Tissue Doppler echocardiography (TDE) has become an established component of the diagnostic ultrasound examination; it permits an assessment of myocardial motion using Doppler ultrasound imaging, often with color coding. The technique uses frequency shifts of ultrasound waves to calculate myocardial velocity; this is similar to routine Doppler ultrasound to assess blood flow, but its technological features focus on lower velocity frequency shifts. (See "Principles of Doppler echocardiography".)
Although Doppler ultrasound has been in widespread clinical use to assess intracardiac blood flow and noninvasive hemodynamics for many years, interest in TDE increased significantly when the color-coded TDE method was introduced [1-6]. Routine echocardiographic assessment of regional left ventricular (LV) wall motion is subjective because it is determined by visual determination of endocardial excursion and wall thickening. TDE offers the promise of an objective measure to quantify regional and global LV function through the assessment of myocardial velocity data.
Two techniques are used to assess myocardial function: pulsed-TDE and color-coded TDE, which is an extension of the pulsed-Doppler technique. This modality has been applied in several clinical settings, particularly in the assessment of global and regional LV systolic function. Other uses include assessment of LV diastolic function, estimation of LV filling pressures, determination of LV dyssynchrony for cardiac resynchronization therapy (CRT), and the distinction of different cardiac diseases.
Tissue Doppler ultrasonography utilizes modifications of blood flow Doppler technology and calculates velocity from frequency shifts in received ultrasound data in a similar manner. Thus, the fundamental units are velocity observed from the echocardiographic transducer as a frame of reference. A primary advantage of tissue Doppler echocardiography (TDE) is that Doppler shifts of tissue motion are of high amplitude, being approximately 40 dB higher than Doppler signals from blood flow [1,7]. An instrumentation feature common to both pulsed and color-coded TDE involves removal of the high-pass filter used for routine Doppler to assess blood flow in order to focus on the lower velocity values of myocardial motion [1,2,7].
Pulsed-TDE — Pulsed-TDE is available on most commercial echocardiography systems. The details of TDE set-up are unique to each system, but TDE is generally executed though a system preset feature. Operation is then very similar to routine pulsed-Doppler, with adjustments of the scale and sweep speed to optimize the spectral display, similar to pulsed-Doppler of blood flow. The gate of the sample volume is usually opened to 1 cm and directed to assess the region of interest. Routine color flow instrumentation uses the autocorrelator technique to calculate and display multigated points of color-coded blood velocity along a series of ultrasound scan lines within a two-dimensional sector . Color-coded blood velocity data are then superimposed on conventional gray scale two-dimensional images in real time.