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

Simulations of the effects of scheduled abdominal aortic aneurysm repair on survival

I simulated survival with and without scheduled repair of abdominal aortic aneurysms with different diameters in different populations. The results imply that scheduled repair should be determined by the combination of a patient's monthly mortality hazard and aneurysm diameter. The median survival of some patients will be extended by the scheduled repair of aneurysms smaller than 55 mm, whereas the median survival of other patients will be curtailed by repair of any aneurysm. The results also suggest that, on average, surveillance is futile: the effect of scheduled aneurysm repair on an individual's median survival did not change but the cohort effect diminished as patients died during surveillance. The results of the U.K. Small Aneurysm Study were reproduced in simulation and are compatible with the repair of aneurysms smaller than 55 mm diameter. Epidemiological simulations suggest that past randomised controlled trials underestimate the effect of aneurysm repair today.

Screening for abdominal aortic aneurysm

Guidelines are systematically developed statements to assist patients and providers in choosing appropriate health care for specific clinical conditions. Consensus exists across guidelines on one-time screening of elderly men to detect and treat abdominal aortic aneurysm (AAA) ≥5.5 cm. However, the recommendations regarding other age groups, imaging intervals for small AAAs, inclusion of women, and cost-effectiveness have not been universally adopted. As many countries are considering the initiation of an AAA screening program, this is an overview on the current status of such programs.

Age-specific incidence, risk factors and outcome of acute abdominal aortic aneurysms in a defined population

BACKGROUND

Contemporary population-based data on age-specific incidence and outcome from acute abdominal aortic aneurysm (AAA) events are needed to understand the impact of risk factor modification and demographic change, and to inform AAA screening policy.

METHODS

In a prospective population-based study (Oxfordshire, UK, 2002-2014), event rates, incidence, early case fatality and long-term outcome from all acute AAA events were determined, both overall and in relation to the four main risk factors: smoking, hypertension, male sex and age.

RESULTS

Over the 12-year interval, 103 incident acute AAA events occurred in the study population of 92,728 (men 72·8 per cent; 59·2 per cent 30-day case fatality rate). The incidence per 100,000 population per year was 55 in men aged 65-74 years, but increased to 112 at age 75-84 years and to 298 at age 85 years or above. Some 66·0 per cent of all events occurred in those aged 75 years or more. The incidence at 65-74 years was highest in male smokers (274 per 100,000 population per year); 27 (96 per cent) of 28 events in men aged less than 75 years occurred in ever-smokers. Mean(s.d.) age at event was lowest in current smokers (72·2(7·2) years), compared with that in ex-smokers (81·2(7·0) years) and never-smokers (83·3(7·9) years) (P < 0·001). Hypertension was the predominant risk factor in women (diagnosed in 93 per cent), with 20 (71 per cent) of all 28 events in women occurring in those aged 75 years or above with hypertension. The 30-day case fatality rate increased from 40 per cent at age below 75 years to 69 per cent at age 75 years or more (P = 0·008).

CONCLUSION

Two-thirds of acute AAA events occurred at age 75 years or above, and more than 25 per cent of events were in women. Taken with the strong associations with smoking and hypertension, these findings could have implications for AAA screening.

Systematic review of cardiovascular disease and cardiovascular death in patients with a small abdominal aortic aneurysm

Background

Screening for abdominal aortic aneurysm (AAA) has reduced the rate of AAA rupture. However, cardiovascular disease is still a major cause of death in men with an AAA. The aim of this study was to assess cardiovascular risk in patients with a small AAA.

Methods

Standard PRISMA guidelines were followed. Analysis was performed of studies reporting cardiovascular outcomes in patients with a small AAA (30–54 mm). Weighted metaregression was performed for cardiovascular death in patients with a small AAA, and the prevalence of cardiovascular disease was reviewed.

