AORTIC DISSECTION

Aortic dissection refers to a life-threatening condition in which there is bleeding into the wall of the large aortic artery. The aorta is the largest artery in the body and is divided into the ascending aorta, aortic arch, and the descending aorta. The aorta usually measures about 3 cm, or just over 1 inch, wide. The ascending aorta is located in the chest and is attached to the heart; it measures approximately 2 to 2½ inches in length. The aortic arch, as its name states, arches around the chest from right to left behind the upper part of the sternum (chest bone). The descending aorta travels down from the chest into the abdomen before it divides into the arteries that lead to the lower legs.

The wall of the artery is divided into three layers called the intima (the inner layer), the media (the middle muscular layer), and the adventitia (the outer layer). Aortic dissection results from a tear or wearing out of the inner layer that allows blood to dissect and split the inner layer from the outer layer.

Aortic dissection usually occurs in the older population, but it can affect people between the ages of 40 to 70 years. Aortic dissection occurs in approximately 2 people out of 10,000 population. Although the specific cause is not known, aortic dissection is most commonly associated with patients with hypertension or atherosclerosis. Other associated diseases include certain connective tissue disorders such as Marfan's syndrome and Ehlers-Danlos syndrome (see other topics in Ferri's Patient Teaching Guides for these disorders). Infections such as syphilis can lead to stretching and dilation of the artery called an aneurysm. Aneurysms are prone to dissect as well.

Aortic dissections usually present with chest pain described as sharp and tearing located beneath the sternum and radiating to the shoulders, neck, arms, and in between the shoulder blades or in the back. The pain is sudden and can be severe. Other associated symptoms may include shortness of breath, sweats, confusion, fainting, lightheadedness, and apprehension.

Some of the pertinent physical findings include elevated blood pressure, rapid heart rate, and different blood pressure readings between both arms. A new heart murmur with the above chest pain should raise suspicion along with any new neurologic findings such as disorientation and decreased concentration.

Aortic dissection can be catastrophic. Sudden death can occur from rupture of the aortic dissection into the sac surrounding the heart, leading to pericardial tamponade (when there is so much blood or fluid in the sac around the heart that it prevents the heart from relaxing or performing an effective contraction). Sudden death or significant heart failure can occur when the dissection disrupts the main valve of the heart, called the aortic valve.

Kidney failure, stroke, and heart attacks are other potential complications of aortic dissection because the main arteries branching off from the aorta that feed these organs can be involved as the dissection extends.

It is essential to diagnose aortic dissection, since treatment is aimed at preventing the above-mentioned complications. Aortic dissection is usually diagnosed by the symptoms mentioned above along with a computed tomography (CT) scan of the chest or abdomen. If the dissection is thought to be in the chest, the physician may order a transesophageal echocardiogram (a probe that is place into the mouth and inserted down into the esophagus to take a picture of the aorta lying in front of it). Other imaging studies may be ordered, including a magnetic resonance imaging (MRI) scan or angiography (placing a thin tube called a catheter into the leg artery and passing it up to the aorta and injecting dye to take a picture of the aorta).

Once the diagnosis is confirmed, treatment may be either medical or surgical, depending on the site of the dissection. An aortic dissection is classified as type A if it involves the ascending aorta and type B if it involves the descending aorta. The classification is mentioned here because surgery is the recommended treatment for type A dissections and medical management is the recommended treatment for type B dissections. Surgery involves suturing the tear in the aorta as well as suturing the edges of the dissected wall. Medical management includes aggressive control of the blood pressure.

• Control your blood pressure. Most cases of aortic dissection occur in patients with long-standing high blood pressure. Therefore, a low-salt diet, exercise, and weight loss are all important measures to take to reduce the risk of developing high blood pressure and its complications.
• Remember that aortic dissection can be life-threatening, with less than 50% surviving if the dissection ruptures into the abdomen or into the heart or sac surrounding the heart.

• Don't forget to take your high blood pressure pills or your cholesterol pills.
• Don't miss any follow-up appointments. It is important if you have had surgery for dissection or if you are being medically managed to keep all appointments with your primary care physician, cardiologist, and vascular surgeon.
• Don't ignore chest pain!
• Don't forget some of the less common diseases associated with aortic dissection. Marfan's syndrome has been known to present with sudden death from rupture of the aorta.

• If you are having chest pain.
• If you are short of breath.
• If you have abdominal pain radiating to your back and you have a known abdominal aneurysm.
• If you need consultation with a vascular surgeon or cardiologist.

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