The fastest progression of carotid intima media thickness is associated with increased vascular events in the Improve study

Object of study: We measured the 15-month IMT progression in 3703 European high-risk subjects (so defined for the presence of at least three vascular risk factors) enrolled in the IMPROVE Study, and assessed its association with vascular events (VEs) occurring during the subsequent 21.5 months of follow-up. Methods: Progression of mean and maximum IMT of the left and right common carotids, bifurcations, internal carotid arteries and of the whole carotid tree as well as the fastest IMT-progression detected in the whole carotid tree, regardless of its location, were included in a Cox proportional hazards model as predictors of vascular events. Results: All IMTs significantly progressed during 15 months (all p< 0.0001), but only the Fastest-IMTprogr was significantly associated with the risk of VEs (P=0.0025; after adjustment for centre, risk factors, therapies, baseline-IMT and inter-adventitia common carotid diameter). When data were analyzed with reclassification approach, the inclusion of Fastest-IMTprogr into a model based on Framingham risk factors and baseline-IMTs significantly added to the overall risk discrimination (P=0.002). Based on signals and noises, it can be estimated that using the Fastest-IMTprogr 2.0 years of follow-up are sufficient to be 95% confident, at individual level, that an IMT change is a real anatomical change and not the result of measurement variability. The same figure for the best of the other variables considered (IMTmean-max-prog) was13.3 years. Conclusions: The fastest carotid IMT-progression, being associated with an increased risk of VEs in high-risk European patients, represents a novel risk marker, and/or a potential target for therapy.