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

How to improve epidemiological trustworthiness concerning abdominal aortic aneurysms

BACKGROUND

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

METHODS

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

RESULTS

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 However, several pieces of information are missing or outdated, thus systematic renewal is necessary.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

CONCLUSIONS

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

Multimodality magnetic resonance evaluating the effect of enhanced physical exercise on the growth rate, flow haemodynamics, aneurysm wall and ventricular-aortic coupling of patients with small abdominal aortic aneurysms (AAA MOVE trial): a study protocol for an open-label randomised controlled trial

INTRODUCTION

The best lifestyle for small abdominal aortic aneurysms (sAAA) is essential for its conservative management. Physical exercise can improve the cardiopulmonary function of the patients, but it remains unclear which specific type of exercise is most beneficial for individuals with sAAA. The current study was designed to investigate the effect of physician-guided enhanced physical exercise programme on the aorto-cardiac haemodynamic environment, aneurysm sac wall, cardiac function and growth rate of sAAA by multimodality MRI.

METHODS AND ANALYSIS

AAA MOVE study is a prospective, parallel, equivalence, randomised controlled trial. Eligible individuals will be recruited if they are diagnosed with sAAA (focal dilation of abdominal aorta with maximum diameter <5 cm), without contraindication for MRI scanning, or severe heart failure, or uncontrolled arrhythmia. Participants will be randomly allocated to intervention group (physician-guided enhanced physical exercise programme: mainly aerobic training) and control group (standard clinical care) separately in a 1:1 ratio. The primary outcome is 12-month growth rate of sAAA. The first set of secondary outcomes involve multimodality MRI parameters covering flow haemodynamics, aortic wall inflammation and cardiac function. The other secondary outcome (safety end point) is a composite of exercise-related injury, aneurysm rupture and aneurysm intervention. Follow-up will be conducted at 6 and 12 months after intervention.

ETHICS AND DISSEMINATION

This study was approved by the Ethics Committee on Biomedical Research of West China Hospital (approval number: 2023-783) on 16 June 2023. Main findings from the trial will be disseminated through presentations at conferences, peer-reviewed publications and directly pushed to smartphone of participants.

TRIAL REGISTRATION NUMBER

ChiCTR2300073334.

Evidence for overdiagnosis in noncancer conditions was assessed: a metaepidemiological study using the 'Fair Umpire' framework

OBJECTIVES

To evaluate the strength of the evidence for, and the extent of, overdiagnosis in noncancer conditions.

STUDY DESIGN AND SETTING

We systematically searched for studies investigating overdiagnosis in noncancer conditions. Using the 'Fair Umpire' framework to assess the evidence that cases diagnosed by one diagnostic strategy but not by another may be overdiagnosed, two reviewers independently identified whether a Fair Umpire-a disease-specific clinical outcome, a test result or risk factor that can determine whether an additional case does or does not have disease-was present. Disease-specific clinical outcomes provide the strongest evidence for overdiagnosis, follow-up or concurrent tests provide weaker evidence, and risk factors provide only weak evidence. Studies without a Fair Umpire provide the weakest evidence of overdiagnosis.

RESULTS

Of 132 studies, 47 (36%) did not include a Fair Umpire to adjudicate additional diagnoses. When present, the most common Umpire was a single test or risk factor (32% of studies), with disease-specific clinical outcome Umpires used in only 21% of studies. Estimates of overdiagnosis included 43-45% of screen-detected acute abdominal aneurysms, 54% of cases of acute kidney injury, and 77% of cases of oligohydramnios in pregnancy.

CONCLUSION

Much of the current evidence for overdiagnosis in noncancer conditions is weak. Application of the framework can guide development of robust studies to detect and estimate overdiagnosis in noncancer conditions, ultimately informing evidence-based policies to reduce it.

Systematic Review and Meta-Analysis of the Incidence of Rupture, Repair, and Death of Small and Large Abdominal Aortic Aneurysms under Surveillance

BACKGROUND

The ultimate goal of treating patients with abdominal aortic aneurysms (AAAs) is to repair them when the risk of rupture exceeds the risk of repair. Small AAAs demonstrate a low rupture risk, and recently, large AAAs just above the threshold (5.5-6.0 cm) seem to be at low risk of rupture as well. The present review aims to investigate the outcomes of AAAs under surveillance through a comprehensive systematic review and meta-analysis.

METHODS

PubMed, Embase, and the Cochrane Central Register were searched (22 March 2022; PROSPERO; #CRD42022316094). The Cochrane and PRISMA statements were respected. Blinded systematic screening of the literature, data extraction, and quality assessment were performed by two authors. Conflicts were resolved by a third author. The meta-analysis of prevalence provided estimated proportions, 95% confidence intervals, and measures of heterogeneity (I2). Based on I2, the heterogeneity might be negligible (0-40%), moderate (30-60%), substantial (50-90%), and considerable (75-100%). The primary outcome was the incidence of AAA rupture. Secondary outcomes included the rate of small AAAs reaching the threshold for repair, aortic-related mortality, and all-cause mortality.

RESULTS

Fourteen publications (25,040 patients) were included in the analysis. The outcome rates of the small AAA group (<55 mm) were 0.3% (95% CI 0.0-1.0; I2 = 76.4%) of rupture, 0.6% (95% CI 0.0-1.9; I2 = 87.2%) of aortic-related mortality, and 9.6% (95% CI 2.2-21.1; I2 = 99.0%) of all-cause mortality. During surveillance, 21.4% (95% CI 9.0-37.2; I2 = 99.0%) of the initially small AAAs reached the threshold for repair. The outcome rates of the large AAA group (>55 mm) were 25.7% (95% CI 18.0-34.3; I2 = 72.0%) of rupture, 22.1% (95% CI 16.5-28.3; I2 = 25.0%) of aortic-related mortality, and 61.8% (95% CI 47.0-75.6; I2 = 89.1%) of all-cause mortality. The sensitivity analysis demonstrated a higher rupture rate in studies including <662 subjects, patients with a mean age > 72 years, >17% of female patients, and >44% of current smokers.

CONCLUSION

The rarity of rupture and aortic-related mortality in small AAAs supports the current conservative management of small AAAs. Surveillance seems indicated, as one-fifth reached the threshold for repair. Large aneurysms had a high incidence of rupture and aortic-related mortality. However, these data seem biased by the sparse and heterogeneous literature overrepresented by patients unfit for surgery. Specific rupture risk stratified by age, gender, and fit-for-surgery patients with large AAAs needs to be further investigated.

