Aortic Dissection

 
The Aorta is the largest artery in the body which transports oxygen rich blood out of the heart and has been traditionally divided into two parts namely the ascending and descending aorta. ^[1] It comprises three distinct layers. Normally, each of these layers adheres to its neighbour; forming a singular, reinforced blood vessel.

Aortic dissection occurs when the inner layer of the aorta (the tunica intima) is ruptured. Blood enters the region between the tunica intima and the second layer (tunica media), forcing the layers apart. Aortic dissection is a medical emergency and often results quickly in death, even with appropriate treatment.

The majority of aortic dissections occur after gradual deterioration causes the tunica intima to weaken. This deterioration is usually, in turn, caused by high blood pressure, which is identified in a significant majority of those diagnosed with an aortic dissection. Aortic dissection can, however, also be due to structural defects of the heart or injury.

If left unchecked, the build-up of pressure caused by blood between the intima and media layers of the artery can cause the entire wall of the aorta to become ruptured. This leads to severe, rapid blood loss, usually culminating in death.

To identify the needed treatment, a classification system has been devised for aortic dissection namely the Stanford classification. In this classification system, when the tear involves only the ascending aorta, the condition is regarded as type A whereas if the tear is in the descending part, then it is type B. ^[3] Type A is more common and more fatal. ^[2]

Type B Aortic Dissection

The tear in descending aortic dissection or type B typically presents as an intimal tear beyond the left subclavian artery which may be present all the way up to the abdominal area. ^[4]

Causes and Risk Factors

Majority of the patients who belong on type B have hypertension Studies also show that history of cigarette smoking is prominent on these patients. Histories of certain diseases that are common on patients are atherosclerosis, connective tissue disorders and aortic aneurysm. ^[4] Frequently, patients are male between 50 to 70 years old. Some diseases that may increase the risk of having the condition include bicuspid aortic valve, Marfan syndrome, Ehlers-Danlos syndrome and Turner syndrome. Predisposing factors include pregnancy, trauma, cocaine use and surgical complications. ^[5]

Signs and Symptoms

Type B dissection frequently presents as back pain described as intense, sharp or tearing. It can be felt along the chest and abdominal areas. ^[4] Generally, patients who are having aortic dissections may have shortness of breath, excessive sweating, paralysis, difficulty in speaking and may pass out. ^[2]     

Diagnosis

After getting the medical history of the patient and performing physical examination, laboratory exams usually imaging tests are needed such Computerized tomography (CT) scan, Magnetic resonance angiogram (MRA) and Transesophageal echocardiogram (TEE). ^[2]

Treatment

Type A cases frequently necessitate surgery. Patients who have type B dissection can be treated medically or surgically. Drugs are often aimed at lowering the blood pressure. Among these drugs are beta blockers and sodium nitroprusside. Follow up imaging test for periodic monitoring of the condition is often required. ^[2]

References:

1.      http://www.medterms.com/script/main/art.asp?articlekey=2295

2.      http://www.mayoclinic.com/health/aortic-dissection/DS00605/DSECTION=treatments-and-drugs

3.      http://emedicine.medscape.com/article/756835-overview

4.      http://www.aortarepair.com/type-b-aortic-dissection.html

5.      http://www.medicinenet.com/aortic_dissection/page2.htm#what_are_the_causes_of_aortic_dissection