Variations in common carotid artery intima-media thickness during the cardiac cycle: implications for cardiovascular risk assessment.

BACKGROUND: Common carotid artery intima-media thickness (IMT), a measure of atherosclerosis, varies between peak systole and end-diastole. This difference might affect cardiovascular risk assessment. METHODS: IMT measurements of the right and left common carotid arteries were synchronized with an electrocardiogram, using the R wave for end-diastole and the T wave for peak systole. IMT was measured in 2,930 members of the Framingham Offspring Study. Multivariate regression models were generated with end-diastolic IMT, peak systolic IMT, and change in IMT as dependent variables and Framingham risk factors as independent variables. End-diastolic IMT estimates were compared with the upper quartile of IMT on the basis of normative data obtained at peak systole. RESULTS: The average age of the study population was 57.9 years. The average difference in IMT during the cardiac cycle was 0.037 mm (95% confidence interval, 0.035-0.038 mm). End-diastolic IMT and peak systolic IMT had similar associations with Framingham risk factors (total R(2) = 0.292 vs 0.275) and were significantly associated with all risk factors. In a fully adjusted multivariate model, thinner IMT at peak systole was associated with pulse pressure (P < .0001), low-density lipoprotein cholesterol (P = .0064), age (P = .046), and no other risk factors. Performing end-diastolic IMT measurements while using upper quartile peak systolic IMT normative data led to inappropriately increasing by 42.1% the number of individuals in the fourth IMT quartile (high cardiovascular risk category). CONCLUSION: The difference in IMT between peak systole and end diastole is associated with pulse pressure, low-density lipoprotein cholesterol, and age. In this study, the mean IMT difference during the cardiac cycle led to an overestimation by 42.1% of individuals at high risk for cardiovascular disease.

Duke Scholars

Author Michael J Pencina Biostatistics & Bioinformatics, Division of Biostatistics