TTE for Aortic Dissection/ Thoracic Aneurysm?

This week’s image of the week is brought us by Dr. Demestihas and Dr. Stroder. They suspected that their patient had a possible descending thoracic aneurysm/dissection and obtained normal views both transverse and axial of the abdominal aorta as well as the image below (normal para-sternal long view of heart). 

Emergency physicians are able to pick up on thoracic aneurysms/dissections if the following sonographic findings are present on trans thoracic echo (TTE):

1)   1. Dilation of the aortic outflow tract on para-sternal long view. This is more suggestive of aneurysm.

2)   2. Dilation of or flap in descending thoracic aorta on para-sternal long view. This is a better view for aneurysm than dissection because a second view (90 degrees perpendicular to the first) of the aorta at this point is not possible. Therefore, a three dimensional view is not obtainable at this level.

3)   3. New acute aortic valve regurgitation can also be a sign of a dissection extending into the aortic valve.

Please note that all of the above, except for a definite tissue flap in the lumen of the aorta, are secondary signs that are suggestive of, but not diagnostic for an aneurysm or dissection. The bottom line is that trans thoracic echo is not the imaging modality of choice for this disease. CT of the chest with IV contrast or trans esophageal echo would help to definitively make this diagnosis.  Despite the negative TTE, Dr Demesthihas and Dr. Stroder made the diagnosis with a CT contrast study!

For more information on measuring the ascending aorta, see:

Comparison of feasibility and accuracy of transthoracic echocardiography versus computed tomography in patients with known ascending aortic aneurysm.

Tamborini G, Galli CA, Maltagliati A, Andreini D, Pontone G, Quaglia C, Ballerini G, Pepi M.

Am J Cardiol. 2006 Oct 1;98(7):966-9. Epub 2006 Aug 22.

PMID:

 

16996884