Doppler echocardiography

technique using ultrasound to record blood flow velocity in the cardiovascular system. It operates on the principle that blood cells moving toward the ultrasound transducer cause reflected frequency to be greater than transmitted frequency while blood cells moving away from the transducer cause reflected frequency to be lower. The difference between transmitted and reflected frequency is the Doppler shift which is directly related to flow velocity. Continuous wave Doppler uses two transducers; one continuously transmits ultrasound and the other continuously records the reflected ultrasound. Pulsed Doppler uses only one transducer. The continuous wave approach can be used to interrogate higher velocities than is possible with pulsed Doppler. Doppler echocardiography is used to evaluate both systolic and diastolic ventricular function. An important use is estimation of pressure gradient across valvular, conduit, and vascular stenoses utilizing the modified Bernoulli equation. Also, see Doppler ultrasound.

CBH