Growth predictors and prognosis of small abdominal aortic aneurysms

Exploring Drug Re-Purposing for Treatment of Abdominal Aortic Aneurysms: a Systematic Review and Meta-analysis

OBJECTIVE

Large abdominal aortic aneurysms (AAAs) present a significant mortality risk. While numerous medical interventions have been proposed, no drugs have convincingly reduced AAA progression, rupture rates, or repair risk. This systematic review and meta-analysis aimed to assess the impact of re-purposed drugs or dietary supplements on slowing expansion rates, reducing the risk of rupture, or minimising the risk of repair for individuals with AAA.

METHODS

A systematic search was conducted in five databases. Both observational studies and randomised controlled trials were included. Unpublished data from two screening trials were incorporated. Risk of bias was assessed using the Newcastle-Ottawa scale and revised Cochrane risk of bias tool. Meta-analyses were performed for each identified drug subclass and were stratified by overall risk of bias. Results were reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Of 7 484 screened studies, 39 met the inclusion criteria. No studies on dietary supplements were included. A total of 84 cohorts were derived from the included studies, and twelve distinct drug groups underwent meta-analyses. Two drug groups, metformin and statins, were statistically significant in slowing AAA growth. No low risk of bias studies were included for these two drug groups, and the results had very high heterogeneity (I2 > 80%). Both groups had a GRADE certainty of very low. Metformin, excluding high risk of bias studies, presented an estimated mean growth difference of AAA diameter between users and non-users of -0.73 mm/year, whilst statins had an overall estimated mean difference of -0.84 mm/year.

CONCLUSION

This systematic review and meta-analysis suggests that metformin and statins may provide some effect in slowing AAA progression. However, no definitive evidence was found for any of the investigated drugs included in this study. Further research is needed to identify effective medical treatments for AAA progression with more robust methodology.

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.

Excess Mortality for Abdominal Aortic Aneurysms and the Potential of Strict Implementation of Cardiovascular Risk Management: A Multifaceted Study Integrating Meta-Analysis, National Registry, and PHAST and TEDY Trial Data

OBJECTIVE

Previous studies imply a profound residual mortality risk following successful abdominal aorta aneurysm (AAA) repair. This excess mortality is generally attributed to increased cardiovascular risk. The aim of this study was (1) to quantify the excess residual mortality for patients with AAA, (2) to evaluate the cross sectional level of cardiovascular risk management, and (3) to estimate the potential of optimised cardiovascular risk management to reduce the excess mortality in these patients.

METHODS

Excess mortality was estimated through a systematic review and meta-analysis, and through data from the Swedish National Health Registry. Cardiovascular risk profiles were individually assessed during eligibility screening of patients with AAA for two multicentre pharmaceutical AAA stabilisation trials. The potential of full implementation of cardiovascular risk management was estimated through the validated Second Manifestations of ARTerial disease (SMART) risk scores algorithm.

RESULTS

The meta-analysis showed a similarly impaired survival for patients who received early repair (small AAA) or regular repair (≥ 55 mm), and a further impaired survival for patients under surveillance for a small AAA. Excess mortality was further quantified using Swedish population data. The data revealed a more than quadrupled and doubled five year mortality rate for women and men who had their AAA repaired, respectively. Evaluation of the level of risk management of 358 patients under surveillance in 16 Dutch hospitals showed that the majority of patients with AAA did not meet therapeutic targets set for risk management in high risk populations, and indicated a more pronounced prevention gap in women. Application of the SMART risk score algorithm predicted that optimal implementation of risk management guidelines would reduce the 10 year risk of major adverse cardiovascular events from 43% to 14%.

CONCLUSION

Independent of the rupture risk, AAA is associated with a worryingly compromised life expectancy with a particularly poor prognosis for women. Optimal implementation of cardiovascular risk prevention guidelines is predicted to profoundly reduce cardiovascular risk.

Cohort profile: the Utrecht Cardiovascular Cohort-Second Manifestations of Arterial Disease (UCC-SMART) Study-an ongoing prospective cohort study of patients at high cardiovascular risk in the Netherlands

PURPOSE

The Utrecht Cardiovascular Cohort-Second Manifestations of Arterial Disease (UCC-SMART) Study is an ongoing prospective single-centre cohort study with the aim to assess important determinants and the prognosis of cardiovascular disease progression. This article provides an update of the rationale, design, included patients, measurements and findings from the start in 1996 to date.

PARTICIPANTS

The UCC-SMART Study includes patients aged 18-90 years referred to the University Medical Center Utrecht, the Netherlands, for management of cardiovascular disease (CVD) or severe cardiovascular risk factors. Since September 1996, a total of 14 830 patients have been included. Upon inclusion, patients undergo a standardised screening programme, including questionnaires, vital signs, laboratory measurements, an ECG, vascular ultrasound of carotid arteries and aorta, ankle-brachial index and ultrasound measurements of adipose tissue, kidney size and intima-media thickness. Outcomes of interest are collected through annual questionnaires and adjudicated by an endpoint committee.

FINDINGS TO DATE

By May 2022, the included patients contributed to a total follow-up time of over 134 000 person-years. During follow-up, 2259 patients suffered a vascular endpoint (including non-fatal myocardial infarction, non-fatal stroke and vascular death) and 2794 all-cause deaths, 943 incident cases of diabetes and 2139 incident cases of cancer were observed up until January 2020. The UCC-SMART cohort contributed to over 350 articles published in peer-reviewed journals, including prediction models recommended by the 2021 European Society of Cardiology CVD prevention guidelines.

FUTURE PLANS

The UCC-SMART Study guarantees an infrastructure for research in patients at high cardiovascular risk. The cohort will continue to include about 600 patients yearly and follow-up will be ongoing to ensure an up-to-date cohort in accordance with current healthcare and scientific knowledge. In the near future, UCC-SMART will be enriched by echocardiography, and a food frequency questionnaire at baseline enabling the assessment of associations between nutrition and CVD and diabetes.

Type I Interferon Receptor Subunit 1 Deletion Attenuates Experimental Abdominal Aortic Aneurysm Formation

Objective: Type I interferon receptor signaling contributes to several autoimmune and vascular diseases such as lupus, atherosclerosis and stroke. The purpose of this study was to assess the influence of type I interferon receptor deficiency on the formation and progression of experimental abdominal aortic aneurysms (AAAs). Methods: AAAs were induced in type I interferon receptor subunit 1 (IFNAR1)-deficient and wild type control male mice via intra-infrarenal aortic infusion of porcine pancreatic elastase. Immunostaining for IFNAR1 was evaluated in experimental and clinical aneurysmal abdominal aortae. The initiation and progression of experimental AAAs were assessed via ultrasound imaging prior to (day 0) and days 3, 7 and 14 following elastase infusion. Aneurysmal histopathology was analyzed at sacrifice. Results: Increased aortic medial and adventitial IFNAR1 expression was present in both clinical AAAs harvested at surgery and experimental AAAs. Following AAA induction, wild type mice experienced progressive, time-dependent infrarenal aortic enlargement. This progression was substantially attenuated in IFNAR1-deficient mice. On histological analyses, medial elastin degradation, smooth muscle cell depletion, leukocyte accumulation and neoangiogenesis were markedly diminished in IFNAR1-deficient mice in comparison to wild type mice. Conclusion: IFNAR1 deficiency limited experimental AAA progression in response to intra-aortic elastase infusion. Combined with clinical observations, these results suggest an important role for IFNAR1 activity in AAA pathogenesis.

