The aorta is the largest artery in the body, initially being an inch wide in diameter. It receives the cardiac output from the left ventricle and supplies the body with oxygenated blood via the systemic circulation.
The aorta can be divided into four sections: the ascending aorta, the aortic arch, the thoracic (descending) aorta and the abdominal aorta. It terminates at the level of L4 by bifurcating into the left and right common iliac arteries. The aorta classified as a large elastic artery, and more information on its internal structure can be found here.
Branches
The left and right aortic sinuses are dilations in the ascending aorta, located at the level of the aortic valve. They give rise to the left and right coronary arteries that supply the myocardium.
The ascending aorta arises from the aortic orifice from the left ventricle and ascends tobecome the aortic arch. It is 2 inches long in length and travels with the pulmonary trunk in the pericardial sheath.
The aortic arch is a continuation of the ascending aorta and begins at the level of the second sternocostal joint. It arches superiorly, posteriorly and to the left before moving inferiorly.
Branches
The left and right aortic sinuses are dilations in the ascending aorta, located at the level of the aortic valve. They give rise to the left and right coronary arteries that supply the myocardium.
The thoracic (descending) aorta spans from the level of T4 to T12. Continuing from the aortic arch, it initially begins to the left of the vertebral column but approaches the midline as it descends. It leaves the thorax via the aortic hiatus in the diaphragm, and becomes the abdominal aorta.
Branches
In descending order:
Bronchial arteries: Paired visceral branches arising laterally to supply bronchial and peribronchial tissue and visceral pleura. However, most commonly, only the paired left bronchial artery arises directly from the aorta whilst the right branches off usually from the third posterior intercostal artery.
Mediastinal arteries: Small arteries that supply the lymph glands and loose areolar tissue in the posterior mediastinum.
Oesophageal arteries: Unpaired visceral branches arising anteriorly to supply the oesophagus
Pericardial arteries: Small unpaired arteries that arise anteriorly to supply the dorsal portion of the pericardium.
Superior phrenic arteries: Paired parietal branches that supply the superior portion of the diaphragm.
Bronchial arteries: Paired visceral branches arising laterally to supply bronchial and peribronchial tissue and visceral pleura. However, most commonly, only the paired left bronchial artery arises directly from the aorta whilst the right branches off usually from the third posterior intercostal artery.
The abdominal aorta is a continuation of the thoracic aorta beginning at the level of the T12 vertebrae. It is approximately 13cm long and ends at the level of the L4 vertebra. At this level, the aorta terminates by bifurcating into the right and left common iliac arteries that supply the lower body.
Branches
In descending order:
Inferior phrenic arteries: Paired parietal arteries arising posteriorly at the level of T12. They supply the diaphragm.
Coeliac artery: A large, unpaired visceral artery arising anteriorly at the level of T12. It is also known as the celiac trunk and supplies the liver, stomach, abdominal oesophagus, spleen, the superior duodenum and the superior pancreas.
Superior mesenteric artery: A large, unpaired visceral artery arising anteriorly, just below the celiac artery. It supplies the distal duodenum, jejuno-ileum, ascending colon and part of the transverse colon. It arises at the lower level of L1
Median sacral artery: An unpaired parietal artery that arises posteriorly at the level of L4 to supply the coccyx, lumbar vertebrae and the sacrum.
Lumbar arteries: There are four pairs of parietal lumbar arteries that arise posterolaterally between the levels of L1 and L4 to supply the abdominal wall and spinal cord
What is an aortic aneurysm?
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The aorta is the main vessel that carries blood pumped from the heart to the rest of the body. It is shaped like a candy cane and is typically about as wide as a garden hose (2.53.5 cm). An aortic aneurysm is a balloon-like bulge in a portion of the aorta. Aneurysms usually occur where there is a weak spot in the aortic wall. Aortic aneurysms are the 13th leading cause of death in the United States, accounting for an estimated 15,000-20,000 deaths annually.
How are aortic aneurysms classified?
