Aortic Aneurysms: Types, Causes, and Treatment
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An aortic aneurysm is serious because depending on its size, it might rupture and cause life-threatening internal bleeding.
An, 'aortic-aneurysm,' is a bulge in the wall of the aorta, the body's largest artery, which is the blood vessel that carries oxygen-rich blood. Approximately the diameter of a garden hose, this artery extends from a person's heart down through their chest and abdominal region, where it divides into a blood vessel that supplies each of a person's legs. While an aneurysm may develop anywhere along a person's aorta, most of them occur in the section running through a person's abdomen called, 'abdominal aneurysms.' The rest occur in the section that runs through a person's chest, referred to as, 'thoracic aneurysms.'
The weakened artery wall may stretch as blood is pumped through it from the person's heart. The bulge or, 'ballooning,' might be symmetrical or, 'fusiform.' On occasion, an aneurysm may happen because of a localized weakness of the artery wall. Enlargement of a person's aorta may be only mild in degree and referred to as being, 'ectasia.' Generally, if the diameter of the aneurysm is more than one-and-a-half times the size of the average aorta, it is called an aneurysm.
An aortic aneurysm is serious because depending on its size, it might rupture and cause life-threatening internal bleeding. The risk of an aneurysm rupturing increases as the aneurysm becomes larger. The risk of rupture also depends on the location of the aneurysm. Every year, around 15,000 people in America die from a ruptured aortic aneurysm. If detected in time, an aortic aneurysm can usually be repaired through surgical intervention.
Aortic Aneurysm Types
Aortic aneurysms are classified by location, shape and how they are formed. The wall of a person's aorta is made up of three layers; a thin inner layer of smooth cells called the, 'endothelium,' a muscular middle layer which has elastic fingers in it called the, 'media,' and a tough outer layer called the, 'adventitia.' When the walls of the aneurysm have all three layers, they are called, 'true aneurysms.' If the wall of the aneurysm has only the outer layer remaining, it is called a, 'pseudoaneurysm.' Pseudoaneurysms can occur as a result of trauma when the inner layers are torn apart.
Saccular Aneurysms: Saccular aneurysms appear like a small blister on the side of the person's aorta and are asymmetrical. Typically, they are pseudoaneurysms caused by either trauma or are the result of a penetrating aortic ulcer.
Degenerative Aneurysms: Degenerative aneurysms are the most common type of aneurysms and occur as the result of breakdown of the connective tissue and muscular layer. The cause could be high blood pressure, cigarette smoking, or genetic conditions.
Thoracic Aortic Aneurysms: Thoracic aneurysms may occur anywhere along the aorta above the diaphragm, including the ascending aorta, the aortic arch, as well as the descending thoracic aorta. Generally, thoracic aortic aneurysms are treated by thoracic surgeons.
Fusiform Aneurysms: The majority of fusiform aneurysms are true aneurysms. The weakness is often times along an extended section of the person's aorta and involves the entire circumference of their aorta. The weakened portion appears as a generally symmetrical bulge.
Dissecting Aneurysms: Dissecting aneurysms occur when a tear starts within the wall of a person's aorta, causing the three layers to separate. The dissection causes the wall of the person's aorta to weaken and the aorta enlarges. Dissections can occur any place along a person's aorta and treatment depends on its location. Often, those involving the ascending aorta are treated with emergency surgery, while those involving the descending thoracic aorta are treated with medication. While dissections are uncommon, they are the most common of the acute aortic syndromes. If left untreated they are deadly.
Abdominal Aortic Aneurysms: Abdominal aortic aneurysms are located along the part of the aorta that passes through a person's abdomen. Continuing from the thoracic aorta, the abdominal aorta carries blood down through a person's abdomen until it eventually splits off into two smaller arteries that provide blood to a person's legs and pelvis. Abdominal aortic aneurysms are much more common than thoracic aortic aneurysms and comprise around 75% of aortic aneurysms. They may affect anyone, yet are most often seen in men between the ages of 40 and 70. The majority of abdominal aortic aneurysms are caused by atherosclerosis.
Causes of Aortic Aneurysms
Aortic aneurysms are most often caused by damage to the artery wall due to atherosclerosis more commonly known as, "hardening of the arteries." Atherosclerosis is caused by a buildup of cholesterol and other fatty deposits in the arteries and hypertension. Additional causes of aortic aneurysms can include the following:
- Dissection or tearing of the artery wall
- Congenital weakness of the artery wall
- Weakening of the artery wall from high blood pressure or smoking
At times, the cause of an aneurysm is not clear. Aneurysms may also be hereditary.
