AORTA: AAA, DISSECTION

Aortic Ultrasound Pearls & Pitfalls

• Start imaging in transverse midway between xyphoid and navel and try to find a good window. Look for the aorta over spine pattern.
• If you are unsure if you are on a vascular structure use color flow or doppler split-screen to be certain.
• Remember the IVC is compressible while the aorta is not. This is sometimes referred to as a positive “wink” sign.
• Sometimes the IVC appears to pulsate due to its proximity to the aorta
• View the entire aorta in at least two planes: transverse and longitudinal.
• Take your measurements in the transverse plane, outer wall to outer wall. Normal diameter is up to 2cm with distal tapering. An aneurysm is defined as a diameter >3cm or lack of tapering. Any aneurysm in a symptomatic patient is an emergency. In an asymptomatic patient, elective surgery is usually considered once the diameter exceeds 5cm.
• Do not be fooled by calcifications (white) and clot (gray/liver density) which may mislead your diameter measurements.
• Image lots of normals, so that you gain experience.
• If you can’t find the aorta try starting the longitudinal view just below the xyphoid
• Look for saccular aneurysms. They can fool you. This is one reason to image the ENTIRE aorta.

Want more educational images? Check out the ED Atlas on CD

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Aorta: Aneurysms

Normal Aorta with labels: Transverse

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Normal Aorta with labels: Longitudinal

SMA = Superior Mesenteric Artery

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4.5cm AAA with spine & normal IVC 

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AAA: Transverse

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AAA: Long

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AAA: Transverse

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TRICK: For difficult Aorta Localization use the Doppler/B-mode split screen.
(AAA Transverse on left. Doppler pulse wave on right.)

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AAA: Transverse

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Aortic Dissections Pearls and Pitfalls

• Most dissections, about 90%, will progress into the abdominal aorta. Therefor start where you are familiar. Look for a hyper-echoic flap.

• A flap within the aorta will usually move with each pulse. A flap will not extend beyond the inner wall of the aorta. If it does, it is likely an artifact.

• Check the sub-xyphoid and parasternal views for evidence of pericardial effusion and tamponade.

• Next look at the descending thoracic aorta behind the heart. On the parasternal long axis view it will be seen in cross-section as a circle which normally should be less than 42mm in diameter. Rotate into the plane of the aorta to get a long axis view as you continue to check for a flap.

• Finally check the aortic arch with a supra-sternal view. Have the patient turn his or her head to the right and orient your probe in the plane of the aortic arch.

• Consider a quick bedside echo in chest pain patients where there is some suspicion for dissection. If you do see a dissection or a pericardial effusion the heightened urgency it gives you may mean the difference between a good outcome and a bad one.

Dissection: transverse abdominal level

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Dissection: longitunial at level of abdomen

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Dissection: suprasternal veiw of dilated aortic arch with flaps

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Dissection: transverse at level of abdomen

 

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Do you want a pocket reference that has essential material on ED Ultrasound as well as other imaging, labs, EKG’s, procedures, risk management and more?

Then get Side Kick: Emergency Medicine

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