For routine
Doppler examination of patients with suspected valvular heart disease,
it is usually best to begin by using the apical window. This allows
selective orientation of the Doppler beam as parallel as possible
to the direction of assumed flow through the mitral and tricuspid
valves. It also allows the largest Doppler shift to be recorded
and the strongest signals to be reflected back to the Doppler transducer.
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| Fig.1.42 |
The imaging mode of the system may be used to acquire an apical
four-chamber view as seen schematically in Figure 1.42. The PW Doppler
sample volume can then be positioned on the atrial or ventricular
sides of the mitral or tricuspid valves. The right panel of Figure
1.42 shows schematic representations of the normal spectral outputs
through the mitral (sample site 3) and tricuspid valves (sample
site 1).
In most normal individuals, whether the sample volume is on the
atrial or ventricular sides of the mitral and tricuspid valves results
in spectral flow outputs that are quite similar. In the presence
of valvular disease, however, markedly different flow patterns are
encountered depending upon sample volume position.
When in the apical four chamber view, slight superior angulation
of the scan plane will allow the operator to encounter the left
ventricular outflow tract. An operator can almost always obtain
Doppler flow data from the ventricular side of the aortic valve.
In some patients data may also be obtained from the aortic root
side. A complete PW Doppler evaluation would continue with movement
of the sample volume from place to place in the standard, and then
intermediate points.
Continued practice repositioning the PW cursor and sample volume
in the various portions of the cardiac chambers accessible from
the apical four chamber view will eventually provide the novice
operator with an appreciation of the spatial locations and directions
of normal and abnormal flows. The heart chambers are actually three
dimensional structures and an abnormal flow jet may be directed
anywhere within this three dimensions. An experienced operator will
be able to track an abnormal jet even if it is directed out of a
standard two-dimensional plane.
The apical window is also an excellent position for obtaining some
initial experience with continuous wave Doppler. Placing the CW
transducer directly over the apical impulse (located by palpation)
and angling the beam somewhat leftward and posteriorly will usually
result in a typical mitral flow profile. It is wise for the beginner
to practice locating flow through the mitral valve as the flow profile
resembles the appearance of the mitral valve on M-mode and is readily
recognized. Marked medial redirection of the CW beam from the apex
will result in a flow profile through the tricuspid valve. Because
pressures are higher on the left side of the heart, velocities are
generally higher on the left when compared to the right in normal
and diseased states. Exceptions to this rule are encountered in
severe pulmonary hypertension or stenosis.
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| Fig.1.43 |
The ranges of normal peak flow velocities are shown in Figure 1.43.
Notice that the normal flows are slightly higher in children than
adults and slightly higher on the left side of the heart in comparison
to the right.
After some experience, an operator can become very skillful with
minor manipulation of the CW transducer.
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| Fig.1.44 |
The difference between the various waveforms obtained from the
ventricular apex using a CW transducer is shown in Figure 1.44.
At first, the beam is directed superiorly to encounter aortic
insufficiency and stenosis (Figure 1.44 panel A). The insufficiency
is directed toward the transducer and appears on the spectral
display in diastole. The aortic stenosis flow moves away from
the transducer in systole. The CW is then angled midway between
ventricular outflow and inflow (Figure 1.44 panel B) and encounters
a mixed diastolic profile with mitral inflow superimposed on the
aortic insufficiency. Progressive angulation through the mitral
valve demonstrates a pure mitral inflow in diastole with mitral
insufficiency in systole (Figure 1.44 panel C).
The problem of recording flow across mitral and aortic valve simultaneously
(Figure 1.44 panel B). results partly from the fact that the ultrasound
beam width is large enough to detect more than one jet. Failure
to appreciate this may lead the unwary beginner to diagnose mitral
stenosis, for example, when only aortic regurgitation is present.>
 |
| Fig.1.45 |
The apical window also supplies an opportunity for examination of
left sided flow with PW Doppler echocardiography by movement of
the imaging plane to the apical two-chamber view (Fig. 1.45). This
view is obtained by rotating the two-dimensional transducer counterclockwise
and 90 degrees from the apical four chamber view and is particularly
suited for examination of both left ventricular inflow (Fig. 1.45,
sample sites 1 and 2) and outflow (sample sites 3 and 4). Flow velocity
profiles through the mitral valve resemble those obtained in the
apical four-chamber view and are directed toward the transducer
in diastole. It is a little easier to position and hold the pulsed
sample volume on the aortic side of the aortic valve using the two-chamber
approach rather than the four-chamber with extreme superior angulation.
2004