Combined use of carotid IMT and traditional risk factors in predicting cardiovascular events in intermediate risk individuals

Introduction: Carotid artery intima media thickness (IMT) plays a key role in atherosclerosis assessment. We performed a longitudinal, observational study to investigate whether Max-IMT, measured in clinical practice, can be combined with the Framingham Risk Score (FRS) to improve the prediction of cardiovascular events in patients at low/intermediate risk (FRS <20%) for such events. Material and Methods: 1969 patients attending our Lipid Clinic received ultrasonic measurements of Max-IMT and its distribution was presented in age- and sex-specific tables from which a Max-IMT percentile (IMTperc) was derived for each patient. 242 patients with FRS <20% were followed-up for about 5 years. 24 of them had a cardiovascular event in the next 5 years. Results: Both FRS and IMTperc were independent outcome predictors (P<0.006 and p<0.02, respectively; Cox model), with hazard ratio of 9.5 (95% CI 2.4, 37.5; P=0.001) in patients in whom both IMTperc and FRS were above specific values. In Kaplan-Meier analyses, adding the IMTperc improved the predictive value of the FRS (χ2=13.7, p=0.003; log-ramk test). Patients with elevated values (even though FRS <20%) had the same risk as patients with 20% <FRS30%. The FRS underestimated the risk of patients with an IMTperc above the specific value. An equation to adjust the FRS on the basis of a raised IMTperc is suggested. Conclusions: The combined use of conventional risk factors and ultrasonic measurements of carotid IMT significantly increases the ability to predict cardiovascular events in patients at low/intermediate risk.