Abstract 1012: Added Value of the Common and Internal Carotid Intima-media Thickness (IMT) for the Prediction of Cardiovascular Events: The Framingham Offspring Study
Purpose: Carotid intima-media thickness (IMT) can be measured in the common carotid artery (CCA) or the proximal internal carotid artery (ICA). We study which measurement might add predictive value to the Framingham Risk Score.
Materials and methods: Framingham risk factors, the mean CCA IMT and the maximum ICA IMT (max ICA IMT) were measured in 2946 members of the Framingham Offspring Cohort mean age 58 years, 55% women. Cardiovascular outcomes were evaluated over an average 7.2 years of follow-up. Multivariable Cox-proportional hazards models were used to determine the incremental predictive value of IMT to risk factors. Reclassification of non-incident/incident cases was evaluated using low, intermediate and high Framingham risk score levels after adding IMT.
Results: There were 297 cardiovascular events during follow-up. After adjustment for risk factors, the standardized hazard ratio for max ICA IMT and mean CCA IMT were 1.21 (95% C.I.: 1.13, 1.29; p<0.0001) and 1.12 (95% C.I.: 1.02, 1.24; p<0.02) respectively. The C-statistic for a risk factor only model was 0.748 (95% C.I. = 0.719, 0.776), increased significantly when max ICA IMT was added to the model (0.757; 95% C.I. = 0.730, 0.785) and not mean CCA IMT (0.751; 95% C.I. = 0.723, 0.779). The net reclassification improvement was significant for max ICA IMT (p= 0.0002) and not for mean CCA IMT (p= 0.99).
Conclusion: Max ICA IMT is more strongly predictive of cardiovascular outcomes than mean CCA IMT and adds predictive value to the Framingham risk factors and risk score.