Types and Causes of Aortic Aneurysms
The aorta is the major blood vessel of the body carrying blood from the heart through the chest and abdomen giving off branches to all organs. An aneurysm is an enlargement in the diameter of the artery twice its normal size that can occur in any blood vessel. The normal diameter of the aorta can vary depending on its anatomical location in the body, gender, and age of the patient. In general, the diameter of the aorta is between 1.5 and 2.5 centimeters.
An aortic aneurysm occurs when there is a weakening in the wall of the aorta. The various reasons for weakening of the aortic wall are infection, atherosclerosis, trauma, high blood pressure and inheritable diseases/conditions, such as Marfan Syndrome and Bicuspid Aortic Valve. The cause of an aortic aneurysm may give insight of the natural history of the aneurysm, likelihood and timing of treatment.
Aortic aneurysms are named according to the segment of the aorta, which is enlarged. In addition, various classifications of aorta aneurysms indicate the extent of the aneurysm, as well as the segment involved. A true aneurysm is when all the layers of the aortic wall are weakened, as opposed to a false or pseudoaneurysm when only the outer layer is weakened.
Aneurysms can expand over time however, prediction of when and in whom is difficult. The size, location and the patient’s other medical problems, smoking habits may influence the growth rate of aortic aneurysms. Aortic aneurysms related to an aortic dissection can expand more rapidly and develop complications. Patients with underlying genetic connective disorder, such as Marfan disease and Elher-Danlos Syndrome are more likely to develop aneurysms and expand quickly.
Aortic Aneurysm Symptoms
Most aortic aneurysms do not cause symptoms until they are very large or develop a complication. As aneurysms enlarge they sometimes cause symptoms such as pressure on adjacent structures, for example, hoarseness by pulling on the nerve to the larynx or difficulty swallowing by compressing the esophagus. Asymptomatic aortic aneurysms are usually discovered by a non-specific imaging study performed for another medical condition. However, most common symptoms of aortic aneurysms are vague chest pain, sharp back pain and abdominal pulsation.
Most large aortic aneurysms are concerning due to the possibility of rupture or development of a dissection (a partial tearing of the blood vessel wall). If an aneurysm expands rapidly, tears or leaks, individuals typically experience severe pain. If a patient carries a diagnosis of an aortic aneurysm these symptoms should prompt immediate medical attention preferably in an emergency room.
In an individual with an aortic aneurysm that is not causing symptoms the decision to recommend elective surgery is based on the opinion that the risk of rupture is significantly greater than the risk of the surgery. Factors such as age, the presence of heart, lung, and kidney disease impact not only on surgical risk but also the risk of rupture. Reliance on a single factor such as maximum aortic diameter to indicate the necessity for surgery is no longer sufficient. Careful analysis of operative results and the natural course of unoperated aneurysms allow more accurate and individualized treatment.
The aorta can be divided into several sections (see Illustration):
Aortic root: begins at the aortic annulus and incorporates the aortic sinuses, aortic valve, and ends at the sinotubual junction.
Ascending aorta: starts at the sinotubual junction and ends at the takeoff of the inominate artery (brachiocephalic artery).
Aortic arch: continues after the inominate artery and ends at the subclavian artery. This portion of the aorta curves (arch) from the anterior portion of the chest cavity towards the back.
Descending aorta: begins after the takeoff of the subclavian artery and courses down the thorax through the diaphragm.
Abdominal aorta: the thoracic (descending) aorta becomes the abdominal aorta once it passes through the diaphragm. The abdominal aorta ends in the pelvis when it divides into the iliac arteries.
Allan Stewart, MD
Director, Aortic Surgery Program
Department of Cardiovascular Surgery
The Mount Sinai Health System
1190 Fifth Ave: Box 1028
Assistant: Debra Segreti