CXCR4 - a possible serum marker for risk stratification of abdominal aortic aneurysms

Background: Abdominal aortic aneurysm (AAA) rupture is still associated with a mortality rate of 80-90%. Imaging techniques or molecular fingerprinting for patient-specific risk stratification to identify pending rupture are still lacking. The chemokine (C-X-C motif) receptor (CXCR4) activation by CXCL12 ligand has been identified as a marker of inflammation and atherosclerosis, associated with AAA. Both are highly expressed in the aortic aneurysm wall. However, it is still unclear whether different expression levels of CXCR4 and CXCL12 can distinguish ruptured AAAs (rAAA) from intact AAAs (iAAA). Patients and methods: Abdominal aortic tissue samples (rAAA: n=29; iAAA: n=54) were excised during open aortic repair. Corresponding serum samples from these patients (n=9 from rAAAs; n=47 from iAAA) were drawn pre-surgery. Healthy aortic tissue samples (n=8) obtained from adult kidney donors during transplantation and serum samples from healthy adult volunteers were used as controls (n=5 each). Results: CXCR4 was mainly expressed in the media of the aneurysmatic tissue. Focal positive staining was also observed in areas of inflammatory infiltrates within the adventitia. In tissue lysates, no significant differences between iAAA, rAAA, and healthy controls were observed upon ELISA analysis. In serum samples, the level of CXCR4 was significantly increased in rAAA by 4-fold compared to healthy controls (p=0.011) and 3.0-fold for rAAA compared to iAAA (p<0.001). Furthermore a significant positive correlation between aortic diameter and serum CXCR4 concentration was found for both, iAAA and rAAA (p=0.042). Univariate logistic regression analysis showed that increased CXCR4 serum concentrations were associated with AAA rupture (OR: 4.28, 95% CI: 1.95-12.1, p=0.001). Conclusions: CXCR4 concentration was significantly increased in serum of rAAA patients and showed a significant correlation with an increased aortic diameter. The level of CXCR4 in serum was associated with a more than 4-fold risk increase for rAAA and thus could possibly serve as a biomarker in the future. However, further validation in larger studies is required.

Early Repair of Aortic Wall Structural Defect by "Net" Endoprosthesis to Arrest the Aneurysm without Interference with Aortic Branch Vessel Perfusion

Current treatments of aortic aneurysm include surgical or endovascular, respectively, anatomical or functional, substitution of the aneurysm tract; however, with these methods, perfusion of at least some collateral branches cannot be fully restored, leading to the risk of paraplegia. We present a novel endovascular “net” prosthesis to strengthen the aortic wall while preserving perfusion of collateral branches. This consists of a polyester mesh “net”-layered conduit in a variable cylindrical shape, which is personalized based on patient computed tomography scan images, and is defined by circular crossing spirals of a thin nitinol wire. The prosthetic conduit, shrunk by compressing the nitinol spirals, can be inserted into the vascular lumen and expanded in situ. Then, the insertion control device can be fully removed. Thus, the, “net” prosthesis, positioned inside the aorta in stable contact with the intimal wall for 2 to 5 months, is colonized by neointima and spontaneously moved deeper into the aortic wall in contact with the media, thus being ideally able to stabilize aortic diameter without interference with collateral branch blood perfusion. This new, (ideally) paraplegia-free procedure is aimed at curing the aortic wall structural defect, thus arresting the aneurysm from further progression. This contrasts with current treatments, indicated by aneurysm dimensions for their implied complication risk, which are actually for prophylaxis of impending rupture or dissection rather than fortification of the natural aorta. Moreover, this new approach can be used alongside open surgical procedures (personalized external aortic root support) as well as a frozen “net” elephant trunk technique, for full aortic stabilization.

Contrast-enhanced US Evaluation of Endoleaks after Endovascular Stent Repair of Abdominal Aortic Aneurysm

Ruptured abdominal aortic aneurysm (AAA) carries high morbidity and mortality. Elective repair of AAA with endovascular stent-grafts requires lifetime imaging surveillance for potential complications, most commonly endoleaks. Because endoleaks result in antegrade or retrograde systemic arterialized flow into the excluded aneurysm sac, patients are at risk for recurrent aneurysm sac growth with the potential to rupture. Multiphasic CT has been the main imaging modality for surveillance and symptom evaluation, but contrast-enhanced US (CEUS) offers a useful alternative that avoids radiation and iodinated contrast material. CEUS is at least equivalent to CT for detecting endoleak and may be more sensitive. The authors provide a general protocol and technical considerations needed to perform CEUS of the abdominal aorta after endovascular stent repair. When there are no complications, the stent-graft lumen has homogeneous enhancement, and no contrast material is present in the aneurysm sac outside the stented lumen. In patients with an antegrade endoleak, contrast material is seen simultaneously in the aneurysm sac and stent-graft lumen, while delayed enhancement in the sac is due to retrograde leak. Recognition of artifacts and other potential pitfalls for CEUS studies is important for examination performance and interpretation. Online supplemental material is available for this article. ^©RSNA, 2022.

Infrarenal Remains Infrarenal-EVAR Suitability of Small AAA Is Rarely Compromised despite Morphological Changes during Surveillance

The aim was to analyze small abdominal aortic aneurysm (AAA) morphology during surveillance with regard to standard endovascular aortic repair (EVAR) suitability. This retrospective single-center study included all patients (n = 52, 48 male, 70 ± 8 years) with asymptomatic AAA ≤ 5.4 cm undergoing ≥2 computed tomography angiography(CTA)/magnetic resonance imaging (MRI) studies (interval: ≥6 months) between 2010 and 2018. Aneurysm diameter, neck quality (shape, length, angulation, thrombus/calcification), aneurysm thrombus, and distal landing zone diameters were compared between first and last CTA/MRI. Resulting treatment plan changes were determined. Neck shortening occurred in 25 AAA (mean rate: 2.0 ± 4.2 mm/year). Neck thrombus, present in 31 patients initially, increased in 16. Average AAA diameters were 47.7 ± 9.3 mm and 56.3 ± 11.6 mm on first and last CTA/MRI, mean aneurysm growth rate was 4.2 mm/year. Aneurysm thrombus was present in 46 patients primarily, increasing in 32. Neck thrombus growth and neck length change, aneurysm thrombus amount and aneurysm growth and aneurysm growth and neck angulation were significantly correlated. A total of 46 (88%) patients underwent open (12/46) or endovascular (34/46) surgery. The planned procedure changed from EVAR to fenestrated EVAR in two patients and from double to triple fenestrated EVAR in one. Thus, standard EVAR suitability was predominantly maintained as the threshold diameter for surgery was reached despite morphological changes. Consecutively, a possibly different pathogenesis of infra- versus suprarenal AAA merits further investigation.