Symptoms and Diagnosing Aortic Aneurysms
The simple fact is - most aortic aneurysms have no symptoms. Most people with them are diagnosed with a chest X-ray or a CAT scan for evaluation of another condition such as lung disease, or during routine examinations. Symptoms might occur due to the aneurysm pressing on nearby organs or tissue, or if the aneurysm leads to dissection. Symptoms of dissection include severe tearing pain the back or chest, cold or numb extremities, stroke, or abdominal pain.
Abdominal aortic aneurysms might be diagnosed by a doctor during a physical examinations, or at times people notice a pulsating mass in their abdomen. The first hint of an aortic aneurysm might be an abnormal chest X-ray. A doctor may also diagnose one through use of an echocardiograph or MRI.
Treating Aortic Aneurysms
Treatment for an aneurysm depends on its size and location and the person's overall health. If the aneurysm is small the person has no symptoms, a doctor might suggest a watch-and-wait approach with regularly scheduled images of the aneurysm to check its size. If; however, the person's aneurysm is large enough, or if the aneurysm is growing more than 1 centimeter each year - surgery might be the best option.
Treating Aortic Dissections
Dissections might involve the ascending aorta alone, the descending thoracic and abdominal aorta alone, or the person's entire aorta. The risk of death depends on the extent of the dissection. It is highest for those aneurysms involving the ascending aorta. Due to this, the majority of these aneurysms are treated surgically as an emergency.
Dissections of the descending thoracic aorta may often times be treated with blood pressure control. The medical treatment of aortic dissection includes aggressive control of blood pressure and heart rate while the person's aorta heals. The risk of death with medical treatment of descending thoracic aortic dissection is approximately 10%. If surgery is required the risk jumps to around 30%.
After the acute dissection has healed, adequate control of blood pressure might eliminate the need for surgery. Lifelong monitoring of the diameter of the person's aorta is required because a previously dissected descending thoracic aorta might enlarge and rupture.
Open Abdominal or Chest Surgery
The standard treatment for aneurysm after it meets the indications for surgery is replacement of the portion of the aorta with an artificial graft. Usually, a graft is made from Dacron, a material that will not wear out. The graft is sewn in place using a permanent suture material.
The operation, to include the incision that is made, depends upon the location of the aneurysm. If the aneurysm is close to the person's aortic valve, an incision in the front of the person's chest such as a median sternotomy might be used. If the aneurysm is close to the person's valve, the aortic valve might have to be repaired or replaced. Surgery on the aortic arch is usually done from the front. If the aneurysm involves the person's descending thoracic aorta, which lies in the left chest, or the thoracic abdominal aorta, an incision on the left side of the chest will likely be required. If the aneurysm is confined to the person's abdomen, an incision is made either in the person's abdomen, or on their side.
A treatment has been developed to repair an aneurysm without major surgery. A number of surgeons have been using less invasive endovascular surgery on abdominal aortic aneurysms. The procedure results in less trauma to a person's aorta, less loss of blood, and fewer days in intensive care. Because results with endovascular repair of abdominal aortic aneurysms have been encouraging, similar techniques are being developed to treat thoracic aortic aneurysms.
Endovascular surgery might benefit people who need surgery, yet are at high risk of complications because of pre-existing medical issues. Not everyone; however, is a good candidate for the procedure. The appropriate choice of procedure, open versus endovascular, depends on a number of factors and is best determined by the medical team and the person.
With endovascular surgery, a synthetic graft is attached to the end of a thin tube or catheter which is then inserted into the person's bloodstream, often through an artery in the person's leg. Watching the progress of the catheter on an X-ray monitor, a surgeon threads the stent-graft to the weak portion of the person's aorta where the aneurysm is located.
After it is in place, the graft is expanded. The stent-graft reinforces the weakened section of the person's aorta to prevent rupture of the aneurysm. The metal frame is expanded like a spring to hold tightly against the wall of the aorta, cutting off the blood supply to the aneurysm. The blood then flows through the stent-graft, avoiding the aneurysm. The aneurysm commonly shrinks over a period of time.
Aortic Aneurysm Fact Sheet
Aortic Aneurysms - Cleveland Clinic
Thoracic aortic aneurysm
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