Results

Twenty-one articles were identified describing patients with an AAA, and the prevalence of, and death from, cardiovascular disease. Ten of these reported cardiovascular death rates in patients with a small AAA. Some 2323 patients with a small AAA were identified; 335 cardiovascular deaths occurred, of which 37 were due to AAA rupture. Metaregression demonstrated that the risk of cardiovascular death was 3·0 (95 per cent c.i. 1·7 to 4·3) per cent per year in patients with a small AAA (R2 = 0·902, P &lt; 0·001). The prevalence of ischaemic heart disease (44·9 per cent), myocardial infarction (26·8 per cent), heart failure (4·4 per cent) and stroke (14·0 per cent) was also high in these patients.

Conclusion

The risk of cardiovascular death in patients with a small AAA is high and increases by approximately 3 per cent each year after diagnosis. Patients with a small AAA have a high prevalence of cardiovascular disease. Patients a small AAA should be considered for lifestyle modifications and secondary cardiovascular protection.

Screening for abdominal aortic aneurysms in outpatient primary care clinics

BACKGROUND

The US Preventive Services Task Force (USPSTF) guidelines recommend one-time abdominal aortic aneurysm ultrasound screening for men aged 65 to 75 years who ever smoked. Reported screening rates have been 13% to 26% but did not include computed tomography, magnetic resonance imaging, and nonaortic abdominal ultrasound, which provide adequate visualization of the aorta. The objective of this study was to evaluate rates of screening performed intentionally with ultrasound and incidentally with other abdominal imaging, determine rates of redundant screening, and evaluate patient and physician characteristics associated with screening.

METHODS

Cross-sectional study of patient encounters in 2007 and 2012 to determine abdominal aortic aneurysm screening trends in primary care practices. Participants included all patients who were seen in a primary care office and were eligible for screening by USPSTF guidelines. The primary outcome was percentage of eligible patients screened for abdominal aortic aneurysm by ultrasound or other abdominal imaging.

RESULTS

There were 15,120 patients eligible for screening in 2007, and 22,355 in 2012. Screening with ultrasounds increased from 3.6% in 2007 to 9.2% in 2012. Screening with any imaging that included the aorta increased from 31% in 2007 to 41% in 2012. Of 2595 screening ultrasounds performed in either cohort, 800 (31%) were performed on patients who had already undergone another imaging modality. Of 153 physicians who had >50 eligible patients, rates of abdominal aortic aneurysm screening ranged from 7.5% to 79% (median 39%, interquartile range 31%-47%), and rates of ultrasound screening ranged from 0% to 47% (median 6.3%, interquartile range 3.6%-11.4%). Physician characteristics positively associated with screened patients included female sex (odds ratio [OR] 1.32; 95% confidence interval [CI], 1.12-1.54), specialty (Internal Medicine vs Family Medicine: OR 1.32; 95% CI, 1.14-1.54), and location (academic medical center vs family health center: OR 1.30; 95% CI, 1.04-1.62).

CONCLUSIONS

Abdominal aortic aneurysm screening rates remain below 50%, but are improving over time. Screening by individual physicians varied widely, indicating substantial opportunity for educational interventions. Most abdominal aortic aneurysm screening is completed incidentally, and some patients later undergo unnecessary ultrasound screening. Before ordering screening, physicians and electronic health record-based reminder tools should ensure that the aorta has not been previously visualized.

Abdominal aortic feminism

A 79-year-old woman presented to a private medical practice 2 years previously for an elective ultrasound screening scan. This imaging provided the evidence for a diagnosis of an abdominal aortic aneurysm (AAA) to be made. Despite having a number of recognised risk factors for an AAA, her general practitioner at the time did not follow the guidance set out by the private medical professional, that is, to refer the patient to a vascular specialist to be entered into a surveillance programme and surgically evaluated. The patient became symptomatic with her AAA, was admitted to hospital and found to have a tender, symptomatic, 6 cm leaking AAA. She consented for an emergency open AAA repair within a few hours of being admitted to hospital, despite the 50% perioperative mortality risk. The patient spent 4 days in intensive care where she recovered well. She was discharged after a 12 day hospital stay but unfortunately passed away shortly after her discharge from a previously undiagnosed gastric cancer.

