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

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.