Aortic Dissection

 

• 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

 

*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 

 

 

CT of abdominal aorta show intimal flap (dark line)
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 

·        Diagnosis 

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 

Timing	Death
Immediate	3%
Within 24 hours	20-30%
By end of 1st week	50%
By 3 weeks	60%
By 3 months	80%
Alive at 1 year	10-20%

 WH/03