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The physiological impact of the nonlinearity of arterial elasticity in the ambulatory arterial stiffness index.

Abstract：

:The ambulatory arterial stiffness index (AASI) is claimed to be a new estimator for arterial rigidity. It was recently defined as one minus the slope of the linear regression of systolic to diastolic ambulatory pressure during 24 h. Although several reports testify its clinical relevance, the explanation of how this new index is conceptually associated with arterial stiffness remains controversial. In this work we hypothesize that nonlinear arterial elasticity is behind AASI physiological principles. To that end, random number generators were used to emulate arterial cross-sectional area (CSA) during 24 h. Pressure values were calculated using linear and nonlinear elasticity models for rigid and compliant arteries. The AASI was calculated from simulated pressures and also analytically predicted for each model. Additionally, invasive aortic pressure and CSA were continuously measured in a conscious sheep during 24 h to test the nonlinear model. We found that analytical solutions agreed with simulation outcomes; for the nonlinear model, the AASI was higher in rigid arteries with respect to compliant arteries (0.51 versus 0.38) and the linear model systematically predicted AASI = 0. For in vivo pressure measurements, AASI was 0.31. Using the measured pulsatile CSA and an estimation of the elastic constant for the nonlinear model, the AASI was accurately predicted with errors below 5%. We conclude that the AASI is higher in stiffer arteries due to the nonlinear behavior of the arterial wall. With a nonlinear arterial function, the slope of the linear regression of diastolic to systolic pressures during 24 h depends on the product of an elastic constant by the pulsatile CSA. As the elastic constant dominates the product, the reported associations between the AASI and arterial stiffness indices now have a consistent explanation.

journal_name

Physiol Meas

journal_title

Physiological measurement

authors

Craiem D,Graf S,Salvucci F,Chironi G,Megnien JL,Simon A,Armentano RL

doi

10.1088/0967-3334/31/7/012

subject

Has Abstract

pub_date

2010-07-01 00:00:00

pages

1037-46

issue

eissn

0967-3334

issn

1361-6579

pii

S0967-3334(10)25773-8

journal_volume

pub_type

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The physiological impact of the nonlinearity of arterial elasticity in the ambulatory arterial stiffness index.