Aortic-Brachial Pulse Wave Velocity Ratio: A Blood Pressure-Independent Index of Vascular Aging

Abstract

Aortic stiffness, a cardiovascular risk factor, depends on the operating mean arterial pressure (MAP). The impact of aortic stiffness on cardiovascular outcomes is proposed to be mediated by the attenuation or the reversal of the arterial stiffness gradient. We hypothesized that arterial stiffness gradient is less influenced by changes in MAP. We aimed to study the relationship between MAP and aortic stiffness, brachial stiffness, and arterial stiffness gradient. In a cross-sectional study of a dialysis cohort (group A, n=304) and a cohort of hypertensive or kidney transplant recipient with an estimated glomerular filtration rate of >45 mL/min/1.73 m² (group B, n=114), we assessed aortic and brachial stiffness by measuring carotid-femoral and carotid-radial pulse wave velocities (PWV). We used aortic-brachial PWV ratio as a measure of arterial stiffness gradient. Although there was a positive relationship between MAP and carotid-femoral PWV (R²=0.10 and 0.08; P<0.001 and P=0.003) and MAP and carotid-radial PWV (R²=0.22 and 0.12; P<0.001 and P<0.001), there was no statistically or clinically significant relationship between MAP and aortic-brachial PWV ratio (R²=0.0002 and 0.0001; P=0.8 and P=0.9) in group A and B, respectively. Dialysis status and increasing age increased the slope of the relationship between MAP and cf-PWV. However, we found no modifying factor (age, sex, dialysis status, diabetes mellitus, cardiovascular disease, and class of antihypertensive drugs) that could affect the lack of relationship between MAP and aortic-brachial PWV ratio. In conclusion, these results suggest that aortic-brachial PWV ratio could be considered as a blood pressure-independent measure of vascular aging.

Keywords: aorta; arterial pressure; arterial stiffness; hemodynamics; pulse wave velocity.