Relationship between ultrasound assessment of arterial wall properties and blood pressure

Physical properties of an artery can be described in terms of stiffness, distensibility, and compliance. Changes in these properties can predict atherosclerosis disease, but it is necessary to identify an index that is independent of changes in blood pressure. We measured common carotid artery diameter and pulsatile change with an ultrasonic phase-locked, echo-tracking system in 7 subjects whose mean brachial blood pressure had varied 15 mm Hg or more within a month. Patients taking antihypertensive agents were excluded from the study. We measured changes in arterial diameter (n = 41) at least four times during the study period and calculated the pressure-strain elastic modulus (Ep), distensibility coefficient (DC), cross-sectional compliance (CC) and stiffness parameter (beta) from inner diameter, its pulsatile change, and blood pressure. The correlation coefficients of mean blood pressure with each index are as follows: Ep, 0.53; DC, 0.58; CC, 0.63; beta, 0.21. When mean blood pressure increased 1 mm Hg, the change in each index at 100 mm Hg was as follows: Ep, 1.48 +/- 1.30%; DC, -1.05 +/- 0.97%; CC, -0.69 +/- 0.90%; beta, 0.45 +/- 1.11%. Among the four indices that measure the properties of the arterial walls, stiffness parameter beta was the least dependent on blood pressure. Thus, it appears to have usefulness as an index of arterial wall sclerosis.