Chest Pain 9 days ago

A 28yo patient with known Marfan's was dragged into ED by his mum. He had a 4cm aortic root which was being monitored. NINE days ago he had central CP which lasted 2 hours. He had presented to an emergency department but had left without being seen. He tells me "I googled chest pain from dissection and it said it should be tearing and going through to the back. I didn't have that so I went home when it got better."

Mum, was a bit more worried and dragged him to our ED.

In ED on this day, he was painfree, normal obs and examination. 

This is his echo PLAx:

PLAx: annotated on still image

Can you see a dissection flap?

In experienced hands, the sensitivity and specificity of TTE for type A dissection can be approximately 80-90% (1). 

A recent study (2) looked at the accuracy of a protocolised  bedside US called SPEED performed by emergency residents who had completed 4 hours echo training + 3 week US rotation. For proximal aortic dissection, SPEED showed a sensitivity of 93%, specificity of 90% and PPV 26% and NPV 99%. Echo features they looked for to predict proximal aortic dissection were:

  • Pericardial effusion

  • Intimal flap

  • Dilated proximal aorta >3.5cm

This study was multicentre, prospective study with 103 emergency residents performing the bedside echo on patients with CP; 41 supervising attendings reviewed the accuracy of the scans. Of the 1314 study cohort 23 patients had a type A dissection. In the study, a dilated aorta had a 100% sensitivity for dissection and an intimal flap 100% specificity for dissection. However a dissection flap in the proximal aorta is not as easy to visualise as in the abdominal aorta. 

Importantly the accuracy of TTE for type B dissection is much lower than type A. Abdominal aorta visualisation with the abdominal probe is better for type B dissection. 

In the suprasternal notch view, the dissection flap may be seen to extend along the arch and the down the descending aorta with the arch view from the suprasternal notch. It can be hard to see the flap in the suprasternal notch view, especially if the flap is parallel with the beam of the US, but if seen, it is very specific for dissection. 

For how to examine the aorta from the suprasternal notch click the button below

Aortic arch - Suprasternal Notch

Aortic regurgitation is another sign associated with dissection.

So finally, bedside echo is a great first line investigation for aortic dissection. If features of disscetion are seen, it can expedite further Ix and definitive management. BUT it is not a rule out test in this difficult and potentially lethal condition.

REFERENCES

1. Mani N, Cherian N, Burkert J, Jarman RD. Bedside-focused transthoracic echocardiography in acute atraumatic thoracic aortic syndrome: a systematic review and meta-analysis of diagnostic accuracy. Eur J Emerg Med. 2024 Dec 1;31(6):398-412.

2. Gibbons R, Smith D, Feig R, Muflur M, Constantino T. The sono- graphic protocol for the emergent evaluation of aortic dissections (SPEED protocol): a multi-center, prospective, observational study. Acad Emerg Med. 2024;31