SonoPro Tips and Tricks for Aortic Aneurysm and Dissection

Written by: John Li, MD (NUEM ‘24) Edited by: Andra Farcas, MD (NUEM ‘21) Expert Commentary by: John Bailitz, MD & Shawn Luo, MD (NUEM ‘22)

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SonoPro Tips and Tricks

Welcome to the NUEM Sono Pro Tips and Tricks Series where Sono Experts team up to take you scanning from good to great for a problem or procedure! For those new to the probe, we recommend first reviewing the basics in the incredible FOAMed Introduction to Bedside Ultrasound Book and 5 Minute Sono. Once you’ve got the basics beat, then read on to learn how to start scanning like a Pro!

Aortic ultrasound is a staple in emergency point of care ultrasound. It has incredible sensitivity (97.5-100%) and specificity (94.1-100%) in detecting abdominal aortic aneurysms and can provide a diagnosis for critically ill patients in seconds. [1-4] However, it can often be a technically difficult study for beginner sonographers due to shadowing bowel gas and patient body habitus. Follow along in this installment of our Sono Pro Tips and Tricks Series to become an expert in finding aortas!

Beyond the classic elderly male smoker with abdominal, flank, or back pain, what are other scenarios where you would use aortic ultrasound?

1. Older patients with limb ischemia - an aortic aneurysm can have atherosclerosis or a mural thrombus which can embolize and cause an arterial occlusion!

2. “But they fixed my aorta!” Aortic endograft leakage can sometimes present with symptoms that are similar to a AAA rupture, such as back pain, flank pain, or hemodynamic instability.

How to scan like a Pro

Always Start Smart: Aortic ultrasound can be tricky because of factors that seem out of our control, such as bowel gas or patient body habitus.

1. When scanning for an abdominal aortic aneurysm, start scanning in the epigastric region with a transverse view and apply constant pressure, gently pushing the bowel gas out of the way as you slide the probe down towards the patient’s feet.

2. Tell your patients to bend their knees! This relaxes the abdominal musculature and can help you move bowel gas or make better contact with the probe.

What if you still can’t see it? Try looking in the right upper quadrant view of the FAST exam!

1. Start with your probe in the right mix-axillary line and use the liver as your acoustic window. You may need to fan anteriorly or posteriorly depending on the patient’s body habitus and your positioning.

2. Unfortunately, this view predominantly visualizes the superior aspect of the abdominal aorta, and it can be difficult to visualize the inferior abdominal aorta or the bifurcation.

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Here we are looking at a modified RUQ view, where the aorta is visualized on the bottom part of the screen using the liver as an acoustic window. (acep.org)

Pro Pickups!

1. What’s that weird aneurysm?

   • Most people are familiar with the classic fusiform aortic aneurysm, but saccular aneurysms can be easily missed because of shadowing bowel gas obstructing parts of the aorta. Saccular aneurysms actually have a higher risk of rupture and repair is recommended for smaller diameters.

Here you can see two images in the longitudinal axis of the different kinds of abdominal aortic aneurysms. On the left is a saccular aneurysm and on the right is a fusiform one. Be sure to pay attention to the mural thrombus in the walls of both of these aortas - they can embolize and cause arterial occlusions! (med.emory.edu)

2. How big is that aorta anyways?

• Be sure to always measure the aorta from outside wall to outside wall!

• Many aortic aneurysms have a mural thrombus or intraluminal clot, and it can be very easy to mistake these for extra-luminal contents.

• Remember the concerning numbers: >5.5cm for men and >5cm for women!

What the Pros Do Next

Abdominal Aortic Aneurysm

1. If the patient is hemodynamically unstable (defined as BP <90/60, altered mental status, or other signs of end-organ damage), go straight to the OR!

2. If the patient is hemodynamically stable (defined as the absence of any of the above), then the next step is to obtain further imaging, such as a CT Angiogram, which is the imaging gold standard.

   • If you are concerned about a large AAA that could be a contained leak but the patient is hemodynamically stable, then we recommend an emergent vascular surgery consult

   • If you find a small AAA (defined as <5cm in women or <5.5cm in men) that you do not think is actively contributing to the patient’s symptoms, then we recommend outpatient vascular surgery follow up

SonoPro Tips - Where to Learn More

Do you want to review more examples of pathologic images that you may see when you are doing an aortic ultrasound? Be sure to check out The Pocus Atlas by our expert editor Dr. Macias. Aortic pathology is quite rare, and going through these images will help immensely in recognizing this diagnosis in emergent situations.  If you’re interested in looking at some of the evidence behind aortic ultrasound, be sure to check out the evidence atlas here as well.

