the evidence basis for surveillance intervals.

METHODS

This was a systematic review of the literature published before January 2010, which identified 61 potentially eligible reports. Detailed review yielded 15 studies providing growth rates for aneurysms 3·0-5·5 cm in diameter (14 in millimetres per year, 1 as percentage change per year). These studies included 7630 people (predominantly men) enrolled during 1976-2005.

RESULTS

The pooled mean growth rate was 2·32 (95 per cent confidence interval 1·95 to 2·70) mm/year but there was very high heterogeneity between studies; the growth rate ranged from - 0·33 to + 3·95 mm/year. Six studies reported growth rates by 5-mm diameter bands, which showed the trend for growth rate to increase with aneurysm diameter. Simple methods to determine growth rate were associated with higher estimates. Meta-regression analysis showed that a 10-mm increase in aneurysm diameter was associated with a mean(s.e.m.) 1·62(0·20) mm/year increase in growth rate. Neither mean age nor percentage of women in each study had a significant effect. On average, a 3·5-cm aneurysm would take 6·2 years to reach 5·5 cm, whereas a 4·5-cm aneurysm would take only 2·3 years.

CONCLUSION

There was considerable variation in the reported growth rates of small aneurysms beyond that explained by aneurysm diameter. Fuller evidence on which to base surveillance intervals for patients in screening programmes requires a meta-analysis based on individual patient data.

Analysis of aortic wall stress and rupture risk in patients with abdominal aortic aneurysm with a gender perspective

OBJECTIVE

The most commonly used predictor of rupture of an abdominal aortic aneurysm (AAA) is the diameter; however, this does not estimate the true risk for each patient. Why women with AAAs have an increased growth rate, weaker aortic wall, and increased risk for rupture is yet unclear. It is likely that geometrical and biomechanical properties contribute to found gender differences. Several studies have shown that peak wall stress (PWS) and peak wall rupture risk (PWRR), predicted by a finite element (FE) analysis of AAAs derived from computed tomography (CT), is a better predictor of rupture than maximum diameter. The purpose of this study was to investigate if women with AAAs have an increased PWS and PWRR using an FE model compared to men.

METHOD

Fifteen men and 15 women (AAAs 4-6 cm) were included. AAA geometry was derived from CT scans, and PWS and PWRR were estimated using the FE method. Comparisons were made by t test and Mann-Whitney test.

RESULTS

Mean age (women 73 years old vs men 71 years old) and mean AAA diameter was similar (49.7 mm vs 50.1 mm) for women and men. PWS did not differ for women 184 and men 198 kPa. PWRR was 0.54 (0.28-0.85) for women and 0.43 (0.24-0.66) for men, P = .06.

CONCLUSION

This is the first analysis of stress and strength of the aneurysm wall with a gender perspective. The reported higher rupture risk for women has previously not been tested with geometrical and biomechanical properties. PWS did not differ, but the PWRR was slightly higher in women. However, the difference did not reach statistical significance, probably due to the small sample size. In summary, the results in the present study suggest that differences in biomechanical properties could be a contributing explanation for the higher rupture risk reported for female patients with AAAs.

Thrombus volume is associated with cardiovascular events and aneurysm growth in patients who have abdominal aortic aneurysms

BACKGROUND

Patients with abdominal aortic aneurysms (AAA) are predisposed to cardiovascular events and often experience continual expansion of their aneurysm. Cardiovascular events and expansion rates are positively correlated with aneurysm size. AAA is usually associated with intraluminal thrombus, which has previously been implicated in AAA pathogenesis. This study prospectively assessed the association of infrarenal abdominal aortic thrombus volume with cardiovascular events and AAA growth.

METHODS

Ninety-eight patients with AAAs underwent computed tomography angiography (CTA). The volume of infrarenal aorta thrombus was measured by a previously validated technique. Patients were monitored prospectively for a median of 3 years (interquartile range [IQR], 2.0-3.6 years), and cardiovascular events (nonfatal stroke, nonfatal myocardial infarction, coronary revascularization, amputation, and cardiovascular death) were recorded. Of the original patients, 39 underwent repeat CTA a median of 1.5 years (IQR, 1.1-3.3 years) after entry to the study. Kaplan-Meier and Cox proportional analysis were used to examine the association of aortic thrombus with cardiovascular events and average weighted AAA growth.

RESULTS

There were 28 cardiovascular events during follow-up. The incidence of cardiovascular events was 23.4% and 49.2% for patients with small (smaller than the median) and large (median or larger) volumes of aortic thrombus, respectively, at 4 years (P = .040). AAA thrombus volume of median or larger was associated with increased cardiovascular events (relative risk [RR] 2.8, 95% confidence interval [CI], 1.01-5.24) independent of other risk factors, including initial AAA diameter, but was only of borderline significance when patients were censored at the time of AAA repair (RR, 2.35; 95% CI, 0.98-5.63). In the subset of patients with CTA follow-up, the median annual increase in AAA volume was 5.1 cm³ (IQR, 0.8-10.3 cm³). Annual AAA volume increase was positively correlated with initial AAA diameter (r = 0.44, P = .006) and thrombus volume (r = 0.50, P = .001). Median or larger aortic thrombus volume was associated with rapid AAA volume increase (≥ 5 cm/y), independent of initial aortic diameter (RR, 15.0; 95% CI, 1.9-115.7; P = .009).

CONCLUSION

In this small cohort, infrarenal aortic thrombus volume was associated with the incidence of cardiovascular events and AAA progression. These results need to be confirmed and mechanisms underlying the associations clarified in large further studies.