What is an enlarged aorta?
An aortic aneurysm is the abnormal enlargement of a portion of the aorta. It arises when a segment of the vessel wall is weakened due to any number of factors and this causes a bulging. This can be a balloon-like bulge known as a saccular aneurysm or a widening of an entire segment of the aorta which is called a fusiform aneurysm. The size of aneurysms may vary thereby expanding the diameter of the aorta by 50% or more of the norm. These variations in aneurysms is discussed further under types of aortic aneurysms.
The aorta is the largest artery in the human body, arising from the left ventricle of the heart (ascending aorta). It curves around (arch of the aorta) and descends (descending aorta) through the chest cavity (thoracic aorta) and abdomen (abdominal aorta). The abdominal aorta is the more common site of aortic aneurysms, especially the infrarenal part of the aorta. The suprarenal abdominal aorta and descending part of the thoracic aorta are affected only 10 to 20% of the time while the ascending aorta is rarely affected. While the pathogenesis is understood, the exact cause for the development of an aortic aneurysm is still unclear. Various risk factors have been identified but will not predispose every person to develop an aneurysm.
Causes of Aortic Aneurysms
The two most common causes of aortic aneurysms are atherosclerosis and hypertension. Atheroma formation (atherosclerosis) and the stress caused by high pressure against the walls (hypertension) weakens the wall, especially if the repair mechanisms are not able to compensate for structural degradation.
Other causes of an aortic aneurysm includes :
- Vasculitis – inflammation of the artery wall.
- Infection – mycotic aneurysm which arises when the infectious process involves the vessel wall (infectious vasculitis).
- Trauma – injury to the blood vessel.
- Congenital defects – affects the formation of the vessel wall
- Genetic abnormalities – affects the connective tissue in the vessel wall as is seen with Marfan’s syndrome
- Family history of aneurysms
Although cigarette smoking is associated with the atherosclerosis, hypertension and vasculitis, it is may also be seen as an independent risk factor for the development of an aortic aneurysm. A family history of an aortic aneurysm is a significant risk factor even in the absence of other predisposing factors like hypertension, atherosclerosis, genetic abnormalities and congenital defects.
Signs and Symptoms of an Enlarged Aorta
The signs and symptoms of an aortic aneurysm varies greatly depending on whether it occurs within the thoracic (thoracic aneurysm – TA) or abdominal aorta (abdominal aortic aneurysm – AAA) or involves both parts (thoracoabdominal aortic aneurysm – TAA). Most importantly an aneurysm is silent (asymptomatic) until it enlarges to the point where it is impacting on surrounding structures, leads to a dissection or ruptures, often with fatal consequences.
Below are some of the signs and symptoms that may be seen with an enlarged aorta.
Thoracic aortic aneurysm
A thoracic aortic aneurysm rarely presents with symptoms unless there is an impending rupture or aortic dissections. Most cases are discovered during a chest x-ray.
- Chest pain but may also present with back pain or epigastric pain (upper middle abdomen)
- Abnormal breathing sounds like a stridor if pressing against the trachea or bronchus
- Hoarse voice if pressing against the recurrent laryngeal nerve
- Shortness of breath
- Abdominal or chest tenderness
Abdominal aortic aneurysm
- Pulsatile abdominal mass – patients may report feeling a throbbing/pulsating in the abdomen
- Gastrointestinal symptoms like feeling full after eating small amounts, nausea and vomiting if the aneurysm is pressing against the stomach or duodenum
- Pain – abdominal, back, groin
- Abdominal or chest tenderness