Abstract 3006: Conduit and Resistance Artery Function are Both Impaired in Lower Extremities of Older Diabetics: Assessment Using Magnetic Resonance Imaging
Background: Atherosclerotic vascular disease is preceded by endothelial dysfunction. Diabetes and older age are associated with systemic endothelial dysfunction, measured as reduced flow mediated dilation (FMD) of the brachial artery. However, less is known about the effects of diabetes and older age on endothelial function of lower extremities, despite the fact that peripheral arterial disease develops more severely in legs than arms. We investigated the association of diabetes and older age with conduit (femoral) artery FMD in the lower extremity. We also investigated whether reduced femoral FMD is due to impaired vasodilator function of the downstream resistance arteries, which provide the stimulus for femoral FMD.
Methods: We studied 82 subjects in three groups: 33 subjects (16 male/17 female) aged 26±5 years with no cardiovascular risk factors, 30 subjects (14 male/16 female) aged 58±6 years with no other risk factors, and 19 subjects (14 male/5 female) aged 61±6 years with type 2 diabetes without clinical atherosclerosis. Femoral arterial radius and systolic shear rate were directly measured at rest and during post-occlusive hyperemia using magnetic resonance imaging. Conduit artery reactivity (FMD) and resistance artery reactivity (hyperemic shear rate) were measured. Hyperemic shear rate and FMD were each compared between groups. Multiple regression analysis was used to determine whether risk group and hyperemic shear rate predicted FMD independently.
Results: Hyperemic shear rate was greater in young healthy (YH) than older healthy (OH) subjects (843±157 vs. 680±236 sec−1, p<.001) and was greater in OH than older diabetic (OD) subjects (549±183 sec−1, p<0.02). FMD was greater in YH than OH (4.23±3.62 vs. 0.74±2.92 %, p<0.0001) and was greater in OH than OD (−0.62±2.37 %, p<0.02). By multiple regression, risk group remained a predictor of FMD (p<0.001) after adjusting for the effect of hyperemic shear rate on FMD (p<0.004).
Conclusions: In lower extremities, both conduit and resistance arterial function are reduced in older nondiabetics and both are more reduced in older diabetics. The risk of developing peripheral arterial disease in older age and diabetes may be related to impaired function of both the conduit and resistance arteries.