What is an aneurysm?
The aorta is the main artery supplying oxygenated blood to the body (for more information on the aorta click here). It is a complicated structure with a diameter that varies along its length. An aneurysm is a bulge in the vessel due to an underlying weakness in the vessel wall and is defined as a permanent dilatation of a blood vessel to greater than 50% of its normal size. The “normal” size of the aorta is unlikely to be the same for two different people, it varies based on the size of the individual expressed as a body surface area. People with a larger body surface area will have a larger diameter of the aorta. Men have a larger aorta than women. As a rough guide the diameter of the aorta ranges from 1.5cm to 3cm. Your surgeon may assess the size of the aorta using a range of different imaging techniques, these include:
- Transthoracic or tranoesophageal echocardiogram
- Computed Tomography (CT) aortagram
Why is it important?
Aneurysms can result in severe and life threatening complications that include rupture and dissection. A thoracic aneurysm is important to monitor as the larger the diameter of the aneurysm, the greater the tension on the wall meaning a higher chance of a complication occurring. Many patients with an aneurysm of a smaller size can be safely managed with medications and surveillance. Some patients will require an operation; this depends not only on the size of the aneurysm but also the presence of other medical problems such as heart, lung and kidney disease.
Symptoms of a thoracic aneurysm
Most aneurysms are symptom free until they reach a size at which they compress other structures. Symptoms can include:
- Breathing difficulties and noisy breathing (stridor) if the aneurysm encroaches on the upper airway (trachea),
- Difficulty swallowing (dysphagia) to compression of the oesophagus
- A persistent cough
- Vague pain in the chest.
Severe chest pain may represent a medical emergency due to a rupture of the aneurysm or an aortic dissection (for more information on aortic dissection click here)
Factors contributing to aneurysm formation
Important risk factors for thoracic aortic aneurysm include:
- High blood pressure (hypertension)
- High cholesterol
- Male gender
- Advancing age.
Several genetic conditions exist that affect the vessel wall causing an increased risk of aneurysm formation and rupture. These include Marfan syndrome, Loeys-Deitz syndrome and Ehlers-Danlos syndrome.
Other rare causes of aortic aneurysm include inflammatory disorders such as giant cell arteritis and Takaysu arteritis or untreated infections including syphilis, salmonella and tuberculosis.
Management of thoracic aortic aneurysms
Smaller aneurysms that are asymptomatic are managed conservatively through surveillance and the management of risk factors. Blood pressure is aggressively managed using medications such as beta-blockers. Smoking cessation and management of high cholesterol may also be beneficial.
Surveillance of the aneurysm involves regular imaging of the aorta to determine size of the aneurysm and the rate of expansion of the aneurysm.
The size at which an operation is recommended for thoracic aortic aneurysms is not the same for everyone. For people with a bicuspid aortic valve, Marfan syndrome or other connective tissue disorders and for patients in whom the rate of expansion of the aneurysm is >0.5cm/year, an operation will be offered with a smaller aneurysm.
For patients with an aneurysm of the ascending aorta, an open operation in which the dilated segment of the aorta is removed and replaced with a synthetic tube is usually recommended, if necessary, the aortic valve can be replaced at the same time. For some patients with an aneurysm of the descending aorta an open operation may not be necessary. For these patients, a collapsible wire mesh, or stent, is inserted in the dilated aneurysm. The decision on the type of procedure offered should be discussed with your surgeon.
Goldfinger JZ, Halperin JL, Marin ML, Stewart AS, Eagle KA, Fuster V. Thoracic Aortic Aneurysm and Dissection. Journal of the American College of Cardiology. 2014;64(16):1725-39.
Booher AM, Eagle KA. Diagnosis and management issues in thoracic aortic aneurysm. American Heart Journal. 2011;162(1):38-46.e1.
Ruddy JM, Jones JA, Ikonomidis JS. Pathophysiology of Thoracic Aortic Aneurysm (TAA): Is it not one Uniform Aorta? Role of Embryologic Origin. Progress in cardiovascular diseases. 2013;56(1):68-73.