This week’s VOTW is brought to you by Dr. Ye, Dr. J Yang and Dr. Quinn!
A 58 year old male presented to the ED after fall. He was tachycardic to 120s, febrile and diagnosed with Flu A as well as alcohol withdrawal. He had an elevated troponin for which a POCUS was performed which showed…
Clip 1 shows a parasternal long axis view of the heart with multiple findings. First there is a pericardial effusion with possible RV collapse during systole concerning for tamponade. There is also a large, ovular, immobile, structure approximately 7cm in diameter where the left atrium should be. Based on our knowledge of anatomy, the differential includes dilated fluid-filled esophagus or thoracic aortic aneurysm.
The answer was found on CT chest to be a 7cm x 6cm descending thoracic aortic aneurysm (TAA) with a intra-aneurysmal thrombus with marked mass effect on the left atrium (CT image below).
Since Dr. Danta already did a wonderful VOTW on cardiac tamponade, this weeks’ topic is the thoracic aorta!
POCUS for the thoracic aorta
We can evaluate the thoracic aorta on POCUS for aneurysm or dissection. Unlike the abodminal aorta, we can only visualize certain snippets of the thoracic aorta. This results in a lower sensitivity (67-90%) (1) and cannot be used as rule out test for dissection.
Best views for visualizing the thoracic aorta
Parasternal long view – Aortic root, proximal ascending aorta, portion of descending aorta
Supra-sternal notch view – Aortic arch (here's a good video on how to get this view: https://www.youtube.com/watch?v=gv6yZNOIchE)
Parasternal short view - depending on your angle, you can sometimes see the descending aorta in its long axis
Normal diameter measurements
Thoracic aorta < 4cm (remember FOUR-acic aorta)
Abdominal aorta < 3cm
Iliac arteries < 1.5cm
Pearls
Measure the aortic root distal to the sinus of valsalva from leading edge to leading edge.
The RV, aortic root, LA should appear 1:1:1 in size in the parasternal long view. If the ascending aorta looks larger than the LA or RV, this would be concerning for an aneurysm.
Increase your depth on the parasternal long to include the descending aorta posterior to the left atrium. You might catch a descending thoracic aortic aneurysm or dissection and the descending aorta also helps differentiate pericardial vs pleural effusion.
Back to the patient
Both vascular surgery and cardiothoracic surgery were consulted for this patient during admission but he remained too sick from his medical illnesses that he was not deemed a candidate for surgical intervention.
References
Fengju Liu, Lianjun Huang. Usefulness of ultrasound in the management of aortic dissection. Rev. Cardiovasc. Med. 2018, 19(3), 103–109.
Happy scanning,
Your Sono team