On quantifying plaque size and intima-media thickness in carotid and femoral arteries. Comments on results from a prospective ultrasound study in patients with familial hypercholesterolemia.

Abstract

The aim of the present analysis in an ongoing observational study was to evaluate the possibility of measuring plaque size in ultrasound images from carotid and femoral arteries and the usefulness of quantitative plaque measurements in such a prospective study. Twenty-five patients with carotid plaques were identified in a group of patients with familial hypercholesterolemia (n = 50) compared with 7 subjects in a low-risk control group (n = 47). Only 20 of the 32 recorded plaques were accessible for quantitative follow-up measurements of area, base length, and thickness, which represents only 21% of all subjects investigated. In contrast, paired observations of intima-media thickness in the common carotid artery were available in 98% and in the carotid bulb in 87% of the subjects investigated. In those with paired observations of plaque area available, the data indicated a close relationship between the 2-year change recorded in plaque area and the 2-year change in intima-media thickness measured in a 10-mm-long predefined section of the carotid bulb (r = .81, P < .001, n = 19). The corresponding relationship between change in plaque area and change in a 10-mm-long section of the common carotid artery was r = .38 and P < .05 (n = 20). Quantitative measurements of plaques in the femoral arteries were also performed, but the results from these measurements were in most cases judged not to be useful. However, measurements of intima-media thickness in a 15-mm-long predefined section of the common femoral artery may be performed in a reproducible way in most patients. We conclude that the usefulness of plaque area measurements in prospective studies of the carotid artery seems limited because plaques available for quantitative measurements are present in only a small proportion of subjects. However, reproducible measurements of intima-media thickness in a predefined section of the carotid bulb are achievable in most subjects, and our data indicate that the changes recorded over time in the carotid bulb closely mirror changes occurring in the size of atherosclerotic plaques within the carotid artery region. In addition, present data indicate that measurements of intima-media thickness in the common carotid artery complement measurements performed in the carotid artery bulb in the study of early atherosclerosis.