What Is An Aortic Aneurysm?


An aortic aneurysm is a bulge in the main blood vessel in the body known as the aorta.

The aorta1 is shaped like a curved candy cane and carries oxygen-rich blood up from the heart and then back down through the chest and to the stomach. An aneurysm2 develops when a section of the blood vessel dilates and balloons.

An aortic aneurysm can get bigger over time which could lead it to burst and cause life-threatening bleeding. A rupture is fatal 80% of the time so early detection is important.3

Types of aortic aneurysm

Abdominal aortic aneurysm

An abdominal aortic aneurysm (AAA) occurs in the ‘handle’ of the candy cane-shaped aorta; the part that points down and through the abdomen (stomach).4 AAAs are responsible for three-quarters of aortic aneurysms.3

Thoracic aortic aneurysm

A thoracic aortic aneurysm (TAA) occurs in the curved part of the aorta that points upwards from the heart and backs down through the chest. They are less common than abdominal, possibly because the wall in the thoracic aorta is thicker and stronger as it has to pump blood upwards.4

Causes of aortic aneurysm

An aortic aneurysm happens when there is weakness in the wall of the aorta. Blood pumping through the vessel puts pressure on the wall and causes it to balloon.2 It is difficult to know exactly how and why this happens but we know it involves inflammatory cells, sent by the immune system, that attack the vessel wall and cause it to thin and expand.5 Several risk factors can lead to an aortic aneurysm.

Risk factors

  • Age - Aortic aneurysms are most common in over 65s.6 This is likely due to the thinning of vessel walls with age
  • Sex - Men are more prone to aortic aneurysms than women.7 Women usually suffer at an older age (over 70) and when they have additional risk factors
  • Smoking - Being a current or previous smoker is a huge risk factor, particularly for abdominal aortic aneurysms.6 Continuing to smoke with an aortic aneurysm makes it more likely to grow and/or rupture
  • High blood pressure - A risk factor for both types but the main risk factor for thoracic aortic aneurysms.6 Increased pressure on the aortic walls can cause them to bulge
  • Other Cardiovascular conditions - Includes atherosclerosis (narrowing of the arteries), coronary heart disease and peripheral heart disease6
  • Genetics - If you have a family member that has suffered from an AAA you are more likely to be affected6 

Having certain genetic conditions carries the risk of a thoracic aortic aneurysm such as connective tissue disorders and congenital heart diseases.8

Signs and symptoms of an aortic aneurysm

A lot of the time there will be no aortic aneurysm symptoms until it bursts, but you may experience breathlessness or pain in the stomach, lower back or chest that doesn’t go away.4 An AAA may present as pulsing in the stomach like a heartbeat.7

Signs of a ruptured aortic aneurysm include:7

  • Sudden severe pain in the stomach, lower back or chest
  • Sweaty, pale or clammy skin
  • Fast heart rate
  • Shortness of breath
  • Dizziness or fainting 

Diagnosis of an aortic aneurysm

Aortic aneurysms are usually identified through an ultrasound, typically a CT scan. In England, there is an NHS AAA screening programme, offered to men over 65.7 Women over 70 with underlying risk factors can also ask for a referral. There is no screening offered for TAAs as they are harder to scan for but if you are worried about symptoms then seek advice from your doctor.3 

Management and treatment for an aortic aneurysm

If an aortic aneurysm is detected on an ultrasound then it is categorised as small (3-4.4cm across), medium (4.5-5.4cm across) or large (over 5.5cm).7 Aortic aneurysms usually grow around 1-2mm per year and a small aneurysm or medium aneurysm will be monitored regularly for changes in size.3 You may be offered medications that improve blood flow, lower body pressure or manage cholesterol.4 Larger aneurysms usually require surgery unless the risk of operating is too great.


Endovascular aneurysm repair (EVAR)

This is a minimally invasive surgery where a thin tube (catheter) is inserted, usually through the groin, and positioned in the aorta.4 The tube attaches to the vessel wall and forms a seal to re-line and support the aorta, preventing blood from entering the aneurysm. You may also hear this referred to as a stent.

Open aneurysm repair

A large cut is made in the chest or stomach to replace the aneurysm with a graft. This surgery may also be performed if the aneurysm has already burst. 


