I don't know about you, but aortic stenosis cases seem to be my bread and butter. I seem to see more patients with aortic stenosis than with any other pathology.
Well, part of that is, of course, attributable to the region where my echo lab is located. Regardless, aortic stenosis plays an important role in our entire lifetime of exploration as aortic stenosisHerzsonograph.
Unfortunately, with the recent trend of seeing more patients in less time, we all tend to make mistakes when evaluating the aortic valve. This is especially true if this unfortunate trend continues.
In this post, we will look at some of the most common mistakes we all make when measuring aortic valve velocity during our AS cases.
The fact is, even though our patients don't have aortic stenosis, we still measure aortic valve velocities in everyone we see (or at least we should!).
With the machines we use today, we have many tools that we can use to accurately assess aortic valve peak velocities using echocardiography.
These tools include:
- Ultraschall 2D
- Espectral Doppler
In our routine echo studies, we use all three instruments to assess the structure and function of the aortic valve.
But it is spectral Doppler that we use to measure peak aortic valve velocities.
Unfortunately, there are some very simple mistakes that can cause us to underestimate or overestimate these gradients.
Here are the top 4:
The 4 most common errors in measuring the maximum velocity of the aortic valve
1. Increased Doppler angle
A false Doppler angle is by far one of the most common errors encountered by cardiac sonographers when trying to measure the peak aortic valve gradient.
Remember to learn more about theDoppler equationand cosine theta? What what!? Yes, you may need to go back to the depths of your mind. But I know it's there!
In short, we must keep our ultrasound beam parallel to the direction of blood flow. We have a 20-degree window to work through before things start to get worse real fast. It is always best to aim for 0 degrees, as any non-zero angle will result in an underestimated reading.
The more angles you have in relation to the direction of blood flow, the less accurate your peak aortic velocity measurement will be. And just so you knowThis error will always be an underestimate.
But what about the angle correction feature in the echo machine?
All of our ultrasound machines have this feature, but should we use it? In short, no. The reason for this is that blood flows in 3 dimensions and the correct angle cursor only works in 2 dimensions.
Although the cursor artificially provides a cos theta of 0 for the correct echo machine angle, this is only an approximation as there is no way to tell which way blood is flowing in this third dimension.
For this reason theThe American Society of Echocardiography does not recommend the use of the angle correction cursor when interpreting aortic valve gradient measurements..
Things you can do to improve the Doppler angle
- Continue rolling the patient to the side. If this does not improve the angle, try rolling the patient backwards.
- Goes down an intercostal space. This often opens up the LVOT and gives you a nice straight line parallel to the blood flow.
- Do not report peak aortic valve velocities with angle correction. Just use the angle correction feature as a tool to figure out what the minimum top speeds might be. But again, do not report these measurements.
2. LVOT does not open fully
This is a common mistake made by new cardiac sonographers or experienced sonographers who simply rush through the exam.
In this case, the cursor is thrown up on the current 2D image and CW Doppler is turned on. Therefore, the Doppler signal shown first is considered the correct one. The sonographer may even take 2 or 3 measurements of these erroneous Doppler signals.
The problem is that not all patients deliver an open LVOT that is fully open and parallel to the ultrasound beam. This is especially true for older patients with aortic stenosis. Over the years, the heart can remodel itself, making the LVOT almost perpendicular to the ultrasound beam.
As you can imagine, measurements made this way can be very inaccurate. I have seen situations where patients had severe aortic stenosis but only slight slopes were recorded... with differences of more than 2 m/s! These are significant differences.
Just a reminder to make sure the LVOT is fully open as much as possible when evaluating aortic valve velocities.
3. Massive artifact
This is one of the most common mistakes that we are tempted to make when measuring TR peak gradient. But it is also a common error in measuring the peak Doppler trace of the aortic valve.
What essentially happens is that weoverestimateAortic valve velocity, including thin light Doppler signal that goes beyond true peak velocity as part of aortic tracking.
This is simply an artifact and has nothing to do with true aortic blood flow. So be careful not to include these artifacts.
What can you do to avoid aortic velocity measurement artifacts?
- Reduce the overall Doppler gain and compression settings. This often removes much of this subtle artifact.
- Decrease the Doppler scale. This not only helps you make much more accurate measurements, but also gives you a better chance of distinguishing between the artifact and the actual Doppler spectral trace of the aortic valve.
- Measure multiple Doppler waveforms of the aortic valve. If in doubt, perform several measurements to validate your results.
4. Measures that just don't make sense
Pay close attention to whether or not the measurements you record actually make sense.
What I want to say is, think about what the aortic valve looks like in 2D. Does the valve appear stenotic? Is it thick? Are the aortic valve leaflets open or fixed?
If the aortic valve appears abnormal, you should perform Doppler scanning in anticipation of abnormal Doppler spectral recordings.
This common error in echocardiographs is associated with the failure to fully open the LVOT. If the technician sees that the valve is abnormal but the Doppler recordings of aortic valve peak velocity are close to normal, something is wrong and it's time to find out what it is and how to fix it.
This applies to all aspects of your echocardiogram exam. Always look at your measurements, both 2D and Doppler, and make sure they make sense.
Tips for Meaningful Measurements
- Always look at every measurement you take. This applies to both 2D measurements and Doppler measurements.
- When things don't add up, find out what's wrong and fix it. Then take the measurement again.
We not only measure the maximum aortic valve gradient in patients with aortic stenosis. We should do that with every patient. You may discover that the patient has a subaortic membrane causing an obstruction in the LVOT that you missed.
For patients with aortic stenosis, take the extra time to ensure that you are not only obtaining the absolute maximum velocity, but also tracking the true spectral Doppler trace.
- Keep an ultrasound beam as parallel as possible to the blood flow.
- Open the LVOT and aortic valve as much as possible.
- Reduce Doppler gain and Doppler spectral scale to avoid measurement artifacts.
- Always look at your measurements and ask yourself if they make sense compared to what you see with your own eyes.
1. How to Calculate Aortic Valve Area Using the Equation of Continuity
2.The Pedoff Probe: Become a Pro in Blind CW Doppler
3.Spectral Doppler: what it is and how it is used in ultrasound!
Echocardiography Pocket Card Set
- Highly recommended for new and experienced sonographers.
- Carry it in your pocket, machine or table
- Parameters of diastolic dysfunction
- Regional Wand Movement
- prosthetic valve gradients
- valve morphology and much more!
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- Echocardiography: Journal of Cardiovascular Ultrasound and Related Techniques Vol. 21 Number 2 2004
- American Society of Echocardiography