Growth predictors and prognosis of small abdominal aortic aneurysms

Visceral adiposity is not associated with abdominal aortic aneurysm presence and growth

Previous studies in rodent models and patients suggest that visceral adipose could play a direct role in the development and progression of abdominal aortic aneurysm (AAA). This study aimed to assess the association of visceral adiposity with AAA presence and growth. This study was a case-control investigation of patients that did (n=196) and did not (n=181) have an AAA who presented to The Townsville Hospital vascular clinic between 2003 and 2012. Cases were patients with AAA (infra-renal aortic diameter >30 mm) and controls were patients with intermittent claudication but no AAA (infra-renal aortic diameter <30 mm). All patients underwent computed tomography angiography (CTA). The visceral to total abdominal adipose volume ratio was estimated from CTAs by assessing total and visceral adipose deposits using an imaging software program. Measurements were assessed for reproducibility by repeat assessments on 15 patients. AAA risk factors were recorded at entry. Forty-five cases underwent two CTAs more than 6 months apart to assess AAA expansion. The association of visceral adiposity with AAA presence and growth was examined using logistic regression. Visceral adipose assessment by CTA was highly reproducible (mean coefficient of variation 1.0%). AAA was positively associated with older age and negatively associated with diabetes. The visceral to total abdominal adipose volume ratio was not significantly associated with AAA after adjustment for other risk factors. Patients with a visceral to total abdominal adipose volume ratio in quartile four had a 1.63-fold increased risk of AAA but with wide confidence intervals (95% CI 0.71-3.70; p=0.248). Visceral adiposity was not associated with AAA growth. In conclusion, this study suggests that visceral adiposity is not specifically associated with AAA presence or growth although larger studies are required to confirm these findings.

Analysis of multiple genetic polymorphisms in aggressive-growing and slow-growing abdominal aortic aneurysms

BACKGROUND

The natural history of abdominal aortic aneurysms (AAAs) suggests that some remain slow in growth rate whereas many develop a more accelerated growth rate and reach a threshold for intervention. We hypothesized that different mechanisms are responsible for AAAs that remain slow growing and never become actionable vs the aggressive AAAs that require intervention and may be reflected by distinct associations with genetic polymorphisms.

METHODS

AAA growth rate was determined from serial imaging data in 168 control and 141 AAA patients with ultrasound or computed tomography imaging studies covering ∼5 years. Genetic polymorphisms all previously reported as showing a significant correlation with AAA with functional effects on the expression or function were determined by analysis of the genomic DNA, including angiotensin 1 receptor (rs5186), interleukin-10 (IL-10; rs1800896), methyl-tetrahydrofolate reductase (rs1801133), low-density lipoprotein receptor-related protein 1 (LRP1; rs1466535), angiotensin-converting enzyme (rs1799752), and several matrix metalloproteinase 9 (MMP-9) single nucleotide polymorphisms.

RESULTS

Of the AAA patients, 81 were classified as slow AAA growth rate (<3.25 mm/y) vs 60 with aggressive AAA growth rate (>3.25 mm/y, those presenting with a rupture, or those with maximal aortic diameter >5.5 cm [male] or >5.0 cm [female]). Discriminating confounds between the groups were identified by logistic regression. Analyses identified MMP-9 p-2502 single nucleotide polymorphism (odds ratio [OR], 0.54; 95% confidence interval [CI], 0.31-0.94; P = .029) as a significant confound discriminating between control vs slow-growth AAA, MMP-9 D165N (OR, 0.49; 95% CI, 0.26-0.95; P = .035) and LRP1 (OR, 4.99; 95% CI, 1.13-22.1; P = .034) between control vs aggressive-growth AAAs, and methyltetrahydrofolate reductase (OR, 2.99; 95% CI, 1.01-8.86; P = .048), MMP-9 p-2502 (OR, 2.19; 95% CI, 1.05-4.58; P = .037), and LRP1 (OR, 4.96; 95% CI, 1.03-23.9; P = .046) as the statistically significant confounds distinguishing slow-growth AAAs vs aggressive-growth AAAs.