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

Background and Aim

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

Methods and Results

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

Conclusions

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

Remodeling of abdominal Aortic Aneurysm Sac following EndoVascular Aortic Repair: Association with Clinical, Surgical, and Genetic factors

After successful EndoVascular Aortic Repair (EVAR), abdominal aortic aneurysms (AAA) sac will undergo negative remodeling (i.e. shrinkage) as a measure of successful exclusion. Determinants of shrinkage after EVAR are not fully known. In 84 post-EVAR patients, time course of AAA diameter after repair and occurrence of endoleaks (ELs) have been correlated with clinical history, medications, anthropometric data, vascular anatomy, and matrix metalloprotease (MMP) genetic variants (namely MMP-1 rs1799750, MMP-3 rs35068180, MMP-9 rs2234681, rs917576, rs917577, MMP-12 rs652438, and TIMP1 rs4898). During follow-up, 41 ELs were detected in 37 patients (44%, 10.4 events/100 pt./y), accounting for AAA dilation or reduced shrinkage (P<0.001). High-flow ELs (type 1 and/or 3) occurrence was associated with warfarin use, MMP9 rs17577 polymorphism, and unfavorable anatomy, while low-flow type 2 ELs occurred more often in TIMP1 rs4898 non-T carriers. In EL-free patients, AAA diameter decreased for the first three years, (-4, -3 and - 2 mm/year respectively) and remained stable thereafter. Shrinkage between two measurements (n= 120) was associated with smaller AAA diameter at the baseline, peripheral arterial disease (PAD), patients' older age at intervention, and G-/G- genotype in MMP1 rs1799750 (binary logistic regression, P=0.0001). Aneurysmal sac shrinking occurs for few years after EVAR, only in patients without EL, and is related to older age, PAD, smaller aneurysm size and putative lower MMP1 expression while EL occurrence prevents such a remodeling and is mainly related to local-acting factors like unfavorable anatomy, anticoagulation, and MMP9 and TIMP1 genetic polymorphisms.

The effect of diabetes on abdominal aortic aneurysm growth over 2 years

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a common progressive disease and a significant cause of morbidity and mortality. Prior investigations have shown that diabetes mellitus (DM) may be relatively protective of AAA incidence and growth. The Non-invasive Treatment of Aortic Aneurysm Clinical Trial (N-TA³CT) is a contemporary study of small AAA growth that provides a unique opportunity to validate and explore the effect of DM on AAA. Confirming the effect of DM on AAA growth in this study may present opportunities to explore for clues to potential biologic mechanisms as well as inform current patient management.

METHODS

This is a secondary analysis examining the association of diabetes and aneurysm growth within N-TA³CT: a placebo-controlled multicenter trial of doxycycline in 261 patients with AAA maximum transverse diameters (MTDs) between 3.5 and 5 cm. The primary outcome is the change in the MTD from baseline as determined by computed tomography (CT) scans obtained during the trial. Secondary outcome is the growth pattern of the AAA. Baseline characteristics and growth patterns were assessed with t tests (continuous) or χ² tests (categorical). Unadjusted and adjusted longitudinal analyses were performed with a repeated measures linear mixed model to compare AAA growth rates between patients with and without diabetes.

RESULTS

Of 261 patients, 250 subjects had sufficient imaging and were included in this study. There were 56 patients (22.4%) with diabetes and 194 (77.6%) without. Diabetes was associated with higher body mass index and increased rates of hypercholesterolemia and coronary artery disease (P < .05). Diabetes was also associated with increased frequency of treatment for atherosclerosis and hypertension including treatment with statin, angiotensin-converting enzyme inhibitor, angiotensin II receptor blocker, anti-platelet, and diuretic therapy (P < .05). Baseline MTD was not significantly different between those with (4.32 cm) and without DM (4.30 cm). Median growth rate for patients with diabetes was 0.12 cm/y (interquartile range, 0.07-0.22 cm/y) and 0.19 cm/y (interquartile range, 0.12-0.27 cm/y) in patients without DM, which was significantly different on unadjusted analysis (P < .0001). Diabetes remained significantly associated with AAA growth after adjustment for other relevant clinical factors (coef, -0.057; P < .0001).

CONCLUSIONS

Patients with diabetes have more than a 35% reduction in the median growth rates of AAA despite more severe concomitant vascular comorbidities and similar initial sizes of aneurysms. This effect persists and remains robust after adjusted analysis; and slower growth rates may delay the time to reach repair threshold. Rapid growth (>0.5 cm/y) is infrequent in patients with DM.

Statins reduce mortality after abdominal aortic aneurysm repair: A systematic review and meta-analysis

OBJECTIVE

The necessity and efficacy of statin treatment for abdominal aortic aneurysm (AAA) remains controversial. This systematic review and meta-analysis was conducted to investigate the effects of statin therapy on the outcomes of patients with AAA.

METHODS

The Cochrane library, Embase, and MedLine were searched comprehensively to identify relevant cohort studies and randomized controlled trials. The primary outcomes included short- and long-term mortality after AAA repair, and secondary outcomes included the incidence of perioperative cardiovascular complications, sac shrinkage after endovascular aneurysm repair, and the growth rate of the aneurysms. Short-term mortality was defined as all-cause 30-day or in-hospital postoperative mortality. Long-term mortality was defined as the all-cause mortality at the end of follow-up period (≥1 year). A random effects model was used to combine the results of included studies. Forest plots were created to show the pooled results of each outcome.

RESULTS

One post hoc analysis of a randomized trial and 36 cohort studies (n = 134,290 patients) were included in this systematic review. The average score of included studies by Newcastle-Ottawa Scale was 7.76. Patients taking or not taking statin therapy were all diagnosed with unruptured AAA, and 59.9% of these patients were given statin therapy. Compared with statin nonusers, patients in statin therapy had significantly lower long-term mortality (odds ratio, 0.67; 95% confidence interval, 0.59-0.75; P < .001; I² = 71.7%), and short-term mortality after aneurysmal repair (odds ratio, 0.51; 95% confidence interval, 0.36-0.73; P < .001; I² = 81.4%). No significant difference was found between patients taking or not taking statin treatment on perioperative cardiovascular complications or sac shrinkage after endovascular aneurysm repair or growth rate of AAA under surveillance.

CONCLUSIONS

These findings suggest that statin use is associated with a significant decrease in long- and short-term mortality in patients after AAA repair. Based on these results, statin therapy is worth being used in clinical practice for the management of AAA.

Risk reduction and pharmacological strategies to prevent progression of aortic aneurysms

INTRODUCTION

While size thresholds exist to determine when aortic aneurysms warrant surgical intervention, there is no consensus on how best to treat this disease before aneurysms reach the threshold for intervention. Since a landmark study in 1994 first suggested ß-blockers may be useful in preventing aortic aneurysm growth, there has been a surge in research investigating different pharmacologic therapies for aortic aneurysms - with very mixed results.

