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The Changing Left Ventricle

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Doppler Changes in Valvular Regurgitation
Velocity Pressure Relationships

Doppler echocardiographic findings are strongly influenced by the pressure gradients between chambers according to the Bernoulli equation. This relationship is simplified to:

p2-p1=4V2

Fig.2.3

and is very important to understand for further appreciation of the wealth of information available in the Doppler velocity spectral display. The Doppler spectral recordings from mild and severe mitral regurgitation are shown in
Figure 2.3
to illustrate this point further. As describes above, small degrees of mitral regurgitation produce very high pressure differences between the left ventricle and the left atrium. Minor degrees of regurgitation will, therefore, result in very high velocity jets as a consequence of these great pressure differences. Severe mitral regurgitation results in relatively smaller differences between the two chambers. These smaller pressure gradients result in relatively lower velocity jets. This, of course, assumes that the systolic pressures within the ventricles are similar in both situations.

Thus, the severity of valvular regurgitation is not reflected in an increase in the velocity of the regurgitant jet as detected by Doppler echocardiography. As will be demonstrated in more detail later, the inverse is usually the case. With greater degrees of regurgitation, pressures will rise in the chamber receiving the regurgitant volume leading to a general decrease in the velocity of the resultant Doppler spectral recording.

Another important implication of the increase in velocity in regurgitant jets is that almost all degrees of valvular regurgitation result in a velocity increase above 1.5 m/sec. The practical effect of these higher velocities on Doppler recordings is that aliasing is almost always produced in pulsed wave Doppler interrogations of valvular regurgitation. This is results in the fact that pulsed Doppler echocardiography may be used for detection of the location of the turbulence (or area of the jet) but not its peak velocity.

Fig.2.4

This is demonstrated in the idealized drawing of spectral recordings resulting from a mitral insufficiency jet shown in
Figure 2.4.
The left panel shows systolic turbulent flow moving away from a transducer positioned at the apex. The full profile is recorded by CW Doppler. When the same jet is interrogated by PW Doppler, aliasing occurs.

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