ABSTRACT
Tissue Doppler imaging (TDI) provides valuable information on myocardial mechanics. It does however have certain limitations. Pulsed-wave TDI permits the measurement of myocardial velocity in a specific region. To perform pulsed-wave TDI, the sonographer places the sample volume in the region of interest. The resultant pulsed-wave TDI recording shows a mitral annular velocity towards the transducer which corresponds to the annular myocardium moving towards the apex as the LV contracts longitudinally during systole. As with ‘standard’ colour Doppler, colour TDI is based upon the principle of pulsed-wave Doppler. TDI measures myocardial velocity, and if the velocities at two points in the myocardium are known then the difference between these velocities gives a measure of strain rate. TDI is unable to distinguish between active motion and passive motion. When measuring myocardial velocity using TDI, it is important to remember that pulsed-wave TDI measures peakvelocity whereas colour TDI measures mean velocity.
