Abstract P340: Associations between Subclinical Carotid Atherosclerosis and Future Risk of Abdominal Aortic Aneurysm: the Atherosclerosis Risk in Community (ARIC) Study

Abstract

Background: Abdominal aortic aneurysm (AAA) is a potentially lethal vasculopathy that shares multiple risk factors with conventional atherosclerotic disease, including advanced age, male sex, hypertension, and smoking. However, it is still debated whether subclinical atherosclerosis is an independent risk factor for AAA. Hypothesis: Subclinical carotid atherosclerosis is positively associated with future risk of AAA, independent of shared cardiovascular risk factors. Methods: We included 15,363 ARIC participants (74% whites) who had measures of carotid ultrasound at baseline (1987-89) at 45-64 years of age. Carotid intima-media thickness (cIMT) was measured bilaterally in the common carotid artery, carotid bifurcation, and internal carotid artery. Mean cIMT was estimated by combining the averages of cIMT measures at the 6 carotid sites. The presence of atherosclerotic plaque at any of the 6 segments was defined based on wall thickness ≥1.5 mm, or the presence of luminal encroachment or irregular intimal surface, or characteristics of arterial wall structural heterogeneity. Clinical AAAs were ascertained through hospital discharge diagnoses and death certificates through 2010. We used Cox proportional hazard models to examine the association between baseline carotid ultrasound measures and subsequent occurrence of clinical AAA. Results: In the total study sample (age 54±6 years, 45% men), the median (25 th to 75 th percentiles) cIMT at baseline was 0.71 (0.62 to 0.82) mm. Over an average of 21 years of follow up, a total of 392 clinical AAAs (74% male and 85% Whites) were ascertained. After adjustment for age, sex and race, participants in the highest quartile of baseline cIMT had 2.25 times higher risk of AAA (95% CI: 1.81, 2.79) compared to those in the lower 75 percentile. The presence of carotid atherosclerotic plaque at baseline was associated with 1.77 times increased risk of AAA (95% CI: 1.44, 2.17) after adjustment for age, sex and race. The associations for cIMT and atherosclerotic plaque remained significant after additional adjustment for baseline height, pack-years of smoking, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and hypertension: HR=1.66 (95% CI: 1.32, 2.08) for cIMT quartile 4 vs lower 75 percentile and 1.34 (95% CI: 1.08, 1.66) for presence of carotid atherosclerotic plaque. Further exclusion of participants with history of coronary heart disease or stroke at baseline slightly attenuated but did not abolish the associations of cIMT and atherosclerotic plaque with AAA (p<0.05 after the exclusions). Conclusion: Our study findings suggest that subclinical carotid atherosclerosis in middle-age is independently associated with future risk of clinical AAA.