Case Details: 48 yrs old lady with tearing pain chest on CT angiography shows large, dissection of the entire aorta , including Ascending aorta , with celiac, SMA, renal arising from true lumen (cerebral vessels showing no dissection) with cobweb sign and beak signs positive.
Teaching points by Dr MGK Murthy, Dr Pritam, CT Technologist: Mr Shekhar
1. Aortic dissection occurs when the blood enters medial layer through a penetrating ulcer or tear of intima
2. Two types: Acute, when clinical symptoms <14 and=”” chronic=”” days=”” when=””>14 days
More useful , Stanford A: involvement of ascending aorta & or arch, possibly descending as well (requires surgery)
Stanford B: Descending aorta and / arch distal to left subclavian and beyond (medial management unless complications )
Debakey’s I- ascending aorta/ arch and possibly beyond
Debakey’s II- only ascending aorta
Debkey’s III– descending aorta
3. If it involves coronaries , it may produce tamponade and death with Becks Traid positive (a) low blood pressure or narrow pulse pressure, (b) muffled heart sounds and (c) raised JVP
4. Usually presents with tearing pain chest or end organ schema . CT angiography helpful
(disadv = does not detect site of intimal tear)
Signs- Dilated aorta, double lumen, Intimal flap , intramural hematoma, Mercedes-Benz sign(three distinct intimal flaps that have a triradiate configuration similar to the Mercedes-Benz logo ) (supposed to indicate secondary dissection in the dissected segment)(triple-barreled aortic dissection ) and Windsock sign(intimo-intimal intussusception between the true and false dissected lumens of the thoracic aorta(potentially fatal sign)
5. Differences between false lumen (blood filled channel) and true lumen (lined by intima) important . Exit tear produces the two lumens.
How to identify on CT angio?
(b) cobweb sign (slender linear areas of low attenuation specific to the false lumen due to residual ribbons of media that have incompletely sheared away )
(c) Beak sign( an acute angle between the dissection flap and the outer wall) represents the end of the false lumen and propagating region (can be high density or low density)
(d) low contrast density (delayed contrast entry)
(e) may be low density if completely thromboses
(f) Left renal artery usually arises from it
(a) compressed and smaller
(b) Outer wall calcification
(c) celiac,SMA, right renal arise from it
6 Usually elderly chronic hypertensives ( etiology medial layer degeneration). Others connective tissue disorders/ atherosclerosis( aetiology penetrating ulcer) / Pregnancy/ vasculitis
7 CXR – widened superior mediastinum more than 8cm , irregular aortic contour/ pushing of the calcification inside(more than 1cm) and double aortic contour etc. Repair of dilated ascending aorta more than 60mm (more than 45mm when connective tissue disorders present) may prevent potential dissection.
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