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Parham Eshtehardi MD @CoronaryDoc
, 12 tweets, 9 min read Read on Twitter
What’s Your “Shear Stress”?

Want to Know More?

Relax & Read ⤵️ #Tweetorial by @CoronaryDoc + @arnavkumar

⚡️Coronary Wall Shear Stress in 12 Tweets ⚡️

Main Readings:
#ACCImaging @ACCCardioEd
Wall shear stress (#WSS) is the frictional force of blood exerted tangential to endothelial surface of vessel wall & expressed in variety of units (1Pa=1N/m2=10 dynes/cm2)

It is derived from
• luminal geometry
• flow rate
• blood viscosity
• near wall velocity values
In vivo WSS calculations are derived from computational fluid dynamic (#CFD) simulations created from reconstructed 3D vessel geometries (from biplane angio/IVUS/OCT/CT/MR) combined with patient-specific pulsatile inlet/outlet velocity values (Doppler wire or other methods)
WSS is a local force & values vary over a cardiac cycle

For clinical studies, time-averaged values are generally used & could be divided to low, physiologic, and high WSS

WSS could be averaged across the circumference of a vessel or across smaller sectors
As a local mechanical force, WSS heavily affects bio-function of vascular endothelial & smooth muscle cells via diverse mechanisms ⤵️

Non-physiologic (⬇️ or ⬆️) WSS promote plaque progression & transformation of stable to unstable (high-risk) plaque
Distribution of WSS in a vessel is heterogeneous & in addition to boundary conditions, depends on geometry, curvatures, bifurcations, and plaque burden

Highest WSS is generally found at the plaque/lesion throat

⬆️ WSS is dominant WSS found in areas with high plaque burden
#Endothelial dysfunction (EDFx) occurs early in development of atherosclerosis & is associated with worse CV outcome & angina

We showed for the first time that segments with ⬇️ WSS co-localize with severe EDFx in patients with non-obstructive CAD
Longitudinal clinical studies have demonstrated that coronary segments exposed to ⬇️ WSS show significant plaque progression, change in plaque composition & constrictive remodeling; highlighting role of ⬇️ WSS in early development of #atherosclerosis
⬆️ WSS induces specific changes in endothelial cell behavior, exacerbating inflammation and stimulating progression of atherosclerotic lipid core & has been shown in clinical studies to be associated with morphological features of high-risk (#vulnerable) plaque
In the first clinical outcome study, using #FAME II database, we showed that high WSS in proximal segments of lesions predict MI in patients with obstructive CAD

WSS had incremental prognostic value over #FFR

WSS was calculated using bi-plane angiograms
While geometry for WSS calculation was historically derived from #IVUS, WSS can also be derived from biplane #angiography, #MRA & #CTA

These promising modalities provide faster, more accessible, and less invasive method of CFD simulation & WSS calculation
Novel 3D vessel & scaffold/stent reconstruction to derive strut-level WSS has been used to to study @AbbottCardio #BVS device/flow interactions during bioresorption process

These novel methods of WSS assessment are expected to guide future stent design
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