References

1. Rubano E, Mehta N, Caputo W, Paladino L, Sinert R. Systematic review: emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm. Acad Emerg Med. 2013 Feb;20(2):128-38. doi: 10.1111/acem.12080. PMID: 23406071.

2. Hunter-Behrend, Michelle, and Laleh Gharahbaghian. “American College of Emergency Physicians.” ACEP // Home Page, 2016, www.acep.org/how-we-serve/sections/emergency-ultrasound/news/february-2016/tips-and-tricks-big-red---the-aorta-and-how-to-improve-your-image/.

3. Ma, John, et al. Ma and Mateer's Emergency Ultrasound. McGraw-Hill Education, 2020.

4. Mallin, Mike, and Matthew Dawson. Introduction to Bedside Ultrasound: Volume 1. Emergency Ultrasound Solutions, 2013.

5. Macias, Michael. TPA, www.thepocusatlas.com/.

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Expert Commentary

Another great Sono Pro Post! Thank you John Li and Andra for helping everyone move from good to great when scanning for Abdominal Aortic Aneurysms. As noted, this application defines Emergency Ultrasound as a fast (pun intended), accurate, and life saving diagnostic tool for every EM physicians tool belt. When consistent probe pressure does not do the trick, consider the RUQ view for a quick look. Since most AAA’s are fusiform, this may quickly confirm your suspicions and prompt the call to get the OR ready. Be sure to visualize the entire abdominal aorta throughout in both short and long axis to identify saccular aneurysms and even the rare aortic occlusion!

John Bailitz, MD

Vice Chair for Academics, Department of Emergency Medicine

Professor of Emergency Medicine, Feinberg School of Medicine

Northwestern Memorial Hospital

Shawn Luo, MD

PGY4 Resident Physician

Northwestern University Emergency Medicine

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How To Cite This Post:

[Peer-Reviewed, Web Publication] Li, J. Farcas, A. (2021 Oct 11). SonoPro Tips and Tricks for Aortic Aneurysm. [NUEM Blog. Expert Commentary by Bailitz, J. Shawn, L.]. Retrieved from http://www.nuemblog.com/blog/sonopro-tips-and-tricks-for-aortic-aneurysm

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SonoPro Tips and Tricks for Pulmonary Embolism

Written by: Megan Chenworth, MD (NUEM ‘24) Edited by: Abiye Ibiebele, MD (NUEM ‘21) Expert Commentary by: John Bailitz, MD & Shawn Luo, MD (NUEM ‘22)

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SonoPro Tips and Tricks

Welcome to the NUEM Sono Pro Tips and Tricks Series where Sono Experts team up to take you scanning from good to great for a problem or procedure! For those new to the probe, we recommend first reviewing the basics in the incredible FOAMed Introduction to Bedside Ultrasound Book and 5 Minute Sono. Once you’ve got the basics beat, then read on to learn how to start scanning like a Pro!

Did you know that focused transthoracic cardiac ultrasound (FOCUS) can help identify PE in tachycardic or hypotensive patients? (It has been shown to have a sensitivity of 92% for PE in patients with an HR>100 or SBP<90, and approaches 100% sensitivity in patients with an HR>110 [1]). Have a hemodynamically stable patient with PE and wondering how to risk stratify? FOCUS can identify right heart strain better than biomarkers or CT [2].

Who to FOCUS on?

1. Patients presenting with chest pain or dyspnea without a clear explanation, or with a clinical concern for PE. The classic scenario is a patient with pleuritic chest pain with VTE risk factors such as recent travel or surgery, systemic hormones, unilateral leg swelling, personal or family history of blood clots, or known hypercoagulable state (cancer, pregnancy, rheumatologic conditions).

2. Patients presenting with unexplained tachycardia or dyspnea with VTE risk factors

3. Unstable patients with undifferentiated shock

4. When PE is suspected but CT is not feasible: such as when the patient is too hemodynamically unstable to be moved to the scanner, too morbidly obese to fit on the scanner, or in resource-limited settings where scanners aren’t available

   1. One may argue AKI would be another example of when CT is not feasible (though there is some debate over the risk of true contrast nephropathy - that is a discussion for another blog post!)

How to scan like a Pro

1. Key is to have the patient as supine as possible - this may be difficult in truly dyspneic patients

2. If difficulty obtaining views arise, the left lateral decubitus position helps bring the heart closer to the chest wall

FOCUS on these findings

You only need one to indicate the presence of right heart strain (RHS).

