Combination of carotid intima-media thickness and plaque for better predicting risk of ischaemic cardiovascular events

Background Several indices of carotid atherosclerosis have been studied to investigate their associations with the risk of cardiovascular disease. However, the best index of carotid atherosclerosis that predicts the risk of cardiovascular disease remains unclear. Objective To investigate the index that best reflects the relationship between carotid atherosclerosis and subsequent ischaemic cardiovascular disease (ICVD) events. Design An observational longitudinal study with a 5-year follow-up. Participants 1734 Chinese subjects (623 men, 1111 women) aged 43-79 years at baseline. Main outcome measures ICVD events, including coronary heart disease and ischaemic stroke. Results Carotid intima-media thickness (IMT) at baseline was significantly associated with the risk of ICVD among participants without carotid plaque (multivariable adjusted HR=1.59, 95% CI 1.04 to 2.45) but not among those with plaque (HR=1.04, 95% CI 0.78 to 1.39). However, the total area of plaques (HR=1.29, 95% CI 1.08 to 1.55), the number of plaques (HR=1.14, 95% CI 1.02 to 1.27) and the number of segments with plaque (HR=1.45, 95% CI 1.09 to 1.93) were all significantly associated with ICVD in participants with plaque. Thus, carotid IMT and the number of segments with plaque were combined to establish a summary index-the total burden score (TBS) of carotid atherosclerosis-which was shown to improve the prediction of the 5-year risk of ICVD significantly compared with IMT or the number of segments with plaque alone. The c-statistics and net reclassification index showed that TBS improved the risk prediction by increases of 6.0% and 17.1%, respectively, compared with the conventional risk score. Conclusion The TBS could significantly improve the prediction of ICVD risk and should be used in clinical practice and future studies.