Clinical and therapeutic value of carotid intima-media thickness

Carotid Intima Media Thickness (IMT) has been widely used to predict cardiovascular events in primary and secondary prevention studies. Yet, the power of IMT to reclassify risk level on top of conventional risk assessment based on classical risk factors remains unsettled. In fact, recent data indicate that the prognostic power of IMT is lower than that provided by the identification of carotid plaques. The role of IMT as surrogate endpoint to assess the efficacy of cardiovascular protective therapies is also still debated. In fact, no studies have ever been designed and powered to show a relationship between changes in carotid IMT during follow-up and cardiovascular events. Recently, two meta-analysis of trials using IMT as surrogate endpoint failed to demonstrate an association between IMT regression and cardiovascular events. The reasons for the lack of predictive role for changes in IMT are uncertain. It has been shown that IMT is not a pure atherosclerotic index, being substantially affected by age and hemodynamic factors including blood pressure and vessel wall shear stress. In addition, the status of carotid vessels does not strictly reflect that of coronary arteries. Finally, intra and inter-observer variability of measurements may further limit the association between IMT changes in individual patients and cardiovascular risk. Thus, IMT represents a valuable risk marker in population studies but its role for tailoring cardiovascular therapy in clinical practice remains currently uncertain.