Tasty Morsels of EM 063 – Traumatic Aortic Injury

Stimulated by a post over at Echo Praxis and a corrective tweet from Karim Brohi

This is a blunt traumatic aortic injury leading to pseudoaneurysm. It's NOT a dissection. https://t.co/FbMZ3tYkMI

— Karim Brohi (@karimbrohi) December 18, 2015

I think I have a vague memory of this from several years ago but this was an opportunity to properly look into it.

Most of this comes from a generally poor understanding of aortic diseases. I know I’ve got myself in a muddle before with thoracic aortic aneurysms and thoracic aortic dissections and occasionally confabulating with the dissecting thoracic aneurysm…

Traumatic aortic injury is somewhat similar with most folk (including myself apparently) labelling it simply as an aortic dissection when in fact it probably isn’t.

Where do you see these injuries:

• 90% at the isthmus (the bit of the descending aorta between left subclavian and ligamentum arteriosum). The idea is that aorta is a bit tethered here and it’s a point of force transmission
• 5% in the ascending aorta

When should you consider it?

• Most of it seems to be mechanism driven (deceleration). With the era of pan scan, most severe trauma patients are getting CT which is going to be the test of choice for most.
• The O’Connor paper referenced below is a bit old but it does contain a little bit of literature on examination findings. These findings are likely late like most of these things but worth looking for.
  • high BP in the upper limbs with
  • low BP in the lower limbs
  • big mediastinum on CXR
• Lots of people with an aortic injury have a wide mediastinum but that doesn’t necessarily mean the aorta is ruptured. Most of the blood in the mediastinum is coming from much smaller mediastinal vessels and the wide mediastinum is simply reflective of severe trauma to the area and a reason to look further.

Types of traumatic aortic injury

• the Mokrane paper cited below suggests a grading system I-IV with I and II being conservatively managed and III/IV for intervention, ideally endovascular and occasionally open repairs. Though management is no doubt a topic of controversy that i’ll not delve into
• I
  • intimal tear or localised haematoma
• II
  • pseudoaneurysm involving <50% of aortic diameter
• III
  • pseudoaneurysm involving <50% of aortic diameter
• IV
  • rupture or complete transection of the aorta

Pitfalls

• there are lots of imaging artefacts from beam hardening to cardiac pulsation that can look like aortic injuries but aren’t. I remember seeing this years ago and we all got very excited and I think the patient even got transferred before someone caught on it was all artefact
• in the oldies there’s often lots of plaque on the aorta and these are easily confused for lower grade injuries

Karim, of course, also had some tips distinguishing the aortic dissection (usually a medical disease with surgical treatment) from a traumatic aortic injury (a traumatic injury with an interventional treatment):

Dissection is hypertension/atherosclerotic disease with long dissection flap. Complications like malperfusion…. https://t.co/Z5gzvAFBda

— Karim Brohi (@karimbrohi) December 21, 2015

Dissection treatment usually conservative with BP control in the first instance…. https://t.co/Z5gzvAFBda

— Karim Brohi (@karimbrohi) December 21, 2015

If you see a dissection then probably it was either ore-existing or it caused the accident!… https://t.co/Z5gzvAFBda

— Karim Brohi (@karimbrohi) December 21, 2015

Dissections don't rupture… unless much later the false aneurysm becomes aneurysmal… https://t.co/Z5gzvAFBda

— Karim Brohi (@karimbrohi) December 21, 2015

Whereas a traumatic aortic injury is a tear and (usually) a false aneurysm. Free rupture is the concern here. https://t.co/Z5gzvAFBda

— Karim Brohi (@karimbrohi) December 21, 2015

References:

• Trauma.org
• Radioaedia.org
• Mokrane FZ, Revel-Mouroz P, Saint Lebes B, Rousseau H. Traumatic injuries of
  the thoracic aorta: The role of imaging in diagnosis and treatment. Diagn Interv
  Imaging. 2015 Jul-Aug;96(7-8):693-706. doi: 10.1016/j.diii.2015.06.005. Epub 2015
  Jun 27. PubMed PMID: 26122129. [PubMed]
• St Emlyns Podcast with Karim Brohi on vascular injuries
• O’Connor. Diagnosing traumatic rupture of the thoracic aorta in the emergency department EMJ – Full Text