AREAS COVERED

We have reviewed the existing literature on medical therapies used for thoracic and abdominal aortic aneurysms in humans. These include ß-blockers, angiotensin II receptor blockers, and angiotensin-converting enzyme inhibitors as well as miscellaneous drugs such as tetracyclines, macrolides, statins, and anti-platelet medications.

EXPERT OPINION

While multiple classes of drugs have been explored for risk reduction in aneurysm disease, with few exceptions results have been disappointing with an abundance of contradictory findings. The vast majority of studies have been done in patients with abdominal aortic aneurysms or thoracic aortic aneurysm patients with Marfan Syndrome. There exists a striking gap in the literature when it comes to pharmacologic management of non-Marfan Syndrome patients with thoracic aortic aneurysms. Given the differences in pathogenesis, this is an important future direction for aortic aneurysm research.

Pathophysiological Aspects of the Development of Abdominal Aortic Aneurysm with a Special Focus on Mitochondrial Dysfunction and Genetic Associations

Abdominal aortic aneurysm (AAA) is a complex degenerative vascular disease, with considerable morbidity and mortality rates among the elderly population. The mortality of AAA is related to aneurysm expansion (the enlargement of the aortic diameter up to 30 mm and above) and the subsequent rupture. The pathogenesis of AAA involves several biological processes, including aortic mural inflammation, oxidative stress, vascular smooth muscle cell apoptosis, elastin depletion, and degradation of the extracellular matrix. Mitochondrial dysfunction was also found to be associated with AAA formation. The evidence accumulated to date supports a close relationship between environmental and genetic factors in AAA initiation and progression. However, a comprehensive pathophysiological understanding of AAA formation remains incomplete. The open surgical repair of AAA is the only therapeutic option currently available, while a specific pharmacotherapy is still awaited. Therefore, there is a great need to clarify pathophysiological cellular and molecular mechanisms underlying AAA formation that would help to develop effective pharmacological therapies. In this review, pathophysiological aspects of AAA development with a special focus on mitochondrial dysfunction and genetic associations were discussed.

Atorvastatin and growth, rupture of small unruptured intracranial aneurysm: results of a prospective cohort study

Background and aims:

The role of statins in unruptured intracranial aneurysm (UIA) growth and rupture remains ambiguous. This study sought to determine whether atorvastatin is associated with aneurysm growth and rupture in patients harboring UIA <7 mm.

Methods:

This prospective, multicenter cohort study consecutively enrolled patients with concurrent UIA <7 mm and ischemic cerebrovascular disease from four hospitals between 2016 and 2019. Baseline and follow-up patient information was recorded. Because of the strong anti-inflammatory effect of aspirin, patients using aspirin were excluded. Patients taking atorvastatin 20 mg daily were atorvastatin users. The primary and exploratory endpoints were aneurysm rupture and growth, respectively.

Results:

Among the 1087 enrolled patients, 489 (45.0%) took atorvastatin, and 598 (55%) took no atorvastatin. After a mean follow-up duration of 33.0 ± 12.5 months, six (1.2%) and five (0.8%) aneurysms ruptured in atorvastatin and non-atorvastatin groups, respectively. In the adjusted multivariate Cox analysis, UIA sized 5 to <7 mm, current smoker, and uncontrolled hypertension were associated with aneurysm rupture, whereas atorvastatin [adjusted hazard ratio (HR) 1.495, 95% confidence interval (CI) 0.417–5.356, p = 0.537] was not. Of 159 patients who had follow-up imaging, 34 (21.4%) took atorvastatin and 125 (78.6%) took no atorvastatin. Aneurysm growth occurred in five (14.7%) and 21 (16.8%) patients in atorvastatin and non-atorvastatin groups (mean follow-up: 20.2 ± 12.9 months), respectively. In the adjusted multivariate Cox analysis, UIAs sized 5 to <7 mm and uncontrolled hypertension were associated with a high growth rate; atorvastatin (adjusted HR 0.151, 95% CI 0.031–0.729, p = 0.019) was associated with a reduced growth rate.

Conclusions:

We conclude atorvastatin use is associated with a reduced risk of UIA growth, whereas atorvastatin is not associated with UIA rupture.

Methodology for Estimation of Annual Risk of Rupture for Abdominal Aortic Aneurysm

BACKGROUND AND OBJECTIVE

Estimating patient specific annual risk of rupture of abdominal aortic aneurysm (AAA) is currently based only on population. More accurate knowledge based on patient specific data would allow surgical treatment of only those AAAs with significant risk of rupture. This would be beneficial for both patients and health care system.

METHODS

A methodology for estimating annual risk of rupture (EARR) of abdominal aortic aneurysms (AAA) that utilizes Bayesian statistics, mechanics and patient-specific blood pressure monitoring data is proposed. EARR estimation takes into consideration, peak wall stress in AAA computed by patient-specific finite element modeling, the probability distributions of wall thickness, wall strength, systolic blood pressure and the period of time that the patient is known to have already survived with the intact AAA. Initial testing of proposed approach was performed on fifteen patients with intact AAA (mean maximal diameter 51mm±8mm). They were equipped with a pressure holter and their blood pressure was recorded over 24 hours. Then, we calculated EARR values for four possible scenarios - without considering any days of survival prior identification of AAA at computed tomography scans (EARR_0), considering past survival of 30 (EARR_30), 90 (EARR_90) and 180 days (EARR_180). Finally, effect of patient-specific blood pressure variability was analyzed.

RESULTS

Consideration of past survival does indeed significantly improve predictions of future risk: EARR_30 (1.04%± 0.87%), EARR_90 (0.67%± 0.56%) and EARR_180 (0.47%± 0.39%) which are unrealistically high otherwise (EARR_0 5.02%± 5.24%). Finally, EARR values were observed to vary by an order as a consequence of blood pressure variability and by factor of two as a consequence of neglected growth.

CONCLUSIONS

Methodology for computing annual risk of rupture of AAA was developed for the first time. Sensitivity analyses showed respecting patient specific blood pressure is important factor and should be included in the AAA rupture risk assessment. Obtained EARR values were generally low and in good agreement with confirmed survival time of investigated patients so proposed method should be further clinically validated.

Therapeutic Potential of Heme Oxygenase-1 in Aneurysmal Diseases

Abdominal aortic aneurysm (AAA) and intracranial aneurysm (IA) are serious arterial diseases in the aorta and brain, respectively. AAA and IA are associated with old age in males and females, respectively, and if rupture occurs, they carry high morbidity and mortality. Aneurysmal subarachnoid hemorrhage (SAH) due to IA rupture has a high rate of complication and fatality. Despite these severe clinical outcomes, preventing or treating these devastating diseases remains an unmet medical need. Inflammation and oxidative stress are shared pathologies of these vascular diseases. Therefore, therapeutic strategies have focused on reducing inflammation and reactive oxygen species levels. Interestingly, in response to cellular stress, the inducible heme oxygenase-1 (HO-1) is highly upregulated and protects against tissue injury. HO-1 degrades the prooxidant heme and generates molecules with antioxidative and anti-inflammatory properties, resulting in decreased oxidative stress and inflammation. Therefore, increasing HO-1 activity is an attractive option for therapy. Several HO-1 inducers have been identified and tested in animal models for preventing or alleviating AAA, IA, and SAH. However, clinical trials have shown conflicting results. Further research and the development of highly selective HO-1 regulators may be needed to prevent the initiation and progression of AAA, IA, or SAH.

