Aortic dissection

Definition

Aortic dissection (dissection means separation) is a true life-threatening emergency that occurs when a tear develops in the lining of the aorta. The tear

allows blood to flow between the inner and middle layers of the aorta, which weakens the outer wall. If the outer wall of the aorta ruptures, death is likely. Even a brief delay in diagnosis and treatment of an aortic dissection can substantially decrease the chance of survival.

Description

The aorta is the long, thick artery that carries blood from the heart to the body. It is made up of three layers: the inner layer or intima, the middle layer or media, and the outer layer or adventitia. The aortic valve is located where the left ventricle of the heart and aorta meet. Upon leaving the heart, the aorta rises toward the head. This section is called the ascending or proximal aorta. The aorta then turns downward forming the aortic arch and descends into the abdomen. This section is called the descending or distal aorta. Aortic dissections are classified by where on the aorta the tear occurs.

Type A aortic dissections are tears in the ascending aorta. This type of aortic dissection is the more common and more dangerous of the two types.

About 90% of all aortic dissections occur in the ascending aorta within 4 in (10 cm) of the aortic valve. Type B aortic dissections involve a tear in the descending aorta.

Demographics

Aortic dissections usually occur in people between the ages of 45 and 70, with the highest frequency found in the 50–65 age group. Dissection occurs in men three times more often than in women, with the highest rate in white men. Aortic dissections are uncommon, and the absolute prevalence is difficult to calculate, as many people who die before receiving treatment are misdiagnosed as having succumbed to a fatal heart attack (myocardial infarction). One study estimates that aortic dissection occurs in one of every 10,000 patients admitted to the hospital. In an autopsy study, 1 of every 350 cadavers was found to have an aortic dissection.

Causes and symptoms

An aortic dissection develops because a tear occurs in the inner lining of the aorta. Once a tear is present, blood forms a second channel that flows between the inner and middle layer of the blood vessel. Eventually this causes the middle and the outer layer to separate (dissect). If the outer layer of the aorta is sufficiently weakened, it can rupture, spewing blood into the chest or abdominal cavity and depriving other organs of blood (ischemia ). Aortic ruptures are often fatal.

Certain conditions make it more likely that a tear will develop in the inner layer of the aorta. These conditions include:

• atherosclerosis (hardening of the arteries), which is more likely to cause type A dissections.
• chronic uncontrolled hypertension (high blood pressure), which is more likely to cause type B dissections.
• aortic valve defects.
• constriction of the aorta (aortic coarctation).
• Turner syndrome, an inherited chromosomal disorder.
• Inherited connective tissue disorder including Marfan syndrome, Ehlers-Danlos syndrome, and pseudoxanthoma elasticum. (The aorta is made of connective tissue.)
• crack cocaine use, which temporarily raises blood pressure.
• blunt force trauma to the chest, such as hitting the steering wheel during a vehicular crash.
• pregnancy, which sometimes causes aortic dissection in otherwise healthy women.
• syphilis, a sexually transmitted disease.
• heart surgery procedures, such as cardiac catheterization.

The most notable symptom of aortic dissection is sudden excruciating pain . Pain often begins in the chest and then moves under the shoulder blades or to the back. The pain may also move to the jaw, neck, arms, legs, abdomen, or hips. The pain is described as a ripping, shredding, stabbing type pain that comes out of nowhere. It may be accompanied by mental confusion (a very common symptom), difficulty breathing even when lying down, fainting , heavy sweating, nausea, vomiting, weakness, or paralysis of some part of the body.

Diagnosis

Symptoms of an aortic dissection are similar to those of many other heart and health problems. The location, quality, and type of onset of the pain are an important factors in diagnosing an aortic dissection. A difference in blood pressure between the right and left arms or the arm and the ankle also suggest an aortic dissection.

QUESTIONS TO ASK YOUR DOCTOR

Most people experiencing an aortic dissection will not be in any condition to ask questions before their emergency surgery. After surgery they may want to ask some of the following questions:

• How long will I be in the hospital?
• Will I go to an inpatient or outpatient rehabilitation program?
• What type of activities might I be able to do in 3 months, 6 months, 1 year?
• How often will I need check-ups?
• What type of social services are available to help me and my family during my recovery and rehabilitation?

A chest x ray may show a widened area in the aorta depending on where the dissection is located. Other screening tests include computerized tomography (CT) scans using a contrast dye that creates cross-sectional pictures of the chest or a magnetic resonance angiogram (MRA) that uses magnetic resonance imaging and contrast material to look specifically at the blood vessels. If a type A dissection is suspected, a transesophageal echocardiogram may be done. This gives a very clear picture of where the dissection is located.

