Aortic Dissection

* 3:1 male to female predominance
* Over the age of 40
* Hemorrhage in the media (at vasa vasorum) leading to either

1. Hemorrhage in the wall (less common)
2. Hemorrhage separate media from adventitia

· Predisposing factors
o Hypertension (most commonly)
o Atherosclerosis
o Cystic medial necrosis
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


·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

CT of abdominal aorta shows intimal flap (dark line -red arrow)
with true lumen anteriorly and false lumen posteriorly

o Angiography

• - Intimal flap
• - Double lumen
• - Compression of true lumen by false channel
• - Increase in aortic wall thickness > 10 mm
• - Obstruction of branch vessels