Abstract P331: Associations Of Coronary Heart Disease With Common Carotid Artery Near And Far-wall Intima-Media Thickness (IMT): The Multi-Ethnic Study Of Atherosclerosis.

Background: Intima-media thickness (IMT) as measured on ultrasound images of the common carotid artery (CCA) is associated with cardiovascular events and used to measure the effects of lipid lowering interventions. Far wall CCA IMT is favored over near wall IMT based on the physics of ultrasound. Materials and Methods: We studied 6606 members of the Multi-Ethnic Study of Atherosclerosis (MESA), a longitudinal cohort study (mean age 62.1 years; 52.7% female) who had near wall and far wall CCA IMT measurements. Multivariable linear regression models were used to estimate model goodness-of-fit of near wall IMT, far wall IMT, and mean IMT with Framingham risk factors (FRF). Multivariable Cox proportional hazards models were used to estimate hazard ratios for incident coronary heart disease (CHD) events for each IMT variable. Change in Harrell’s C-statistic was used to compare the incremental value of each IMT variable when added to FRF. Results: Mean IMT had the strongest association with risk factors (R2 = 0.31), followed by the near wall (R2 = 0.26) and far wall IMT (R2 = 0.22). Far wall IMT improved the prediction of coronary artery disease events (change in C statistic: 0.009; 95% Confidence Intervals: 0.004, 0.015; p= 0.001) as did mean IMT (p=0.033) but near wall IMT did not. Conclusion: Far wall CCA IMT had the strongest association with incident CHD whereas combined near wall and far wall IMT had the strongest association with risk factors. Selected IMT variables may give different results in intervention trials than in outcome studies.