As an aortic aneurysm grows it is at risk of tearing or bursting. A tear in the aneurysm (an aortic dissection) lets blood leak between the vessel walls and causes the narrowing of the vessel. This can reduce/stop blood flow to the rest of the body and the build-up in pressure can cause the aneurysm to burst (rupture).

If the aneurysm ruptures then it causes life-threatening internal bleeding. It is possible to fix with surgery but only if treated quickly. 


How can I prevent an aortic aneurysm?

Aortic aneurysms are strongly associated with age, sex and genetics so you may not be able to prevent an aortic aneurysm but you should focus on maintaining a healthy lifestyle. Avoiding smoking and keeping your blood pressure low are important factors for preventing/reducing the severity of aortic aneurysms.

How common is an aortic aneurysm?

AAA are much more common than thoracic and the highest prevalence has been found in white male smokers aged 50-79.9 It is thought AAAs affect 1.3-8.9% of the male population, with the rate rapidly increasing over age 65. They are 4-6 times more common in males than in women.4,6,8

When should I see a doctor?

If you are experiencing any of the above symptoms you should seek urgent medical attention. 


An aortic aneurysm is a bulge in the main blood vessel either in the chest (thoracic) or stomach (abdominal). It is caused by a weakness in the aortic wall which balloons in response to the pressure of pumping blood. They are most common in men over 65, particularly those who smoke. Other risk factors include high blood pressure, other cardiovascular conditions and having a close family member who has suffered. Often aortic aneurysms don’t present any symptoms before they burst and are only detected through screening programmes. Ruptured or larger aneurysms are treated through the insertion of a stent or graft.


  1. Your aorta: the pulse of life [Internet]. www.heart.org. [cited 2023 Apr 29]. Available from: https://www.heart.org/en/health-topics/aortic-aneurysm/your-aorta-the-pulse-of-life
  2. What is an Aneurysm? [Internet]. www.heart.org. [cited 2023 Apr 29]. Available from: https://www.heart.org/en/health-topics/aortic-aneurysm/what-is-an-aneurysm
  3. All about aortic aneurysm [Internet]. [cited 2023 Apr 29]. Available from: https://www.bhf.org.uk/informationsupport/heart-matters-magazine/medical/all-about-aortic-aneurysm
  4. Aortic aneurysm [Internet]. Cleveland Clinic. [cited 2023 Apr 29]. Available from: https://my.clevelandclinic.org/health/diseases/16742-aorta-aortic-aneurysm
  5. Ailawadi G, Eliason JL, Upchurch GR. Current concepts in the pathogenesis of abdominal aortic aneurysm. J Vasc Surg. 2003 Sep;38(3):584–8. 
  6. Aortic aneurysm - causes and risk factors | nhlbi, nih [Internet]. 2022 [cited 2023 Apr 29]. Available from: https://www.nhlbi.nih.gov/health/aortic-aneurysm/causes
  7. Abdominal aortic aneurysm [Internet]. nhs.uk. 2017 [cited 2023 Apr 29]. Available from: https://www.nhs.uk/conditions/abdominal-aortic-aneurysm/
  8. Mathur A, Mohan V, Ameta D, Gaurav B, Haranahalli P. Aortic aneurysm. Journal of Translational Internal Medicine [Internet]. 2016 Apr 1 [cited 2023 May 2];4(1):35–41. Available from: https://sciendo.com/article/10.1515/jtim-2016-0008
  9. Moll FL, Powell JT, Fraedrich G, Verzini F, Haulon S, Waltham M, et al. Management of abdominal aortic aneurysms clinical practice guidelines of the European society for vascular surgery. Eur J Vasc Endovasc Surg. 2011 Jan;41 Suppl 1:S1–58. 
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Holly Morgan

PhD in Molecular and Cellular Biology, University of Leeds
MNatSci BSc Natural Sciences, University of Leeds

Holly is currently working as a scientist developing biological drugs for the pharmaceutical industry. During her PhD she worked on methods to conjugate molecules to proteins for biopharmaceutical use. Outside of work, she enjoys combining her love of science and writing to produce articles for Klarity’s health library.

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