Aortic Dissections

Aortic dissection

An aortic dissection is a tear in the inner lining of the aorta. This tear allows blood to flow through the walls of the aorta rather than remaining in the central channel (lumen). The two major types of aortic dissection, type A and type B, are defined by the location of the tear.

• Type A dissection—The tear begins in the ascending aorta and progresses throughout the vessel, often extending as far as the arteries in the leg.
• Type B dissection—The tear is located just past the left subclavian artery (the blood vessel beneath the collarbone that supplies the left arm).

The distinction between the two types is important, as it guides the management of the disease.

Symptoms

Type A dissections are surgical emergencies, with a mortality rate of 1 percent per hour after onset. Patients often feel as though they are having a heart attack. Specific symptoms include:

• Sudden and severe "tearing" or "crushing" pain between the shoulder blades or behind the sternum
• Inability to find a comfortable position
• Profound hypertension (extremely high blood pressure)

Diagnosis

Upon the patient's arrival at the emergency room, the first step is to control blood pressure and to provide pain control, while simultaneously mobilizing the operating room personnel. Prompt diagnosis is essential and is made by CT scan of the chest and/or a transesophageal echocardiography (TEE—ultrasound images of the heart taken from within the esophagus).

If a type A aortic dissection is strongly suspected, the patient is transported directly from our emergency room or an outside hospital to the operating room for a confirmation diagnosis via TEE. For those found to be positive, the surgical repair is immediately begun.

Type B dissections are medical emergencies; surgery is reserved for complications of the disease. The tear is typically located just after the aorta connects to the left subclavian artery and may progress along the entire length of the thoracic and abdominal aorta. The initial treatment is control of hypertension through medications. Often these patients will not require surgical correction.

Complications

Type A dissection are associated with many acute and chronic complications. Emergency intervention is required to prevent death. The most lethal acute complications are:

1. Exsanguinating hemorrhage: aortic rupture causing extreme blood loss
2. Aortic valve incompetence: failure of the aortic valve leading to rapid heart failure
3. Coronary artery dissection: loss of blood from the coronary arteries to the heart muscle causing a heart attack (myocardial infarction)
4. Cardiac tamponade: accumulation of blood in the pericardium (sac surrounding the heart) leading to heart failure
5. Carotid artery dissection: loss of blood from the carotid arteries to the brain arteries causing acute stroke

Type A or B dissection can also cause a process known as malperfusion syndrome. Because blood flows in the walls of the aorta rather than through the vessel itself, not enough blood may reach its intended destination. This condition may cause organ failure, most frequently involving the kidneys and intestines. The result may be temporary or permanent kidney failure and dead bowel, which may necessitate extensive bowel resection.