A ruptured mycotic aortic aneurysm in a patient with urinary retention: A case report

Symptomatic abdominal aortic aneurysm (AAA) is a diagnosis that is a true emergency. Since AAAs are typically asymptomatic prior to rupturing, they can easily be missed. When an abdominal aortic aneurysm becomes symptomatic and ruptures, the ramifications can be catastrophic for the patient. We present a case of a 55-year-old male who presented with urinary retention and suprapubic pain. Computerized tomography demonstrated a rapidly expanding AAA and signs of impending rupture. Emergent vascular surgical repair was performed successfully. There was concern for mycotic nature of the AAA with recent COVID-19 infection and possible bacteremia. This case demonstrates the need for maintaining a wider differential when examining patients and avoiding anchoring bias and serves as a point of discussion for potential complications of COVID-19 infection.

Creating Interactive Three-Dimensional Applications to Visualise Novel Stent Grafts That Aid in the Treatment of Aortic Aneurysms

Three-Dimensional (3D) medical animations incorporated into applications are highly beneficial for clinical outreach and medical communication purposes that work towards educating the clinician and patient. Aortic aneurysms are a clinically important area to communicate with multiple audiences about various treatment options; both abdominal and thoracic aortic aneurysms were selected to create 3D animations and applications to educate medical professionals and patients regarding treatment options. Fenestrated endovascular aortic repair (FEVAR) and thoracic endovascular aortic repair (TEVAR) are both tried and tested minimally invasive surgical methods for treating thoracic aortic aneurysms respectively. The Terumo Aortic Custom Relay Proximal Scalloped stent graft and Fenestrated Anaconda stent graft were both designed specifically for these procedures; however, it can be difficult to visually communicate to clinicians and patients in a straightforward way how these devices work. Therefore, we have developed two interactive applications that use 3D visualisation techniques to demonstrate how these aortic devices function and are implemented. The objective of these applications is to engage both clinicians and patients, therefore demonstrating that the addition of anatomically accurate 3D visualisations within an interactive interface would have a positive impact on public engagement while also ensuring that clinicians will have the best possible understanding of the potential uses of both devices, enabling them to exploit their key features to effectively broaden the treatable patient population.Detailed anatomical modelling and animation was used to generate realistic and accurate rendered videos showcasing both products. These videos were integrated into an interactive application within a modern, professional graphic interface that allowed the user to explore all aspects of the stent device. The resulting applications were broken down into three modules: deployment, clinical performance and features. Following application development, these applications were evaluated by professionals in the field. Overall, positive feedback was received regarding the user-friendly nature of the applications and highly effective animations to showcase the products. The clinical applications and feature modules were particularly successful, while the deployment modules had a neutral response. Biomedical applications such as these show great potential for communicating the key features of medical devices and promoting discussion between clinicians and patients; further testing would need to be conducted on a larger group of participants in order to validate the learning effectiveness of the applications.

Molecular Imaging of Abdominal Aortic Aneurysms with Positron Emission Tomography: A Systematic Review

OBJECTIVE

Previous studies on the relationship between positron emission tomography (PET) images and abdominal aortic aneurysm (AAA) progression have shown contradictory results, and the objective of this study was to systematically review the role of PET in predicting AAA prognosis.

DATA SOURCES

PubMed, Embase, and Web of Science were searched for studies evaluating the correlation between PET imaging results and AAA growth, repair, or rupture.

REVIEW METHODS

Two authors independently performed the study search, data extraction, and quality assessment following a standard method.

RESULTS

Of the 11 studies included in this review, nine used ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET and computed tomography (CT) imaging, whereas the remaining two used ¹⁸F-sodium fluoride (¹⁸F-NaF) PET/CT and ¹⁸F-FDG PET/magnetic resonance imaging (MRI). Findings from the ¹⁸F-FDG PET/CT studies were contradictory. Six studies found no significant association or correlation, and two studies found a significant negative correlation between ¹⁸F-FDG uptake and AAA expansion. Additionally, one study found that the ¹⁸F-FDG uptake was statistically positively related to the expansion rate in a specific AAA subgroup whose AAAs expanded significantly. Two studies suggested that increased ¹⁸F-FDG uptake was significantly associated with AAA repair, while the other studies either found no association between ¹⁸F-FDG uptake and AAA rupture or repair or failed to report the occurrence of clinical events. One PET/CT study that used ¹⁸F-NaF as a tracer showed that an increased tracer uptake was significantly associated with AAA growth and clinical events. Finally, the ¹⁸F-FDG PET/MRI study indicated that ¹⁸F-FDG uptake was not significantly correlated with AAA expansion.

CONCLUSION

A definitive role for ¹⁸F-FDG PET imaging for AAA prognosis awaits further investigation, and new PET tracers such as ¹⁸F-NaF have the potential to be a promising method for predicting AAA clinical outcomes.

Neutrophils as Regulators and Biomarkers of Cardiovascular Inflammation in the Context of Abdominal Aortic Aneurysms

Neutrophils represent up to 70% of circulating leukocytes in healthy humans and combat infection mostly by phagocytosis, degranulation and NETosis. It has been reported that neutrophils are centrally involved in abdominal aortic aneurysm (AAA) pathogenesis. The natural course of AAA is growth and rupture, if left undiagnosed or untreated. The rupture of AAA has a very high mortality and is currently among the leading causes of death worldwide. The use of noninvasive cardiovascular imaging techniques for patient screening, surveillance and postoperative follow-up is well established and recommended by the current guidelines. Neutrophil-derived biomarkers may offer clinical value to the monitoring and prognosis of AAA patients, allowing for potential early therapeutic intervention. Numerous promising biomarkers have been studied. In this review, we discuss neutrophils and neutrophil-derived molecules as regulators and biomarkers of AAA, and our aim was to specifically highlight diagnostic and prognostic markers. Neutrophil-derived biomarkers may potentially, in the future, assist in determining AAA presence, predict size, expansion rate, rupture risk, and postoperative outcome once validated in highly warranted future prospective clinical studies.