Effect of blood pressure lowering drugs and antibiotics on abdominal aortic aneurysm growth: a systematic review and meta-analysis

OBJECTIVE

There is currently no medical treatment proven to limit abdominal aortic aneurysm (AAA) progression. The aim of this systematic review and meta-analysis was to pool data from previous randomised controlled trials assessing the efficacy of blood pressure-lowering and antibiotic medications in limiting AAA growth and AAA-related events, that is, rupture or repair.

METHODS

A systematic literature search was performed to identify randomised controlled trials that examined the efficacy of blood pressure-lowering medications or antibiotics in reducing AAA growth and AAA-related events. AAA growth (mm/year) was measured by ultrasound or computed tomography imaging. Meta-analyses were performed using random effects models. A subanalysis was conducted including trials that investigated tetracycline or macrolide antibiotics.

RESULTS

Ten randomised controlled trials including 2045 participants with an asymptomatic AAA were included. Follow-up was between 18 and 63 months. Neither blood pressure-lowering medications (mean growth±SD 2.0±2.4 vs 2.3±2.7 mm/year; standardised mean difference (SMD) -0.07, 95% CI -0.19 to 0.06; p=0.288) or antibiotics (mean growth±SD 2.6±2.1 vs 2.6±2.5 mm/year; SMD -0.11, 95% CI -0.38 to 0.16; p=0.418) reduced AAA growth or AAA-related events (blood pressure-lowering medications: 92 vs 95 events; risk ratio (RR) 0.86, 95% CI 0.66 to 1.11; p=0.244; and antibiotics: 69 vs 73 events; RR 0.93, 95% CI 0.69 to 1.25; p=0.614). The subanalysis of antibiotics showed similar results.

CONCLUSIONS

This meta-analysis suggests that neither blood pressure-lowering medications or antibiotics limit growth or clinically relevant events in people with AAAs.

A Novel Hybrid Drug Delivery System for Treatment of Aortic Aneurysms

Ongoing aortic wall degeneration and subsequent aneurysm exclusion failure are major concerns after an endovascular aneurysm repair with a stent-graft. An ideal solution would be a drug therapy that targets the aortic wall and inhibits wall degeneration. Here, we described a novel drug delivery system, which allowed repetitively charging a graft with therapeutic drugs and releasing them to the aortic wall in vivo. The system was composed of a targeted graft, which was labeled with a small target molecule, and the target-recognizing nanocarrier, which contained suitable drugs. We developed the targeted graft by decorating a biotinylated polyester graft with neutravidin. We created the target-recognizing nanocarrier by conjugating drug-containing liposomes with biotinylated bio-nanocapsules. We successfully demonstrated that the target-recognizing nanocarriers could bind to the targeted graft, both in vitro and in blood vessels of live mice. Moreover, the drug released from our drug delivery system reduced the expression of matrix metalloproteinase-9 in mouse aortas. Thus, this hybrid system represents a first step toward an adjuvant therapy that might improve the long-term outcome of endovascular aneurysm repair.

High-risk factors related to the occurrence and development of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a common and potentially dangerous vascular disease with many risk factors related to its occurrence and development. This review collects the results from recent studies of different comorbidities including hypertension, diabetes, and hyperlipidemia and summarizes their connections with AAA development and its underlying mechanisms. We believe that hypertension, diabetes, and hyperlipidemia can affect AAA occurrence and development, but more studies are needed to further explore the mechanisms.

Statins Reduce Abdominal Aortic Aneurysm Growth, Rupture, and Perioperative Mortality: A Systematic Review and Meta-Analysis

Background

There are no recognized pharmacological treatments for abdominal aortic aneurysms (AAA), although statins are suggested to be beneficial. We sought to summarize the literature regarding the effects of statins on human AAA growth, rupture, and 30‐day mortality.

Methods and Results

We conducted a systematic review and meta‐analysis of randomized and observational studies using the Cochrane CENTRAL database, MEDLINE, and EMBASE up to June 15, 2018. Review, abstraction, and quality assessment were conducted by 2 independent reviewers, and a third author resolved discrepancies. Pooled mean differences and odds ratios with 95% confidence intervals were calculated using random effects models. Heterogeneity was quantified using the I² statistic, and publication bias was assessed using funnel plots. Our search yielded 911 articles. One case‐control and 21 cohort studies involving 80 428 patients were included. The risk of bias was low to moderate. Statin use was associated with a mean AAA growth rate reduction of 0.82 mm/y (95% confidence interval 0.33, 1.32, P=0.001, I²=86%). Statins were also associated with a lower rupture risk (odds ratio 0.63, 95% confidence interval 0.51, 0.78, P<0.0001, I²=27%), and preoperative statin use was associated with a lower 30‐day mortality following elective AAA repair (odds ratio 0.55, 95% confidence interval 0.36, 0.83, P=0.005, I²=57%).

Conclusions

Statin therapy may be associated with reduction in AAA progression, rupture, and lower rates of perioperative mortality following elective AAA repair. These data argue for widespread statin use in AAA patients.

Clinical Trial Registration

URL: http://www.crd.york.ac.uk. Unique identifier: CRD42017056480.

Current Status and Perspectives on Pharmacologic Therapy for Abdominal Aortic Aneurysm

Background:

Abdominal aortic aneurysm (AAA), a common disease involving the segmen-tal expansion and rupture of the aorta, has a high mortality rate. Therapeutic options for AAA are cur-rently limited to surgical repair to prevent catastrophic rupture. Non-surgical approaches, particularly pharmacotherapy, are lacking for the treatment of AAA.

Objective:

We review both basic and clinical studies and discuss the current challenges to developing medical therapy that reduces AAA progression.

Results:

Studies using animal models of AAA progression and human AAA explant cultures have identified several potential targets for preventing AAA growth. However, no clinical studies have con-vincingly confirmed the efficacy of any pharmacologic treatment against the growth of AAA. Thus, there is as yet no strong recommendation regarding pharmacotherapy to reduce the risk of AAA pro-gression and rupture.

Conclusion:

This review identifies concerns that need to be addressed for the field to progress and dis-cusses the challenges that must be overcome in order to develop effective pharmacotherapy to reduce AAA progression in the future.

