Tissue
Velocity Gradient
TDI can measure the difference in
velocities of adjacent myocardial tissues (velocity gradient), and this can be
used to assess the viability and deformation (strain) of the myocardium. The
velocity of the endocardium is normally higher than that of the epicardium,
thus producing a tissue velocity gradient. In akinetic but viable or
nontransmurally infracted myocardium, the myocardial velocity gradient
persists, but there is no velocity gradient in scarred or transmurally
infarcted myocardium.
Because days to weeks are needed for myocardial
contractility to recover after successful reperfusion of an occluded coronary
artery, measurements of the tissue velocity gradient can be useful in patients
with an acute myocardial infarction. To record or display the myocardial
velocity gradient, the direction of myocardial contractility needs to be
aligned in parallel with the direction of the ultrasound beam. Therefore,
imaging views are limited to the parasternal windows to image anterior or
posterior walls.
Thank you so much.
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