Thoracic aortic aneurysms often grow slowly and usually without symptoms, making them difficult to detect. Some aneurysms will never rupture. Many start small and stay small, although many expand over time. How quickly an aortic aneurysm may grow is difficult to predict.

As a thoracic aortic aneurysm grows, some people may notice:

• Tenderness or pain in the chest
• Back pain
• Hoarseness
• Cough
• Shortness of breath

Aortic aneurysms can develop anywhere along the aorta, which runs from your heart through your chest and abdomen. When they occur in the chest, they are called thoracic aortic aneurysms. Aneurysms can occur anywhere in the thoracic aorta, including the ascending aorta near the heart, the aortic arch in the curve of the thoracic aorta and the descending aorta in the lower part of the thoracic aorta.

Aneurysms that form in the lower part of your aorta — called abdominal aortic aneurysms — are more common than thoracic aortic aneurysms. An aneurysm can also occur in between the upper and lower parts of your aorta. This type of aneurysm is called a thoracoabdominal aneurysm.

Factors that can contribute to an aneurysm's development include:

• Hardening of the arteries (atherosclerosis). As plaque builds up on your artery walls, they become less flexible, and the additional pressure can cause them to weaken and bulge. High blood pressure and high cholesterol are risk factors for hardening of the arteries. This is more common in older people.
• Genetic conditions. Aortic aneurysms in younger people often have a genetic cause. People who are born with Marfan syndrome, a genetic condition that affects the connective tissue in the body, are particularly at risk of a thoracic aortic aneurysm. Those with Marfan syndrome may have a weakness in the aortic wall that makes them more susceptible to aneurysm. People with Marfan syndrome often have distinct physical traits, including tall stature, very long arms, a deformed breastbone and eye problems.

Besides Marfan syndrome, Ehlers-Danlos, Loeys-Dietz and Turner syndromes, and other family-related disorders can cause an aortic aneurysm. Ehlers-Danlos syndrome causes your skin, joints and connective tissue to be fragile and makes your skin stretch easily.

• Other medical conditions. Inflammatory conditions, such as giant cell arteritis and Takayasu arteritis, may cause thoracic aortic aneurysms.
• Problems with your heart's aortic valve. Sometimes people who have problems with the valve that blood flows through as it leaves the heart (aortic valve) have an increased risk of thoracic aortic aneurysm. This is mainly true for people who were born with a bicuspid aortic valve, meaning the aortic valve has only two cusps instead of three.
• Untreated infection. Though it is a rare cause of thoracic aortic aneurysm, it's possible to develop this condition if you've had an untreated infection, such as syphilis or salmonella.
• Traumatic injury. Rarely, some people who are injured in falls or motor vehicle crashes develop thoracic aortic aneurysms.

Thoracic aortic aneurysm risk factors include:

• Age. Thoracic aortic aneurysms occur most often in people age 65 and older.
• Tobacco use. Tobacco use is a strong risk factor for the development of an aortic aneurysm.
• High blood pressure. Increased blood pressure damages the blood vessels in the body, raising your chances of developing an aneurysm.
• Buildup of plaques in your arteries (atherosclerosis). The buildup of fat and other substances that can damage the lining of a blood vessel (atherosclerosis) increases your risk of an aneurysm. This is a more common risk in older people.
• Family history. People who have a family history of aortic aneurysm are at increased risk of having one. Those with a family history of aneurysms tend to develop aneurysms at a younger age and are at higher risk of rupture. This is a primary risk factor in younger people.
• Marfan syndrome and related disorders. If you have Marfan syndrome or related disorders, such as Loeys-Dietz syndrome or Ehlers-Danlos syndrome, you have a significantly higher risk of a thoracic aortic aneurysm.
• Bicuspid aortic valve. Nearly half of those who have an aortic valve with two cusps instead of three (bicuspid aortic valve) may develop an aortic aneurysm.

Tears in the wall of the aorta (dissection) and rupture of the aorta are the main complications of thoracic aortic aneurysm. A ruptured aortic aneurysm can lead to life-threatening internal bleeding. In general, the larger the aneurysm, the greater the risk of rupture.

Signs and symptoms that your thoracic aortic aneurysm has burst include:

• Sudden, intense and persistent chest or back pain
• Pain that radiates to your back
• Trouble breathing
• Low blood pressure
• Loss of consciousness
• Shortness of breath
• Trouble swallowing
• Weakness or paralysis of one side of the body, difficulty speaking, or other signs of stroke

Blood clot risk

Another complication of aortic aneurysms is the risk of blood clots. Small blood clots can develop in the area of the aortic aneurysm. If a blood clot breaks loose from the inside wall of an aneurysm, it can block a blood vessel elsewhere in your body, possibly causing serious complications.