What Is An Aortic Aneurysm?
Aortic aneurysm describes an aorta that is enlarged in size. If it becomes significantly large it can lead to catastrophic complications. The aorta is the large blood vessel that the heart pumps into via the aortic valve every time it beats. Incredibly the aorta pumps around 200,000,000 liters of blood around the body in a lifetime. The aorta supplies the body with blood and is the largest blood vessel. Many blood vessels arise from the aorta that supply various organs and parts of the body with blood, for example the carotid artery that supplies the head comes from the aorta. An aortic aneurysm is when the aorta is noted to enlarge. For example the normal aorta is about 2-3 cm wide. Some aortic aneurysms reach 5,6 or 7cm, or even larger.
Thoracic vs. Abdominal Aortic Aneurysm
Aortic aneurysms in the top half of the chest are generally known as thoracic aortic aneurysms and those in the abdomen are known as abdominal aortic aneurysms. The aorta leaves the heart, goes up to the top of the body then bends and goes down towards the legs. The part of the aorta that is in the chest is known as the thoracic aorta, the part that is in the abdomen area is known as the abdominal aorta. In the thoracic aorta, the part that goes up from the heart to the top of the body is known as the ascending aorta, the bend at the top of the body is known as the aortic arch, and the part that travels down towards the leg is known as the descending aorta. This is important in describing aortic aneurysms, for example, ascending aortic aneurysm vs. descending aortic aneurysm.
Many aortic aneurysms will never become large enough to need any surgical treatment. Technically to be an aortic aneurysm the aorta just needs to be larger than the normal values for any given person. Importantly, however, many aortic aneurysms will never get large enough to worry about. There are various factors that determine the size of a normal aorta, these include age, sex and body size. The elderly, men and larger people will have larger aortas.
Symptoms Of An Aortic Aneurysm
Aortic dissection, the feared complication of aortic aneurysms may present with a tearing pain that is felt to go through to the back. Many aortic aneurysms will be clinically silent which means that there are no associated symptoms. These will just be picked up on routine scans. In some cases however symptoms may lead to the diagnosis. Pain may be present, in thoracic aortic aneurysms the pain will be in the chest, and in abdominal aortic aneurysms the pain will be in the abdomen. In a dissection, which is one of the most feared complications of an aortic aneurysm, there may be a tearing feeling and the pain often is felt through to the back and is intense in nature. Very large aortic aneurysms can cause compression of nearby structures, those in the chest for example can press on the food pipe and cause difficulty swallowing or persistent coughing. In large aortic aneurysms, the aneurysm may be felt to be pulsating on the physical exam.
Diagnosing Aortic Aneurysms – Tests
When it comes to diagnosing, characterizing and following aortic aneurysms, and planning interventions, CT scan is the most commonly used test.
Chest X-Ray – A simple chest X-ray may show widening of the aorta that can be suggestive of an aneurysm.
Echocardiogram – This is an ultrasound scan of the heart that looks not only at heart structures, but can also give excellent detail of the ascending aorta as it leaves the heart. This can show enlargement and may be used to assess changes in the aorta over time.
TEE – This is an ultrasound scan of the heart known as a transesophageal echocardiogram where a probe is inserted in to the food pipe to take close up pictures of the heart. The TEE is excellent in diagnosing structural heart disease such as thoracic aortic aneurysms and any associated complications.
Abdominal Ultrasound – This is an ultrasound scan of the abdomen that can look at abdominal aortic aneurysms, it is good for diagnosing and also looking at aortic size. It is painless and low cost and so often used as a screening tool.
CT Scan – This is the most widespread test used to diagnose aortic aneurysms, offers excellent detail and is widely available. The only downside to this test is the need for contrast dye and also radiation exposure, which means its not ideal in young people requiring repeated tests, or in those with kidney disease.
MRI Scan – MRI scanning gives excellent quality images of the aorta and aneurysms and is very reproducible and therefore good for serial imaging over time to follow size. Drawbacks include availability and the fact it is not very practical if needed for an emergency.
Key Factors In Imaging of Aortic Aneurysm
The measurements taken should be taken in the same place ideally each time the aorta is measured especially when looking at serial follow-ups over time. Risks of tests should be taken in to account, for example radiation risks, procedural risks and so on. If comparing aortic aneurysms on follow up scans, the same imaging tool should be used each time ideally. The aorta should be measured at many different levels.