CONCLUSIONS

Logistic regression identified different genetic confounds for the slow-growth and aggressive-growth AAAs, indicating a potential for different genetic influences on AAAs of distinct aggressiveness. Future logistic regression studies investigating for potential genetic or clinical confounds for this disease should take into account the growth rate and size of the AAA to better identify confounds likely to be associated with aggressive AAAs likely to require intervention.

Diabetes and abdominal aortic aneurysms

Epidemiologic evidence suggests that patients with diabetes may have a lower incidence of abdominal aortic aneurysm (AAA); however, the link between diabetes and AAA development and expansion is unclear. The aim of this review is to analyze updated evidence to better understand the impact of diabetes on prevalence, incidence, clinical outcome, and expansion rate of AAA. A systematic review of literature published in the last 20 years using the PubMed and Cochrane databases was undertaken. Studies reporting appropriate data were identified and a meta-analysis performed using the generic inverse variance method. Sixty-four studies were identified. Methodological quality was "fair" in 16 and "good" in 44 studies according to a formal assessment checklist (Newcastle-Ottawa). In 17 large population prevalence studies there was a significant inverse association between diabetes and AAA: pooled odds ratio (OR) 0.80; 95% confidence intervals (CI) 0.70-0.90 (p = .0009). An inverse association was also confirmed by pooled analysis of data from smaller prevalence studies on selected populations (OR 0.59; 95% CI 0.35-0.99; p = .05), while no significant results were provided by case-control studies. A significant lower pooled incidence of new AAA in diabetics was found over six prospective studies: OR 0.54; 95% CI 0.31-0.91; p = .03. Diabetic patients showed increased operative (30-day/in-hospital) mortality after AAA repair: pooled OR 1.26; 95% CI 1.10-1.44; p = .0008. The increased operative risk was more evident in studies with 30-day assessment. In the long-term, diabetics showed lower survival rates at 2-5 years, while there was general evidence of lower growth rates of small AAA in patients with diabetes compared to non-diabetics. There is currently evidence to support an inverse relationship between diabetes and AAA development and enlargement, even though fair methodological quality or unclear risk of bias in many available studies decreases the strength of the finding. At the same time, operative and long-term survival is lower in diabetic patients, suggesting increased cardiovascular burden. The higher mortality in diabetics raises the question as to whether AAA repair should be individualized in selected diabetic populations at higher AAA rupture risk.

Statins Promote Residual Aneurysm Sac Regression Following Endovascular Aortic Aneurysm Repair

Background:

Regression of the residual sac is indicative of successful endovascular aortic aneurysm (EVAR) repair. Using color duplex ultrasound (CDU), we monitored the residual aneurysm sac following EVAR and correlated sac behavior with perioperative risk factors.

Methods:

Of 145 patients with EVAR, 106 (73.1%) patients between January 01, 2003, and July 01, 2010, had at least 2 consecutive postoperative scans and thus were eligible for inclusion. Mean (± standard deviation [SD]) CDU scans per person was 4.6 (±1.4). All were conducted by the same technologist using a standard protocol on the same machine. Aneurysm sac change in centimeters and percentage terms was calculated. The presence or absence of an endoleak was also recorded. Change in aneurysm sac size was correlated with preoperative risk factors.

Findings:

Mean sac size change at 1 month was a decrease of 0.24 cm, equating to a percentage change of 4.3%. At 7 months, the decrease was 0.59 cm (9.8%), at 12 months, 0.73 cm (12.4%), at 18 months 0.92 cm (15.8%), and at 36 months 1.0 cm (16.6%). Both univariate and multivariate analyses demonstrated that statin therapy ( P = .002) was the only risk factor variable positively associated with aneurysm regression while the presence of an endoleak was inversely related to sac reduction ( P = .01).

Interpretation:

Maximum aneurysmal sac reduction seems to occur in the first year following endograft implantation. Statin therapy appears to be associated with an increased likelihood of sac regression following EVAR. Further investigation of the role of statins in the biology of abdominal aortic aneurysmal disease is warranted.