Pharmacologic Management of Aneurysms

Current management of aortic aneurysms relies exclusively on prophylactic operative repair of larger aneurysms. Great potential exists for successful medical therapy that halts or reduces aneurysm progression and hence alleviates or postpones the need for surgical repair. Preclinical studies in the context of abdominal aortic aneurysm identified hundreds of candidate strategies for stabilization, and data from preoperative clinical intervention studies show that interventions in the pathways of the activated inflammatory and proteolytic cascades in enlarging abdominal aortic aneurysm are feasible. Similarly, the concept of pharmaceutical aorta stabilization in Marfan syndrome is supported by a wealth of promising studies in the murine models of Marfan syndrome-related aortapathy. Although some clinical studies report successful medical stabilization of growing aortic aneurysms and aortic root stabilization in Marfan syndrome, these claims are not consistently confirmed in larger and controlled studies. Consequently, no medical therapy can be recommended for the stabilization of aortic aneurysms. The discrepancy between preclinical successes and clinical trial failures implies shortcomings in the available models of aneurysm disease and perhaps incomplete understanding of the pathological processes involved in later stages of aortic aneurysm progression. Preclinical models more reflective of human pathophysiology, identification of biomarkers to predict severity of disease progression, and improved design of clinical trials may more rapidly advance the opportunities in this important field.

Abdominal Aortic Aneurysm: Evolving Controversies and Uncertainties

Abdominal aortic aneurysm (AAA) is defined as a permanent dilatation of the abdominal aorta that exceeds 3 cm. Most AAAs arise in the portion of abdominal aorta distal to the renal arteries and are defined as infrarenal. Most AAAs are totally asymptomatic until catastrophic rupture. The strongest predictor of AAA rupture is the diameter. Surgery is indicated to prevent rupture when the risk of rupture exceeds the risk of surgery. In this review, we aim to analyze this disease comprehensively, starting from an epidemiological perspective, exploring etiology and pathophysiology, and concluding with surgical controversies. We will pursue these goals by addressing eight specific questions regarding AAA: (1) Is the incidence of AAA increasing? (2) Are ultrasound screening programs for AAA effective? (3) What causes AAA: Genes versus environment? (4) Animal models: Are they really relevant? (5) What pathophysiology leads to AAA? (6) Indications for AAA surgery: Are surgeons over-eager to operate? (7) Elective AAA repair: Open or endovascular? (8) Emergency AAA repair: Open or endovascular?

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.

An evaluation of the effect of an angiotensin-converting enzyme inhibitor on the growth rate of small abdominal aortic aneurysms: a randomised placebo-controlled trial (AARDVARK)

BACKGROUND

Although data are inconsistent, angiotensin-converting enzyme inhibitors (ACE-Is) have been associated with a reduced incidence of abdominal aortic aneurysm (AAA) rupture in analysis of administrative databases.

OBJECTIVES

(1) To investigate whether or not the ACE-I perindopril (Coversyl arginine, Servier) reduces small AAA growth rate and (2) to evaluate blood pressure (BP)-independent effects of perindopril on small AAA growth and to compare the repeatability of measurement of internal and external aneurysm diameters.

DESIGN

A three-arm, multicentre, single-blind, randomised placebo-controlled trial.

SETTING

Fourteen hospitals in England.

PARTICIPANTS

Men or women aged ≥ 55 years with an AAA of 3.0-5.4 cm in diameter by internal or external measurement according to ultrasonography and who met the trial eligibility criteria.

INTERVENTIONS

Patients were randomised to receive 10 mg of perindopril arginine daily, 5 mg of the calcium channel blocker amlodipine daily or placebo daily.

MAIN OUTCOME MEASURES

The primary outcome was AAA diameter growth using external measurements in the longitudinal plane, which in-trial studies suggested was the preferred measure. Secondary outcome measures included AAA rupture, AAA repair, modelling of the time taken for the AAA to reach the threshold for intervention (5.5 cm) or referral for surgery, tolerance of study medication (measured by compliance, adverse events and quality of life) and a comparison of the repeatability of measures of internal and external AAA diameter. Patients were followed up every 3-6 months over 2 years.

RESULTS

In total, 227 patients were recruited and randomised into the three groups, which were generally well matched at baseline. Multilevel modelling was used to determine the maximum likelihood estimates for AAA diameter growth. No significant differences in the estimates of annual growth were apparent [1.68 (standard error 0.02) mm, 1.77 (0.02) mm and 1.81 (0.02) mm in the placebo, perindopril and amlodipine groups, respectively]. Similarly, no significant differences in the slopes of modelled growth over time were apparent between perindopril and placebo (p = 0.78) or between perindopril and amlodipine (p = 0.89). The results were essentially unaffected by adjustment for potential confounders. Compliance, measured by pill counts, was good throughout (> 80% at all visit time points). There were no significant in-trial safety concerns. Six patients withdrew because of adverse events attributed to the study medications (n = 2 perindopril, n = 4 amlodipine). No patients ruptured their AAA and 27 underwent elective surgery during the trial (n = 9 placebo, n = 10 perindopril, n = 8 amlodipine).

CONCLUSIONS

We were unable to demonstrate a significant impact of perindopril compared with placebo or amlodipine on small AAA growth over a 2-year period. Furthermore, there were no differences in the times to reach a diameter of 5.5 cm or undergo surgery among the three groups. Perindopril and amlodipine were well tolerated by this population. External AAA measurements were found to be more repeatable than internal measurements. The observed AAA growth measurement variability was greater than that expected pre trial. This, combined with slower than expected mean growth rates, resulted in our having limited power to detect small differences between growth rates and hence this adds uncertainty to the interpretation of the results. Several further analyses are planned including a multivariate analysis of determinants of AAA growth, an evaluation of the possible differential effect of perindopril on fast AAA growth and an investigation into the roles of central BP and BP variability on AAA growth.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN51383267.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 20, No. 59. See the NIHR Journals Library website for further project information. The NIHR Biomedical Research Centre based at Imperial College NHS Trust supported the trial. Servier provided perindopril at no charge.

Meta-analysis of the association between peripheral artery disease and growth of abdominal aortic aneurysms

Background

The role of atherosclerosis in the pathogenesis of abdominal aortic aneurysm (AAA) is controversial. Atherosclerosis-associated peripheral artery disease (PAD) has been reported to be a risk factor for AAA in population screening studies; its relationship with AAA growth is controversial.

Methods

A systematic search of MEDLINE, Scopus, CINAHL and the Cochrane Central Register of Controlled Trials was conducted in April 2016 and repeated in January 2017. Databases were screened for studies reporting AAA growth rates in patients with, and without PAD. The included studies underwent quality assessment and, where possible, were included in the meta-analysis. A subgroup analysis was performed, including only studies that adjusted for confounding factors.

Results

Seventeen studies, including a total of 4873 patients, met the review entry criteria. Data from 15 studies were included in the meta-analysis. There was marked heterogeneity in study design, methodology and statistical analyses used. In the main analysis, PAD was associated with reduced AAA growth (mean difference – 0·13, 95 per cent c.i. –0·27 to –0·00; P = 0·04). However, statistical significance was not maintained in sensitivity analysis. In a subanalysis that included only data adjusted for other risk factors, no significant association between PAD and AAA growth was found (mean difference –0·11, –0·23 to 0·00; P = 0·05).

Conclusion

This systematic review suggests that currently reported studies demonstrate no robust and consistent association between PAD and reduced AAA growth.

