Dr Chua Soo Yeng Benjamin
Aortic aneurysms affect 3 – 4% of adults aged 60 and above, and are more common in men. They are characterised by an abnormal enlargement and ballooning of the aorta, the main artery that carries blood from the heart to the rest of the body. The aorta is situated next to the spine and extends from the chest into the abdomen. It gives off blood supply branches to the spinal cord, liver, stomach, intestines and kidneys before dividing to form arteries that supply the pelvic organs and lower limbs.
An aortic aneurysm occurs when the diameter of the aorta enlarges by more than 50%. Risk factors include heavy smoking and chronic conditions such as hypertension and atheroscleorosis. Genetic conditions may also predispose the aorta wall connective tissues to be weak. Aortic aneuryms are commonly known as AAA (Abdominal Aortic Aneurysm) when they occur in the abdomen or TAA (Thoracic Aortic Aneurysm) when in the chest.
In its early stages, when an aortic aneurysm is small in size (<5cm diameter), the risk of spontaneous rupture is small. However, it should be monitored by a vascular surgeon.
If the aneurysm continues to grow (>5cm diameter), the walls of the aorta can become thinned out and lose their ability to stretch, and become unable to support the force of blood flow. The aneurysm could burst, causing serious internal bleeding and death.
As the aneurysm increases in diameter, the risk of rupture also increases. For example, a 5 – 6 cm diameter aneurysm has a 10 – 20% cumulative risk of rupture per year and one that is more than 9 cm has more than 50% cumulative risk of rupture per year. The mortality risk from a ruptured aneurysm is as high as 50 – 80%.
Patients are commonly pain-free and have no symptoms until the aneurysm has grown significantly or ruptures. Most patients are diagnosed after being investigated for other problems, usually after a CT scan. Patients or physicians can sometimes feel a pulsating mass in the abdomen.
When symptoms do develop, the most common is severe pain. For abdominal aneurysms, there will be persistent, severe abdominal and back pain that is not relieved by position or medication. For thoracic aneurysms, the pain will be in the chest and upper back.
Other symptoms include feelings of indigestion, especially if the aneurysm is large, compressing the stomach and intestines. The aneurysms usually have a significant amount of blood clots within the sac. The blood clots can break off and travel downwards into the arteries supplying the liver and gut, kidneys or down the leg arteries (distal embolisation). This can cause patients to experience severe abdominal pain which is life-threatening (gut ischaemia), kidney failure or develop pain and gangrene spots of the legs and feet. Some aortic aneurysms can become infected by blood-borne bacteria, and patients develop fever and abdominal pain.
The development of symptoms indicate that the aneurysm may rupture or start leaking. Once this happens, patients can have severe abdominal and back pain and look pale with a fast heartbeat. If left untreated, they can collapse.
Most are diagnosed based on physical examination. The most basic imaging needed is an ultrasound scan of the aorta. This is often used as a screening test or to confirm the presence of the aneurysm. However, the best imaging for diagnosis is a detailed CT scan of the aorta with contrast. The CT scan will provide detailed information about the nature, size and configuration of the aneurysm and how it relates to the surrounding arteries and organs, which helps in planning appropriate treatment.
An aneurysm needs to be treated when:
Treatment is best done on a planned and elective basis and can be safe and effective. Treatment of emergency ruptured aneurysms has very significant risk of death.
Treatment of an aortic aneurysm requires detailed understanding of the aneurysm anatomy and expert planning, and some technical competence is also required to perform surgery. There are two types of treatment for AAA:
This is a major operation done under general anaesthesia. It involves making a long abdominal incision and direct exposure of the aneurysm, putting clamps to control blood loss before cutting open the aneurysm and replacing it with a graft. For difficult AAA, the arteries that supply the abdominal organs may be reconstructed. The abdomen is then closed up. Open surgery for TAA is more complex as it involves access into the chest cavity. Sometimes, patients have to be put on cardiopulmonary bypass (heart-lung machine).
Patients must be medically fit to undergo general anaesthesia as well as open surgery. Patients usually have to stay in the ICU for a few days and in the hospital for up to ten days post-surgery.
These are covered stents (stent grafts) that come compressed. When released inside the aneurysm (thoracic or abdominal), the stent grafts re-line or cover the aneurysm from inside, preventing it from rupturing. The whole stent graft can be inserted through the femoral arteries in the groin via a small puncture hole (< 1 cm) in the skin. For more complex aneurysms, additional puncture wounds may be made in the upper arm arteries. Due to the minimally invasive nature of EVAR or TEVAR, most cases can be done under sedation and local anaesthesia or a light general anaesthesia. Recovery for patients is faster and most patients can be discharged 24 to 48 hours post-surgery.
Stent graft surgery is suitable for patients who are elderly and at high risk for general anaesthesia and open invasive surgery. These patients usually have pre-existing history or are at risk of cardiac disease or strokes.
The post-surgery recovery depends on the type of surgery done. Patients who have had aortic repair usually spend the first two days in ICU and up to ten days in hospital before being discharged. In the immediate 24 hours post-surgery, patients are usually fasted and observed for bowel movement before being allowed fluids. A CT scan is usually repeated at one, three and 12 months post-surgery. Often, patients do not require long-term follow-up care beyond one to two years after surgery.
For patients undergoing stent graft surgery, a surveillance CT or ultrasound scan is repeated at 1, 3, 6, 12 and 24-month intervals post-surgery together with follow-up clinic visits. Patients are also followed up for life as a small percentage of aneurysms treated by stent grafts can develop new leaks around the stents, causing the aneurysm to enlarge again.
The choice of which aortic surgery a patient should undergo depends on a few criteria.
Patients should have a good discussion with a vascular surgeon once they are diagnosed with an aortic aneurysm, as there are good treatment options available.
This article was first posted by ezyhealth on 31st March, 2015