Arterial Stiffness Gradient

Abstract

Background: Aortic stiffness is a strong predictor of cardiovascular mortality in various clinical conditions. The aim of this review is to focus on the arterial stiffness gradient, to discuss the integrated role of medium-sized muscular conduit arteries in the regulation of pulsatile pressure and organ perfusion and to provide a rationale for integrating their mechanical properties into risk prediction.

Summary: The physiological arterial stiffness gradient results from a higher degree of vascular stiffness as the distance from the heart increases, creating multiple reflective sites and attenuating the pulsatile nature of the forward pressure wave along the arterial tree down to the microcirculation. The stiffness gradient hypothesis simultaneously explains its physiological beneficial effects from both cardiac and peripheral microcirculatory points of view. The loss or reversal of stiffness gradient leads to the transmission of a highly pulsatile pressure wave into the microcirculation. This suggests that a higher degree of stiffness of medium-sized conduit arteries may play a role in protecting the microcirculation from a highly pulsatile forward pressure wave. Using the ratio of carotid-femoral pulse wave velocity (PWV) to carotid-radial PWV, referred to as PWV ratio, a recent study in a dialysis cohort has shown that the PWV ratio is a better predictor of mortality than the classical carotid-femoral PWV.

Key messages: Theoretically, the use of the PWV ratio seems more logical for risk determination than aortic stiffness as it provides a better estimation of the loss of stiffness gradient, which is the unifying hypothesis that explains the impact of aortic stiffness both on the myocardium and on peripheral organs.

Keywords: Aortic stiffness; Arterial stiffness gradient; End-organ damage; Medium-sized muscular artery; Mortality.

Fig. 1

Hemodynamic impact of arterial stiffness gradient. a In normal condition, aortic stiffness is lower than that of medium-sized conduit arteries, creating wave reflections and therefore attenuating pulse pressure transmission to the circulation. b When aortic stiffness increases with minimal changes of stiffness in medium-sized conduit arteries, the forward pressure wave is less attenuated (i.e. there is less reflection), therefore the forward pulse wave is transmitted to the microcirculation stimulating myogenic response and enhanced wave reflection from the microcirculation. This condition could potentially lead to hypoperfusion and organ dysfunction. Reprinted from Briet et al. [9] with permission.

Fig. 2

cf- and cr-PWVs in a dialysis population. a The figure shows increasing cf-PWV (○) and decreasing cr-PWV (●) with increasing age. b Early premature loss of stiffness gradient as evaluated by cf-PWV/cr-PWV (PWV ratio). The results are obtained using data from 310 patients from a prevalent dialysis cohort as reported by Fortier et al. [26], using direct measurements of the distance between two arterial sites. Dots are mean, and bars represent the 95% CI.