Mechanical properties of the common carotid artery in Williams syndrome

Abstract

OBJECTIVE: To determine whether arterial wall hypertrophy in elastic arteries was associated with alteration in their mechanical properties in young patients with Williams syndrome. METHODS: Arterial pressure and intima-media thickness, cross sectional compliance, distensibility, circumferential wall stress, and incremental elastic modulus of the common carotid artery were measured non-invasively in 21 Williams patients (mean (SD) age 8.5 (4) years) and 21 children of similar age. RESULTS: Systolic and diastolic blood pressures were higher in Williams patients (125/66 v 113/60 mm Hg, p < 0.05). The mean (SD) intima-media thickness was increased in Williams patients, at 0.6 (0.07) v 0.5 (0.03) mm (p < 0. 001). Normotensive Williams patients had a lower circumferential wall stress (2.1 (0.5) v 3.0 (0.7) mm Hg, p < 0.01), a higher distensibility (1.1 (0.3) v 0.8 (0.3) mm Hg(-1).10(-2), p < 0.01), similar cross sectional compliance (0.14 (0.04) v 0.15 (0.05) mm(2). mm Hg(-1), p > 0.05), and lower incremental elastic modulus (7.4 (2. 0) v 14.0 (5.0) mm Hg.10(2); p < 0.001). CONCLUSIONS: The compliance of the large elastic arteries is not modified in Williams syndrome, even though increased intima-media thickness and lower arterial stiffness are consistent features. Therefore systemic hypertension cannot be attributed to impaired compliance of the arterial tree in this condition.