Carotid intima-media thickness, plaques, and Framingham risk score as independent determinants of stroke risk

Abstract

Background and Purpose - The Framingham stroke risk score (FSRS) and Framingham cardiovascular risk score (FCRS) estimate the individual absolute cardiovascular and stroke risks. Common carotid artery intima-media thickness (CCA-IMT) and carotid plaques (CPs) are markers of subclinical atherosclerosis and help in the early identification of presymptomatic individuals. The purpose of this study was to correlate Framingham risk score (FRS) with CCA-IMT and CPs and evaluate their respective contribution to stroke risk. Methods - In 510 consecutive patients with brain infarction and 510 matched controls, we calculated the FSRS and FCRS for each individual and performed carotid ultrasonography. Mean CCA-IMT was measured off-line at a central core laboratory, and presence of CPs was assessed. Results - FRS progressively increased according to tertiles of CCA-IMT (P for trend <0.0001). The part of the variances of FSRS and FCRS explained by CCA-IMT was respectively 11% and 20%. The relationships between CCA-IMT and FRS were significantly different between patients with or without CPs (P for interaction <0.005). With increasing CCA-IMT, the 10-year FRS gradually increased between 10% and 20% in the presence of CPs and between 5% and 20% in the absence of CPs. Multiple conditional logistic regression for matched sets showed that CCA-IMT, FCRS, and CPs were independently associated with stroke risk, with an odds ratio of 1.68 (1.25 to 2.26; P=0.0006), 2.16 (1.57 to 2.98; P<0.0001), and 2.73 (1.68 to 4.44; P<0.0001), respectively, meaning that each of them may be important for evaluation of the individual cardiovascular risk. Conclusions - CCA-IMT, CPs, and FRSs correlated well. The CCA-IMT value may help discriminate between subjects at low or high 10-year risk. © 2005 American Heart Association, Inc.