Aortic Aneurysms

Definition

An aortic aneurysm is a weak spot in the wall of the aorta, the primary artery that carries blood from the heart to the head and extremities.

Description

There are three common types of aortic aneurysms.

Saccular and fusiform aneurysms are balloon-like swellings of the arterial wall that can occur in the portion of the aorta within the chest or, most commonly, just below the kidney in the abdomen.

A dissecting aneurysm is a longitudinal, blood-filled split in the lining of the artery, usually occurring in the aortic arch near the heart.

Some 15,000 Americans die suddenly each year from rupture of an aneurysm in the aorta, which is the ninth leading cause of death in men over age 55.

Ballooning of an artery (aneurysm) can be caused by pressure on a weakened section of the arterial wall, or by a dissection - a split in the three layers of tissue comprising the aortic wall, so that blood seeps between them. As blood continues to push against the "thin-skinned" area, the wall stretches further, placing it at increased risk for rupture - a potentially catastrophic event.

The aorta, the largest human artery, is the Nile River of the body. During the average lifetime, it transports some 200 million liters of blood, while withstanding the force of up to 3 billion heartbeats. The arteries that feed all of the body's organs branch off from the aorta, which emerges from the heart and runs the length of the torso. It divides at the hip into the two iliac arteries that supply blood to both legs.

The aorta is an inch in diameter and has thick walls to withstand the force of the blood that courses through it. Not surprisingly, something amiss in this vessel can mean serious trouble. The most common, and greatest, danger is an aortic aneurysm.

Aortic aneurysms can develop anywhere along the aorta. Those in the chest are called thoracic aneurysms. However, more than three-quarters of aortic aneurysms occur in the abdomen, most commonly below the renal arteries that supply the kidneys.

Small aneurysms are unlikely to rupture but should be monitored regularly with imaging exams. Aneurysms never go away by themselves, and 80 percent grow larger.

Studies show that, on average, aneurysms expand by about an eighth- to a quarter-inch in diameter per year, though the rate of expansion increases as the aneurysm grows.

Medications cannot cure the aneurysm, but they may be prescribed to reduce blood pressure in hypertensives, so that the pounding force of the blood against the wall of the aorta is lessened.

Causes and Risk Factors

Aortic aneurysms are four times more common in men than in women and usually strike those aged 50 to 80. Stiffened, less flexible arteries affected by atherosclerosis are implicated in about 95 percent of aortic aneurysms. Often, hypertension compounds the problem by causing elevated blood pressure to hammer away at the weakened area, stretching it even further.

Aortic aneurysms can also result from injuries, and are common in certain hereditary conditions, such as Marfan's syndrome - a connective tissue disorder that has caused several athletes to die suddenly from aortic dissections.

Symptoms

Aneurysms can be small, or grow to the size of a grapefruit. They can affect only the muscular middle layer of the aorta (a saccular aneurysm) or protrude uniformly around the aorta's whole diameter (a fusiform aneurysm). Most are symptomless, especially when small.

Symptoms occur in only one quarter of patients, and tend to increase as aneurysms enlarge and begin to press on nerves, organs or other blood vessels. The most common symptom is a throbbing, or pulsation, in the abdomen. Sometimes, abdominal or lower back pain occurs.

Symptoms of a thoracic aneurysm may include pain in the shoulders, lower back, neck, or abdomen; a dry cough; or hoarseness from the pressure of the aneurysm on the nerves controlling the vocal cords. However, these symptoms are frequently misdiagnosed.

Other symptoms may be a throbbing lump in the abdominal area, severe backache, leg pain or a feeling of coldness in the leg (due to an embolus from a clot formed in an abdominal aneurysm), or severe abdominal pain (due to the rupture of an abdominal aneurysm.)

Diagnosis

Even when it does not cause symptoms, aneurysms may be felt by abdominal palpation during a physical exam, and many thoracic aneurysms can be seen on a routine chest x-ray.

To determine size and type, a newly found aneurysm should be evaluated by more sophisticated tests - a CT scan, MRI, or an abdominal sonogram in the case of an abdominal aortic aneurysm, or transesophageal echocardiography, MRI, or a CT scan in the case of a thoracic aneurysm.

Treatment

Immediate surgery is usually required for a dissecting aortic aneurysm. Certain dissections can be treated with medicine.

Dissecting aneurysms are particularly dangerous, because of the high risk that the tear will extend completely through the aortic wall and sever the vessel. Sixty percent of ruptured thoracic aneurysms are a result of dissection.

Surgery is also indicated for rapidly enlarging aortic abdominal aneurysms. Plum-size aneurysms (with a diameter of about 2.5 to 3 inches) fall into this danger zone. Without surgery, patients with this size aneurysm face a 50 percent chance of dying from rupture within a year; a 75 percent chance in two years; and an over 90 percent chance within five years.

In surgery to repair the aorta, a flexible, synthetic tube is placed inside the aneurysm like a liner. The aneurysm itself is not removed.

When done electively, the hour-long operation to insert the graft is not complicated and is relatively safe. However, those with cardiovascular disease, who are at higher risk from any surgery, may be advised to undergo a bypass operation or angioplasty prior to the aneurysm repair.

Questions to Ask Your Doctor

Where is the aneurysm located?

What type of aneurysm is it?

What is its size?

Is it rapidly growing?

What threat does it pose?

Is surgery indicated?

What are the risks involved?

How often have you performed this surgery?