Abdominal aorta aneurysm: an exceptional expression of atherosclerotic disease in type II diabetes.

An aortic abdominal aneurysm (AAA) is a potentially lethal disease. In a population with one or multiple cardiovascular risk factors, its prevalence is estimated at 1.6% (aneurysm size .3 cm) and 0.5% (aneurysm size .4 cm), with a higher occurrence in male vs. female patients. In the presence of type II diabetes, the prevalence of all cardiovascular disease (including carotid stenosis, AAA, and peripheral artery disease) is doubled. The Veterans Affairs Cooperative Study Investigators study showed a higher prevalence of AAA in their screened population. In addition, a negative association was found between AAA and the presence of diabetes (with no difference in male vs. female). Despite the fact that AAA is an expression of atherosclerotic disease (with a large amount of pro-inflammation), the prevalence of AAA in diabetic patients is less than expected. In other words, AAA in diabetes is a non-frequent macrovascular complication related to atherosclerotic disease. Such a conclusion appears quite remarkable; premature macrovascular disease in other vascular beds (e.g. presence of microalbuminuria and increased intima-media thickness of the carotid artery) is already present in an early (pre-) diabetic stage. Do diabetic patients display a marked AAA expansion and, consequently, should they be followed more aggressively? This important clinical question is tackled by Golledge et al. In a large screening cohort (in which 12% of subjects had diabetes), males with a small AAA (between 30 and 34 mm) were prospectively followed for AAA expansion by ultrasound for 3 years. Diabetes was defined as fasting blood glucose levels .7.0 mmol/L, or history of, or treatment for hyperglycaemia according to the American Diabetes Association 2006 guidelines. They found that the co-existence of diabetes resulted in a less expanding AAA with a mean yearly increase in aortic diameter of 0.63 mm in patients with diabetes, vs. 1.20 mm in non-diabetic patients. Unfortunately, they did not report whether suprarenal AAA or infrarenal AAA prevailed in their cohorts and whether renal function was impaired due to a juxtarenal position, since an impaired renal function is a predictor for worse clinical outcome (e.g. mortality). In addition, all their evaluations of AAA size have been performed with an transabdominal ultrasound which is known to be less precise than CT scanning, especially for infrarenal AAA. Furthermore, it should be noted that the initial size of small AAAs is a major determinant for progression in growth rate. In a large prospective observational study, small infrarenal AAAs (3.0–3.9 cm) expanded slowly, whereas larger ones (4.0–4.9 cm) had a higher expansion rate. However, these differences in expansion rate between smaller and larger AAAs were not seen in diabetic subjects. Despite a reduced prevalence of AAA in diabetic patients, co-existence of diabetes has been associated with a decreased 2.5-year survival due to co-existing atherothrombotic coronary disease. Taken together, these observations show that the AAA expansion rate in diabetes is delayed compared with non-diabetic patients. Therefore, a small AAA in diabetic patients will probably not reach .5 cm in size within a 5 year interval, which is an indicator of the need for surgical repair. In their report, Golledge et al. found that patients with diabetes, after adjusting for smoking history and co-existence of peripheral arterial disease, had an odds ratio of 0.18 [0.06–0.57; 95% confidence interval (CI)] of experiencing above median growth compared with those in the non-diabetic cohort (even after including dyslipidaemia and glucose). In addition, no statistical association was found for serum glucose levels and a marker for advanced glycation, N1-carboxymethyl lysine (CML). Unfortunately, Golledge et al. could not show blood glycated haemoglobin (HbA1c), a wellknown marker that reflects average glucose burden. These observations are quite surprising and may have clinical importance;