Prehabilitation exercise therapy before elective abdominal aortic aneurysm repair

BACKGROUND

An abdominal aortic aneurysm (AAA) is an abnormal dilation in the diameter of the abdominal aorta of 50% or more of the normal diameter or greater than 3 cm in total. The risk of rupture increases with the diameter of the aneurysm, particularly above a diameter of approximately 5.5 cm. Perioperative and postoperative morbidity is common following elective repair in people with AAA. Prehabilitation or preoperative exercise is the process of enhancing an individual's functional capacity before surgery to improve postoperative outcomes. Studies have evaluated exercise interventions for people waiting for AAA repair, but the results of these studies are conflicting.

OBJECTIVES

To assess the effects of exercise programmes on perioperative and postoperative morbidity and mortality associated with elective abdominal aortic aneurysm repair.

SEARCH METHODS

We searched the Cochrane Vascular Specialised register, Cochrane Central Register of Controlled Trials, MEDLINE, Embase, CINAHL (Cumulative Index to Nursing and Allied Health Literature), and Physiotherapy Evidence Database (PEDro) databases, and the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 6 July 2020. We also examined the included study reports' bibliographies to identify other relevant articles.

SELECTION CRITERIA

We considered randomised controlled trials (RCTs) examining exercise interventions compared with usual care (no exercise; participants maintained normal physical activity) for people waiting for AAA repair.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies for inclusion, assessed the included studies, extracted data and resolved disagreements by discussion. We assessed the methodological quality of studies using the Cochrane risk of bias tool and collected results related to the outcomes of interest: post-AAA repair mortality; perioperative and postoperative complications; length of intensive care unit (ICU) stay; length of hospital stay; number of days on a ventilator; change in aneurysm size pre- and post-exercise; and quality of life. We used GRADE to evaluate certainty of the evidence. For dichotomous outcomes, we calculated the risk ratio (RR) with the corresponding 95% confidence interval (CI).

MAIN RESULTS

This review identified four RCTs with a total of 232 participants with clinically diagnosed AAA deemed suitable for elective intervention, comparing prehabilitation exercise therapy with usual care (no exercise). The prehabilitation exercise therapy was supervised and hospital-based in three of the four included trials, and in the remaining trial the first session was supervised in hospital, but subsequent sessions were completed unsupervised in the participants' homes. The dose and schedule of the prehabilitation exercise therapy varied across the trials with three to six sessions per week and a duration of one hour per session for a period of one to six weeks. The types of exercise therapy included circuit training, moderate-intensity continuous exercise and high-intensity interval training. All trials were at a high risk of bias. The certainty of the evidence for each of our outcomes was low to very low. We downgraded the certainty of the evidence because of risk of bias and imprecision (small sample sizes). Overall, we are uncertain whether prehabilitation exercise compared to usual care (no exercise) reduces the occurrence of 30-day (or longer if reported) mortality post-AAA repair (RR 1.33, 95% CI 0.31 to 5.77; 3 trials, 192 participants; very low-certainty evidence). Compared to usual care (no exercise), prehabilitation exercise may decrease the occurrence of cardiac complications (RR 0.36, 95% CI 0.14 to 0.92; 1 trial, 124 participants; low-certainty evidence) and the occurrence of renal complications (RR 0.31, 95% CI 0.11 to 0.88; 1 trial, 124 participants; low-certainty evidence). We are uncertain whether prehabilitation exercise, compared to usual care (no exercise), decreases the occurrence of pulmonary complications (RR 0.49, 95% 0.26 to 0.92; 2 trials, 144 participants; very low-certainty evidence), decreases the need for re-intervention (RR 1.29, 95% 0.33 to 4.96; 2 trials, 144 participants; very low-certainty evidence) or decreases postoperative bleeding (RR 0.57, 95% CI 0.18 to 1.80; 1 trial, 124 participants; very low-certainty evidence). There was little or no difference between the exercise and usual care (no exercise) groups in length of ICU stay, length of hospital stay and quality of life. None of the studies reported data for the number of days on a ventilator and change in aneurysm size pre- and post-exercise outcomes.

AUTHORS' CONCLUSIONS

Due to very low-certainty evidence, we are uncertain whether prehabilitation exercise therapy reduces 30-day mortality, pulmonary complications, need for re-intervention or postoperative bleeding. Prehabilitation exercise therapy might slightly reduce cardiac and renal complications compared with usual care (no exercise). More RCTs of high methodological quality, with large sample sizes and long-term follow-up, are needed. Important questions should include the type and cost-effectiveness of exercise programmes, the minimum number of sessions and programme duration needed to effect clinically important benefits, and which groups of participants and types of repair benefit most.

Outcomes of Small Incidental Abdominal Aortic Aneurysms in Octogenarian and Nonagenarian Patients in Northern Spain

OBJECTIVE

Greater population life expectancy and consistent improvement in diagnostic techniques have increased the diagnosis of abdominal aortic aneurysms (AAAs) in the elderly population. The aim was to study the natural history of small (< 55 mm) incidental AAAs in octogenarian and nonagenarian patients to assess the need for follow up and/or invasive treatment.

METHODS

This was a retrospective analysis of a prospective registry. Patients ≥ 80 years old at the time of diagnosis of a < 55 mm AAA in 1988-2018 were selected. Clinical and anatomical characteristics were registered. Patients were divided in three groups: 30 - 39 mm, 40 - 49 mm, and 50 - 54 mm AAA. The outcome variables were aorto-iliac rupture, AAA reaching a surgical threshold (≥ 55 mm), and death. A descriptive statistical analysis was performed and life tables, Kaplan-Meier curves, and uni- and multivariable Cox regression were used.

RESULTS

Three hundred and ten patients were included, 256 (82.6%) men, with mean index age of 84.5 years (standard deviation [SD] 3.5), and median follow up of 37.9 months (interquartile range [IQR] 18.2 - 65.4). Eighteen (5.8%) AAAs ruptured; four of these patients were operated on and only one survived. Sixty-two (20%) AAA reached a surgical size; eight were repaired electively, with 0% early mortality. The survival rates were 81%, 70%, and 38% at one, two, and five years. The rupture rates were 1%, 2%, and 6% and the AAAs reaching surgical threshold were 1%, 4%, and 19% for the same time periods. AAA size < 40 mm was an independent protective factor from rupture (0.13; 95% confidence interval [CI] 0.03 - 0.48), reaching surgical threshold (0.08; 95% CI 0.04 - 0.16) and death (0.63; 95% CI 0.42 - 0.95).

