Abstract P673: Intima-Media Thickness at the Near or Far Wall of the Common-Carotid-Artery in Cardiovascular Risk Assessment

Abstract

Background: Current guidelines recommend measuring carotid intima-media thickness (IMT) at the far wall of the common-carotid-artery (CCA). Objectives: To reliably quantify associations of near vs. far wall CCA-IMT with cardiovascular risk and their added predictive values. Methods: We analyzed participant-level data of 16 prospective studies from the Proof-ATHERO consortium. We pooled study-specific hazard ratios for cardiovascular disease (CVD, defined as coronary heart disease or stroke) using random-effects meta-analysis. Results: Individual records were available for 41,941 participants (mean age 61 years [SD=11]; 53% female; 16% with history of CVD; 10,423 CVD events, median follow-up 9.3 years). Mean baseline values of near and far wall CCA-IMT were 0.83 (SD=0.28) and 0.82 (SD=0.27) mm, differed by a mean of 0.02 mm (95% limits of agreement: -0.40 to 0.43) and were moderately correlated (r=0.44; 95% CI: 0.39-0.49). Near and far wall CCA-IMT were both approximately linearly associated with CVD risk. The respective hazard ratios per SD higher value were 1.18 (95% CI: 1.14-1.22; I 2 =30.7%) and 1.20 (1.18-1.23; I 2 =5.3%) when adjusted for age, sex, and history of CVD, and 1.09 (1.07-1.12; I 2 =8.4%) and 1.14 (1.12-1.16; I 2 =1.3%) in a multivariable adjusted model (all P<0.001). Assessing CCA-IMT at both walls provided a greater C-index improvement than assessing CCA-IMT at one wall only (+0.0046 vs. +0.0023 for near [P<0.001] or +0.0037 for far wall [P=0.006]). Conclusions: The associations of near and far wall CCA-IMT with incident CVD were positive, approximately linear, and similarly strong. Improvement in risk discrimination was highest when CCA-IMT was measured at both walls.