Aortic dissection

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Aortic dissection

Cardiovascular system

Cardiac tumors

Cardiac tumors




Aortic dissection


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USMLE® Step 1 questions

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High Yield Notes

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Aortic dissection

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USMLE® Step 1 style questions USMLE

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A 28-year-old man is brought to the emergency department after being involved in a high-speed motor vehicle collision. The patient was a restrained driver traveling on the highway when he suddenly slammed into the back of a stopped semi-truck. Upon arrival to the emergency department, the patient reports severe substernal chest pain radiating to his left shoulder blade. His temperature is 37.0°C (98.6°F), pulse is 104/min, respirations are 18/min and blood pressure is 185/100 mmHg. Physical examination shows bruising over the anterior chest wall, but no crepitus is felt on palpation. Shoulder examination shows full passive and active range of motion bilaterally. A chest X-ray is obtained (see below):  

Reproduced from: Radiopaedia  

Which of the following is the most likely location of injury?   

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Aortic dissection p. 309

associations with p. 728

hypertension p. 306

Marfan syndrome p. 714

Marfan syndrome as cause p. 306

Bicuspid aortic valve

aortic dissection and p. 309

Cardiac tamponade p. 481

aortic dissection and p. 309

Connective tissue diseases

aortic dissection and p. 310


aortic dissection in p. 309

Hypertension p. 306

aortic dissection and p. 309, 728

Marfan syndrome

aortic dissection and p. 309


An aortic dissection is where part of the tunica intima (which is the endothelial, or the innermost layer of a blood vessel) of the aorta is ripped off. What happens is a tear in the tunica intima of the aorta forms, and the high-pressured blood flowing through the aorta begins to tunnel between the tunica intima and the tunica media, separating the two layers. This is widely accepted as an unideal situation.

Now as the high-pressured blood continues to shear more and more of the tunica intima off the tunica media, blood starts to pool between the two layers, increasing the outside diameter of the blood vessel. The area where blood collects between the tunica intima and the media is called a false lumen, and the true lumen is the regular lumen of the blood vessel.

Since high pressure is a cause of aortic dissection, it’s no surprise that the aorta is the prime target for this problem. So what causes aortic dissections? Well, chronic hypertension is the major cause, whether the hypertension is caused by stress or from increased blood plasma volume like in pregnancy. Blood vessel coarctation, which is the narrowing of a blood vessel, also can cause dissection.

Aortic dissections most often happen in the first 10 cm of the the aorta closest to the heart. In order for an aortic dissection to occur, an underlying condition usually has to exist that weakens the aorta’s wall. Connective tissue disorders like Marfan’s and Ehlers-Danlos syndrome can cause a dissection, as well as a decreased blood flow to the vasa vasorum. Aneurysms can be a cause of aortic dissection as well, and incidentally dissection can also cause aneurysms because again, the dissection weakens the blood vessel wall.

In other words, weak walls can lead to outpouching of the blood vessel or a break in the tunica intima, and both of these weaken the walls further.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "Acute Type A Aortic Dissection" Cardiology Clinics (2017)
  5. "Aortic dissection: medical, interventional and surgical management" Heart (2016)
  6. "Acute aortic dissection: pathogenesis, risk factors and diagnosis" Swiss Medical Weekly (2017)

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