CONCLUSION

The risk of late rupture of small incidental AAA diagnosed in octogenarian and nonagenarian patients is very small, especially when the AAA is < 40 mm in diameter. In contrast, global mortality is high. Conservative management seems sensible, with strict selection of the patients who would benefit from follow up and eventual repair.

Imaging Predictive Factors of Abdominal Aortic Aneurysm Growth

Background: Variable imaging methods may add important information about abdominal aortic aneurysm (AAA) progression. The aim of this study is to assess available literature data regarding the predictive imaging factors of AAA growth. Methods: This systematic review was conducted using the PRISMA guidelines. A review of the literature was conducted, using PubMed, EMBASE and CENTRAL databases. The quality of the studies was assessed using the Newcastle-Ottawa Scale. Primary outcomes were defined as AAA growth rate and factors associated to sac expansion. Results: The analysis included 23 studies. All patients (2244; mean age; 69.8 years, males; 85%) underwent imaging with different modalities; the initial evaluation was followed by one or more studies to assess aortic expansion. AAA initial diameter was reported in 13 studies (range 19.9–50.9 mm). Mean follow-up was 34.5 months. AAA diameter at the end was ranging between 20.3 and 55 mm. The initial diameter and intraluminal thrombus were characterized as prognostic factors associated to aneurysm expansion. A negative association between atherosclerosis and AAA expansion was documented. Conclusions: Aneurysm diameter is the most studied factor to be associated with expansion and the main indication for intervention. Appropriate diagnostic modalities may account for different anatomical characteristics and identify aneurysms with rapid growth and higher rupture risk. Future perspectives, including computed mathematical models that will assess wall stress and elasticity and further flow characteristics, may offer valuable alternatives in AAA growth prediction.

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.

Multiperspective Ultrasound Strain Imaging of the Abdominal Aorta

Current decision-making for clinical intervention of abdominal aortic aneurysms (AAAs) is based on the maximum diameter of the aortic wall, but this does not provide patient-specific information on rupture risk. Ultrasound (US) imaging can assess both geometry and deformation of the aortic wall. However, low lateral contrast and resolution are currently limiting the precision of both geometry and local strain estimates. To tackle these drawbacks, a multiperspective scanning mode was developed on a dual transducer US system to perform strain imaging at high frame rates. Experimental imaging was performed on porcine aortas embedded in a phantom of the abdomen, pressurized in a mock circulation loop. US images were acquired with three acquisition schemes: Multiperspective ultrafast imaging, single perspective ultrafast imaging, and conventional line-by-line scanning. Image registration was performed by automatic detection of the transducer surfaces. Multiperspective images and axial displacements were compounded for improved segmentation and tracking of the aortic wall, respectively. Performance was compared in terms of image quality, motion tracking, and strain estimation. Multiperspective compound displacement estimation reduced the mean motion tracking error over one cardiac cycle by a factor 10 compared to conventional scanning. Resolution increased in radial and circumferential strain images, and circumferential signal-to-noise ratio (SNRe) increased by 10 dB. Radial SNRe is high in wall regions moving towards the transducer. In other regions, radial strain estimates remain cumbersome for the frequency used. In conclusion, multiperspective US imaging was demonstrated to improve motion tracking and circumferential strain estimation of porcine aortas in an experimental set-up.

Runx2 (Runt-Related Transcription Factor 2)-Mediated Microcalcification Is a Novel Pathological Characteristic and Potential Mediator of Abdominal Aortic Aneurysm

OBJECTIVE

Abdominal aortic aneurysms (AAAs) are highly lethal diseases without effective clinical predictors and therapeutic targets. Vascular microcalcification, as detected by fluorine-18-sodium fluoride, has recently been recognized as a valuable indicator in predicting atherosclerotic plaque rupture and AAA expansion. However, whether vascular microcalcification involved in the pathogenesis of AAA remains elusive. Approach and Results: Microcalcification was analyzed in human aneurysmal aortas histologically and in AngII (angiotensin II)-infused ApoE^-/- mouse aortas by fluorine-18-sodium fluoride positron emission tomography and X-ray computed tomography scanning in chronological order in live animals. AAA patients' aortic tissue showed markedly enhanced microcalcification in the aortic media within the area proximal to elastic fiber degradation, compared with non-AAA patients. Enhanced fluorine-18-sodium fluoride uptake preceded significant aortic expansion in mice. Microcalcification-positive mice on day 7 of AngII infusion showed dramatic aortic expansion on subsequent days 14 to 28, whereas microcalcification-negative AngII-infused mice and saline-induced mice did not develop AAA. The application of hydroxyapatite, the main component of microcalcification, aggravated AngII-induced AAA formation in vivo. RNA-sequencing analysis of the suprarenal aortas of 4-day-AngII-infused ApoE^-/- mice and bioinformatics analysis with ChIP-Atlas database identified the potential involvement of the osteogenic transcriptional factor Runx2 (runt-related transcription factor 2) in AAA. Consistently, vascular smooth muscle cell-specific Runx2 deficiency markedly repressed AngII-induced AAA formation in the ApoE^-/- mice compared with the control littermates.

CONCLUSIONS

Our studies have revealed microcalcification as a novel pathological characteristic and potential mediator of AAA, and targeting microcalcification may represent a promising strategy for AAA prevention and treatment.

Validation of a preoperative prediction model for mortality within 1 year after endovascular aortic aneurysm repair of intact aneurysms

OBJECTIVE

Most would agree that at least 1-year survival is necessary after intact abdominal aortic aneurysm (AAA) repair to appropriately justify the cost and risk of the procedure. No validated clinical decision instruments exist to predict survival after endovascular aneurysm repair (EVAR) beyond the perioperative period. The purpose of this analysis was to create a preoperative prediction model for 1-year mortality after EVAR for intact AAA in the Society for Vascular Surgery Vascular Quality Initiative.

METHODS

All intact EVARs in the Society for Vascular Surgery Vascular Quality Initiative from 2011 to 2015 were randomly divided into training (n = 17,836) and validation (n = 2500) data sets, and 31 preoperative candidate predictors were identified. A logistic regression model for 1-year mortality was created, and bootstrapped stepwise variable elimination was used to reduce this model to a best subset of predictors. Penalized maximum likelihood estimation was used to correct for potential overfitting. The final model was internally validated by bootstrapping the area under the curve (AUC) and the calibration slope and intercept, and its performance when applied to the training and validation data sets was compared.