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.

Effect of statin drugs on thoracic aortic aneurysms

Pharmacologic interventions for thoracic aneurysms remain poorly characterized. The results of a pilot study by our group suggested improved outcomes among patients with thoracic aortic aneurysm who were taking statins. In the present study, we undertook a comprehensive analysis of a larger cohort of patients from the Database of the Aortic Institute at Yale-New Haven Hospital. A total of 1,560 patients met the inclusion criteria. The adverse events (i.e., death, dissection, or rupture) and surgery rates for patients with (n = 369, 24%) and without (n = 1,191, 76%) statin therapy were compared. We evaluated 3 anatomic components of the aorta: root, ascending and arch, and descending and thoracoabdominal aortic aneurysms. A smaller proportion of the statin group had adverse events: overall, 7% versus 15%; ascending and arch, 6% versus 15%; and descending and thoracoabdominal aortic aneurysms, 8% versus 20%. Also, a smaller proportion of statin patients required surgery: overall, 48% versus 60%; ascending and arch, 51% versus 62%; and descending and thoracoabdominal aortic aneurysms, 36% versus 59% (p <0.001 to 0.01). The protective effect of statins was seen in all segments, except the aortic root. Log-rank evaluation of the interval to an adverse event or surgery was longer among statin-treated patients (p <0.001). Logistic regression analysis found statin use, angiotensin receptor blocker use, and chronic obstructive pulmonary disease were associated with decreased adverse events, and statin use, angiotensin receptor blocker use, β-blocker therapy, and age were associated with a decreased odds of requiring surgery. Multiple logistic regression analysis found only statins were associated with a decreased odds of an adverse event and that statins, coronary artery disease, and chronic obstructive pulmonary disease were associated with a decreased odds of undergoing surgery. In conclusion, these findings provide a medicinal option for the arsenal of treatment options for patients with aneurysms of the thoracic aorta.

Local wall thickness in finite element models improves prediction of abdominal aortic aneurysm growth

OBJECTIVE

Growing evidence suggests that peak wall stress (PWS) derived from finite element analysis (FEA) of abdominal aortic aneurysms (AAAs) predicts clinical outcomes better than diameter alone. Prior models assume uniform wall thickness (UWT). We hypothesize that the inclusion of locally variable wall thickness (VWT) into FEA of AAAs will improve its ability to predict clinical outcomes.

METHODS

Patients with AAAs (n = 26) undergoing radiologic surveillance were identified. Custom MATLAB algorithms generated UWT and VWT aortic geometries from computed tomography angiography images, which were subsequently loaded with systolic blood pressure using FEA. PWS and aneurysm expansion (as a proxy for rupture risk and the need for repair) were examined.

RESULTS

The average radiologic follow-up time was 22.0 ± 13.6 months and the average aneurysm expansion rate was 2.8 ± 1.7 mm/y. PWS in VWT models significantly differed from PWS in UWT models (238 ± 68 vs 212 ± 73 kPa; P = .025). In our sample, initial aortic diameter was not found to be correlated with aneurysm expansion (r = 0.26; P = .19). A stronger correlation was found between aneurysm expansion and PWS derived from VWT models compared with PWS from UWT models (r = 0.86 vs r = 0.58; P = .032 by Fisher r to Z transformation).

CONCLUSIONS

The inclusion of locally VWT significantly improved the correlation between PWS and aneurysm expansion. Aortic wall thickness should be incorporated into future FEA models to accurately predict clinical outcomes.

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.

Statins and noncardiac vascular disease

PURPOSE OF REVIEW

To discuss the beneficial effects of statin treatment in patients with peripheral arterial disease (PAD), abdominal aortic aneurysms (AAAs), atherosclerotic renal artery stenosis (ARAS) and carotid artery disease.