Local Diameter, Wall Stress, and Thrombus Thickness Influence the Local Growth of Abdominal Aortic Aneurysms

Purpose: To investigate the influence of the local diameter, the intraluminal thrombus (ILT) thickness, and wall stress on the local growth rate of abdominal aortic aneurysms. Methods: The infrarenal aortas of 90 asymptomatic abdominal aortic aneurysm (AAA) patients (mean age 70 years; 77 men) were retrospectively reconstructed from at least 2 computed tomography angiography scans (median follow-up of 1 year) and biomechanically analyzed with the finite element method. Each individual AAA model was automatically sliced orthogonally to the lumen centerline and represented by 100 cross sections with corresponding diameters, ILT thicknesses, and wall stresses. The data were grouped according to these parameters for comparison of differences among the variables. Results: Diameter growth was continuously distributed over the entire aneurysm sac, reaching absolute and relative median peaks of 3.06 mm/y and 7.3%/y, respectively. The local growth rate was dependent on the local baseline diameter, the local ILT thickness, and for wall segments not covered by ILT, also on the local wall stress level (all p<0.001). For wall segments that were covered by a thick ILT layer, wall stress did not affect the growth rate (p=0.08). Conclusion: Diameter is not only a strong global predictor but also a local predictor of aneurysm growth. In addition, and independent of the diameter, the ILT thickness and wall stress (for the ILT-free wall) also influence the local growth rate. The high stress sensitivity of nondilated aortic walls suggests that wall stress peaks could initiate AAA formation. In contrast, local diameters and ILT thicknesses determine AAA growth for dilated and ILT-covered aortic walls.

An evaluation of the effect of an angiotensin-converting enzyme inhibitor on the growth rate of small abdominal aortic aneurysms: a randomized placebo-controlled trial (AARDVARK)

Aims

The AARDVARK (Aortic Aneurysmal Regression of Dilation: Value of ACE-Inhibition on RisK) trial investigated whether ACE-inhibition reduces small abdominal aortic aneurysms (AAA) growth rate, independent of blood pressure (BP) lowering.

Methods and results

A three-arm, multi-centre, single-blind, and randomized controlled trial (ISRCTN51383267) was conducted in 14 hospitals in England. Subjects aged ≥55 years with AAA diameter 3.0–5.4 cm were randomized 1:1:1 to receive perindopril arginine 10 mg, or amlodipine 5 mg, or placebo and followed 3–6 monthly over 2 years. The primary outcome was aneurysm growth rate (based on external antero-posterior ultrasound measurements in the longitudinal plane), determined by multi-level modelling to provide maximum likelihood estimates. Two hundred and twenty-four subjects were randomized (2011–2013) to placebo (n = 79), perindopril (n = 73), or amlodipine (n = 72). Mean (SD) changes in mid-trial systolic BP (12 months) were 0.5 (14.3) mmHg, P = 0.78 compared with baseline, −9.5 (13.1) mmHg (P < 0.001), and −6.7 (12.0) mmHg (P < 0.001), respectively. No significant differences in the modelled annual growth rates were apparent [1.68 mm (SE 0.2), 1.77 mm (0.2), and 1.81 mm (0.2), respectively]. The estimated difference in annual growth between the perindopril and placebo groups was 0.08 mm (CI −0.50, 0.65). Similar numbers of AAAs in each group reached 5.5 cm diameter and/or underwent elective surgery: 11 receiving placebo, 10 perindopril, and 11 amlodipine.

Conclusion

Small AAA growth rates were lower than anticipated, but there was no significant impact of perindopril compared with placebo or placebo and amlodipine, combined despite more effective BP lowering.

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.

Non-invasive Treatment of Abdominal Aortic Aneurysm Clinical Trial (N-TA(3)CT): Design of a Phase IIb, placebo-controlled, double-blind, randomized clinical trial of doxycycline for the reduction of growth of small abdominal aortic aneurysm

OBJECTIVES

The Non-Invasive Treatment of Abdominal Aortic Aneurysm Clinical Trial (N-TA(3)CT) is a Phase IIb randomized, placebo-controlled clinical trial, testing doxycycline (100mg bid) for inhibition of growth in the greatest transverse, orthogonal diameter of small abdominal aortic aneurysms (AAA).

METHODS

We will enroll 258 patients, ≥55years of age who have AAA, men: 3.5-5.0cm and women: 3.5-4.5cm on CT scans confirmed centrally. The primary outcome is growth in maximal transverse, orthogonal diameter from baseline to 24-month follow-up. Secondary analyses address doxycycline effects on clinical events, aneurysm volume, and biomarkers. Primary analysis will be performed according to the principle of intention-to-treat accounting for death and ruptures by use of normal scores in analysis of covariance. At the time of the data file reported, 200 subjects have been randomized. We started enrollment in mid-2013 and will complete enrollment by mid-2016.

RESULTS

Participant average age=70.9years, (SD=7.6years) and maximum transverse diameter=4.3cm for men (SD=0.4) and 4.0cm for women (SD=0.3).

CONCLUSION

N-TA(3)CT is a critical experiment to determine whether doxycycline reduces growth of small AAA and systemic markers of inflammation previously seen in bench experiments and observational human studies to be associated with AAA growth. Our patient population baseline measurements agree with the design assumptions supporting our expectation of 90% power or greater to reject a null hypothesis in favor of an alternative hypothesis when growth is reduced by at least 40%.

REGISTRATION

clinicaltrials.gov #NCT01756833.

Inhibition of early AAA formation by aortic intraluminal pentagalloyl glucose (PGG) infusion in a novel porcine AAA model

Background

The vast majority of abdominal aortic aneurysms found in screening programs are small, and as no effective treatment exits, many will expand until surgery is indicated. Therefore, it remains intriguing to develop a safe and low cost treatment of these small aneurysms, that is able to prevent or delay their expansion.

In this study, we investigated whether intraluminal delivered pentagalloyl glucose (PGG) can impair the early AAA development in a porcine model.

Methods

The infrarenal aorta was exposed in thirty pigs. Twenty underwent an elastase based AAA inducing procedure and ten of these received an additional intraluminal PGG infusion. The final 10 were sham operated and served as controls.

Results

All pigs who only had an elastase infusion developed macroscopically expanding AAAs. In pigs treated with an additional PGG infusion the growth rate of the AP-diameter rapidly returned to physiological values as seen in the control group. In the elastase group, histology revealed more or less complete resolution of the elastic lamellae in the media while they were more abundant, coherent and structurally organized in the PGG group. The control group displayed normal physiological growth and histology.

Conclusion

In our model, intraluminal delivered PGG is able to penetrate the aortic wall from the inside and impair the early AAA development by stabilizing the elastic lamellae and preserving their integrity. The principle holds a high clinical potential if it can be translated to human conditions, since it, if so, potentially could represent a new drug for stabilizing small abdominal aneurysms.

•

Pentagalloyl glucose impairs the early AAA development in a porcine model.

•

Pentagalloyl glucose stabilizes arterial elastic lamellae and preserves their integrity.

•

Pentagalloyl glucose can penetrate the arterial wall in large AAA prone arteries from the inside.

•

Pentagalloyl glucose, a potential new drug for stabilizing small abdominal aneurysms.

