Doppler Techniques for Aortic Stenosis and Aortic Regurgitation
©Walter Rasmussen, R.D.C.S.
When aortic stenosis is present and there is normal left ventricular systolic function, the continuous wave Doppler signal will show a high intensity, triangular velocity profile, typically coming to a narrow point at an elevated peak velocity. The following image demonstrates a Doppler signal below the baseline with transducer position at the apical window.
Above: The Spectral Doppler scale is adjusted to fully occupy the graph so that better visual assessment and more accurate measurements can be made. Notice that the reverse flow signal is not cut-off at the top of the graph.
Above: The typical two-dimensional, apical 3-chamber view image used for cursor placement in the assessment of aortic stenosis/regurgitation.
When using CW Doppler for assessment of aortic stenosis, careful placement of the cursor is critical to distinguishing it from both mitral and tricuspid insufficiency, which when present, can be recorded just a few millimeters away from the aortic valve as the examples demonstrate below.
Each of above are taken from the apical window at slightly different cursor position.
The importance of Doppler Audio:
The Spectral Doppler image shown above, is only a compressed visual representation of the actual audio signal. It is through listening to the Doppler audio sound, that the sonographer can be certain that the best spectral Doppler image has been obtained. The Doppler audio sound helps the sonographer position the transducer and the CW cursor within the center of the stenotic jet, resulting in the display of a narrower and higher velocity peak to the spectral Doppler profile.
Even with careful observation of the spectral Doppler image and attention to the Doppler audio output, because of a poor signal or the inability to get good alignment with the blood flow, a blunted peak velocity sometimes cannot be avoided and will result in under-estimation of peak and mean pressure gradients and thus, the severity of aortic stenosis.
Please see the following topics for a description of the use of the Pedoff transducer for the performance of a complete assessment of aortic stenosis: Using the Pedoff Probe for Echocardiography; Pedoff Tranducer Assessment of Aortic Stenosis;
Aortic Regurgitation Doppler:
If aortic regurgitation is present, adjust the scale so that both forward and reverse blood flow is recorded on the chart. An optimal AR jet may not be obtained from the same cursor position as the aortic systolic jet and so, re-adjustment of the transducer position or angle may be necessary. The AR jet typically has a rapid rise to its peak velocity in early diastole, followed by a broad deceleration slope, which lasts throughout diastole. In situations where there is a trace of aortic regurgitation on Color Doppler, it may be impossible to record a complete AR velocity profile and an undue amount of time need not be spent on it.