top of page

Why is flow-mediated dilation dependent on arterial size?

Assessment of the shear stimulus using phase-contrast magnetic resonance imaging

Harry A Silber 1, Pamela Ouyang, David A Bluemke, Sandeep N Gupta, Thomas K Foo, Joao A C Lima Affiliations expand

  • PMID: 15345491

  • DOI: 10.1152/ajpheart.00612.2004

Abstract Flow-mediated dilation (FMD) is strongly dependent on arterial size, but the reasons for this phenomenon are poorly understood. We have previously shown that FMD is greater in small brachial arteries because the shear stress stimulus is greater in small brachial arteries. However, it is unclear why the shear stimulus is greater in small arteries. Furthermore, this relationship has not been investigated in other, differently sized arterial beds. Postischemic systolic shear stress and resulting FMD were evaluated in the brachial and femoral arteries of 24 young, healthy adults using phase-contrast magnetic resonance imaging. Arterial shear and radius were calculated from the velocity profile via a best-fit parabola before and after occlusion. Summing the velocity pixels provided hyperemic systolic flow. FMD was proportional to hyperemic shear in the brachial and femoral arteries (P < 0.0001, r = 0.60). Hyperemic systolic flow was proportional to radius2 (P < 0.0001, r = 0.93). Applying this relationship to the Poiseuille equation (shear is proportional to flow/radius3) shows that hyperemic shear is proportional to radius2/radius3 and, therefore, explains why hyperemic shear is proportional to 1/radius. We conclude that FMD is proportional to hyperemic systolic shear stress in both the brachial and the femoral arteries. The hyperemic shear stimulus for FMD is greater in small arteries due to the dependence of postischemic systolic flow on radius squared. Therefore, greater FMD in small arteries does not necessarily reflect better conduit artery endothelial function. Evaluating the shear stimulus using phase-contrast magnetic resonance imaging enhances the understanding of mechanisms underlying FMD.

Similar articles

  • The relationship between vascular wall shear stress and flow-mediated dilation: endothelial function assessed by phase-contrast magnetic resonance angiography.Silber HA, Bluemke DA, Ouyang P, Du YP, Post WS, Lima JA.J Am Coll Cardiol. 2001 Dec;38(7):1859-65. doi: 10.1016/s0735-1097(01)01649-7.PMID: 11738285

  • The impact of a cold pressor test on brachial artery handgrip exercise-induced flow-mediated dilation.Stuckless TJ, Pyke KE.Vasc Med. 2015 Oct;20(5):409-16. doi: 10.1177/1358863X15586473. Epub 2015 May 28.PMID: 26021703

  • Local shear stress and brachial artery flow-mediated dilation: the Framingham Heart Study.Mitchell GF, Parise H, Vita JA, Larson MG, Warner E, Keaney JF Jr, Keyes MJ, Levy D, Vasan RS, Benjamin EJ.Hypertension. 2004 Aug;44(2):134-9. doi: 10.1161/01.HYP.0000137305.77635.68. Epub 2004 Jul 12.PMID: 15249547 Clinical Trial.

  • Flow-mediated dilation stimulated by sustained increases in shear stress: a useful tool for assessing endothelial function in humans?Tremblay JC, Pyke KE.Am J Physiol Heart Circ Physiol. 2018 Mar 1;314(3):H508-H520. doi: 10.1152/ajpheart.00534.2017. Epub 2017 Nov 22.PMID: 29167121. Review.

  • The relationship between shear stress and flow-mediated dilatation: implications for the assessment of endothelial function.Pyke KE, Tschakovsky ME.J Physiol. 2005 Oct 15;568(Pt 2):357-69. doi: 10.1113/jphysiol.2005.089755. Epub 2005 Jul 28.PMID: 16051630 . Review.

See all similar articles

Cited by

  • Investigation on the differences of hemodynamics in normal common carotid, subclavian, and common femoral arteries using the vector flow technique.Song D, Liu M, Dong Y, Hong S, Chen M, Du Y, Li S, Xu J, Gao W, Dong F.Front Cardiovasc Med. 2022 Nov 17;9:956023. doi: 10.3389/fcvm.2022.956023. eCollection 2022.PMID: 36465451.

  • Association of Vascular Properties With the Brain White Matter Hyperintensity in Middle-Aged Population.Hannawi Y, Vaidya D, Yanek LR, Johansen MC, Kral BG, Becker LC, Becker DM, Nyquist PA.J Am Heart Assoc. 2022 Jun 7;11(11):e024606. doi: 10.1161/JAHA.121.024606. Epub 2022 May 27.PMID: 35621212.

  • The effects of alcohol consumption on flow-mediated dilation in humans: A systematic review.Hwang CL, Piano MR, Phillips SA.Physiol Rep. 2021 May;9(10):e14872. doi: 10.14814/phy2.14872.PMID: 34042304.

  • Ultrasound Based Computational Fluid Dynamics Assessment of Brachial Artery Wall Shear Stress in Preeclamptic Pregnancy.Pewowaruk RJ, Racine J, Iruretagoyena JI, Roldán-Alzate A.Cardiovasc Eng Technol. 2020 Dec;11(6):760-768. doi: 10.1007/s13239-020-00488-6. Epub 2020 Oct 6.PMID: 33025370.

  • Wall Shear Stress Measurements Based on Ultrasound Vector Flow Imaging: Theoretical Studies and Clinical Examples.Du Y, Goddi A, Bortolotto C, Shen Y, Dell'Era A, Calliada F, Zhu L.J Ultrasound Med. 2020 Aug;39(8):1649-1664. doi: 10.1002/jum.15253. Epub 2020 Mar 3.PMID: 32124997.

See all "Cited by" articles

Recent Posts

See All


bottom of page