Shining a light on thoracic aortic disease

Problems with the body's main pipeline for blood often overlooked, misdiagnosed.

Published: August, 2010

A thoracic aortic aneurysm is a weak spot in the aorta, the main pipeline for blood from the heart to the body. The weak spot has the potential to dissect or rupture, cutting off the supply of life-sustaining blood to the rest of the body.

Such events aren't rare. Several hundred thousand Americans have these weak patches, called aneurysms (ANN-you-rizms). National statistics say that aortic aneurysms account for approximately 45,000 deaths a year. That is probably an underestimate, since some aneurysm-related deaths are mistakenly classified as cardiac arrests.

In this article, we focus on thoracic aortic aneurysms, the type that is harder to detect and diagnose compared to the more common abdominal aortic aneurysms.

Delivery system

The aorta begins deep in the heart. It emerges from the top of the powerful left ventricle, curves up and over the heart in a gentle arch, then descends into the chest and through the muscular diaphragm into the abdomen (see "Thoracic aorta"). It ends around the belly button, where it splits into two smaller arteries, one for each leg. From start to end, arteries branch off to nourish the heart, brain, arms, kidneys, liver, stomach, intestines, and every other part of the body. The stretch of the aorta from its start in the heart to the top of the diaphragm is called the thoracic aorta; the section below the diaphragm is the abdominal aorta.

Thoracic aorta

illustration of heart showing location of the thoracic aorta

The thoracic aorta begins where the left ventricle ends at the aortic valve and continues down through the chest. A weakening of the artery wall in this region is called a thoracic aortic aneurysm.

A healthy aorta is about 1 inch (2.5 centimeters [cm]) wide, or about the diameter of a garden hose. It tends to be a little wider at the root, where it emerges from the aortic valve, and a bit smaller along the arch. If a section of the firm but elastic outer wall of the aorta weakens, the vessel can bulge out at that spot. Such a bulge is called an aneurysm.

Some aneurysms are relatively harmless. Others can lead to the catastrophic problems known as dissection or rupture. For now, size is the best and only guide to the health threat posed by an aneurysm.

Dissection. The most common consequence of an aortic aneurysm, dissection occurs when a tear develops in the inner lining of the aortic wall. The inner and outer layers peel apart, creating an extra channel for blood inside the aorta. It may do no harm, or it may allow blood to bypass the outflow to certain organs or tissues, leaving them without a blood supply. This can cause a heart attack, stroke, kidney damage, and other problems.

Rupture. A break in all three layers of the aortic wall is termed a rupture. Blood pours from the aorta into the chest. This massive internal bleeding can quickly lead to shock and death.

Aneurysm dissection

illustration of heart showing an aneurysm dissection

Dissection of an aneurysm occurs when a rip appears in the inner layer of the aortic wall and it peels away from the middle layer. Blood flows through an extra channel inside the aorta wall that may bypass the outflow to certain organs or tissues, leaving them without a blood supply.

Early warning system for a thoracic aortic aneurysm

Thoracic aortic disease is a stealth condition. It develops slowly and silently, usually without any symptoms. And it often flies under doctors' radar, in part because no single medical specialty lays claim to the aorta as it passes through the chest, leaving it in a sort of medical limbo.

Today, most thoracic aneurysms are found by chance on CT scans or echocardiograms of the chest and heart done for some other reason. But checking everyone for a thoracic aortic aneurysm doesn't make sense, because most people don't have one. But a more structured approach to looking for a thoracic aortic aneurysm could save lives. A good place to start is in people likely to have the condition. This includes individuals with any of the following:

A bicuspid aortic valve. Between 1% and 2% of Americans are born with an aortic valve that has two flaps (a bicuspid valve) instead of the normal three flaps (a tricuspid valve). As many as half of people with a bicuspid aortic valve eventually develop an enlarged thoracic aorta. If you have been told you have a bicuspid aortic valve, you should be checked for a thoracic aneurysm.

Early aortic valve surgery. Failure of the aortic valve before age 70 is often due to a bicuspid valve.

Certain genetic conditions. Thoracic aortic aneurysm is common in individuals with genetic conditions such as Marfan syndrome, Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome, Turner syndrome, and others.

Family history. If you have a thoracic aortic aneurysm, urge your siblings, children, or parents to be checked for one. The reverse holds as well — if a parent, sibling, or child has a thoracic aneurysm, you should be tested for one, too. The same is true if you have a close relative who has died of an aortic dissection or rupture or unexplained cardiac arrest.

Even if you don't have any of these risk factors, if you are having a CT scan of your heart or chest, or an echocardiogram of your heart, ask your doctor to ask the radiologist to check (that means measure) the diameter of your aorta.

Who needs to be checked for a thoracic aortic aneurysm?

You should be tested for a thoracic aortic aneurysm if you

  • have a bicuspid aortic valve, have had a bicuspid aortic valve replaced, or have a parent, sibling, or child with one.
  • had surgery to replace or repair an aortic valve at a relatively young age (under age 70).
  • have a parent, sibling, or child who has a thoracic aortic aneurysm or who has experienced a rupture or dissection of an aneurysm.
  • have Marfan syndrome, Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome, Turner syndrome, or other genetic condition associated with aortic aneurysms.

What to do about a thoracic aortic aneurysm

If fixing a thoracic aneurysm were a safe, simple, complication-free procedure, intervention would immediately follow detection. But repairing a thoracic aortic aneurysm is usually a major operation, the kind you don't want to undergo unless you absolutely must. (In even the best centers, 1% to 2% of people have a stroke or die as a result of a planned aneurysm-repair operation.) That's why most people live with a thoracic aneurysm for as long as it is safe, checking its size every year with a CT scan or echocardiogram, controlling their blood pressure, and avoiding the handful of things that might make it burst before its time: lifting heavy weights, excessive strenuous exercise, or use of cocaine or other illicit drugs.

If the thoracic aortic aneurysm stays small, great — the chance that a small, stable aneurysm will burst is quite low. But a fast-growing aneurysm (more than 0.5 cm per year) or one that is approaching a diameter of 5 to 5.5 cm requires treatment. For people with Marfan syndrome or other genetic conditions, the trigger point for surgery may be as low as 4.0 cm.

Know the warning signs of a thoracic aortic aneurysm

Another reason to know you have a thoracic aortic aneurysm is so you can sound the alarm and avoid the delays or misdiagnoses that can befall people when a dissection occurs.

Two common tests — a CT scan or a transesophageal echocardiogram — that aren't often done for people suspected of having a heart attack or muscle pain can nail down the diagnosis.

Doctors once thought that dissection or rupture of the thoracic aorta had almost unmistakable signs and symptoms. But just as they've gradually come to realize that heart attacks can cause a variety of symptoms, so, too, can an aortic dissection. The classic symptom is sudden onset of severe pain in the chest, back, or abdomen that has a ripping, stabbing, or tearing feel. Unlike heart attacks, which generally start out with low-grade pain or discomfort, the pain of a dissecting aneurysm is usually immediately intense and unwavering.

If you have an aneurysm and you have sudden onset of chest, neck, back, or abdominal pain, or something doesn't feel right in your chest, get to an emergency department, describe what is going on, and say 'I have a thoracic aneurysm, I need a CT scan right away.

Image: Thinkstock

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