Regarding Aortic Dissection

Regarding Aortic Dissection answer the following questions:

1. What is acute aortic dissection?
2. What is the most common cause of aortic dissection in the general population, in men younger than 40 years, and in women younger than 40 years?
3. What is the most sensitive initial diagnostic test for aortic dissection?
4. Where are the most common points of origin for aortic dissections?

Answers:
1. What is acute aortic dissection?
Acute aortic dissection results from a tear in the aortic intima. Driven by systemic pressure, arterial blood enters the diseased media of the vessel. Within this layer, blood creates a separation plane as it dissects the aorta longitudinally. The area of dissection filled with blood is called the false lumen. The shear forces of the dissecting blood can cause additional intimal tears. As the false lumen fills  with blood, it may compress the true lumen, resulting in obstruction of major arteries.
Infrequently, dissection can be initiated by hemorrhage into the media without an intimal tear.

2. What is the most common cause of aortic dissection in the general population, in men younger than 40 years, and in women younger than 40 years?
In the ascending aorta, the most common cause of aortic dissection in the general population is medial degeneration usually associated w ith aging and hypertension.
In the abdominal aorta, atherosclerosis plays a more important role.

• In men younger than 40 years, the most common cause of dissection is Marfan's syndrome associated with the more typical cystic medial degeneration lesions. 
• In women younger than 40 years, 50% of all dissections occur during pregnancy.

3. What is the most sensitive initial diagnostic test for aortic dissection?
The sensitivities of transesophageal echocardiography (TEE), magnetic resonance imaging (MRI), and computed tomography (CT) scan for detection of dissection are similar, with TEE probably having a slight advantage. In most cases, the preferred initial modality is CT scanning because of
availability, safety, and convenience.
If the patient is not stable, TEE should be considered first as it can be performed in a monitored setting w here acute medical therapy can be administered.

4. Where are the most common points of origin for aortic dissections?
The most common point of origin for ascending aortic dissection is within 2 inches. of the aortic valve. For descending aortic dissection, this point is at the ligamentum arteriosum, just beyond the takeoff of the left subclavian artery