RECENT FINDINGS

Evidence suggests that statins may reduce the progression (or even reverse the development) of carotid artery stenosis and AAAs. Statins also improve several indices (e.g. serum creatinine) and preserve renal function in ARAS. In patients with PAD, statins are associated with improved claudication distance and time, reduced cardiovascular events, and improved graft patency rates should these patients undergo surgery. Finally, statins are associated with improved perioperative and long-term morbidity and mortality rates in all vascular patients whether they undergo surgery or endovascular procedures.

SUMMARY

Routine statin treatment should be implemented for all vascular patients to ensure a reduced progression of their disease, as well as a reduction in cardiovascular events.

Recent advances in pharmacotherapy development for abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a common disease causing segmental expansion and rupture of the aorta with a high mortality rate. The lack of nonsurgical treatment represents a large and unmet need in terms of pharmacotherapy. Advances in AAA research revealed that activation of inflammatory signaling pathways through proinflammatory mediators shifts the balance of extracellular matrix (ECM) metabolism toward tissue degradation. This idea is supported by experimental evidence in animal models that pharmacologic intervention at each pathological step can prevent AAA development. Previously, we identified c-Jun N-terminal kinase (JNK), a pro-inflammatory signaling molecule, as a therapeutic target for AAA. Abnormal activation of JNK in AAA tissue regulates multiple pathological processes in a coordinated manner. Pharmacologic inhibition of JNK tips the ECM balance back towards repair rather than degradation. Interventions targeting signaling molecules such as JNK in order to manipulate multiple pathological processes may be an ideal therapeutic strategy for AAA. Furthermore, the development of biomarkers as well as appropriate drug delivery systems is essential to produce clinically practical pharmacotherapy for AAA.

Statin therapy is associated with aneurysm sac regression after endovascular aortic repair

BACKGROUND

Several anatomic factors have been identified as predictive of sac behavior after endovascular aneurysm repair (EVAR). The effects of statin therapy on aneurysm sac size reduction remain controversial. This study tested the hypothesis that statin therapy enhances aneurysmal sac regression after EVAR.

METHODS

This monocentric retrospective study included patients with abdominal aortic aneurysms treated by EVAR using the Zenith (Cook, Bloomington, Ind) graft device. We excluded patients presenting with perioperative sac enlargement factors such as endoleaks, endotension, infectious, inflammatory, ruptured, or anastomotic aneurysms. We prospectively assessed standard clinical and anatomic data, as well as statin use, at the time of EVAR and during follow-up. The primary end point was the decrease in the largest transverse aortic diameter at 24 months compared with the preoperative diameter.

RESULTS

Among 166 patients treated by a Zenith device and meeting the inclusion criteria, 120 were identified as statin users and 46 as nonstatin users, with comparable characteristics. At 24 months of follow-up, statin group patients had a greater aneurysm sac reduction (25% vs 14%; P < .0001). At a threshold of 5 mm in diameter regression, statin use was a positive factor of retraction (odds ratio, 7.93; 95% confidence interval, 3.22-15.52; P < .0001). Multivariate analysis revealed statin use was an independent predictive factor of sac regression (adjusted odds ratio, 9.39; 95% confidence interval, 3.45-25.56).

CONCLUSIONS

This study showed that statin use was predictive of sac regression after EVAR with the Zenith graft device. This effect needs to be confirmed by larger randomized trials or by large population evaluation.

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.

Do statins reduce the risk of aneurysm development: a case-control study

Object

Recent studies in rats have demonstrated that statins may have an inhibitory effect on intracranial aneurysm (IA) development. The purpose of this study was to assess whether long-term statin use is associated with a reduced risk of IA formation in humans.

Methods

This was a single-center case-control study that included consecutive patients admitted to the authors' institution between January 1, 2005, and December 31, 2008. A case was defined as a patient with a cerebral angiography–confirmed diagnosis of IA. Three controls were matched to each case based on age, sex, and index year of hospital admission. The primary exposure of interest was cumulative statin use. Conditional logistic regression was used to assess the relationship between statin intake and incidence of IA.

