The aorta is the largest artery in the body. It is the main blood vessel that carries blood from the heart to the rest of the body. It is situated mainly next to the spine and extends from the heart into the chest, down to the abdomen and into the pelvis where it branches into the iliac arteries. From the iliac arteries, it then goes down to form the main blood supply to the lower limbs. During its course, it gives off vital branches that form the key arterial blood supply to vital organs such as the liver and stomach (Celiac artery), the intestines (the Superior Mesenteric Artery) and the kidneys (the Renal Arteries).
An aortic aneurysm develops when the wall of the aorta weakens and begins to bulge outwards like a balloon. Over time, the aneurysm can enlarge and if left untreated can spontaneously rupture, resulting in massive internal bleeding. Aortic aneurysms can develop along the whole course of the aorta, either in the chest (a Thoracic Aortic Aneurysm or TAA), in the abdomen (an Abdominal Aortic Aneurysm or AAA) or in the region stretching from the thorax into abdomen (a Thoraco-Abdominal Aortic Aneurysm or TAAA). Risk factors for the development of aortic aneurysms include chronic smoking, older age (more than 65 yrs), hypertension, the presence of heart disease and the presence of congenital soft tissue diseases (Marfan’s syndrome etc) and a strong family history. Aortic aneurysms are also more predominant in males.
In its early stages, when an aortic aneurysm is small, it does not pose an immediate health risk. However, it requires regular close monitoring and follow-up. This usually involves repeat ultrasound or CT scans at 3-6 monthly intervals.
In later stages however, if the aortic aneurysm continues to grow, the walls of the aorta or iliac arteries can become thin and lose their ability to stretch. The weakened sections of wall may become unable to support the force and pressure of blood flow. Such an aneurysm could burst, causing serious internal bleeding and death. The widest transverse diameter of the aneurysm is used as an indicator of risk of spontaneous rupture. It is widely accepted that an aneurysm with a diameter more than 5 cm is at significant risk of rupture and the risk increases with larger diameters. Other markers for aneurysm rupture include the presence of a saccular aneurysm (an round outpouching of the aorta), the presence of infection (an infected or mycotic aneurysm), or rapid growth in diameter of the aneurysm (more than 0.5 cm within 6 months).
Unfortunately, in most cases patients with aortic aneurysms have no symptoms. The presence of the aneurysm is usually detected incidentally during examinations done for other medical reasons. More commonly, the aneurysms are detected on ultrasound or CT scans done for other purposes e.g, ureteric stones, constipation etc. Some patients (or their doctors) may feel a pulsating or throbbing mass in their abdomen.
For patients who do develop symptoms, the most common one is pain. The pain can be in the chest or abdomen and usually has associated back pain. The pain is often described as persistent and severe, with no remission. Patients often find that nothing can be done to relieve the pain. The development of such pain is an ominous sign as it indicates that the aneurysm may be about to rupture. However, if there is severe pain and the patient loses consciousness, it indicates that the aneurysm may have ruptured.
Other symptoms include the development of persistent fever and blood bacterial infection (an infected or mycotic aneurysm), pain in the lower limbs or gangrene patches in the toes (blood clots from within the aneurysm sac breaking off and travelling down into the leg arteries and blocking blood flow) and recurrent vomiting after eating (compression of the stomach and small intestine by the large aneurysm).
Diagnosis is based on clinical examination where an aneurysm can be felt as a throbbing mass in the abdomen. More often, an ultrasound scan or CT scan is recommended for confirmation of an aneurysm. Patients are advised to undergo screening for aortic aneurysms if they are chronic smokers, have a long history of hypertension and a family history of aortic aneurysms.
Aortic aneurysms should be treated under the following circumstances: when they are more than 5cm in diameter, if they are increasing in size rapidly, development of persistent pain or when related complications develop such as infection, rupture or clots from the sac travelling down the leg arteries.
There are two types of treatment for aortic aneurysms:
Open surgical repair: This is the traditional method of aneurysm repair and involves making long incisions or cuts on the chest wall (for TAA) or abdomen (for AAA) or both (for TAAA), cutting the surrounding tissue down to the aneurysm before applying clamps to stop blood flow so that the aneurysm can be excised and replaced with an artificial tube graft. Open repair is a sturdy method but has significant morbidity and mortality risks due to its invasive nature. It is this recommended only for younger patients with low surgical risk.
Minimally invasive repair using covered stent grafts also known as EndoVascular Aortic Repair (EVAR): This involves the deployment of special covered stents inside the aneurysm such that it relines the aneurysm and excludes it from the arterial blood pressure circulation. The stents are inserted through the leg femoral arteries via small (1cm) incisions in the groin. X-ray guidance (fluoroscopy) is used to help position the stent grafts correctly inside the aneurysms. The EVAR procedure does not require big incisions and the aortic blood flow is not disrupted by clamps during the procedure. As such, EVAR can be done for older patients or patients with many co-morbid disease who have higher surgical risks. Also, due to its minimally invasive nature, EVAR can be done under local anaesthetic and mild sedation. EVAR is also recommended for difficult and complex aneurysms involving the key organ arteries (thoracoabdominal aneurysm or TAAA) or for thoracic aneurysms (TAA) where exposure of the aorta in open repair is associated with significant morbidity.
Post surgery Recovery: Patients who undergo open aneurysm repair usually require ICU care in bed for up to 1 week post-surgery. They usually take about 1 month to 6 weeks to fully recover from the incisions made during open repair.
Patients who undergo EVAR usually do not require ICU stay and usually spend one night in a high-dependency ward. Because there are no major incisions, patients usually are up and about in 8 hours and are discharged well in 48 hours post-surgery. In selected cases, young and fit patients can have EVAR done and discharged on the same day.
After the aortic aneurysm has been treated, all patients should have regular follow-up for life. This is because aortic aneurysm disease is degenerative in nature and can continue to develop in other parts of the aorta that were previously aneurysm free. It is not uncommon for a patient with an abdominal aneurysm to subsequently develop a thoracic aneurysm and vice versa. This is especially so if the patient still has persistent risk factors such as smoking and hypertension. Follow-up post aneurysm repair requires repeat ultrasound scans and CT scans to be done at regular intervals (6 monthly at first and then annually). This is especially so for patients who have undergone the EVAR procedure and the scans are done to detect leaks around the covered stent graft.