Scientific second-order 'nudging' or lobbying by interest groups: the battle over abdominal aortic aneurysm screening programmes

The idea that it is acceptable to 'nudge' people to opt for the 'healthy choice' is gaining currency in health care policy circles. This article investigates whether researchers evaluating Abdominal Aortic Aneurysm Screening Programmes (AAASP) attempt to influence decision makers in ways that are similar to popular 'nudging' techniques. Comparing two papers on the health economics of AAASP both published in the BMJ within the last 3 years, it is shown that the values chosen for the health economics modelling are not representative of the literature and consistently favour the conclusions of the articles. It is argued (1) that this and other features of these articles may be justified within a Libertarian Paternalist framework as 'nudging' like ways of influencing decision makers, but also (2) that these ways of influencing decision makers raise significant ethical issues in the context of democratic decision making.

Academic vascular unit collaboration with advertising agency yields higher compliance in screening for abdominal aortic aneurysm

To improve compliance with abdominal aortic aneurysm (AAA) screening in low compliance areas, individually tailored invitations were developed in collaboration with a professional advertising agency. Compliance increased in two intervention municipalities from 71.4% in 2010–2012 to 78.1% in 2013 (p = 0.025), and was then higher [odds ratio 1.7; 95% confidence interval 1.1–2.6; p = 0.013] than in two control municipalities in which compliance was unchanged (417/552 [75.5%] in 2010–12 and 122/180 [67.8%] in 2013). Compliance with AAA-screening can be increased by collaboration with a professional advertising agency, albeit at a comparably high cost.

Monocyte activity is linked with abdominal aortic aneurysm diameter

BACKGROUND

Systemic inflammation and increased matrix metalloproteinase (MMP) cause elastin degradation leading to abdominal aortic aneurysm (AAA) expansion. Several prospective studies report that statin therapy can reduce AAA expansion through anti-inflammation. We hypothesize that monocyte activity plays a pivotal role in this AAA development and this study examines patient peripheral blood monocyte cell adhesion, transendothelial migration, and MMP concentrations between AAA and non-AAA patients.

MATERIALS AND METHODS

Peripheral blood was collected and monocytes isolated from control (n=15) and AAA (n=13) patients. Monocyte adhesion, transmigration, and permeability assays were assessed. Luminex assays determined MMP-9 and tissue inhibitor of metalloproteinase-4 (TIMP-4) concentrations from cell culture supernatant and patient serum.

RESULTS

AAA patient monocytes showed increased adhesion to the endothelium relative fluorescence units (RFU, 0.33±0.17) versus controls (RFU, 0.13±0.04; P=0.005). Monocyte transmigration was also increased in AAA patients (RFU, 0.33±0.11) compared with controls (RFU, 0.25±0.04, P=0.01). Greater numbers of adhesive (R2=0.66) and transmigratory (R2=0.86) monocytes were directly proportional to the AAA diameter. Significantly higher serum levels of MMP-9 (2149.14±947 pg/mL) were found in AAA patients compared with controls (1189.2±293; P=0.01). TIMP-4 concentrations were significantly lower in AAA patients (826.7±100 pg/mL) compared with controls (1233±222 pg/mL; P=0.02). Cell culture supernatant concentrations of MMP and TIMP from cocultures were higher than monocyte-only cultures.

CONCLUSIONS

Monocytes from AAA patients have greater adhesion and transmigration through the endothelium in vitro, leading to elevated MMP-9 levels and the appropriate decrease in TIMP-4 levels. The ability to modulate monocyte activity may lead to novel medical therapies to decrease AAA expansion.

