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TELECONFRENCES
2004
The Changing Left Ventricle

2003
Aortic Valve Disease: New Dimensions in Evaluation and Management

2002
Heart Failure: Echo's Role in and Emerging Health Crisis

2001
Chest Pain in Children & Adults: The Role of Echo

2000
Mitral Regurgitation: New Concept

1998
The Falling Left Ventricle: Diastolic & Systolic Function

1997
Changing the Outcome of Coronary Artery Disease
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VIDEO ARCHIVES

Chest Pain in Children and Adults

Mitral Regurgitation: New Concepts

Diastolic and Systolic Function

Changing the Outcome of CAD

BROADCAST SUPPLEMENTS
2000 MV
2001 Chest Pain
2002 Heart Failure



Doppler Detection of Valvular Regurgitation
Aortic Regurgitation
Fig.2.10

PW Doppler has been reported to have a sensitivity ranging between 86% and 100% for the detection of aortic regurgitation. PW Doppler examinations for this lesion are best begun using the apical two-or four-chamber two-dimensional views for operator guidance. Figure 2.10 demonstrates a PW Doppler recording from just at the coaptation point of the aortic valve in a normal patient when the transducer was placed at the ventricular apex. Note that some low frequency diastolic sounds are normally encountered, which likely result from blood swirling through the mitral orifice and around the left ventricular outflow tract. The novice should not mistake these low velocity events for evidence of aortic insufficiency.

Fig.2.11

When regurgitation is present, careful searching just on the ventricular side of the aortic valve with PW Doppler reveals the high frequency sounds and diastolic spectral broadening typical of aortic insufficiency. This is shown in Figure 2.11, where almost all regurgitation jets are severely aliased and the top of the spectral trace appears cut off and placed at the bottom of the display. Note that the zero baseline of the spectral display has been moved to the bottom of the display, as described in Unit 1, in an attempt to eliminate the aliased diastolic signal and to provide as much display of the spectral profile as possible. Even with this maneuver, the top of the aliased signal is still missing.

Fig.2.12

Similarly, the best window for the evaluation of aortic insufficiency with CW Doppler is the apical window. Using this approach, aortic insufficiency appears as a holodiastolic, high frequency turbulent jet with spectral broadening and flow toward the transducer as noted in Figure 2.12. The resultant spectral shift is positive (i.e., above the baseline). Doppler spectral recordings of aortic insufficiency are invariably holodiastolic.

It is usually of interest to beginners to Doppler echocardiography who are familiar with auscultation, that the Doppler spectrum in aortic insufficiency has a holodiastolic duration and its duration does not vary with severity. This example serves to highlight the differences between the audible sounds generated by the Doppler shift device and those heard by auscultation. Using the latter approach, the typical murmur of aortic insufficiency is early diastolic and decrescendo. These differences emphasize the fact that the Doppler instrument is not an elaborate electronic stethoscope.

Fig.2.13

The operator should keep in mind some possible causes for false positive or false negative examinations when evaluating patients with suspected aortic insufficiency. One common reason for a false positive test is confusion with mitral valve diastolic inflow, particularly when mitral stenosis is present.
Figure 2.13
shows a CW recording taken from the apical window in a patient with aortic valve disease. Note the different timing of the aortic diastolic jet and the mitral inflow signal. The duration of diastole is longer in aortic insufficiency than mitral inflow.

Fig.2.14

A maneuver performed from the apical window using a CW Doppler transducer is demonstrated in Figure 2.14. The first two beats were obtained with the beam angled toward the left ventricular outflow tract, and demonstrate aortic insufficiency. The beam is then angled toward the mitral orifice where the diastolic jet of mitral stenosis is encountered in the second two beats.

These jets are both diastolic events and are quite similar in contour. Note also that the spectral distribution of both abnormal jets is wide, but much less intense in aortic insufficiency when compared with mitral stenosis. Recognition of the different features of the spectral display in these two lesions, plus a thorough examination of the location of the suspected abnormal diastolic jet using the PW approach, should allow the operator to reliable separate aortic insufficiency from mitral stenosis in most cases.

