Abstract
Arterial wall shear stress (WSS) parameters are widely used for prediction of the initiation and development of atherosclerosis and arterial pathologies. Traditional clinical evaluation of arterial condition relies on correlations of WSS parameters with average flow rate (Q) and heart rate (HR) measurements. We show that for pulsating flow waveforms in a straight tube with flow reversals that lead to significant reciprocating WSS, the measurements of HR and Q are not sufficient for prediction of WSS parameters. Therefore, we suggest adding a third quantity—known as the pulsatility index (PI)—which is defined as the peak-to-peak flow rate amplitude normalized by Q. We examine several pulsating flow waveforms with and without flow reversals using a simulation of a Womersley model in a straight rigid tube and validate the simulations through experimental study using particle image velocimetry (PIV). The results indicate that clinically relevant WSS parameters such as the percentage of negative WSS (P[%]), oscillating shear index (OSI) and the ratio of minimum to maximum shear stress rates (min/max), are better predicted when the PI is used in conjunction with HR and Q. Therefore, we propose to use PI as an additional and essential diagnostic quantity for improved predictability of the reciprocating WSS.
Highlights
Arterial wall shear stresses (WSS) are known as a main regulator of endothelial cell function and vascular structure and condition
In order to demonstrate the capabilities of pulsatility index (PI) in improving prediction of WSS parameters for waveforms with global reverse flow and negative WSS and distinguish those from cases of negative WSS with positive flow rate, we demonstrate in this manuscript the correlation of WSS parameters with Reynolds, Womersley and PI for 14 representative pulsating waveforms
The exceptions are the decrease of P[%] and oscillatory shear index (OSI) with the increasing Reynolds number and increase of those with the PI
Summary
Arterial wall shear stresses (WSS) are known as a main regulator of endothelial cell function and vascular structure and condition. Numerous in-vitro and in-vivo studies have shown that vascular regions with disturbed flow accompanied by turbulent flow, low, oscillatory or instantaneous negative WSS and high WSS gradients are strongly correlated with vascular pathologies, cardiovascular diseases and disorders [1,2,3]. Vascular remodeling and dysfunction were correlated with reciprocating WSS parameters such as the oscillatory shear index (OSI) [4], WSS gradients, percentage of negative wall shear stress (P[%]) or the ratio of minimum to maximum shear stress rates (min/max) [5,6,7]. WSS parameters were shown to have positive correlation with a large variety of vascular dysfunction mechanisms such as reduction in Nitric Oxide (NO) production, endothelial cell activation.
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