Predictive value of carotid 2-dimensional ultrasound

Several pieces of evidence provide a rationale for an association between disease of the extracranial carotid arteries and incident coronary artery disease (CAD): (1) patients with transient ischemic attack are most likely to die from CAD; (2) atherosclerosis of the extracranial carotid arteries is correlated with that of the coronary arteries; (3) stenosis of the extracranial carotid arteries is associated with incident CAD; (4) risk factors for extracranial carotid atherosclerosis are also risk factors for CAD; and (5) there is an association between wall thickness of the extracranial carotid arteries (extracranial intimal medial thickness [IMT]) and prevalent CAD, as well as CAD and stroke. Accordingly, large population-based studies have demonstrated an association between IMT and incident CAD and stroke in younger (Atherosclerosis Risk in Communities study, 45 to 65 years of age) as well as older (Cardiovascular Health Study, > or =65 years of age) samples. IMT, measured at 1 point in time, is likely to be an excellent reflection of an individual's past exposure to risk factors. However, a single measure of IMT might bear an imperfect relation to incident events, because current risk may be influenced more by current risk factor burden than by past exposure. Longitudinal studies have shown an association of risk factors with IMT progression, and clinical trials have demonstrated that lipid-lowering therapy retards the rate of progression of disease. In addition, IMT progression has been shown to correlate with incident CAD. We therefore suggest that the best index of future CAD risk may be progression of IMT rather than IMT itself.