Additional Issues on Screening,Prevention,and Treatment of Abdominal Aortic Aneurysms

Abstract

The prevalence of abdominal aortic aneurysms (AAAs) and AAA-related deaths are steadily declining in some countries as a result of the reduction in smoking rates. It was thus suggested that screening programs that do not target high-risk populations are likely to have very low AAA detection rates. However, this may not apply to other countries that do not exhibit similar reductions in smoking rates. It was assumed that by using the U.S. Preventive Services Task Force screening criteria (men 65-75 years with smoking history) less than 30% of AAAs would be captured. A more extensive scoring system that includes additional risk factors such as the presence of carotid artery or peripheral arterial disease, obesity, hypertension, and so on, may identify almost 90% of AAAs. This article discusses this and other issues on screening, prevention, and treatment of AAAs.

We congratulate Tillman, Lee, and Whitty (2013) for their timely review on abdominal aortic aneurysms (AAAs). A few additional comments are provided.

It has been known for more than 50 years that smoking is a powerful predictor of AAA risk (Hammond & Horn, 1958). This is an important message in terms of prevention. It is also of interest that smoking may exert an adverse effect on other types of aortic disease (Kakafika & Mikhailidis, 2007) and possibly on aortic stiffness (Doonan et al., 2010). Smoking also increases the risk of vascular disease in general and may even adversely influence other risk factors (Katsiki, Papadopoulou, Fachantidou, & Mikhailidis, 2013; Tsiara, Elisaf, & Mikhailidis, 2003).

We do not know if passive smoking increases the risk of AAAs, but it may affect aortic inflammation (Kakafika & Mikhailidis, 2007). It may be very difficult to prove such a relationship because AAA-related deaths also occur in nonsmokers in a percentage as high as 22% (Kent et al., 2010). However, how many of these nonsmokers will be exposed to considerable passive smoking? Whatever the situation, it is important to consider that nonsmokers have a democratic right not to inhale other people’s smoke (Katsiki, Hatzitolios, & Mikhailidis, 2011)!

Independent studies from Sweden (Svensjo et al., 2011), Australia (Norman, Spilsbury, & Semmens, 2011), New Zealand, England, and Wales (Sandiford, Mosquera, & Bramley, 2011) demonstrate a considerable reduction in the prevalence of AAAs due to the reduction in tobacco use in these countries. A similar reduction was reported in AAA-related deaths in the United States from 11,485 in 1991 to <8,000 in 2007 (Centers for Disease Control and Prevention, n.d.). As a consequence of this decline in AAA prevalence, it has been stated that screening programs that do not target high-risk populations are likely to have very low AAA detection rates (Lederle, 2011). Nevertheless, screening programs may be effective in countries with no similar reduction in smoking habits and without having certain epidemiological data on the prevalence of the disease. Additionally, the international dissemination of the current AAA screening programs will help in optimization of screening intervals and benefits of the surveillance of the sub-aneurysmal aorta (Stather, Dattani, Bown, Earnshaw, & Lees, 2013).

The opposite opinion was supported in a retrospective study on 3.1 million patients in which using the U.S. Preventive Services Task Force selection criteria for screening (men 65-75 years with smoking history) only 29.5% of AAAs would be captured. In contrast, the use of a scoring system that included specific risk factors for AAAs (age, gender, high blood pressure, coronary artery disease, lower extremity peripheral arterial disease, carotid artery stenosis, history of a cerebrovascular event, smoking, and obesity) would identify 88.6% of all AAAs, if applied to a population aged 50 to 84 years, or 59% if applied to people 50 to 75 years (Kent et al., 2010). Thus, it has been concluded in a recent study that inappropriate AAA screenings are decreasing, and this demonstrates the greater awareness and application of the AAA screening guidelines by primary care providers (Chun, Teng, Van Spyk, Carson, & Lee, 2013).

In terms of drug treatment for AAAs, we agree with Tillman et al. (2013) that there is nothing definitive to offer (Paraskevas, Wierzbicki, & Mikhailidis, 2012). Nevertheless, we must always consider that AAAs are considered as coronary heart disease equivalents (Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults, 2001). Therefore, aggressive risk factor management is mandatory not only because of possible beneficial effects on AAAs but also because of the high risk of other vascular events (e.g., myocardial infarction). It follows that if screening programs are encouraged, as advocated by Tillman et al. (2013), then more patients with asymptomatic AAAs will receive preventive treatment for all forms of vascular disease. There is indeed evidence that even short-term administration of statins preoperatively decreases AAA perioperative morbidity and mortality (Paraskevas, Liapis, Hamilton, & Mikhailidis, 2006, Paraskevas, Veith, Liapis, Mikhailidis, 2012).

As we get better at preventing and treating all forms of vascular disease, a new risk will emerge. As pointed out by Tillman et al. (2013), lifestyle measures need to be improved in patients with AAAs. An adverse lifestyle (especially smoking) is associated with an increased risk of cancer, which becomes more evident as vascular patients survive for longer periods (Paraskevas, Mikhailidis, & Veith, 2012).

We often hear from patients that now that they are on statins and other preventive treatment, lifestyle measures (with special emphasis on smoking) do not matter much. This is just not true since in some studies the risk of vascular events is higher in smokers taking a statin than in nonsmokers in the placebo group (Milionis, Rizos, & Mikhailidis, 2001). Therefore, despite statin use, the risk remains high in smokers (Athyros et al., 2012).

Research in AAA pathogenesis may be helped by the availability of animal models although undoubtedly these will have some limitations (Paraskevas, Mikhailidis, & Perrea, 2008).

Targeting AAA screening to specific high-risk populations and more research are definitely needed to help achieve the goal set by Tillman et al. (2013)—the eradication of AAA-related mortality. We hope that their vision translates into reality!