Abstract P190: The Associations of Brachial Artery Shear Rate and Endothelial Dysfunction with Age Related Carotid Distensibility

Abstract

Loss of carotid artery distensibility (CD) with age portends of clinical cerebrovascular disease. Endothelial dysfunction mediated by impaired nitric oxide vascular dilatation precedes vascular remodeling and age-related stiffening of arteries. However, it is unknown whether endothelial dysfunction contributes to loss of vascular distensibility with age. Methods: We examined 828 asymptomatic healthy subjects in the GeneSTAR family cohort, identified from index cases with early-onset coronary artery disease. We determined mean CD of both common carotid arteries using ultrasound; CD was quantified as the pulsatile change in lumen diameter/diastolic lumen diameter/brachial pulse pressure. Vascular shear rate (SR) was determined in the brachial artery as 4 х maximum blood flow velocity/maximum lumen diameter, and brachial flow mediated dilatation (FMD), a measure of endothelial dysfunction, as % change in diastolic diameter during reactive hyperemia. We tabulated both rest and hyperemic responses by age, sex and race-indexed tertiles of CD generated by quantile regression. Generalized estimating equations (GEE) were used to estimate the family correlation corrected associations of CD with FMD and SR. Results: The sample was 60% female, 40% African American, with mean age 52 (SD 12) years. While SR was significantly associated with higher tertiles of CD, FMD was not (Table). Adjusted for age, sex and race, every 540/s (1 SD) higher of shear rate was significantly associated with a 6.2% higher CD (p = 0.019) but FMD was not associated at all (p = 0.54). This pattern remained after adjustment for LDL and HDL- cholesterol, hypertension, diabetes and smoking (p = 0.03 and 0.95, respectively). Conclusion: Higher vascular shear rate is associated with preserved arterial distensibility indexed for age. FMD is not related to CD. The pathophysiological interpretations of this finding need further study before either CD or vascular shear rate can be used for assessing stoke risk in a population at increased risk for vascular disease.