Positron Emission Tomography and Magnetic Resonance Imaging of Cellular Inflammation in Patients with Abdominal Aortic Aneurysms

Objectives

Inflammation is critical in the pathogenesis of abdominal aortic aneurysm (AAA) disease. Combined ¹⁸F-fludeoxyglucose (¹⁸F-FDG) positron emission tomography with computed tomography (PET-CT) and ultrasmall superparamagnetic particles of iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) are non-invasive methods of assessing tissue inflammation. The aim of this study was to compare these techniques in patients with AAA.

Materials and methods

Fifteen patients with asymptomatic AAA with diameter 46 ± 7 mm underwent PET-CT with ¹⁸F-FDG, and T2*-weighted MRI before and 24 hours after administration of USPIO. The PET-CT and MRI data were then co-registered. Standardised uptake values (SUVs) were calculated to measure ¹⁸F-FDG activity, and USPIO uptake was determined using the change in R2*. Comparisons between the techniques were made using a quadrant analysis and a voxel-by-voxel evaluation.

Results

When all areas of the aneurysm were evaluated, there was a modest correlation between the SUV on PET-CT and the change in R2* on USPIO-enhanced MRI (n = 70,345 voxels; r = .30; p < .0001). Although regions of increased ¹⁸F-FDG and USPIO uptake co-localised on occasion, this was infrequent (kappa statistic 0.074; 95% CI 0.026–0.122). ¹⁸F-FDG activity was commonly focused in the shoulder region whereas USPIO uptake was more apparent in the main body of the aneurysm. Maximum SUV was lower in patients with mural USPIO uptake.

Conclusions

Both ¹⁸F-FDG PET-CT and USPIO-MRI uptake identify vascular inflammation associated with AAA. Although they demonstrate a modest correlation, there are distinct differences in the pattern and distribution of uptake, suggesting a differential detection of macrophage glycolytic and phagocytic activity respectively.

Coronary artery disease and abdominal aortic aneurysm growth

To determine whether coronary artery disease (CAD) is associated with abdominal aortic aneurysm (AAA) growth, we performed a meta-analysis of currently available studies. Databases including MEDLINE and EMBASE were searched through October 2015 using PubMed and OVID. Search terms included enlargement, expansion, growth, or progression; rate or rates; and abdominal aortic aneurysm. Studies considered for inclusion met the following criteria: the design was unrestricted; the study population was AAA patients with and without CAD; and outcomes included data regarding AAA growth. For each study, growth rates in both the CAD and non-CAD groups were used to generate standardized mean differences (SMDs) and 95% confidence intervals (CIs). Of 664 potentially relevant publications screened initially, we identified 20 eligible studies including data on a total of 7238 AAA patients. A pooled analysis of all 20 studies demonstrated a statistically significant association of CAD with slower AAA growth rates (i.e. a significantly negative association of CAD with AAA growth) in the fixed-effect model (SMD, −0.06 [–0.0592]; 95% CI, −0.12 [–0.1157] to −0.00 [–0.0027]; p = 0.04). There was minimal between-study heterogeneity ( p = 0.16) and a statistically non-significant association of CAD with slower AAA growth rates (i.e. a non-significantly negative association of CAD with AAA growth) in the pooled result from random-effects modeling (SMD, −0.06; 95% CI, −0.13 to 0.01; p = 0.12). In conclusion, CAD may be negatively associated with AAA growth.

A multi-locus genetic risk score for abdominal aortic aneurysm

BACKGROUND

We investigated whether a multi-locus genetic risk scores (GRS) was associated with presence and progression of abdominal aortic aneurysm (AAA) in a case - control study.

METHODS AND RESULTS

The study comprised of 1124 patients with AAA (74 ± 8 years, 83% men, 52% of them with a maximal AAA size ≤ 5 cm) and 6524 non-cases (67 ± 11 years, 58% men) from the Mayo Vascular Disease Biorepository. AAA was defined as infrarenal abdominal aorta diameter ≥ 3.0 cm or history of AAA repair. Non-cases were participants without known AAA. A GRS was calculated using 4 SNPs associated with AAA at genome-wide significance (P ≤ 10(-8)). The GRS was associated with the presence of AAA after adjustment for age, sex, cardiovascular risk factors, atherosclerotic cardiovascular diseases and family history of aortic aneurysm: odds ratio (OR, 95% confidence interval, CI) 1.06 (1.04-1.09, p < 0.001). Adding GRS to conventional risk factors improved the association of presence of AAA (net reclassification index 14%, p < 0.001). In a subset of patients with AAA who had ≥ 2 imaging studies (n = 651, mean (SE) growth rate 2.47 (0.11) mm/year during a mean time interval of 5.41 years), GRS, baseline size, diabetes and family history were each associated with aneurysm growth rate in univariate association (all p < 0.05). The estimated mean aneurysm growth rate was 0.50 mm/year higher in those with GRS > median (5.78) than those with GRS ≤ median (p = 0.01), after adjustment for baseline size (p < 0.001), diabetes (p = 0.046) and family history of aortic aneurysm (p = 0.02).

CONCLUSIONS

A multi-locus GRS was associated with presence of AAA and greater aneurysm expansion.

Endovascular grafts for abdominal aortic aneurysm

During the last two decades, endovascular technology has revolutionized the management of patients with abdominal aortic aneurysm (AAA). Today, endovascular aortic repair (EVAR) is the treatment of choice for the majority of patients with an AAA. Randomized controlled trials provide robust evidence for the indication of AAA repair and the rationale for the use of EVAR in selected patients. However, despite that, practice varies and several areas need further elucidation. Important future challenges and areas of research include the role of medical therapy in AAA, whether the indication for repair should be any different in women and in the elderly, and long-term follow-up of patients undergoing complex EVAR with adjuncts, both for elective treatment and for ruptured AAA. Continuous rapid technical and clinical development is to be expected. In this paper, we review the current practice and evidence of stenting in AAA.

Editor's Choice - Pharmaceutical Management of Small Abdominal Aortic Aneurysms: A Systematic Review of the Clinical Evidence

BACKGROUND

Management of abdominal aortic aneurysms (AAAs) relies on surgical repair of larger AAAs. Consequently medical interventions inhibiting AAA progression could greatly reduce the need for surgical repair. A spectrum of pharmaceutical strategies has been reported, albeit conclusions often appear contradictory. Given the longstanding interest in pharmaceutical AAA stabilization, a systematic review of the available literature is relevant.

OBJECTIVES

The aim is to provide an up to date systematic review of the available data on pharmaceutical therapies for stabilizing or impeding AAA growth.

METHODS

A search using Pubmed, Embase, Web of science, Cochrane, CINAHL, Academic Search Premier, and Science Direct identified 27 eligible papers that studied the clinical effect of the pharmaceutical therapy on AAA diameter growth.

RESULTS

This review shows that there is currently no pharmaceutical strategy that reduces AAA growth. Most studies are of poor methodological quality. Initial promising reports are often not confirmed in subsequent larger studies, raising the possibility of selective reporting.

CONCLUSION

There is currently no pharmaceutical means that halts AAA growth.

