P4.17 Influence of Estimated Wall Shear Rate Indices On Carotid Artery Intima-Media Thickness and Intima-Media Complex Echogenicity

Grey scale median of the carotid artery intima-media complex (IM-GSM) is a recently introduced measurement to characterise the arterial wall. Wall shear stress is thought to influence intima-media thickness (IMT) and to play a major role in the development of atherosclerosis. However, the relationship between wall shear stress and IM-GSM is not well understood. This study examined the relationship between estimated wall shear rate (WSR) indices and IMT as well as estimated WSR indices and IM-GSM. Data from 156 middle-aged and older individuals (66.1±9.5yrs, 58F) were included in this analysis. Common carotid artery diameter, IMT, and blood velocity data were obtained using a Doppler ultrasound machine. Three estimates of WSR were calculated: peak, mean and diastolic WSR. IMT and IM-GSM were analyzed using a semi-automated edge-detection programme. IMT was inversely associated with all WSR indices (peak: r=-0.16, mean: r=-0.22, diastolic: r=-0.25, all p<0.05). IM-GSM was positively associated with mean (r=0.20) and diastolic WSR (r=0.17, both p<0.05). Peak and mean WSR were independent determinants of IMT, and mean and diastolic WSR were independent determinants of IM-GSM after adjustments for age, sex and traditional cardiovascular risk factors. These results show that estimated WSR indices were associated with IMT and IM-GSM, suggesting that WSR may, in part, determine the extent of IMT and the composition of the arterial wall in our cohort.