Sex differences in the association between smoking and abdominal aortic aneurysm

Background

It is unclear whether recommendations about ultrasound screening programmes for abdominal aortic aneurysm (AAA) among men should be extended to include women who smoke. The aim was to examine sex-specific dose–response associations between AAA risk and smoking status, pack-years smoked and time since smoking cessation.

Methods

Women in the Swedish Mammography Cohort and men in the Cohort of Swedish Men were followed up from 1998 to 2011. AAA was identified through linkage of the cohorts to the Swedish Inpatient Register and the Swedish National Register for Vascular Surgery (Swedvasc), and not through general ultrasound screening. Associations were estimated with Cox proportional hazards models.

Results

The cohorts included 35 550 women and 42 596 men, aged 46–84 years. During follow-up, AAA was identified in 199 women and 958 men. The incidence of AAA per 100 000 person-years was 76 among men who never smoked and 136 among women who currently smoke. Regarding AAA risk, women were more sensitive to current smoking (Pinteraction= 0·002). Compared with never smokers, the hazard ratio (HR) for AAA in current smokers with more than 20 pack-years was 10·97 (95 per cent confidence interval 7·41 to 16·26) among women and 6·55 (5·36 to 7·99) among men. Following smoking cessation, women had a more rapid decline in excess risk (Pinteraction &lt; 0·001). The risk was halved after 11 years (HR 0·51, 0·32 to 0·81) among women and after 23 years (HR 0·50, 0·42 to 0·60) among men.

Conclusion

There were sex differences in the associations between smoking status and AAA risk. These data support further investigation of targeted AAA screening among women who smoke.

Cost-effectiveness of the National Health Service Abdominal Aortic Aneurysm Screening Programme in England

BACKGROUND

Implementation of the National Health Service abdominal aortic aneurysm (AAA) screening programme (NAAASP) for men aged 65 years began in England in 2009. An important element of the evidence base supporting its introduction was the economic modelling of the long-term cost-effectiveness of screening, which was based mainly on 4-year follow-up data from the Multicentre Aneurysm Screening Study (MASS) randomized trial. Concern has been expressed about whether this conclusion of cost-effectiveness still holds, given the early performance parameters, particularly the lower prevalence of AAA observed in NAAASP.

METHODS

The existing published model was adjusted and updated to reflect the current best evidence. It was recalibrated to mirror the 10-year follow-up data from MASS; the main cost parameters were re-estimated to reflect current practice; and more robust estimates of AAA growth and rupture rates from recent meta-analyses were incorporated, as were key parameters as observed in NAAASP (attendance rates, AAA prevalence and size distributions).

RESULTS

The revised and updated model produced estimates of the long-term incremental cost-effectiveness of £5758 (95 per cent confidence interval £4285 to £7410) per life-year gained, or £7370 (£5467 to £9443) per quality-adjusted life-year (QALY) gained.

CONCLUSION

Although the updated parameters, particularly the increased costs and lower AAA prevalence, have increased the cost per QALY, the latest modelling provides evidence that AAA screening as now being implemented in England is still highly cost-effective.

Reasons for non-participation in population-based abdominal aortic aneurysm screening

Background

A population-based screening programme for abdominal aortic aneurysm (AAA) started in 2010 in Stockholm County, Sweden. This present study used individual data from Sweden's extensive healthcare registries to identify the reasons for non-participation in the AAA screening programme.

Methods

All 65-year-old men in Stockholm are invited to screening for AAA; this study included all men invited from July 2010 to July 2012. Participants and non-participants were compared for socioeconomic factors, travel distance to the examination centre and healthcare use. The influence of these factors on participation was analysed using univariable and multivariable logistic regression models.

