Ultrasound-determined intima-media thickness and atherosclerosis. Direct and indirect validation.

To evaluate ultrasonographically determined intima-media thickness as a measure of early atherosclerosis, three studies were performed. Ultrasound measurements of intima-media thickness in the carotid artery were directly validated by comparing the same thickness measured by light microscopy. The values were closely correlated (r = .82, P < .001). Intima-media thickness determined by light microscopy was consistently smaller than that determined by ultrasound, probably due to shrinkage during histological preparation. As an indirect validation, mean intima-media thickness was calculated in three large groups of patients with no plaque (n = 224), one plaque (n = 105), and one circumferential or two or more plaques (n = 54) in the carotid bifurcation. Intima-media thickness increased significantly with increasing plaque score, indicating that diffuse intima-media thickening is more pronounced with more severe atherosclerosis. The intima-media thickness also increased with increasing multifactorial cardiovascular risk, reflecting a positive relation between signs of early atherosclerosis and the burden of known risk factors for the disease. Our studies support earlier findings that have found that ultrasonographically determined intima-media thickness is a valid way to study early atherosclerosis.