RESULTS

After elective and nonelective (symptomatic, intact) EVAR, 1-year mortality was 5.5% (n = 900/16,411) and 11.4% (n = 162/1425), respectively. The mean probability of 1-year mortality was 6.0% (n = 1062) in the training set and 5.7% (n = 143) in the validation cohort (P = .12). Significant preoperative predictors of 1-year mortality included chronic obstructive pulmonary disease, age, preoperative renal insufficiency (creatinine concentration ≥1.8 mg/dL or on hemodialysis), ejection fraction <50%, transfer status, body mass index <24 kg/m², preoperative beta-blocker exposure, larger AAA diameter, and lower admission hemoglobin level. Preoperative statin use was found to be protective. The bias-corrected AUC was 0.759 (Hosmer-Lemeshow goodness-of-fit P value of 0.36; calibration intercept, -0.003; slope, 0.999). When applied to the validation data set, the model had AUC of 0.724 (95% confidence interval, 0.676-0.768; calibration intercept, 0.0009; slope, 0.970), which was in excellent agreement with the original data set bias-corrected AUC. Notably, ∼27.5% (n = 4902) had four or more risk factors with a predicted 1-year post-EVAR mortality risk of 10% to 22% despite that 33.2% of these patients had AAA diameters below recommended treatment guideline minimum thresholds.

CONCLUSIONS

This validated preoperative prediction model for 1-year mortality identifies patients less likely to benefit from EVAR. Appropriateness of intact AAA EVAR care delivery can be improved by use of this clinical decision aid to determine which high-risk patients have lower probability of mortality within the first postoperative year relative to their predicted annualized rupture risk.

Spatial Distribution of Abdominal Aortic Aneurysm Surface Expansion and Correlation With Maximum Diameter and Volume Growth

BACKGROUND

Abdominal aortic aneurysm (AAA) growth rate, measured as maximum diameter (Dmax) change over time, is used as a surrogate marker of rupture risk. However, AAA expansion presents significant spatial variability. We aim to record the spatial distribution of regional wall surface expansion.

METHODS

Thirty AAAs were retrospectively studied. Each AAA had one baseline and at least one follow-up computed tomography scan. Three-dimensional AAA models were reconstructed, and change in Dmax and total aneurysm volume was recorded to calculate annual growth rates. Regional surface growth was quantified using the VascForm algorithm, which is based on nonrigid point cloud registration and iterative closest point analysis. Maximum and average surface growths were calculated and correlated with the diameter/volume growth rates. Furthermore, to identify potential correlation between maximum thrombus (intraluminal thrombus) thickness and maximum surface growth, as well as between peak wall stress (PWS) and surface growth, their colocalization was examined.

RESULTS

The median average annual surface growth was 6% (0%-28%), and the maximum surface growth 24% (11%-238%). There was strong evidence of a moderate correlation between Dmax and average as well as maximum surface growth. Regarding volumes, there was strong evidence of a very strong association with average surface growth rate and a moderate association with maximum surface growth rate (rho: 0.91, P < 0.001; rho: 0.7, P < 0.001, respectively). In 51.6% of the follow-ups, maximum surface growth occurred away from Dmax site. Sixteen cases presented maximum surface growth away and fifteen at the region of maximum initial intraluminal thrombus thickness. AAAs in the former group had significantly thinner initial intraluminal thrombus thickness (11.3 vs 19.5 mm, P < 0.001) than those in the latter. Apart from a single case, maximum surface growth did not occur at the PWS region.

CONCLUSIONS

More than half of the lesions display maximum growth away from Dmax, suggesting that a more accurate method of analyzing AAA growth needs to be established in clinical practice that will take into account local surface growth.

The Obsolete Maximum Diameter Criterion, the Evident Role of Biomechanical (Pressure) Indices, the New Role of Hemodynamic (Flow) Indices, and the Multi-Modal Approach to the Rupture Risk Assessment of Abdominal Aortic Aneurysms

Although the therapeutic management of abdominal aortic aneurysms (AAAs) is currently based on the maximum diameter criterion, this has often proved inaccurate and misleading. Conversely, the biomechanical approach, which takes into account the pressure-induced wall stress exerted at every point throughout the aneurysmal surface, has been proven superior in predicting the rupture risk of AAAs, and its value is being increasingly recognized among physicians. More recently, hemodynamic indices, such as flow-induced wall shear stresses, have been indicated as potentially significant determinants of AAA natural history. Ultimately, a statistical model that takes into account all these factors may be relevant for making a sound prediction of the rupture risk of aneurysms and optimizing the management of these patients.

Circulating microRNAs signature correlates with positive [18F]fluorodeoxyglucose-positron emission tomography in patients with abdominal aortic aneurysm

BACKGROUND

Prediction of abdominal aortic aneurysm (AAA) rupture is a challenging issue. Small noncoding microRNAs (miRNAs) are potent regulators of gene expression and are considered as valuable circulating biomarkers. Recently, [¹⁸F]fluorodeoxyglucose (FDG) uptake detected by positron emission tomography (PET) in AAA was correlated with cellular and molecular alterations involved in wall instability and its potential rupture. Our study aimed at identifying circulating miRNAs correlated with a positive PET that could help discriminate patients at high risk of rupture.

METHODS

The level of 372 miRNAs was evaluated by polymerase chain reaction array in plasma from 35 AAA patients displaying no FDG uptake (A0) and 22 patients with a positive PET uptake (A+). The modulated miRNAs were validated by quantitative polymerase chain reaction and measured in aneurysmal tissues from both groups of patients.

RESULTS

Six circulating miRNAs were found significantly modulated in A+ vs A0 patients. They were significantly correlated not only between them but also with the intensity of FDG uptake. Two of them correlated also with the AAA diameter. These miRNAs displayed significant discriminating power between the A+ and A0 groups as determined by receiver operating characteristic curves. Three downregulated circulating miRNAs (miR-99b-5p, miR-125b-5p, and miR-204-5p) were also significantly reduced in the aneurysmal tissue, specifically in the FDG-uptake site, compared with a negative zone in the same aneurysm and with A0 aneurysms. They were further significantly inversely correlated with the expression, at the positive uptake site, of some of their potential gene targets, most notably matrix metalloproteinase 13.

CONCLUSIONS

Six miRNAs were identified as potential new circulating biomarkers of PET+ AAA. Three of these were similarly modulated in the metabolically active aneurysmal wall and might be directly involved in AAA instability.

Abdominal Pain in the Presence of Small Abdominal Aortic Aneurysms: If in Doubt, Cut It Out!