Treatment

Treatment for a type A aortic dissection is always immediate emergency surgery to repair the aorta. Before surgery such drugs as beta blockers may be given to lower blood pressure. Surgery involves removing the damaged portion of the aorta and grafting a plastic or metal tube into the aorta to replace the damaged section. Type B aortic dissections are often treated with surgery, but may be treated with blood pressure lowering (antihypertensive) drugs depending on the location of the dissection and the condition of the patient. Even after successful repair surgery, patients will take medications to control blood pressure for the remainder of their lives.

KEY TERMS

Aorta —The main artery that carries blood from the heart to the rest of the body. The aorta is the largest artery in the body.

Atherosclerosis —A chronic condition characterized by thickening and hardening of the arteries and the build-up of plaque on the arterial walls. Atherosclerosis can slow or impair blood circulation.

Beta blocker —An anti-hypertensive drug that limits the activity of epinephrine, a hormone that increases blood pressure.

Cardiac catheterization —A diagnostic procedure (using a catheter inserted through a vein and threaded through the circulatory system to the heart) which does a comprehensive examination of how the heart and its blood vessels function.

Marfan syndrome —An inherited condition that affects connective tissue throughout the body including weakening the connective tissue found in arteries.

Transesophageal echocardiography —A diagnostic test using an ultrasound device that is passed into the esophagus of the patient to create a clear image of the heart muscle and other parts of the heart.

Ventricle —A lower pumping chambers of the heart. There are two ventricles, right and left. The right ventricle pumps oxygen-poor blood to the lungs to be re-oxygenated. The left ventricle pumps oxygen-rich blood to the body.

Nutrition/Dietetic concerns

A heart healthy diet low in low in saturated (animal) fats and high in fresh fruits, vegetables, and whole grains is recommended by the American Heart Association to reduce the risk of atherosclerosis .

Therapy

After aortic repair surgery, the patient will remain in the intensive care unit for at least a week. When the patient is able, he or she will enter an extensive cardiac rehabilitation program. Recovery from this surgery is a long, slow process.

Prognosis

In the first 24–48 hours after an aortic dissection occurs, the chance of death increases by between 1% and 2% for every hour treatment is delayed. About 75% of people who are not diagnosed and treated for aortic dissection die within two weeks. Individuals who survive surgery have a 10-year survival rate of about 40%.

Prevention

Eating a heart healthy diet, not smoking , maintaining a healthy weight, and controlling blood pressure are steps people can take to help reduce the risk of aortic dissection.

Caregiver concerns

The caregiver's immediate concern is the summoning of emergency aid and getting a prompt and accurate diagnosis for the person in their care. Those people who survive surgery will need extensive, possibly round-the-clock, care and support during their recovery and rehabilitation. Caregivers may benefit from attending a support group for people who are responsible for the seriously ill, as taking care of someone who has had major heart surgery can be psychologically and physically stressful.

Resources

BOOKS

Baliga, Ragavendra R. et al., eds. Aortic Dissection and Related Syndromes. New York, NY: Springer, 2007.

OTHER

“Aortic Dissection.” Mayo Clinic. May 29, 2007 [cited February 27, 2008]. http://www.mayoclinic.com/health/aortic-dissection/DS00605.

“Aortic Dissection.” Medline Plus. May 27, 2006. [cited February 27, 2008]. http://www.nlm.nih.gov/medlineplus/ency/article/000181.htm.

Oslingua, Oladayo and Ramaschandra C. Reddy “Aortic Dissection.” eMedicine.com. January 27, 2005 [cited February 27, 2008]. http://www.emedicine.com/med/topic2784.htm.

Wiesenfarth, John. “Dissection, Aortic.” eMedicine.com. November 8, 2007 [cited February 27, 2008]. http://www.emedicine.com/emerg/topic28.htm.

ORGANIZATIONS

American College of Cardiology, Heart House, 2400 N Street, NW, Washington, DC, 20037, (202) 375-6000, (800) 253-4636 x8603, (202) 375-7000, [email protected], http://www.acc.org.

American Heart Association, 7272 Greenville Avenue, Dallas, TX, 75231, (800) 242-8721, http://www.americanheart.org.

National Heart Lung and Blood Institute Health Information Center, P.O. Box 30105, Bethesda, MD, 20824-0105, 301) 592 8573; TTY: 240 629 3255, 240 629 3246,:[email protected], http://www.nhlbi.nih.gov.

Tish Davidson A. M.