As we saw in Chapter 4, the principles of Doppler imaging can be used not only to assess blood flow but also to assess the movement of the myocardium. This is known as tissue Doppler imaging (TDI). The Doppler signals returning from myocardium are distinct from signals from blood (myocardial motion generates a stronger but lower-velocity signal) and so can be selected with appropriate filtering. The resulting signals can be displayed as colour Doppler images to show myocardial motion or as spectral pulsed-wave Doppler traces to assess motion in specific myocardial regions.

TDI provides valuable information on myocardial mechanics. It does however have certain limitations. Like all Doppler techniques, TDI is heavily angle dependent in that it can only measure motion parallel to the direction of the ultrasound beam. Furthermore, TDI is unable to distinguish between active motion (i.e. myocardial contraction/relaxation) and passive motion (where a region of myocardium is ‘pulled’ by an adjacent segment). The alternative technique of speckle tracking overcomes these limitations and is discussed in detail in Chapter 11.