Evaluating the aortic valve is a routine part of an echocardiogram. There are many methods we use to determine the structure and function of the valve, including 2D, color Doppler and a combination of pulsed & continuous-wave Doppler. With short examination times being a common challenge, it can easily cause measurement errors within our studies. This blog is going to cover 4 errors to avoid when measuring continuous-wave (CW) Doppler tracings of the peak aortic valve velocity.
#1: NOT PARALLEL TO FLOW
One of the most common errors to properly evaluating the peak aortic valve (AV) velocity, is not having the Doppler cursor parallel to flow. Let’s recall back to the days of learning physics:
- Velocity, frequency and angle all determine the frequency of sound waves within a moving object
- Angle between the ultrasound beam and direction of flow should be zero = parallel with blood flow
- Any angle other than zero, will cause underestimation of the true velocity
SCANNING TIPS:
- Move transducer more lateral on patients body
- Have patient lean back a small amount
- Do not use ‘Angle Correction’ feature- likely to cause more error
#2: MEASURING ARTIFACT
Avoid measuring fine linear signals at peak velocity waveform. These fine linear signals should not be included in the velocity tracing.
SCANNING TIPS:
- Decrease Doppler gains to eliminate artifact
- Decrease Doppler scale for accurate tracings
#3: MEASURING INCORRECT VELOCITY TRACING
Mitral regurgitation (MR) velocity can easily be mistaken for the aortic valve (AV) velocity if not paying close attention! We are able to differentiate the two by evaluating the timing at which the velocity occurs.
- MR velocity will occur during both the isovolumic contraction (IVCT) & relaxation time (IVRT) during systole (moments when both valves are closed before & after systole)
- AV velocity will occur after IVCT & ends before IVRT during systole (once the aortic valve opens)
SCANNING TIPS:
- Identify valve clicks on Doppler signal
- Correlate velocity with timing of EKG to identify IVCT & IVRT
#4: MEASURING POST-EXTRA SYSTOLIC BEATS
It’s not uncommon for our patients to have PVC’s throughout their exam. Although we cannot prevent this from occurring, we can be sure to not measure these beats! This includes not measuring the extra beat (PVC) and the following velocity jet.
SCANNING TIPS:
- Let the Doppler signal run for a few seconds
- Only measure signals that are of common velocity strength
- Patients in A-Fib: measure 5-6 velocities for both AV and LVOT
SUMMARY
When evaluating the peak aortic valve CW Doppler velocities, be sure to avoid these 4 common errors:
- Doppler Angle Not Parallel to Flow
- Measuring Fine Linear Artifact at Peak Velocity
- Measuring MR Velocity for Peak AV Velocity
- Measuring Extra-Post Systolic Beat Velocities
Andrea Fields MHA, RDCS
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References:
Lang, R. M., MD, Badano, L. P., MD, & Mor-Avi, V., PhD. (2015). Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. JASE, 28(1), 1-53. Retrieved March 1, 2017, from http://asecho.org/wordpress/wp-content/uploads/2015/01/ChamberQuantification2015.pdf