Results

In total, 1200 patients were included in the study. No overall association was found between statin use and incidence of IA formation (OR 1.08, 95% CI 0.69–1.69), nor when dichotomized into hydrophilic and lipophilic user, or between short (≤12-month) and long (≥36-month) duration of intake. Hypertension and smoking significantly increased the risk of IA development (OR 4.02, 95% CI 2.49–6.45, and OR 1.67, 95% CI 1.02–2.72, respectively).

Conclusions

In contrast to recent experimental reports of the association between statins and a reduction of IA formation, the authors' findings suggest that in humans statins may have no significant beneficial effect on IA suppression.

Surveillance strategies according to the rate of growth of small abdominal aortic aneurysms

The management of small abdominal aortic aneurysms (AAA) is by ultrasound surveillance. The study aimed to calculate their growth rate, identify risk factors and determine appropriate screening intervals. The local screening programme and hospital records were used to identify patients with a small (< 5.5 cm) AAA. The dates and maximum diameter of serial scans of patients with two or more scans were obtained. Patients were subdivided by 0.5 cm increments above 3.0 cm. The rate of growth was calculated by linear regression for each patient using both the absolute measurements and logarithmically (ln) transformed measurements. The 95th centile of growth rate within each subgroup was used to estimate the minimum time to grow to 5.5 cm. A total of 252 were included. The mean (± SD) AAA size on the initial scan was 3.9 (± 0.7) cm. Statin use and initial size were predictive factors for the growth rate. The median rate of growth increased according to size from 0.075 to 0.432 cm/year for AAA < 3.5 cm and > 5.0 cm, respectively. It also steadily increased for ln measurements from 0.022 (or 2.2%/year) to 0.078 or (7.8%/year). The minimum time (months) to reach 5.5 cm was 61, 17, 11 and 5 for AAA < 3.5 cm, 3.5–3.9 cm, 4.0–4.4 cm and 4.5–4.9 cm, respectively. Based on ln measurements, the times were similar at 60, 17, 10 and 4 months. In conclusion, the rate of growth increased steadily with AAA size. An aneurysm < 3.5 cm does not require a repeat scan for 5 years, while those measuring 3.5–3.9 cm and 4.0–4.4 cm require a repeat scan after 17 and 11 months.

What is the relationship between ¹⁸F-FDG aortic aneurysm uptake on PET/CT and future growth rate?

PURPOSE

In this study we investigate the relationship between (18)F-fluorodeoxyglucose (FDG) metabolism and future aneurysm expansion measured by serial duplex ultrasound. Current screening programmes are increasing the identification of patients with abdominal aortic aneurysm (AAA). The management of these patients remains challenging and methods of risk stratification are sought.

METHODS

Thirty-four consecutive patients [31 men, 3 women, median age 75 years, interquartile range (IQR) 71-78] with aortic aneurysms under routine surveillance with serial ultrasound were prospectively recruited for (18)F-FDG positron emission tomography (PET)/CT. A whole vessel type analysis was performed measuring the highest aortic wall (18)F-FDG uptake (standardized uptake value or SUV(max)), and target to background ratio (TBR) for each axial image and median SUV(max) and TBR value were calculated. Institutional Review Board permission and informed patient consent were obtained.

RESULTS

Nine patients failed to undergo 12-month follow-up study (deceased n = 2, withdrew n = 1, failed to attend ultrasound scan n = 5, emergency aneurysm repair n = 1) leaving 25 patients for analysis. The median whole vessel SUV(max) was 1.70 (IQR 1.45-2.08). The median whole vessel TBR was 1.15 (IQR 1.00-1.40). The median aneurysm expansion at 12 months was 2.0 mm (IQR 0.5-5.0). The correlation (r) between (18)F-FDG SUV(max) and ultrasound expansion at 1 year was -0.501 (p = 0.011).

CONCLUSION

The preliminary findings from this observational longitudinal pilot study suggest that there is an inverse trend between (18)F-FDG uptake on PET and future AAA expansion. Aortic aneurysms with lower metabolic activity may therefore be more likely to expand.

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.