It is also possible that a false positive recording of aortic insufficiency may result from inadvertent detection of coronary blood flow. Although coronary flow is mostly diastolic and the size of the Doppler beam is usually large at remote distances from the transducer, it seems unlikely that this is a very frequent cause of false positives in clinical practice.

It is worthwhile to keep in mind that detection of aortic regurgitation by Doppler with a negative cardiac catheterization may not necessarily constitute a false positive study. However, the amount of regurgitation in this situation is probably minimal. Rapid dilution of a small aortic regurgitant jet into the large left ventricular cavity probably accounts for the failure to appreciate this event by angiographic means.

Fig.2.15

The probable reason for a false negative diagnosis of aortic insufficiency is that the jet is small and not easily detected with either pulsed or continuous wave Doppler. Not only may the jet be small, it may move through the interrogating beam with the phases of the cardiac cycle. This makes it difficult to record a full profile because the jet is never positioned in the Doppler beam long enough to record the entire event, as seen in Figure 2.15.

Fig.2.16

Such an occurrence is the likely explanation for the PW Doppler spectral recording shown in
Figure 2.16
. Here, the full diastolic duration of the aortic insufficiency jet is poorly appreciated on some beats. The recording was obtained with the transducer held at the ventricular apex.

 

 

 

Fig.2.17

This phenomenon also may occur due to the phases of the respiratory cycle. This is not because the volume of the jet is varying with respiration. Rather, the direction of the jet is probably changing slightly with respect to the direction of the interrogating Doppler beam as the heart moves up and down with the moving diaphragm. This phenomenon is demonstrated in Figure 2.17 where the full profile of aortic insufficiency is seen from the ventricular apex using CW Doppler. Here the full profile of aortic insufficiency is recorded on some beats and not on others. When this occurs, and differences due to respiration are suspected, the operator should try many different transducer positions and angulations to record as much of the suspected abnormal profile as possible.

 

Fig.2.18

Some jets may be so small as to require interrogation from slightly different transducer positions to record the full profile. The spectral profiles in Figure 2.18 are not the result of a continuous strip recording but are a five-panel composite demonstration of the diastolic appearance of aortic insufficiency from five slightly different apical positions in a patient with aortic insufficiency. The only way to overcome this problem is to be assured that every possible area has been adequately interrogated for aortic insufficiency during the Doppler examination.

Although the apical approach is the most profitable window for the detection of aortic insufficiency, it is worth keeping in mind that some jets are directed eccentrically and may be detectable only from some other window such as the left parasternal. Caution should be exercised, however, when using CW Doppler from parasternal windows. It might be possible to mistake pulmonic insufficiency, which can be recorded in many subjects, for aortic valve insufficiency. Fortunately, most aortic insufficiency encountered from the left parasternal approach is directed posteriorly toward the mitral valve and away from the transducer (a negative jet). This contrasts with pulmonic insufficiency, which is uniformly directed anteriorly into the right ventricle toward the transducer (a positive jet).

Some information as to left ventricular end-diastolic pressure may be gained in the setting of aortic insufficiency. Since the velocity of any jet relates to the pressure drop across the valve, there exists a pressure gradient between the aorta and left ventricle at end-diastole. This pressure gradient may be estimated by measuring the velocity of the aortic regurgitant jet at end-diastole using the simplified Bernoulli equation. Subtracting this pressure from diastolic blood pressure (as measured by cuff at the time of the Doppler examination) provides an estimate of left ventricle end-diastolic pressure.

Fig.2.19

A typical aortic regurgitant jet obtained by CW Doppler from the left ventricular apex is shown in Figure 2.19. In the example shown, the end-diastolic velocity is approximately 1.9 m/sec which corresponds to a pressure gradient estimate of 14mmHg. This patient had severe aortic insufficiency, and the measure diastolic blood pressure was 55mmHg by brachial arterial cuff measurement. This resulted in an end-diastolic pressure estimate of 41 mmHg. At catheterization, the actual measured pressure was 38 mmHg.

It should be noted, however, that this approach only shows satisfactory correlation in patients with severe (3+ to 4+) angiographic aortic insufficiency. Application of this method to individuals with lesser degrees of insufficiency does not yield good correlations with catheterization measurements of left ventricular end-diastolic pressure.

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