Medical Treatment of Aortic Aneurysms
Blood pressure control and addressing common cardiac risk factors is the cornerstone of medical treatment of aortic aneurysms. The goal of medicines in the treatment of aortic aneurysms is to reduce the stress on the aorta by reducing blood pressure and the force of each heart beat. Blood pressure should at least be controlled to below 140/90 levels. It is critical that smokers stop smoking. Smoking has been shown to increase the rate of aortic aneurysm expansion. Treatment of cardiac risk factors such as cholesterol levels, diabetes and obesity should also be addressed.
Minimally Invasive Technique for Thoracic Aortic Aneurysm – TEVAR and EVAR
Minimally invasive options can avoid open surgery for aortic aneurysms and are commonly used, known as EVAR and TEVAR depending on the location of the aneurysm. TEVAR stands for thoracic endovascular aortic repair. EVAR generally refers to the abdominal aortic aneurysm repair. In the TEVAR, the procedure is performed through the artery of the leg and avoids the need for open surgery. In the TEVAR the aortic aneurysm is covered with a stent that is covered with a membrane and prevents enlargement. An appropriately skilled team to determine candidates for TEVAR reviews patients CT scans carefully. The stent graft is entered in to the body in a collapsed state, and then expanded when in the correct area of the aneurysm.
Open Surgery for Aortic Aneurysms
Cardiothoracic surgeons will typically operate on thoracic aortic aneurysms and vascular surgeons will operate on the abdominal aortic aneurysms. Sometimes in extensive aneurysms involving the whole aorta then both may work together. In surgical repair of an aneurysm, the aneurysm portion of the aorta is removed and replaced by a graft. The decision to perform surgery vs. a minimally invasive approach will be determined by specialists who are familiar with these techniques.
Aortic Aneurysm and Aortic Dissection
Aortic dissection is the feared complication of an aortic aneurysm and is a tear in the wall of the aorta that can result in catastrophic outcome. Aortic dissection is the main reason a repair is performed. In aortic aneurysms the wall of the aorta becomes thin and more prone to tearing. An aortic dissection is basically a tear in the wall of the aorta that can extend all the way backward or forward, depending on the type of tear. The tear leads to rapid blood loss and also prevents blood getting to the organs. It is a serious condition with a high chance of death unless treated emergently. Even when treated, there is a high chance of complications. The most common symptom in an aortic dissection is a tearing type pain that extends through to the back.
When to Operate on Aortic Aneurysms
In general the decision to operate on an aortic aneurysm is based on the size of the aorta and also taking in to account other risk factors for complications if the aneurysm were to be left alone. So basically, the risk of operation must be less than the risk of leaving the aortic aneurysm alone.
Intervention on patients with Marfan syndrome and ascending aortic aneurysm
Marfan syndrome is a genetic condition where patients have weak connective tissue, such as that which holds the joints and tissues of the skin together including the blood vessels. This leads to weakness in the aorta and enlargement. Also there is an increased risk of aortic dissection given the weakness of the walls. In patients with Marfan, surgery should be performed in patients with aortic size ≥ 50mm. In patients with Marfan who have a family history of dissection, size increase of > 3mm/year, desire for pregnancy, or a severely leaky aortic valve, surgery may be considered in those with an aortic size >45mm.
Intervention on patients with bicuspid aortic valve and ascending aortic aneurysm
Patients with bicuspid aortic valve have 2 leaflets in the aortic valve rather than the normal 3. These patients are more susceptible to developing aortic stenosis that is a tight aortic valve, and aortic aneurysms. In general patients with a bicuspid aortic valve and aortic aneurysm should undergo operation for the aneurysm if the aortic size is ≥ 55mm. In patients with risk factors for complications such as those with rapid size increase, high blood pressures, family history of complications and others, surgery at an aortic size of >50mm is considered reasonable.
Intervention on patients who need aortic valve surgery and have an ascending aortic aneurysm
In patients already requiring surgery on the aortic valve, lower thresholds for aortic surgery may be used, such as 45mm. Decisions are regarding the need for and the type of operation should be made on a case by case basis by a specialist team.
Intervention on patients with descending aortic aneurysms
In general the minimally invasive TEVAR is preferred over open surgery in patients with descending aortic aneurysms. TEVAR is generally performed in patients with aortic size ≥ 55mm. If TEVAR cannot be performed for technical reasons in patients with descending aortic aneurysm and surgery is the preferred option then it is generally performed when aortic size is ≥ 60mm.
Intervention on patients with abdominal aortic aneurysm
In general, intervention is performed on patients with abdominal aortic aneurysm and aortic size of > 55mm or if the aneurysm displays evidence of rapid increase in size. Both the minimally invasive EVAR, and open surgery are seen as valid options depending on expertise available.