1. Aortic Dissection

2. 3:1 male to female predominance Over the age of 40
Hemorrhage in the media 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

3. Predisposing factors Hypertension (most commonly) Atherosclerosis
Marfan’s syndrome
Coarctation of the aorta
Trauma (rare)
Pregnancy (rare)

4. Aneurysm defined by size criteria
In general, ascending aorta > 5 cm
Descending aorta > 4 cm 

5. Vessels involved with dissection
Any artery can be occluded
Usually the right coronary and three arch vessels are involved with arch aneurysms
Right pulmonary artery and left-sided pulmonary veins may be occluded

6. Types DeBakey Type I DeBakey Type II DeBakey Type III Stanford Type A
Involves entire aorta
DeBakey Type II
Least common
Ascending aorta only
DeBakey Type III
Most common
Descending aorta only
Stanford Type A
Ascending aorta involved
Over half develop aortic regurgitation（返流）
Stanford Type B
Ascending aorta NOT involved

9. True versus false channel
Most dissections arise either just distal to the aortic valve or just distal to aortic isthmus
True versus false channel
False channel usually arises anterior in the ascending aorta and spirals to posterior and left lateral in descending aorta
True channel is usually larger
Slower flow in false channel on MR

10. DeBakey Classification Stanford Classification
Portion of Aorta Involved
Common causes RX
DeBakey Type I  
Stanford Type A (ascending aorta involved)
Involves entire aorta 
Hypertension
Atherosclerosis
Usually surgically*
DeBakey Type II (least common) 
Stanford Type A (ascending aorta involved) 
Ascending aorta only 
Cystic medial necrosis
e.g.Marfan’s
DeBakey Type III (most common) 
Stanford Type B
Descending aorta only 
Hypertension Atherosclerosis
Usually medically
*Goal is to prevent backward involvement of the aortic valve or rupture into pericardium

11. Clinical Sharp, tearing, intractable chest pain
Previously hypertensive, now possible shock
Asymmetric peripheral pulses
Pulmonary edema

12. Imaging Findings Chest films Mediastinal widening
Left paraspinal stripe
Displacement of intimal calcifications
Left pleural effusion
Displacement of endotracheal tube or nasogastric tube

13. MRI CT Intimal flap Slow flow or clot in false lumen
Displacement of intimal calcification
Differential contrast enhancement of true versus false lumen 

14. The roles of CT in the evaluation of suspected aortic dissection are:
Computed tomography of the chest including CTA of the aorta is the investigation of choice for suspected aortic dissection.
The roles of CT in the evaluation of suspected aortic dissection are:
To confirm the diagnosis
Classify the dissection as type A or B
Identify involvement of arterial branches,including the coronary arteries
Delineation of bleeding:mediastinal haematoma,pleural or pericardial（心包） effusion

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

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

17. Diagnosis MRI if available is usually best for imaging ascending aorta
Contrast-enhanced CT can image arch and descending aorta
Transesophageal ultrasound, if available, especially for root and ascending aorta
Angiography