Common carotid intima-media thickness and risk of acute myocardial infarction - The role of lumen diameter

Background - It has been argued that lumen diameter of the common carotid artery should be taken into account in analyses on common carotid intima-media thickness (CIMT) and cardiovascular risk. Yet, no published report has dealt with this issue in detail. Methods - In the Rotterdam study baseline ultrasound images of the carotid arteries were made. During follow-up of 8.2 years, 656 new acute myocardial infarctions ( AMI) occurred. Regression analysis was used to study myocardial infarction relation to right ( or left) common CIMT with various adjustments for right-, or left-sided lumen diameter. Lumen adjustment was made by ( 1) a simple adjustment in a regression equation; ( 2) using the CIMT-to-lumen ratio; ( 3) using arterial mass, calculated as ({pi x[( lumen + near wall CIMT + far wall CIMT)/2](2)} - [pi x (lumen/2)(2)]). Results - AMI disease risk increased per standard deviation increase in common CIMT (0.177 mm): hazard ratio (HR) 1.28 (95% CI, 1.19 to 1.37). When lumen diameter was taken into account the HR was 1.26 ( 95% CI, 1.18 to 1.35). The HR for the CIMT-to-lumen ratio was 1.18 ( 95% CI, 1.11 to 1.27) and for arterial mass 1.28 ( 95% CI, 1.19 to 1.37). Additional analyses indicated that the CIMT-to-lumen ratio at lower CIMT levels appears to reflect arterial remodelling rather than risk of cardiovascular disease. Conclusion - We conclude that using the CIMT-to-lumen ratio yields the weakest associations. Other approaches for adjustment for common carotid lumen diameter do not affect the magnitude or precision of the association of common CIMT to risk of AMI. When the interest is in risk relations the preference goes to either CIMT or arterial mass measurement.