Current status of medical management for abdominal aortic aneurysm

Previous trials indicate that surgical management of small abdominal aortic aneurysms (AAA) does not reduce mortality. The medical management of AAA, however, has to a large degree been ignored until recently. Medical management is not only needed to limit the expansion of small AAAs but also to reduce the high incidence of other cardiovascular events in these patients. In this review current evidence regarding medical therapy for patients with small AAAs is discussed. Four current randomised controlled trials are examining the efficacy of exercise, doxycycline and angiotensin converting enzyme inhibition in limiting AAA progression. A further trial using a mast cell stabilisation agent is expected to start soon. It is anticipated that a range of novel therapies for small AAAs will be identified within the next decade.

Diagnostic and therapeutic strategies for small abdominal aortic aneurysms

Abdominal aortic aneurysms (AAA) affect 5% of the population in developed countries and are characterized by progressive aortic dilatation with an unpredictable time course. This condition is more common in men than in women, and in smokers than in nonsmokers. If left untreated, AAA can result in aortic rupture and death. Pathologically, aortic extracellular matrix degradation, inflammation, and neovascularization are hallmarks of AAA. Diagnosis of AAA and subsequent surveillance utilize established aortic imaging methods, such as ultrasound, CT, and MRI. More-speculative diagnostic approaches include molecular and cellular imaging methods that interrogate the underlying pathological processes at work within the aneurysm. In this Review, we explore the current diagnostic and therapeutic strategies for the management of AAA. We also describe the diagnostic potential of new imaging techniques and therapeutic potential of new treatments for the management of small AAA.

Lower respiratory tract infection and rapid expansion of an abdominal aortic aneurysm: a case report

INTRODUCTION

The rate of abdominal aortic aneurysm expansion is related to multiple factors. There is some evidence that inflammation can accelerate aneurysm expansion. However, the association between pulmonary sepsis and rapid abdominal aortic aneurysm expansion is rarely reported.

CASE PRESENTATION

Here we present a case of a rapidly expanding abdominal aortic aneurysm in a 68-year-old Caucasian man with a concomitant lower respiratory tract infection and systemic sepsis requiring intensive monitoring and urgent endovascular intervention. Our patient had an uncomplicated post-operative recovery and a follow-up computed tomography scan at one month demonstrated no evidence of an endoleak.

CONCLUSION

This case highlights the potential association between pulmonary sepsis and rapid abdominal aortic aneurysm expansion. In such cases, a policy of frequent monitoring should be adopted to identify those patients requiring definitive management.

Rupture rates of small abdominal aortic aneurysms: a systematic review of the literature

BACKGROUND

Small aneurysms of the abdominal aorta (3.0-5.5 cm in diameter) often are managed by regular surveillance, rather than surgery, because the risk of surgery is considered to outweigh the risk of aneurysm rupture. The risk of small aneurysm rupture is considered to be low. The purpose of this review is to summarise the reported estimates of small aneurysm rupture rates.

METHODS AND FINDINGS

We conducted a systematic review of the literature published before 2010 and identified 54 potentially eligible reports. Detailed review of these studies showed that both ascertainment of rupture, patient follow-up and causes of death were poorly reported: diagnostic criteria for rupture were never reported. There were only 14 studies from which rupture rates (as ruptures per 100 person-years) were available. These 14 published studies included 9779 patients (89% male) over the time period 1976-2006 but only 7 of these studies provided rupture rates specifically for the diameter range 3.0-5.5 cm, which ranged from 0 to 1.61 ruptures per 100 person-years.

CONCLUSIONS

Rupture rates of small abdominal aortic aneurysms would appear to be low, but most studies have been poorly reported and did not have clear ascertainment and diagnostic criteria for aneurysm rupture.

Basic Science Review Section: Statin Therapy—Part II: Clinical Considerations for Cardiovascular Disease

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, commonly known as statins, are the medical treatment of choice for hypercholesterolemia. In addition to achieving a therapeutic decrease in serum cholesterol levels, statin therapy appears to promote pleiotropic effects that are independent of changes in serum cholesterol. These cholesterol lowering and pleiotropic effects are beneficial not only for the coronary circulation, but for the myocardium and peripheral arterial system as well. Patients receiving statin therapy must be carefully monitored, however, as statins potentially have harmful side effects and drug interactions. This article is part II of a 2-part review, and it focuses on the clinical aspects of statin therapy in cardiovascular disease.