1. Right ventricular dilation

2. Septal flattening: Highly specific for PE (93%) in patients with tachycardia (HR>100) or hypotension (SBP<90) [1]

3. Tricuspid valve regurgitation

4. McConnell’s sign

   • Definition: Akinesis of mid free wall and hypercontractility of apical wall (example below)

   • The most specific component of FOCUS: 99% specific for patients with HR>100bpm or SBP<90 [1]

5. Tricuspid annular plane systolic excursion (TAPSE)

• The most sensitive single component of FOCUS: TASPE < 2cm is 88% sensitive for PE in tachycardic and hypotensive patients; 93% sensitive when HR > 110 [1]

Where to FOCUS

Apical 4 Chamber (A4C) view: your best shot at seeing it all

1. Find the A4C view in the 5th intercostal space in the midclavicular line

2. Optimize your image by sliding up or down rib spaces, sliding more lateral towards the anterior axillary line until you see the apex with the classic 4 chambers - if the TV and MV are out of the plane, rotate the probe until you can see both openings in the same image; if the apex is not in the middle of the screen, slide the probe until the apex is in the middle of the screen. If you are having difficulty with this view, position the patient in the left lateral decubitus.

3. Important findings:

   1. RV dilation: the normal RV: LV ratio in diastole is 0.6:1. If the RV > LV, it is abnormal. (see in the image below)

   2. Septal flattening/bowing is best seen in this view

   3. McConnell’s sign: akinesis of the free wall with preserved apical contractility

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McConnell’s Sign showing akinesis of the free wall with preserved apical contractility

4. Tricuspid regurgitation can be seen with color flow doppler when positioned over the tricuspid valve

Tricuspid regurgitation seen with color doppler flow

5. TAPSE

• Only quantitative measurement in FOCUS, making it the least user-dependent measurement of right heart strain [3]

• A quantitative measure of how well the RV is squeezing. RV squeeze normally causes the tricuspid annulus to move towards the apex.

• Fan to bring the RV as close to the center of the screen as possible

• Using M-mode, position the cursor over the lateral tricuspid annulus (as below)

• Activate M-mode, obtaining an image as below

• Measure from peak to trough of the tracing of the lateral tricuspid annulus

  • Normal >2cm

How to measure TAPSE using ultrasound

Parasternal long axis (PSLA) view - a good second option if you can’t get A4C

1. Find the PSLA view in the 4th intercostal space along the sternal border

2. Optimize your image by sliding up, down, or move laterally through a rib space, by rocking your probe towards or away from the sternum, and by rotating your probe to get all aspects of the anatomy in the plane. The aortic valve and mitral valve should be in plane with each other.

3. Important findings:

   1. RV dilation: the RV should be roughly the same size as the aorta and LA in this view with a 1:1:1 ratio. If RV>Ao/LA, this indicates RHS.

   2. Septal flattening/bowing of the septum into the LV (though more likely seen in PSSA or A4C views)

Right heart strain demonstrated by right ventricle dilation

Parasternal Short Axis (PSSA) view: the second half of PSLA

Starting in the PSLA view, rotate your probe clockwise by 90 degrees to get PSSA

1. Optimize your image by fanning through the heart to find the papillary muscles - both papillary muscles should be in-plane - if they are not, rotate your probe to bring them both into view at the same time

2. Important findings:

   1. Septal flattening/bowing: in PSSA, it is called the “D-sign”.

“D-sign” seen on parasternal short axis view. The LV looks like a “D” in this view, particularly in diastole.

Subxiphoid view: can add extra info to the FOCUS   

1. Start just below the xiphoid process, pointing the probe up and towards the patient’s left shoulder

2. Optimize your image by sliding towards the patient’s right, using the liver as an echogenic window; rotate your probe so both MV and TV are in view in the same image

3. Important findings

   1. Can see plethoric IVC if you fan down to IVC from RA (not part of FOCUS; it is sensitive but not specific to PE)

Plethoric IVC that is sensitive to PE

What to do next?

Sample algorithm for using FOCUS to assess patients with possible PE.

