Characteristics And Determinants Of Age-related Changes In Brachial And Popliteal Artery Flow-mediated Dilation In Women

Abstract

Flow-mediated dilation (FMD) declines in the brachial artery (BA) with healthy aging in women. However, the physiological determinants of this decline are not welled fined, particularly after the BA FMD response has been normalized to the shear stress stimulus. Furthermore, it is not known whether this diminished FMD is seen in the leg vasculature (popliteal artery, PA), a more hemodynamically significant vascular bed utilized during ambulatory activities. PURPOSE To determine the characteristics and determinants of age-related changes in BA and PA FMD in healthy women. METHODS 41 normally active, healthy women (ages 20–79) were measured for variables including cycle VO2peak, body mass index (BMI) and regional muscle mass (forearm and calf). Resting PA and BA diameters and BA shear rate (SR= blood velocity/diameter, an estimate of shear stress) were measured prior to infiation of an upper arm or leg cuff to suprasystolic pressure for 10 min; post-occlusion diameter measurements and peak BA shear rate were used to calculate BA and PA dilation (% D = % change from baseline to peak diameter) and BA % D normalized to shear stimulus (% D/% change in SR from resting to peak). Simple linear regression was used to determine the age-associated changes in BA and PA FMD; forward/reverse stepwise linear regression was then used to determine the predictors of these age-related changes. RESULTS Resting BA and PA diameters did not differ with age (p>0.05). BA FMD normalized to shear stimulus declined 11.6% /decade with age (p <0.01); the strongest predictors of this decline were age, VO2peak, and forearm muscle mass (cumulative r2=.41; p=0.01). PA % D was not related to age (p>0.05). The only significant predictors of PA FMD were calf muscle mass (p=0.03, r2=.112) and BMI (p=0.03; r2=.121). CONCLUSION These results suggest that agerelated changes in the intrinsic dilator capacity of a conduit artery are limb-specific; additionally, the strong predictive ability of forearm flow-mediated dilation does not exist in the calf with predictors such as regional muscle mass and VO2peak. Supported by College of Health and Human Development Seed Grant #423-22