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Characterization of blood flow patterns and endothelial shear stress during flow-mediated dilation

Francisco Morales-Acuna1, Luis Ochoa2, Carolina Valencia1

  • 1Department of Rehabilitation Sciences, College of Health Sciences, The University of Texas at El Paso, El Paso, TX, USA.

Clinical Physiology and Functional Imaging
|February 17, 2019
PubMed

Insights

Peak flow-mediated dilation (FMD) in healthy young adults is driven by high endothelial shear stress (ESS) during turbulent blood flow. Accurate ESS estimation during FMD requires Womersley

Area of Science:

  • Cardiovascular physiology
  • Biomedical engineering
  • Vascular biology

Background:

  • Endothelial dysfunction is an early indicator of atherosclerosis.
  • Flow-mediated dilation (FMD) is a key measure of endothelial function but lacks standardization for clinical use.
  • Normalizing FMD to endothelial shear stress (ESS) is a proposed solution, but existing methods neglect pulsatile flow characteristics.

Purpose of the Study:

  • To investigate the relationship between endothelial shear stress (ESS) and blood flow patterns during flow-mediated dilation (FMD).
  • To evaluate the accuracy of ESS estimation methods under pulsatile flow conditions.
  • To determine the role of turbulent flow in triggering peak FMD.

Main Methods:

  • Twenty-six healthy young subjects (15 female, 11 male) underwent FMD testing.
  • Blood viscosity was measured using microhematocrit.
  • Endothelial shear stress (ESS) was calculated using Womersley's approximation, considering pulsatile flow dynamics.
  • Blood flow patterns were analyzed based on the critical Reynolds number.

Main Results:

  • Mean FMD was 7.4% with peak dilation at 35 seconds.
  • Endothelial shear stress (ESS) significantly decreased during FMD until peak dilation (P<0.001).
  • Turbulent blood flow was observed in 96.15% of subjects until peak dilation.

Conclusions:

  • High ESS under turbulent flow conditions primarily triggers peak FMD in young healthy individuals.
  • Womersley's approximation is recommended for ESS estimation during FMD due to pulsatile flow and observed turbulent patterns.
  • Poiseuille's law is inadequate for accurately estimating ESS in the context of FMD.
Abstract

Keywords:
endothelial shear stressflow-mediated dilationlaminar blood flowpulsatile blood flowturbulent blood flow

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