Carotid and femoral intima-media thickness as early markers of atherosclerosis. The advantages, the limits

The intima-media thickness (IMT) is defined as the distance between the hyperechogenic inner (blood-intima interface) and outer line (media-adventitia interface) of the arterial wall. It is a surrogate marker of atherosclerotic damage. No consensus guidelines are available on which site and how carotid IMT sampling should be performed, and comparison among data from different studies is difficult. IMT is the "phenotype" of the early phases of atherosclerotic disease and is related to the main traditional risk factors. Moreover, IMT is a marker of organ damage either in the heart or in other vascular districts. Although threshold IMT values for the prediction of cardiovascular events have not been identified, high IMT values are associated with an increased occurrence of cardiovascular events. Indeed, an IMT = 0.9 mm was demonstrated to be associated with an increased cardiovascular risk even after age adjustment. The value of IMT as an independent risk factor is still under debate, especially in young patients at intermediate risk. Moreover, the IMT regression reported in therapeutic trials with statins and antihypertensive drugs was only weakly or not at all associated with a decrease in cardiovascular events. In comparison to carotid IMT, femoral IMT is more strictly correlated with the severity of coronary artery disease and the need for revascularization in effort angina. The simultaneous measurement of carotid and femoral IMT may improve risk stratification in patients with coronary heart disease. The challenge for the future is to establish an IMT cut-off value for a better definition of the individual cardiovascular risk. Such cut-off value may be derived from the combined measurement of carotid and femoral IMT.