7.4 HIGHER CAROTID STRAIN IN INDIVIDUALS WITH DOWN SYNDROME AT REST AND DURING HYPOVOLEMIC SYMPATHOEXCITATION

Abstract

Background: Arterial stiffness and large artery function are independent risk factors for cardiovascular disease.(1) Individuals with Down Syndrome (DS) have autonomic dysfunction and known to have lower incidence of cardiovascular disease.(2) Limited literatures showed no difference in arterial stiffness in DS compared to a healthy, non-DS population using a longitudinal view of the carotid artery.(3,4) However, it is unknown if individuals with DS exhibit different circumferential strain compared to individuals without DS at rest or during a sympathoexcitation stimulus. Purpose: To examine the differences in the carotid artery strain and its responsiveness to sympathoexcitation by hypovolemic lower body negative pressure (LBNP) in individuals with and without DS. Methods: Twenty four volunteers (DS=11, 23 yrs Control=13, 23 yrs) participated in this study. Circumferential strain was measured by ultrasonography B-mode and radial strain from the longitudinal view was calculated using echo tracking analysis at rest, during and after sympathoexcitatory stimulation by LBNP. Changes in hemodynamics (HR, BP) were recorded continuously. Results: Compared with controls, individuals with DS have significantly higher strain values at all stages (p < 0.05) with no group interaction with hypovolemic sympathoexcitation stimulation. However, there were no differences in β-Stiffness or EP, suggesting that the differences in strain were due to differences in blood pressure. Conclusions: Our results demonstrate significantly higher strain value, which indicates greater arterial movement in individuals with DS. However, these differences were likely due to higher BP in persons with DS.