Although small (<5 cm) abdominal aortic aneurysms (AAA) have been associated with symptoms and indication for intervention scarcely, the clinicians should never exclude such potential association especially in the absence of other overt pathological findings. In such cases, a surgical exploration with consequent intervention, if feasible, should be justified to prevent a detrimental evolution in a dubious scenario. In this article, we present 2 cases of patients with small AAA presenting with severe abdominal pain. In the absence of other solid clinical and radiological pathological findings, both patients underwent laparotomy where an inflammatory small AAA was identified and subjected either to resection and restoration with a tube graft or secondary endovascular repair because the periaortic fibrosis precluded the open repair. The characteristics and rationale of treatment modalities are exemplified and discussed.

(18)F-FDG PET scanning of abdominal aortic aneurysms and correlation with molecular characteristics: a systematic review

Purpose

The purpose of this study is to give an overview of studies investigating the role of fludeoxyglucose F18 (¹⁸F-FDG) positron emission tomography (PET) scanning in patients with aortic aneurysms with a focus on molecular characteristics of the aneurysm wall.

Methods

MEDLINE, EMBASE, and the Cochrane database were searched for relevant articles. After inclusion and exclusion, we selected 18 relevant articles reporting on ¹⁸F-FDG PET scanning of aortic aneurysms.

Results

The sample size of studies is limited, and there are no standardized imaging protocols and quantification methods. ¹⁸F-FDG PET scanning was shown to display molecular characteristics of the aortic wall. Different studies showed contradictory findings of aortic ¹⁸F-FDG uptake in aneurysm patients compared to controls.

Conclusions

Non-invasively determining molecular characteristics of aortic wall weakening might lead to better rupture and growth prediction. This might influence the decision of the surgeon between conservative and surgical treatment of aneurysms. To date, there is conflicted evidence regarding the use of ¹⁸F-FDG PET scanning to predict aneurysm rupture and growth. The role of ¹⁸F-FDG PET scanning in rupture risk prediction needs to be further investigated, and standardized imaging protocols and quantification methods need to be implemented.

Electronic supplementary material

The online version of this article (doi:10.1186/s13550-015-0153-8) contains supplementary material, which is available to authorized users.

Rupture rates of untreated large abdominal aortic aneurysms in patients unfit for elective repair

BACKGROUND

Elective abdominal aortic aneurysm (AAA) surgery relies on balancing the risk of the intervention against the risk of the aneurysm causing death. Although much is known about intervention at 5.5 cm, little is known about the fate of the patient unfit for elective surgery at this threshold. Medical therapy and endovascular surgery have revolutionized management of aortic aneurysms in the last 20 years and are thought to have affected rupture rates.

METHODS

MEDLINE via PubMed, EMBASE, and the Cochrane Library Database were searched for studies reporting follow-up of untreated large AAA approach from inception to January 2014. Data were pooled using random-effects analysis with standardized mean differences and 95% confidence intervals (CIs) reported. The primary end points were rupture rates and all-cause mortality per year by AAA size.

RESULTS

The search strategy identified 1892 citations, of which 11 studies comprising 1514 patients experiencing 347 ruptured AAA were included. The overall incidence of ruptured AAA in patients with AAA >5.5 cm was 5.3% (95% CI, 3.1%-7.5%) per year. This represented cumulative yearly rupture rates of 3.5% (95% CI, -1.6% to 8.7%) in AAAs 5.5 to 6.0 cm, 4.1% (95% CI, -0.7% to 9.0%) in AAAs 6.1 to 7.0 cm, and 6.3% (95% CI, -1.8% to 14.3%) in AAAs >7.0 cm. There was no heterogeneity between studies (I(2) = 0%). Only 32% of these patients were offered repair on rupturing an AAA, with a perioperative mortality of 58% (95% CI, 32%-83%). The risk of death from causes other than AAA was higher than the risk of death from rupture.

CONCLUSIONS

Rupture rates of untreated AAA were lower than those currently quoted in the literature. Non-AAA-related mortality in this group of patients is high.

Evidence of Cyclic Changes in the Metabolism of Abdominal Aortic Aneurysms During Growth Phases: ¹⁸F-FDG PET Sequential Observational Study

The rates of growth of medically treated abdominal aortic aneurysms (AAA) are difficult to determine, and relationships with parietal inflammation and with metabolic parameters from (18)F-FDG PET remain unclear. This (18)F-FDG PET sequential observational study was aimed at analyzing the metabolic changes accompanying the growth phases of medically treated AAA.

METHODS

Thirty-nine patients (37 men; age [mean ± SD], 71 ± 12 y) exhibiting small and medically treated AAA (maximal diameter, 46 ± 3 mm) underwent (18)F-FDG PET and CT angiography at baseline and 9 mo later. Clinical and imaging parameter correlates of the 9-mo increase in maximal diameter were investigated; these included (18)F-FDG maximal standardized uptake values (SUVmax) averaged for slices encompassing the AAA volume.

RESULTS

Of the 39 patients, 9 (23%) had a significant (≥2.5 mm) increase in maximal diameter at 9 mo, whereas the remaining 30 did not. The patients with an increase in maximal diameter at 9 mo exhibited lower SUVmax within the AAA at baseline than patients who did not have such an increase (1.80 ± 0.45 vs. 2.21 ± 0.52; P = 0.04); they also displayed a trend toward greater changes in SUVmax at 9 mo (difference between 9 mo and baseline: +0.40 ± 0.85 vs. -0.06 ± 0.57; P = 0.07). Similar levels were ultimately reached in both groups at 9 mo (2.20 ± 0.83 and 2.15 ± 0.66). SUVmax was a significant, yet modest, baseline predictor of the absolute change in maximal diameter during follow-up (P = 0.049).

CONCLUSION

The enhancement in the maximal diameter of small AAA was preceded by a stage with a low level of (18)F-FDG uptake, but this low level of uptake was no longer documented after the growth phases, suggesting a pattern of cyclic metabolic changes.

