Thoracic Aortic Aneurysm

The Aorta is the major blood vessel that carries blood from the heart to all of the organs and limbs. It is divided into several parts: The ascending aorta, arch, descending thoracic aorta (in the chest) and the abdominal aorta. An aneurysm is a localised dilatation/ballooning/swelling of any blood vessel. These occur most frequently in the abdominal aorta but may occur in any part of this major artery, or in other parts of the body. Other aneurysms most commonly related to those in the aorta include popliteal artery aneurysms (behind the knee) and femoral artery aneurysms (in the groin). Other common aneurysms (though not necessarily related) include cerebral aneurysms in the brain. Aortic aneurysms are a serious problem with the risk of rupture or bursting being a cause for sudden death. Rupture (the most feared complication) will mostly occur without any prior warning of the aneurysm even being present.

Figure 1: The aorta (thoracic and abdominal)

Figure 2: Operation showing a large aneurysm of the abdominal aorta.

What causes aortic aneurysms?

The exact cause of aneurysmal disease is yet to be fully elucidated. Generally, the majority of aneurysms are thought to be due to a degenerative inflammatory process that affects the strength of the aortic wall. Aneurysms are most common in men (though do also occur in women) and increase in incidence with increasing age. Aneurysms also seem to be becoming more common in our society above and beyond the aging of our population. Aneurysms can run in families indicating a genetic predisposition and it is important to screen family members of those with aneurysms or those with a previous family member who has had an aneurysm. Aneurysms are rarely seen however before age 50 years (except in families with known connective tissue diseases such as Marfans Syndrome) so screening (with ultrasound) should be delayed until this time. It is also important to remember that if an aneurysm is not present at age 50, it can still develop later so screening on a regular basis (3-5 year intervals) would be recommended.

There is a growing interest around the world in screening for aortic aneurysm disease (similar to screening programmes for breast cancer), including programmes introduced in the United States. No official screening programme has been introduced as yet in Australia. It would be reasonable however to consider talking to your GP if you feel you may be at risk. At risk includes particularly men aged over 55 years of age with a history of past or present cigarette smoking, and anyone over age 50 years of age with a first degree relative (eg parent or brother/sister) with a known history of aortic aneurysm. Screening can be performed with a simple and non-invasive ultrasound examination of the abdomen.

Diagnosis and Symptoms

The majority of aortic aneurysms do not have symptoms. In the past, the most common way of identifying an aortic aneurysm was when they ruptured, leading to massive internal bleeding – unfortunately too late for most people. Rupture of an aortic aneurysm is generally regarded as a fatal condition. Whilst some patients who collapse with this will make it to hospital, most will die at home. Of those that do make it to hospital, approximately 50% will still not survive – a figure that has not improved around the world over many decades despite improvements in surgical techniques and intensive care treatment. Thankfully, the majority of aneurysms are detected early these days and are found incidentally when patients have ultrasounds or CT scans for other problems or symptoms. Early detection of small aneurysms allows them to be closely monitored and larger aneurysms to be treated before they can rupture. If the aneurysm itself presents with symptoms, this is considered a surgical emergency.

Known symptoms include:

  1. Pain in the back or abdomen, often sudden in onset (sometimes mimicking other common causes of pain including kidney stones, peptic ulcers or gall bladder disease)
  2. Sudden loss of consciousness
  3. Low blood pressure

Less common, however aneurysms may present with:

  1. Sudden loss of movement and/or sensation in legs (with suddenocclusion/thrombosis in an aneurysm)
  2. “Trash feet” – painful small dark patches on the toes (small areas of “gangrene”) related to pieces of blood clot (thrombus) within the aortic aneurysm breaking off and travelling to the feet
  3. Vomiting blood, due to erosion of an aortic aneurysm into the bowel (“aorto-enteric fistula”)

Diagnosis of aortic aneurysms is generally based on clinical examination and ultrasound examination. CT scanning however is generally required once an aneurysm reaches a size where treatment is being considered to better determine the anatomical relationship of the aneurysm to the branches of the aorta including especially the arteries to the kidneys (renal arteries) and to the legs (iliac arteries)

When do we treat?

The operative treatment of aortic aneurysms aims to prevent the aneurysm from rupture and thereby improving the life expectancy of the patient. There are several factors that are important to take into consideration when managing patients with aortic aneurysms. Determining the life expectancy of the patient, rupture risk of the aneurysm, and operative risks are some of the first steps.

Aneurysms that are symptomatic are potentially life-threatening emergencies, and emergency or urgent surgery is an important potentially life saving procedure. The surgical risk in this situation is however much higher than when elective treatment can be planned.