Abstract
Aging is associated with impairments in endothelial function and an increased prevalence of atherosclerosis; however, the mechanism(s) contributing to an increased atherosclerotic risk with advanced age remain incompletely defined. Interestingly, atherosclerotic lesions occur preferentially in areas of low mean shear and/or areas with greater oscillatory shear caused by bidirectional flow, suggesting that vascular endothelial function may be affected by shear rate magnitude and patterns. PURPOSE: To evaluate the influence of aging on shear rate patterns in the femoral artery; a vessel prone to atherosclerosis. METHODS: Common femoral artery blood velocity and diameter were measured via Doppler Ultrasound under resting conditions in 14 young (22±1 yr, 7 men) and 12 older (62±2 yr, 6 men) adults. Antegrade, retrograde and mean shear were determined and oscillatory shear was evaluated by calculating an oscillatory shear index (OSI): retrograde shear/(retrograde + antegrade shear). RESULTS: Femoral artery antegrade shear (52.2±3.4 s-1 young vs. 42.3±3.9 s-1 older, P=0.06) and mean shear (40.5±3.2 young s-1 vs. 28.4±3.7 s-1 older, P<0.05) were lower in the older adults, whereas retrograde shear (13.0±1.1 s-1 young vs. 15.5±2.2 s-1 older, P=0.29) was similar between groups. The OSI was 35% greater in the older adults, when compared to the younger subjects (0.20±0.01 au young vs. 0.27±0.02 au, older, P<0.05), indicating that the femoral artery is exposed to greater bidirectional shear throughout the cardiac cycle. Femoral artery diameter was similar between young and older adults (0.87±0.05 cm young vs. 0.87±0.05 cm older, P>0.05); however diameter was consistently lower in women of both groups. No sex-related differences in shear rate magnitude and/or patterns were noted in either group. CONCLUSION: These preliminary findings suggest that healthy aging may be associated with low mean shear, as well as greater oscillatory shear in the femoral artery, potentially promoting a pro-atherogenic endothelial environment. Support: NIH RO1HL093167
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