Growth Rate of Small Abdominal Aortic Aneurysms and Genetic Polymorphisms of Matrix MetalloProteases-1, -3, and -9

Genetic variants of matrix metalloproteases (MMPs)-1, -3, and 9, together with clinical variables, might predict the growth rate (GR) of abdominal aortic aneurysm (AAA). Genotyping of MMP-1 (-1,607 G+/G-), MMP-3 (- 1,171 6A/5A), and MMP-9 microsatellite (13-26 cytosine-adenosine repeats around -90) from peripheral blood was performed in 137 AAA patients with two AAA diameter measurements (at least 3 months to 1 year apart). When the same technique (either ultrasound or computed tomography) was used for the two measurements, yearly GR was estimated and compared with MMP genotype and clinical features by linear and binary logistic regression. Collectively, 36 patients provided 94 observations, with a median GR of 3 mm/year (interquartile range, 0-5.8); GRs in carriers of MMP-1 polymorphism G-/G-, G-/G+, and G+/G+ genotype were 0.3, 3.5, and 4.7mm/year, respectively (p = 0.008). In linear logistic regression, the main determinant of GR was growth arrest (GA, i.e., GR = 0, occurring in 32 observations, 34%). In turn, GA occurred mainly in G-/G- MMP-1 genotype (odds ratio, 3.9; 95% confidence interval, 1.6-9.7; p = 0.002), while variables accounting for GR > 0 were MMP-1 G + /G+ genotype, intake of any antihypertensive drug, and MMP-3 6A/6A genotype. Carriers of none, one, or two/three of these conditions accounted for a GR of 3, 4, and 9 mm/year, respectively (p = 0.001). MMP-1 (-1,607 G+/-) variant is associated to differential GR in AAA: homozygous G deletion variant shows higher GA prevalence and lower GR, while carriers of G + /G+ MMP-1 genotype, together with intake of antihypertensive drugs, and 6A/6A in MMP-3 present cumulative GR increase.

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.

Statins and subarachnoid hemorrhage in Medicare patients with unruptured cerebral aneurysms

BACKGROUND

Statins have been shown to decrease aneurysm progression and rupture in two experimental settings: animals with cerebral aneurysm and humans with abdominal aortic aneurysms.

AIMS

To investigate statin use and outcomes in humans with unruptured cerebral aneurysms through Medicare administrative data.

METHODS

We used a 40% random sample Medicare denominator file and corresponding inpatient, outpatient (2003-2011), and prescription (2006-2011) claims to conduct a retrospective cohort study of patients diagnosed with unruptured cerebral aneurysms, between 2003 and 2011. We used propensity score-adjusted models to investigate the association between statin use and risk of subarachnoid hemorrhage. Secondary analyses repeated the main models stratified on tobacco use status and separately assessed other composite outcomes.

RESULTS

We identified 28 931 patients with unruptured cerebral aneurysms (average age 72·0 years, 72·6% female); mean follow-up was 30·0 months; 41·3% used statins. Overall, 593 patients developed subarachnoid hemorrhage, and 703 underwent treatment before subarachnoid hemorrhage. Current or recent statin use was not associated with a difference in subarachnoid hemorrhage risk (odds ratio, 1·03; 95% conflict of interest 0·86-1·23); models stratified on tobacco use status were nearly identical. No association was observed between statin use and the composite outcome of subarachnoid hemorrhage or aneurysm treatment (odds ratio, 0·94; 95% conflict of interest, 0·84-1·06). The risk of subarachnoid hemorrhage or out-of-hospital death was lower among statin users (odds ratio, 0·69; 95% conflict of interest, 0·64-0·74).

CONCLUSIONS

Statin use by patients with unruptured cerebral aneurysms was not associated with subarachnoid hemorrhage risk. Given the prior animal experimental studies demonstrating a protective effect, further prospective studies are needed to investigate the potential relationship.

Morphologic predictors of aortic expansion in chronic type B aortic dissection

Aim

To identify morphologic factors affecting aortic expansion in patients with uncomplicated type B aortic dissections.

Methods

Computed tomography data of 24 patients (18 male; median age: 61 years), diagnosed with acute uncomplicated type B aortic dissections between 2002 and 2013, were retrospectively reviewed. All patients had at least two computed tomography angiography scans and six months of uneventful follow-up. Computed tomography scans were assessed by two independent readers with regard to presence and number of entry tears. Thoracic and abdominal aortic diameters were derived using image processing software.

Results

Twenty-two of 24 patients showed aortic expansion over a median computed tomography angiographic follow-up of 33.2 months. Annual rates showed an increase of 1.7 mm for total aortic diameter, 2.1 mm for the false and a decrease of −0.4 mm for the true lumen. In three patients (12.5%), aortic diameter exceeded 60 mm during follow-up, and all three patients underwent thoracic endovascular aortic repair. Patients with a maximum aortic diameter <4 cm at baseline showed a significantly higher expansion rate compared to cases with an initial maximum aortic diameter of ≥4 cm ( p=0.0471). A median of two entries (range: 1–5) was recognized per patient. Presence of more than two entry tears ( n = 13) was associated with faster overall diameter expansion (mean annual rates: 2.18 mm vs. 1.16 mm; p = 0.4556), and decrease of the cross-sectional surface of the true lumen over time (annual rate for > 2 entries vs. ≤2 entries: −7.8 mm2 vs. +37.5 mm2; p = 0.0369). Median size of entry tears was 12 mm (range: 2–53 mm).

Conclusions

The results presented herein suggest that uncomplicated type B aortic dissection patients with more than two entry tears and/or an initial maximum aortic diameter of<4 cm are at risk for aortic dilatation and, therefore, may require stricter follow-up including the possible need for early intervention.

Inhibitory effect of statins on inflammation-related pathways in human abdominal aortic aneurysm tissue

HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase inhibitors (statins) have been suggested to attenuate abdominal aortic aneurysm (AAA) growth. However, the effects of statins in human AAA tissues are not fully elucidated. The aim of this study was to investigate the direct effects of statins on proinflammatory molecules in human AAA walls in ex vivo culture. Simvastatin strongly inhibited the activation of nuclear factor (NF)-κB induced by tumor necrosis factor (TNF)-α in human AAA walls, but showed little effect on c-jun N-terminal kinase (JNK) activation. Simvastatin, as well as pitavastatin significantly reduced the secretion of matrix metalloproteinase (MMP)-9, monocyte chemoattractant protein (MCP)-2 and epithelial neutrophil-activating peptide (CXCL5) under both basal and TNF-α-stimulated conditions. Similar to statins, the Rac1 inhibitor NSC23766 significantly inhibited the activation of NF-κB, accompanied by a decreased secretion of MMP-9, MCP-2 and CXCL5. Moreover, the effect of simvastatin and the JNK inhibitor SP600125 was additive in inhibiting the secretion of MMP-9, MCP-2 and CXCL5. These findings indicate that statins preferentially inhibit the Rac1/NF-κB pathway to suppress MMP-9 and chemokine secretion in human AAA, suggesting a mechanism for the potential effect of statins in attenuating AAA progression.