Background and Purpose— Carotid plaque area measured by ultrasound (cross-sectional area of longitudinal views of all plaques seen) was studied as a way of identifying patients at increased risk of stroke, myocardial infarction, and vascular death.

Methods— Patients from an atherosclerosis prevention clinic were followed up annually for up to 5 years (mean, 2.5±1.3 years) with baseline and follow-up measurements recorded. Plaque area progression (or regression) was defined as an increase (or decrease) of ≥0.05 cm² from baseline.

Results— Carotid plaque areas from 1686 patients were categorized into 4 quartile ranges: 0.00 to 0.11 cm² (n=422), 0.12 to 0.45 cm² (n=424), 0.46 to 1.18 cm² (n=421), and 1.19 to 6.73 cm² (n=419). The combined 5-year risk of stroke, myocardial infarction, and vascular death increased by quartile of plaque area: 5.6%, 10.7%, 13.9%, and 19.5%, respectively (P<0.001) after adjustment for all baseline patient characteristics. A total of 1085 patients had ≥1 annual carotid plaque area measurements: 685 (63.1%) had carotid plaque progression, 306 (28.2%) had plaque regression, and 176 (16.2%) had no change in carotid plaque area over the period of follow-up. The 5-year adjusted risk of combined outcome was 9.4%, 7.6%, and 15.7% for patients with carotid plaque area regression, no change, and progression, respectively (P=0.003).

Conclusions— Carotid plaque area and progression of plaque identified high-risk patients. Plaque measurement may be useful for targeting preventive therapy and evaluating new treatments and response to therapy and may improve cost-effectiveness of secondary preventive treatment.