Learning Radiology xray montage

Aortic Dissection
Dissecting Aortic Aneurysm

  • 3:1 male to female predominance
  • Over the age of 40
  • Hemorrhage in the media (at vasa vasorum) leading to either
    • Tear in the weakened intima which breaks into the lumen, or
    • Hemorrhage in the wall (less common)
    • Hemorrhage separate media from adventitia

·   Predisposing factors

o       Hypertension (most commonly)

o       Atherosclerosis

o       Cystic medial necrosis

§         Marfan’s syndrome

o       Coarctation of the aorta

o       Aortic stenosis

o       S/P prosthetic aortic valve

o       Trauma (rare)

o       Pregnancy (rare)

·   Aneurysm defined by size criteria

o       In general, ascending aorta > 5 cm

o       Descending aorta > 4 cm


·        Vessels involved with dissection

o       Any artery can be occluded

o       Usually the right coronary and three arch vessels are involved with arch aneurysms

o       Right pulmonary artery and left-sided pulmonary veins may be occluded

·   Types

o       DeBakey Type I

§     Involves entire aorta

o       DeBakey Type II

§     Least common

·        Ascending aorta only

o       DeBakey Type III

§     Most common

·        Descending aorta only

o       Stanford Type A

§     Ascending aorta involved

·        Over half develop aortic regurgitation

o       Stanford Type B

§     Ascending aorta NOT involved

·       Most dissections arise either just distal to the aortic valve or just distal to aortic isthmus

· True versus false channel

o       False channel usually arises anterior in the ascending aorta and spirals to posterior and left lateral in descending aorta

o       True channel is usually larger

o       Slower flow in false channel on MR


DeBakey Classification

Stanford Classification

Portion of Aorta Involved

Common causes


DeBakey Type I  

Stanford Type A
(ascending aorta involved)

Involves entire aorta 



Usually surgically*

DeBakey Type II
(least common) 

Stanford Type A
(ascending aorta involved) 

Ascending aorta only 

Cystic medial necrosis

e.g. Marfan’s

Usually surgically*

DeBakey Type III
(most common) 

Stanford Type B

Descending aorta only 


Usually medically


*Goal is to prevent backward involvement of the aortic valve or rupture into pericardium


· Clinical

o       Sharp, tearing, intractable chest pain

o       Murmur or bruit of aortic regurgitation

o       Previously hypertensive, now possible shock

o       Asymmetric peripheral pulses

o       Pulmonary edema

· Imaging Findings


o       Chest films  

§         Mediastinal widening

§         Left paraspinal stripe

§         Displacement of intimal calcifications

§         Apical pleural cap

§         Left pleural effusion

§         Displacement of endotracheal tube or nasogastric tube  

o       MRI

§         Intimal flap

§         Slow flow or clot in false lumen

o       CT

§         Intimal flap

§         Displacement of intimal calcification

§         Differential contrast enhancement of true versus false lumen  

o       Angiography

§         Intimal flap

§         Double lumen

§         Compression of true lumen by false channel

§         Increase in aortic wall thickness > 10 mm

§         Obstruction of branch vessels  

· DX


o       MRI if available is usually best for imaging ascending aorta

o       Contrast-enhanced CT can image arch and descending aorta

o       Transesophageal ultrasound, if available, especially for root and ascending aorta

o       Angiography


· Prognosis







Within 24 hours


By end of 1st week


By 3 weeks


By 3 months


Alive at 1 year



dissecting aortic aneurysm

CT of abdominal aorta show intimal flap (dark line)
with true lumen anteriorly and false lumen posteriorly