Abstract 9962: Carotid Intima-Media Thickness and Carotid Distensibility are Associated with Incident Atrial Fibrillation: The Atherosclerosis Risk in Communities (ARIC) Study

Background Increased carotid intima-media thickness (cIMT) and decreased carotid distensibility are associated with an increased risk of myocardial infarction and stroke. It is unclear whether these carotid indices are associated with atrial fibrillation (AF) incidence. In the ARIC cohort, we assessed whether carotid indices are associated with an increased risk of AF and improve risk prediction of AF. Methods We included 10,077 (mean age, 56.8 ± 5.7 yrs; 56% female; 24% black) subjects who were followed from 1990-92 through 2009. cIMT, arterial diameter change (ADC), Peterson’s elastic modulus (Ep), Young’s elastic modulus (YEM), and β index were measured using carotid ultrasound in 1990-92. Incident AF cases were identified from ECGs at study exams and hospitalization discharge codes. We used multivariable Cox proportional hazards models to assess association between carotid indices and AF. Using the CHARGE AF score as the benchmark, we determined improvement in model discrimination by estimating the C statistic and calculating the net reclassification improvement (NRI) and integrated discrimination improvement (IDI). Results During follow-up (median 17.8 yrs), there were 1,028 incident AF cases. Greater levels of cIMT, Ep, and β index were significantly associated with an increased risk of AF (Table 1). The addition of cIMT and cIMT + plaque improved model discrimination marginally: C statistic (95% CI) improved from 0.795 (0.760-0.830) to 0.796 (0.761-0.831) and 0.797 (0.762-0.832), respectively. Although NRI was not statistically significant, IDI was significant for cIMT (P=0.02) and cIMT + plaque (P=0.005). Ep and β index did not improve model discrimination. Conclusions Increased cIMT and decreased carotid distensibility are associated with an increased risk of AF and modestly improve risk prediction of AF. This finding reinforces an emerging viewpoint on AF pathogenesis: AF is not purely an electrical disease, but is also a ‘vascular’ disease.