Assessment of aortic blood flow velocities with continuous wave Doppler ultrasound in the neonate and young child.

Aortic flow velocities can be recorded with pulsed or continuous wave Doppler ultrasound. In the absence of obstruction or regurgitation, changes in flow can be assessed and stroke volume obtained. Continuous wave Doppler ultrasound has the advantage that there is no limit to the velocities that can be recorded. In left ventricular outflow obstruction and coarctation, the pressure drop across these can be calculated from increases in maximal velocity using a modification of the Bernoulli equation. Other systolic high velocity jets such as mitral regurgitation or ventricular septal defect may also be recorded with continuous wave Doppler ultrasound from the suprasternal notch, but they can be distinguished from aortic flow velocities by their timing and duration when the flow signals are recorded together with the electrocardiogram and phonocardiogram. In aortic regurgitation, reversal of flow across the aortic valve in diastole can be shown and with high velocity in the regurgitant jet.