*cannot completely rule out PE, but negative FOCUS makes PE less likely

Limitations to keep in mind:

1. FOCUS is great at finding heart strain, but the lack of right heart strain does not rule out a pulmonary embolism

   1. Systematic review and meta-analysis concluded that the overall sensitivity of FOCUS for PE is 53% (95% CI 45-61%) for all-comers [5]

2. Total FOCUS exam requires adequate PSLA, PSSA, and A4C views – be careful when interpreting inadequate scans

3. Can see similar findings in chronic RHS (pHTN, RHF)

   1. Global thickening of RV (>5mm) can help distinguish chronic from acute RHS

   2. McConell’’s sign is also highly specific for acute RHS, whereas chronic RV failure typically appears globally akinetic/hypokinetic

SonoPro Tips - Where to Learn More

1. Right Heart Strain at 5-Minute Sono: http://5minsono.com/rhs/

2. Ultrasound GEL for Sono Evidence: https://www.ultrasoundgel.org/posts/EJHu_SYvE4oBT4igNHGBrg, https://www.ultrasoundgel.org/posts/OOWIk1H2dePzf_behpaf-Q

3. The Pocus Atlas for real examples: https://www.thepocusatlas.com/echocardiography-2

4. The Evidence Atlas for Sono Evidence: https://www.thepocusatlas.com/ea-echo

References

1. Daley JI, Dwyer KH, Grunwald Z, Shaw DL, Stone MB, Schick A, Vrablik M, Kennedy Hall M, Hall J, Liteplo AS, Haney RM, Hun N, Liu R, Moore CL. Increased Sensitivity of Focused Cardiac Ultrasound for Pulmonary Embolism in Emergency Department Patients With Abnormal Vital Signs. Acad Emerg Med. 2019 Nov;26(11):1211-1220. doi: 10.1111/acem.13774. Epub 2019 Sep 27. PMID: 31562679.

2. Weekes AJ, Thacker G, Troha D, Johnson AK, Chanler-Berat J, Norton HJ, Runyon M. Diagnostic Accuracy of Right Ventricular Dysfunction Markers in Normotensive Emergency Department Patients With Acute Pulmonary Embolism. Ann Emerg Med. 2016 Sep;68(3):277-91. doi: 10.1016/j.annemergmed.2016.01.027. Epub 2016 Mar 11. PMID: 26973178.

3. Kopecna D, Briongos S, Castillo H, Moreno C, Recio M, Navas P, Lobo JL, Alonso-Gomez A, Obieta-Fresnedo I, Fernández-Golfin C, Zamorano JL, Jiménez D; PROTECT investigators. Interobserver reliability of echocardiography for prognostication of normotensive patients with pulmonary embolism. Cardiovasc Ultrasound. 2014 Aug 4;12:29. doi: 10.1186/1476-7120-12-29. PMID: 25092465; PMCID: PMC4126908.

4. Hugues T, Gibelin PP. Assessment of right ventricular function using echocardiographic speckle tracking of the tricuspid annular motion: comparison with cardiac magnetic resonance. Echocardiography. 2012 Mar;29(3):375; author reply 376. doi: 10.1111/j.1540-8175.2011.01625_1.x. PMID: 22432648.

5. Fields JM, Davis J, Girson L, et al. Transthoracic echocardiography for diagnosing pulmonary embolism: a systematic review and meta‐analysis. J Am Soc Echocardiogr 2017;30:714–23.e4.

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Expert Commentary

RV function is a frequently overlooked area on POCUS. Excellent post by Megan looking specifically at RV to identify hemodynamically significant PEs. We typically center our image around the LV, so pay particular attention to adjust your views so the RV is optimized. This may mean moving the footprint more laterally and angle more to the patient’s right on the A4C view. RV: LV ratio is often the first thing you will notice. When looking for a D-ring sign, make sure your PSSA is actually in the true short axis, as a diagonal cross-section may give you a false D-ring sign. TAPSE is a great surrogate for RV systolic function as RV contracts longitudinally. Many patients with pulmonary HTN or advanced chronic lung disease can have chronic RV failure, lack of global RV thickening. Lastly remember, that a positive McConnell’s sign is a great way to distinguish acute RHS from chronic RV failure.

John Bailitz, MD

Vice Chair for Academics, Department of Emergency Medicine

Professor of Emergency Medicine, Feinberg School of Medicine

Northwestern Memorial Hospital

Shawn Luo, MD

PGY4 Resident Physician

Northwestern University Emergency Medicine

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How To Cite This Post:

[Peer-Reviewed, Web Publication] Chenworth, M. Ibiebele, A. (2021 Oct 4). SonoPro Tips and Tricks for Pulmonary Embolism. [NUEM Blog. Expert Commentary by Bailitz, J. Shawn, L.]. Retrieved from http://www.nuemblog.com/blog/sonopro-tips-and-tricks-for-pulmonary-embolism

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