Aortic Dissection

Aortic dissection is a tear in the inner layer of the aorta's wall. Blood can surge through the tear, separating (dissecting) the inner layer from the middle and outer layers.

Most aortic dissections occur in people with high blood pressure, particularly men. About half occur in people over 60. Aortic dissection becomes more likely as people age.

See the figure Understanding Aortic Dissection .

When blood surges through the layers of the aorta's wall, it may accumulate. Then the wall may swell and become distorted. The swelling can completely block the opening of arteries that branch off the aorta. If the arteries that supply blood to the heart (coronary arteries) are blocked, the aortic valve (which controls blood flow between the left ventricle and aorta) may be damaged. Thus, blood cannot flow to vital organs, depriving them of oxygen. Blood sometimes accumulates in the sac around the heart (pericardium), causing a disorder called pericardial effusion. The accumulation of blood prevents the heart from pumping enough blood. The dissection can also cause rupture of the aorta.

Treatment involves controlling blood pressure. Surgery is often needed. Aortic dissection is often fatal. However, for some types of dissections, surgery can prolong life for many years.

Causes and Symptoms

In older people, aortic dissection often results from high blood pressure. The high pressure can cause part of the aorta's wall to deteriorate. Aging itself can cause similar deterioration. Birth defects and connective tissue disorders can cause aortic dissection but usually do so before people reach old age.

Aortic dissection typically causes pain. Usually, the pain is sudden and severe and feels like ripping or tearing. It can be felt in the back, often between the shoulder blades, or in the chest. Sometimes dissection causes only mild back pain, similar to other backaches.

When arteries are blocked, organs may not get enough blood. The consequences depend on which organs are affected and can include the following:

• Stroke if the brain is affected
• Heart attack if the heart is affected
• Sudden abdominal pain if the intestine is affected
• Lower back pain if the kidneys are affected
• Nerve damage that causes numbness, tingling, paralysis, or incontinence if the spinal cord is affected
• Pain in the feet if the leg arteries are affected

Other symptoms may include shortness of breath, loss of consciousness, low blood pressure, or shock. These symptoms can develop if blood accumulates in the sac around the heart, preventing the heart from pumping enough blood. Heart failure may develop if the aortic valve is damaged. The dissected aorta may rupture, causing a person to go into shock and die quickly.

Diagnosis

Doctors may suspect aortic dissection when the pulse or blood pressure is decreased in one or more limbs. With a stethoscope, they may hear a heart murmur.

A chest x-ray sometimes shows signs of dissection but is not conclusive. The diagnosis must be confirmed by another test. The preferred tests are computed tomography (CT) done after dye is injected into a vein, magnetic resonance imaging (MRI), and transesophageal echocardiography. For transesophageal echocardiography, an imaging device is passed down the throat into the esophagus. Occasionally, angiography is necessary. For this test, x-rays are taken while dye is injected through a long, thin tube (catheter) into the aorta.

Treatment and Outlook

People with aortic dissection are admitted to an intensive care unit. Drugs are given intravenously to lower blood pressure and reduce the force of the heart's contractions. Thus, pressure on the aorta's wall is reduced. If the dissection occurs in the part of the aorta close to the heart, surgery is done. The affected part of the aorta is usually replaced with an artificial tube (graft). If the dissection occurs in a part of the aorta farther from the heart, surgery may not be necessary. In these cases, lowering blood pressure may be sufficient.

Without treatment, most people with aortic dissection die within 2 weeks. Dissections that occur in the part of the aorta close to the heart are the most deadly. With treatment, most people who survive the first 2 weeks live for at least another 5 years.