thoracic aortic aneurysm

Introduction

aneurysm of the thoracic aorta is much less common than abdominal aortic aneurysm (AAA) and mainly occurs in those over the age of 60 yrs, although may occur in patients younger than 40yrs if they have a predisposing condition
they are rare, occurring in approximately 6-10 per every 100,000 people.
a dilated thoracic aorta is defined as having a diameter greater than 3.5cm, however in young or small adults, the descending aorta upper limit may be regarded as being 2.3cm, while in larger adults or the elderly, the upper limit for the ascending aorta may be regarded as being 4.3cm
a diameter greater than 4.5cm is regarded as aneurysmal and needs 6-12 monthly monitoring
- some place these patients on statins, ACE inhibitors and beta adrenergic blockers to try to slow the rate of dilatation
surgery is offered when the risk of rupture is greater than the risk of the operation
- thoracic aneurysms are much more difficult to repair and carry much greater risks from treatment than do abdominal aortic aneurysm (AAA)
- elective surgical repair carries a 5% mortality rate
- those larger than 6cm should be considered for endovascular or surgical intervention as they have much higher risks of rupture
- those with Marfan's are often advised to have surgery once it reaches 4.5cm or if one is undergoing heart valve surgery

in contrast to these non-traumatic aneurysms, pseudoaneurysms of the thoracic aorta are usually the result of significant thoracic trauma, both penetrating and blunt, and carry a very high mortality, with 80-90% of patients dying before reaching hospital
see blunt aortic injury and trauma to the chest

10-20% are familial
risk is higher if:
- aneurysms elsewhere
- PH aortic dissection or blunt trauma
- age > 65yrs
- male (3x risk)
- smoker
- hypertension
- hyperlipidaemia
- connective tissue (CT) disorders
- Loeys-Dietz Syndrome
- Turner Syndrome
- syphilis
ascending aorta
- usually in younger patients with:
  - connective tissue (CT) disorders such as Marfan's, Ehler's Danlos, or Loeys-Dietz Syndrome and Turner Syndrome
  - following an aortic dissection or blunt trauma
aortic arch
- atherosclerosis and primary prevention
- following an aortic dissection
- inflammatory such as syphilis, Salmonella
descending thoracic aorta
- usually in elderly patients due to atherosclerosis and primary prevention

most are detected incidentally on thoracic CT scans or angiograms usually performed for other indications

the new FIP metric predicted future aneurysm with 98% accuracy on average three years after the FIP was first measured. ¹⁾
to calculate a personalized FIP, patients need a single 4D flow magnetic resonance imaging (MRI) scan

most are asymptomatic and found incidentally on CXR, echo or CT scan
as they enlarge, some may cause:
- chest pains, back pains, cough, SOB
- dysphagia due to compression of the oesophagus
- hoarse voice due to stretching of the recurrent laryngeal nerve
those with an impending potentially fatal complication such as rapid enlargement, tear or dissection
- may present with severe chest pain as per aortic dissection
- some may present with epigastric pain rather than chest pain
- once bleeding occurs, the patient may present with hypotension, shock, raised inflammatory markers including raised C reactive protein (CRP) which may mimic septic shock, and may also cause nausea, vomiting, dizziness, clamminess and even haemoptysis (aorto-bronchial fistula), or haematemesis (aorto-oesophageal fistula)
- once rupture occurs, mortality is 70-80%
  - some cease bleeding temporarily or survive long enough to allow emergency Open Aneurysm Repair which has a high rate of complications and only a 50% survival rate albeit with a prolonged recovery with lengthy ICU care being required. ²⁾

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