Endothelial Dysfunction Influences Exaggerated Aortic Hemodynamic Responses To Metaboreflex Activation In Postmenopausal Women

INTRODUCTION: Impaired endothelial function precedes the development of increased wave reflection and systolic hypertension, a condition highly prevalent in postmenopausal women. Despite good control at rest, systolic blood pressure (BP) response to exercise is augmented in older women. Endothelial dysfunction (flow-mediated dilation, FMD) has been associated with an exaggerated BP response to exercise. However, the impact of endothelial dysfunction on central hemodynamics during submaximal exercise are not well understood. PURPOSE: To determine the impact of low brachial artery FMD on aortic hemodynamic responses during isometric handgrip (IHG) and post-exercise muscle ischemia (PEMI) in postmenopausal women. METHODS: Thirty-three postmenopausal women (aged 61 ± 7 years) were classified with low (n = 17, ≤ 4.5%) and normal brachial artery FMD (n = 16, ≥ 5.9%). Brachial and aortic BP as well as the amplitude of forward (Pf) and backward (Pb) pressure waves were measured using radial applanation tonometry at rest, 2 minutes of IHG at 30% maximal force, and 3 minutes of PEMI. The hemodynamic responses were analyzed as the change (Δ) from rest to the last minute of IHG and PEMI. RESULTS: FMD was different between groups (Low: 2.8 ± 1.1% vs Normal: 6.6 ± 1.6%, P = 0.001). Brachial systolic BP (SBP) (Low: Δ17 ± 8 vs Normal: Δ12 ± 7, P = 0.032), aortic SBP (Low: Δ16 ± 7 vs Normal: Δ10 ± 6, P = 0.009) and mean arterial pressure (MAP) (Low: Δ13 ± 5 vs Normal: Δ9 ± 7, P = 0.032) responses to IHG were higher in the low compared to the normal FMD group. Pressure wave responses to IHG were similar between groups. Brachial SBP (Low: Δ19 ± 8 vs Normal: Δ14 ± 6, P = 0.025), aortic SBP (Low: Δ19 ± 8 vs Normal: Δ13 ± 6, P = 0.008), MAP (Low: Δ13 ± 6 vs Normal: Δ9 ± 6, P = 0.042), augmentation pressure (AP) (Low: Δ5 ± 3 vs Normal: Δ3 ± 2, P = 0.004), and Pb (Low: Δ6 ± 4 vs Normal: Δ3 ± 2, P = 0.021) were greater in the low FMD compared to the normal FMD group. Pf responses to PEMI were similar between groups. CONCLUSIONS: Postmenopausal women with low FMD have exaggerated aortic SBP and wave reflection responses to muscle metaboreflex activation compared to women with normal FMD. These findings suggest that strategies to improve endothelial function may attenuate the exaggerated aortic SBP load on the left ventricle during exercise in postmenopausal women.