A thoracic aortic aneurysm refers to the dilation of the thoracic aorta. The most commonly affected area is the ascending aorta. The diameter of the thoracic aorta varies depending on several factors (e.g., age and body size), but is normally less than 4.5cm for the ascending and 3.5cm for the descending thoracic aorta.
The first time a patient may become aware of an aneurysm is when it ruptures, causing life-threatening bleeding into the mediastinum cavity. This has an extremely high mortality.
False Aneurysms
There are three layers to the aorta: the intima, media and adventitia.
False aneurysms (or pseudoaneurysm) occur when the inner two layers (intima and media) rupture and there is dilation of the vessel, with the blood only being contained within the outer (adventitia) layer of the aorta. This typically occurs after trauma, such as a road traffic accident. It can also occur after surgery to the aorta or infection in the vessel.
True aneurysms are where the three layers of the aorta are intact but dilated. Aortic dissection is where the blood enters between the intima and media layers.
Risk Factors
- Men are affected significantly more often and at a younger age than women
- Increased age
- Smoking
- Hypertension
- Family history
- Existing cardiovascular disease
- Marfan syndrome and other connective tissue disorders
Presentation
Dilation of the thoracic aorta is often asymptomatic. It may be found incidentally on investigations for other reasons, for example on a chest x-ray, echocardiogram or CT scan.
An aneurysm may cause symptoms due to taking up space within the mediastinum:
- Chest or back pain
- Trachea or left bronchus compression may cause cough, shortness of breath and stridor
- Phrenic nerve compression may cause hiccups
- Oesophageal compression may cause dysphagia (difficulty swallowing food)
- Recurrent laryngeal nerve compression may cause a hoarse voice
Diagnosis
The main investigations for diagnosis and assessment are:
- Echocardiogram
- CT or MRI angiogram
Management
The risk of progression of a thoracic aortic aneurysm can be reduced by treating modifiable risk factors:
- Stop smoking
- Healthy diet and exercise
- Optimising the management of hypertension, diabetes and hyperlipidaemia
Management options depend on individual patient factors and the size. The larger the size of the aneurysm, the higher the risk of rupture.
The options are:
- Surveillance with regular imaging to monitor the size
- Thoracic endovascular aortic repair (TEVAR), with a catheter inserted via the femoral artery inserting a stent graft into the affected section of the aorta
- Open surgery (midline sternotomy) to remove the section of the aorta with the defect in the wall and replace it with a synthetic graft
Complications
- Aortic dissection
- Ruptured aneurysm
- Aortic regurgitation (if the aortic valve is affected)
Ruptured Thoracic Aortic Aneurysm
The risk of rupture increases with the diameter of the aneurysm.
Rupture of a thoracic aortic aneurysm results in bleeding into the mediastinum. There may be bleeding into the:
- Oesophagus, causing haematemesis (vomiting blood)
- Airways or lungs, causing haemoptysis (coughing up blood)
- Pericardial cavity, causing cardiac tamponade (compression of the heart)
A ruptured thoracic aortic aneurysm presents with:
- Severe chest pain or back pain
- Haemodynamic instability (hypotension and tachycardia)
- Collapse
- Death (often patients do not reach hospital)
Emergency open surgery is required, with replacement of the affected section of the aorta with a synthetic graft.
Last updated May 2021
Now, head over to members.zerotofinals.com and test your knowledge of this content. Testing yourself helps identify what you missed and strengthens your understanding and retention.
