Evaluation of arterial stiffness in children with Williams syndrome: Does it play a role in evolving hypertension?

Background Pathologic studies and surgical observations of thickened aortic walls have suggested an increase in aortic stiffness in patients with Williams syndrome. However, in vivo objective evaluation of aortic and arterial stiffness in Williams syndrome are lacking. Moreover, systemic hypertension, although prevalent in Williams syndrome, does not have a well-defined mechanism in this syndrome. Therefore, the purpose of this study was to quantitate aortic stiffness and arterial compliance in an objective manner, as well as to determine their roles in development of hypertension, in children with Williams syndrome. Methods We studied 13 patients with Williams syndrome (aged 3-12 years) and 16 age-matched control subjects. Aortic stiffness was calculated from the β index as follows: β = (ln[Ps/Pd])÷ ([Ds – Dd]/Dd), where Ps and Pd are systolic and diastolic blood pressures and Ds and Dd are systolic and diastolic aortic dimensions, respectively. Arterial compliance (C) was calculated by the area method: C= (Ad × CO × CL) ÷ (At × [Pes – Pd]), where At is the total area and Ad is the area under the diastolic portion of the arterial pulse tracing, CO is the cardiac output, CL is the cycle length, and Pes is aortic end-systolic pressure. Results In patients with Williams syndrome, the β index was 2-fold higher than in control patients (9.02 ± 3.15 vs 4.43 ± 0.96, P < .005). Moreover, there was a strong positive correlation between the β index and the systolic blood pressure (r = 0.8 and P < .0001). Compliance was decreased by 42% (0.41 ± 0.11 vs 0.71 ± 0.10 mL/mm Hg, P < .05), suggesting decreased arterial compliance. Conclusions Our study indicates that in vivo arterial stiffness is increased in patients with Williams syndrome. We speculate that increased arterial stiffness may be the predisposing cause of systemic hypertension in Williams syndrome. (Am Heart J 2001;142:549-55.)