Pathophysiology of abdominal aortic aneurysm relevant to improvements in patients' management

PURPOSE OF REVIEW

Abdominal aortic aneurysm (AAA) is being diagnosed more frequently in older patients due to the increased use of abdominal imaging and the rising average age of western populations. Currently the management of this condition has two important deficiencies: inadequate methods to identify AAAs at risk of progression and rupture and the current lack of effective nonsurgical therapies. In this review recent developments in identifying new diagnostic, prognostic and therapeutic strategies for AAA are discussed.

RECENT FINDINGS

There are growing number of animal and human association studies which have identified markers and strategies of potential value in improving identification, monitoring and treatment of AAA.

SUMMARY

Selective large prospective imaging, biomarker and intervention studies are now required to clearly demonstrate the value of new management pathways for AAA.

Different effects of commonly prescribed statins on abdominal aortic aneurysm wall biology

BACKGROUND

Pharmaceutical stabilisation of the abdominal aortic aneurysm (AAA) wall can delay surgery and improve outcome. Observational studies indicate statins can be used to reduce AAA growth but mechanistic data are scarce. In this study, our aim was to determine the pleiotropic effects of different statins on AAA wall composition.

METHODS

We included 216 patients undergoing open AAA repair, of which 60 used simvastatin, 52 atorvastatin and 23 pravastatin. The AAA wall histology and protein expression (IL 1beta,2,4,5,6,8,10,12, interferon-gamma (IFNgamma), tumour necrosis factor (TNF)alpha,beta, matrix metalloproteinase (MMP)2 and 9 activities, total MMP8,9 and cathepsin A and B levels) between statin users and non-users were compared as also among the use of different statins.

RESULTS

As far as histological inflammation goes, the AAA walls of statin users did not differ from those not using them. After multivariate adjustment for risk factors, pravastatin use was associated with tendencies of increased MMP8 (p = 0.022), active MMP9 (p = 0.040) and higher cathepsin B (p = 0.056) levels. The AAA walls of simvastatin and atorvastatin users showed no differences in proteases or cytokines in multivariate analyses.

CONCLUSIONS

The use of statins was not associated with a decrease in protease levels or inflammation. The trends of elevated protease levels associated with pravastatin use suggest pleiotropic differences among the various statins, supporting the need for further research to target pharmaceutical AAA treatment.

Association of statin prescription with small abdominal aortic aneurysm progression

BACKGROUND

Statins have been suggested to reduce expansion of abdominal aortic aneurysms (AAAs) independent of lipid-lowering effects.

METHODS

We assessed the association of statin treatment and serum low-density lipoprotein (LDL) concentrations with small AAA expansion. Six hundred fifty-two patients undergoing surveillance of small AAAs were entered into the study from 5 vascular centers. In a subset, fasting lipids (n = 451) and other biomarkers (n = 216) were measured. The AAA diameter was followed by ultrasound surveillance for a median of 5 years.

RESULTS

Three hundred forty-nine (54%) of the patients were prescribed statins. Adjusting for other risk factors, statin prescription was not associated with AAA growth (odds ratio [OR] 1.23, 95% CI 0.86-1.76). Above-median AAA growth was positively associated with initial diameter (OR 1.78 per 4.35-mm-larger initial aortic diameter, 95% CI 1.49-2.14) and negatively associated with diabetes (OR 0.37, 95% CI 0.22-0.62). Above-median serum LDL concentration was not associated with AAA growth. Patients receiving statins had lower serum C-reactive protein concentrations but similar matrix metalloproteinase-9 and interleukin-6 concentrations to those not prescribed these medications.

CONCLUSIONS

We found no association between statin prescription or LDL concentration with AAA expansion. The results do not support the findings of smaller studies and suggest that statins may have no benefit in reducing AAA progression.

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.

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.