Aortic aneurysms are commonly classified according to their location. Thoracic aortic aneurysms (TAA) involve the ascending aorta, arch, or descending aorta. Abdominal aortic aneurysms (AAA) affect the aorta in the abdominal cavity. A third type of aneurysm, thoracoabdominal, involves both the descending and abdominal aorta.
What are the symptoms of an aneurysm?
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Most aneurysms have no symptoms until they dissect or get extremely large.
Aortic dissection:
A tear in the inner layer of the aorta that allows blood to flow within the layers of the aorta.
Aortic rupture:
A rupture or hole in the aorta that allows blood to burst or leak out into the body.
Stanford classifies dissections as either:
• Type A (involving the ascending aorta)
• Type B (not involving the ascending aorta)
DeBakey classifies dissections as:
• Type I (affects both the ascending and descending aorta, as well as the aortic arch)
• Type II (affects only ascending aorta)
• Type III (affects only the descending aorta
How is an aneurysm detected ?
Early diagnosis can result in early intervention and dramatic improvements. If an aneurysm or dissection is suspected, an ultrasound scan of the heart (echocardiogram) is usually performed. Computerized tomography (CT) and magnetic resonance imaging (MRI) are now the GOLD STANDARD in imaging to determine the exact position and size of an aortic aneurysm. The treatment of an aortic aneurysm depends upon the severity of the aneurysm or dissection and may include medical management (medication) or surgery.
What factors can increase the risk of developing aortic dissection?
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Factors that can increase your risk for developing aortic dissection include:
Atherosclerosis (or buildup of plaque in the arteries)/high cholesterol and smoking.
Aortic aneurysm. This is an abnormal enlargement or bulge in the aortic wall.
Congenital (“born with”) heart conditions like a bicuspid aortic valve (has two leaflets instead of the normal three) or Turner syndrome.
Other hereditary thoracic aortic conditions that primarily affect the aorta that are also genetically caused.
Family history of aortic dissection.
Vasculitis, specifically aortitis. This inflammatory disease affects the body’s blood vessels.
Age between 50 and 65 years. The aortic wall loses its elasticity with age.
Strenuous powerlifting may increase the speed of development of aneurysms or dissection in susceptible people.
How is aortic dissection treated?
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Treatment of aortic dissection depends upon the location of the tear and dissection. Immediate surgery is needed for Type A aortic dissection (i.e., when it involves the first part of the aorta close to the heart). Type B aortic dissection requires emergency surgery if the dissection cuts off blood flow to your vital organs including your kidneys, intestines, legs or even your spinal cord. Urgent surgery is needed if there are certain high-risk features noted on CT scan imaging. Less severe cases may be treated with medication initially, delaying surgery until complications develop.
Surgery and Endovascular Treatment
How is aortic disease treated?
Graft replacement:
With this approach, a portion of the damaged section of the aorta is removed and a synthetic fabric tube (graft) is sewn directly in its place
Endovascular stent-graft repair:
With this approach, a stent graft — a synthetic fabric tube supported by metal wire stents (like a scaffold) — is used to repair the aorta from within. Endovascular surgery involves making the repair inside your aorta. A small incision is made in your groin and a catheter, with the fabric-lined stent attached, is delivered and deployed into the aorta under x-ray guidance. At the repair site, the stent graft is released and — like a spring or umbrella — opens up, relining and providing reinforcement to the weak area in the aorta.
Endovascular stent-graft repair:
With this approach, a combination of conventional open surgery and endovascular stent-graft technique is used to repair the aorta. This is used when the repair must extend into the aortic arch where branch vessels to the brain and arms arise. This may be performed during the emergency operation for Type A dissection or as a two-stage repair with a bypass from a vessel in the neck to help set up an endovascular repair for Type B dissection. One of the most common hybrid procedures is called the “elephant trunk” or “frozen elephant trunk” procedure. First, the segment of the aorta close to the heart as well as the aortic arch (the segment of the aorta that supplies blood to the brain) is replaced and repaired. An additional graft, or stent graft, is left hanging into the descending aorta, like the trunk of an elephant. The graft is ready to receive the endovascularly placed stent-graft when the second surgery is performed.