Results

The participation rate for AAA screening was 77·6 per cent (18 876 of 24 319 men invited). The prevalence of AAA (aortic diameter more than 2·9 cm) among participants was 1·4 per cent. The most important reasons for non-participation in the multivariable regression analyses were: recent immigration (within 5 years) (odds ratio (OR) 3·25, 95 per cent confidence interval 1·94 to 5·47), low income (OR 2·76, 2·46 to 3·10), marital status single or divorced (OR 2·23, 2·08 to 2·39), low level of education (OR 1·28, 1·16 to 1·40) and long travel distance (OR 1·23, 1·10 to 1·37). Non-participants had a higher incidence of stroke (4·5 versus 2·8 per cent; P &lt; 0·001) and chronic pulmonary disease (2·9 versus 1·3 per cent; P &lt; 0·001). Daily smoking was more common in residential areas where the participation rate for AAA screening was low.

Conclusion

Efforts to improve participation in AAA screening should target the groups with low income, a low level of education and immigrants. The higher morbidity in the non-participant group, together with a higher rate of smoking, make it probable that this group also has a high risk of AAA.

High prevalence of abdominal aortic aneurysm in patients with three-vessel coronary artery disease

OBJECTIVES

Currently, the prevalence of abdominal aortic aneurysm (AAA) in patients with coronary artery disease (CAD) and the correlation between CAD severity and AAA prevalence are not clearly known. We conducted a prospective study to determine the prevalence of AAA in patients undergoing coronary angiography and to determine the risk factors and a coronary profile associated with AAA.

METHODS

Over an 18-month period, abdominal aortic ultrasound was performed on 1,000 patients undergoing coronary angiography for suspected or known CAD, or prior to valve surgery. Clinical characteristics and coronary profile were collected from the patients.

RESULTS

The overall number of previously repaired, already diagnosed, and new cases of AAA in the study population was 42, yielding a prevalence of 4.2%. Among the patients with newly detected AAAs, only two had an AAA diameter of >54 mm and were therefore treated surgically. In men aged ≥ 65 years, the prevalence reached 8.6%, while in men with three-vessel CAD it was 14.4%. Multivariate analysis showed that age ≥ 65 years (p = .003), male gender (p = .003), family history of AAA (p = .01), current smoking (p = .002), and three-vessel CAD (p < .001) were significantly associated with a higher prevalence of AAA.

CONCLUSION

The prevalence of AAA was high in men aged ≥ 65 years and in those with three-vessel CAD regardless of age. While our findings do not prove the cost-effectiveness of screening for AAA in these high risk patients, they do support the usefulness of a quick ultrasound examination of the abdominal aorta during routine transthoracic echocardiography in such patients.

Modeling the Growth of Infrarenal Abdominal Aortic Aneurysms

BACKGROUND

Abdominal aortic aneurysm (AAA) growth is a complex process that is incompletely understood. Significant heterogeneity in growth trajectories between patients has led to difficulties in accurately modeling aneurysm growth across cohorts of patients. We set out to compare four models of aneurysm growth commonly used in the literature and confirm which best fits the patient data of our AAA cohort.

METHODS

Patients with AAA were included in the study if they had two or more abdominal ultrasound scans greater than 3 months apart. Patients were censored from analysis once their AAA exceeded 5.5 cm. Four models were applied using the R environment for statistical computing. Growth estimates and goodness of fit (using the Akaike Information Criterion, AIC) were compared, with p-values based on likelihood ratio testing.

RESULTS

Of 510 enrolled patients, 264 met the inclusion criteria, yielding a total of 1861 imaging studies during 932 cumulative years of surveillance. Overall, growth rates were: (1) 0.35 (0.31,0.39) cm/yr in the growth/time calculation, (2) 0.056 (0.042,0.068) cm/yr in the linear regression model, (3) 0.19 (0.17,0.21) cm/yr in the linear multilevel model, and (4) 0.21 (0.18,0.24) cm/yr in the quadratic multilevel model at time 0, slowing to 0.15 (0.12,0.17) cm/yr at 10 years. AIC was lowest in the quadratic multilevel model (1508) compared to other models (P < 0.0001).

CONCLUSION

AAA growth was heterogeneous between patients; the nested nature of the data is most appropriately modeled by multilevel modeling techniques.