Various structures are seen in two-dimensional planes; hence mental conceptualization is still required because the heart is three-dimensional. Now, newer technology has evolved and live three-dimensional echocardiography is a reality.
Doppler examination' provides hernodynamic information regarding blood flow in the heart and great vessels i.e. comparable to that obtained by cardiac catheterization. It relies on analysis of a shift in the frequency of ultrasound beam due to interaction with moving targets. Doppler studies are usually performed in conjunction with standard echocardiographic imaging. Two types of Doppler examination are:
a) Pulse Wave Doppler (PW) which gives velocity of blood flow at the level of sample volume placed along ultrasound beam
b) Continuous Wave Doppler (CW) which records velocities all along the ultrasound beam.