Increased expression and activation of absent in melanoma 2 inflammasome components in lymphocytic infiltrates of abdominal aortic aneurysms

Chronic vascular inflammation is a key hallmark in the pathogenesis of abdominal aortic aneurysm (AAA). Recent investigations have suggested that the inflammasome, a cytosolic multiprotein complex that recognizes pathogen-associated molecular patterns, plays a role in atherosclerosis. However, its role in AAA inflammation has not yet been investigated. This pilot study analyzed inflammasome activation and its intramural localization in 24 biopsy samples from 11 patients with asymptomatic AAA versus 12 aortic samples from apparently healthy controls. Using a histological inflammation scale, we identified grade 2/3 inflammatory changes with lymphoid aggregates/tertiary lymphoid organs in 21 out of 24 AAA samples, whereas only 7 of the 12 control samples exhibited local grade 1 inflammatory changes. Strong expression levels of "apoptosis-associated speck-like protein with a caspase recruitment domain" (ASC), caspase-1, caspase-5 and "absent in melanoma 2" (AIM2) were detected by immunohistochemistry in both sporadic infiltrating lymphoid cells and lymphoid aggregates located in the outer media and adventitia of AAA samples. In contrast, inflammasome-positive cells were restricted to cholesterol plaque-associated areas and to single infiltrating cells in control aortas. Analysis of gene expression using real-time polymerase chain reaction (PCR) revealed significantly increased median mRNA levels of the inflammasome core components PYCARD (ASC), CASP1 (Caspase-1) and IL1B (IL-1β) in AAA tissue compared with normal aorta. Moreover, significantly increased median amounts of AIM2 protein and mature caspase-5 (p20) were found in samples associated with high rupture risk compared with paired low rupture risk samples of the same AAA patient. We conclude from our data that AAA-associated lymphoid cells are capable of inflammasome signaling, suggesting that inflammasome activation is involved in the chronic inflammatory process driving AAA progression.

Abdominal aortic aneurysm imaging with 3-D ultrasound: 3-D-based maximum diameter measurement and volume quantification

The clinical reliability of 3-D ultrasound imaging (3-DUS) in quantification of abdominal aortic aneurysm (AAA) was evaluated. B-mode and 3-DUS images of AAAs were acquired for 42 patients. AAAs were segmented. A 3-D-based maximum diameter (Max3-D) and partial volume (Vol30) were defined and quantified. Comparisons between 2-D (Max2-D) and 3-D diameters and between orthogonal acquisitions were performed. Intra- and inter-observer reproducibility was evaluated. Intra- and inter-observer coefficients of repeatability (CRs) were less than 5.18 mm for Max3-D. Intra-observer and inter-observer CRs were respectively less than 6.16 and 8.71 mL for Vol30. The mean of normalized errors of Vol30 was around 7%. Correlation between Max2-D and Max3-D was 0.988 (p < 0.0001). Max3-D and Vol30 were not influenced by a probe rotation of 90°. Use of 3-DUS to quantify AAA is a new approach in clinical practice. The present study proposed and evaluated dedicated parameters. Their reproducibility makes the technique clinically reliable.

Final follow-up of the Multicentre Aneurysm Screening Study (MASS) randomized trial of abdominal aortic aneurysm screening

BACKGROUND

The long-term effects of abdominal aortic aneurysm (AAA) screening were investigated in extended follow-up from the UK Multicentre Aneurysm Screening Study (MASS) randomized trial.

METHODS

A population-based sample of men aged 65-74 years were randomized individually to invitation to ultrasound screening (invited group) or to a control group not offered screening. Patients with an AAA (3·0 cm or larger) detected at screening underwent surveillance and were offered surgery after predefined criteria had been met. Cause-specific mortality data were analysed using Cox regression.

RESULTS

Some 67 770 men were enrolled in the study. Over 13 years, there were 224 AAA-related deaths in the invited group and 381 in the control group, a 42 (95 per cent confidence interval 31 to 51) per cent reduction. There was no evidence of effect on other causes of death, but there was an overall reduction in all-cause mortality of 3 (1 to 5) per cent. The degree of benefit seen in earlier years of follow-up was slightly diminished by the occurrence of AAA ruptures in those with an aorta originally screened normal. About half of these ruptures had a baseline aortic diameter in the range 2·5-2·9 cm. It was estimated that 216 men need to be invited to screening to save one death over the next 13 years.

CONCLUSION

Screening resulted in a reduction in all-cause mortality, and the benefit in AAA-related mortality continued to accumulate throughout follow-up.

REGISTRATION NUMBER

ISRCTN37381646 (http://www.controlled-trials.com).

Technical advances with newer aortic endografts provide additional support to withhold the early endovascular repair of small abdominal aortic aneurysms until it is really needed

The idea of early endovascular aortic repair (EVAR) of "small" abdominal aortic aneurysms (AAAs) has gained attention over "watchful waiting," mostly due to the concern for losing the anatomic suitability for endovascular repair over time. Generally, small AAAs have longer, smaller, less angulated necks, and less tortuous iliac arteries than larger ones. Though the borderline anatomic characteristics were assumed to be contraindications for older generation endografts, the modifications of modern devices seem promising to overcome those limitations, in order to treat the small AAAs when reaching the 5.5 cm threshold. Moreover, early endovascular intervention has been proven neither cost effective nor beneficial for the patients' quality of life. This article evaluates the technical progress that could overcome the difficulties of those small AAAs that present technically demanding anatomies, thus advocating endovascular intervention when they reach the diameter threshold.

Geometrical factors as predictors of increased growth rate or increased rupture risk in small aortic aneurysms

Abdominal Aortic Aneurysms (AAAs) are focal dilation of the aorta that can lead to excessive enlargement and rupture over time. Current practice suggests intervention when the maximum diameter exceeds 5.5 cm, since in this diameter range the annual rupture risk outweighs the operative mortality. However, small AAA (<5.5 cm), though infrequently, may rupture or produce symptoms. Evidence from large randomized studies of small AAAs support the heterogeneity in patterns of growth and rupture potential among small AAAs. Elevated wall stress values have been implicated in AAAs rupture and rapid enlargement. Additionally, many studies have identified a strong correlation between certain geometric factors and elevated stress values. In this article we discuss the possibility that geometrical factors may have a predictive value to identify those small AAAs that have an increased risk of rupture or growth rate either during initial examination or during follow-up, making them amenable for early repair.

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.

Expanding Current EVAR Indications to Include Small Abdominal Aortic Aneurysms: A Glimpse of the Future

The traditional criterion of maximum transverse diameter is not sufficient to differentiate the small abdominal aortic aneurysms (AAAs) that are either prone to rupture or prone to enlarge rapidly. Wall stress may be a more reliable indicator with respect to these tasks. We review the importance of geometric features in rupture- or growth-predictive models and stress the need for further evaluation and validation of geometric indices. This study may lead to identifying those small AAAs that could justify early endovascular intervention.