Abdominal
Aortic Aneurysm
An abdominal aortic
aneurysm, also called AAA or triple A, is a bulging,
weakened area in the wall of the aorta (the largest
artery in the body) resulting in an abnormal widening
or ballooning greater than 50 percent of the normal
diameter (width).
The
aorta extends upward from the top of the left
ventricle of the heart in the chest area (ascending
thoracic aorta), then curves like a candy cane
(aortic arch) downward through the chest area
(descending thoracic aorta) into the abdomen (abdominal
aorta). The aorta delivers oxygenated blood pumped
from the heart to the rest of the body.
The
most common location of arterial aneurysm formation
is the abdominal aorta, specifically, the segment
of the abdominal aorta below the kidneys. An abdominal
aneurysm located below the kidneys is called an
infrarenal aneurysm. An aneurysm can be characterized
by its location, shape, and cause.
The shape of an
aneurysm is described as being fusiform or saccular
which helps to identify a true aneurysm. The more
common fusiform shaped aneurysm bulges or balloons
out on all sides of the aorta. A saccular shaped
aneurysm bulges or balloons out only on one side.
A pseudoaneurysm,
or false aneurysm, is an enlargement of only the
outer layer of the blood vessel wall. A false
aneurysm may be the result of a prior surgery
or trauma. Sometimes, a tear can occur on the
inside layer of the vessel resulting in blood
filling in between the layers of the blood vessel
wall creating a pseudoaneurysm.
The
aorta is under constant pressure as blood is ejected
from the heart. With each heart beat, the walls
of the aorta distend (expand) and then recoil
(spring back), exerting continual pressure or
stress on the already weakened aneurysm wall.
Therefore, there is a potential for rupture (bursting)
or dissection (separation of the layers of the
aortic wall) of the aorta, which may cause life-threatening
hemorrhage (uncontrolled bleeding) and, potentially,
death. The larger the aneurysm becomes, the greater
the risk of rupture.
Because an aneurysm
may continue to increase in size, along with progressive
weakening of the artery wall, surgical intervention
may be needed. Preventing rupture of an aneurysm
is one of the goals of therapy.
An abdominal
aortic aneurysm may be caused by multiple factors
that result in the breaking down of the well-organized
structural components (proteins) of the aortic
wall that provide support and stabilize the wall.
The exact cause is not fully known.
Atherosclerosis
(a build-up of plaque, which is a deposit of fatty
substances, cholesterol, cellular waste products,
calcium, and fibrin in the inner lining of an
artery) is thought to play an important role in
aneurysmal disease, including the risk factors
associated with atherosclerosis, such as:
- age (greater than 60)
- male (occurrence in
males is four to five times greater than that
of females)
- family history (first
degree relatives such as father or brother)
- genetic factors
- hyperlipidemia (elevated
fats in the blood)
- hypertension (high
blood pressure)
- smoking
- diabetes
Other
diseases that may cause an abdominal aneurysm
include:
- genetic disorders of
connective tissue (abnormalities that can affect
tissues such as bones, cartilage, heart, and
blood vessels), such as Marfan syndrome, Ehlers-Danlos
syndrome, Turner’s syndrome, and polycystic
kidney disease
- congenital (present
at birth) syndromes, such as bicuspid aortic
valve or coarctation of the aorta
- giant cell arteritis
- a disease that causes inflammation of the
temporal arteries and other arteries in the
head and neck, causing the arteries to narrow,
reducing blood flow in the affected areas; may
cause persistent headaches and vision loss
- trauma
- infectious aortitis
(infections of the aorta) due to infections
such as syphilis, salmonella, or staphylococcus.
These infectious conditions are rare.
Abdominal
aortic aneurysms may be asymptomatic (without
symptoms) or symptomatic (with symptoms).
About
three of every four abdominal aortic aneurysms
are asymptomatic and may be found upon routine
physical examination by the discovery of a pulsating
mass in the abdomen. An aneurysm may also be discovered
by x-ray, computed tomography scan (CT scan),
or magnetic resonance imaging (MRI) that is being
done for other conditions. Since abdominal aneurysm
may be present without symptoms, it is referred
to as the “silent killer” because
it may rupture before being diagnosed.
Pain
is the most common symptom of an abdominal aortic
aneurysm. The pain associated with an abdominal
aortic aneurysm may be located in the abdomen,
chest, lower back, or groin area. The pain may
be severe or dull. The occurrence of pain is often
associated with the imminent (about to happen)
rupture of the aneurysm.
Acute,
sudden onset of severe pain in the back and/or
abdomen may represent rupture and is a life threatening
medical emergency.
The
symptoms of an abdominal aortic aneurysm may resemble
other medical conditions or problems. Always consult
your physician for more information.
In addition
to a complete medical history and physical examination,
diagnostic procedures for an aneurysm may include
any, or a combination, of the following:
- computed tomography
scan (Also called a CT or CAT scan.) - a diagnostic
imaging procedure that uses a combination of
x-rays and computer technology to produce cross-sectional
images (often called slices), both horizontally
and vertically, of the body. A CT scan shows
detailed images of any part of the body, including
the bones, muscles, fat, and organs. CT scans
are more detailed than general x-rays.
- magnetic resonance
imaging (MRI) - a diagnostic procedure that
uses a combination of large magnets, radiofrequencies,
and a computer to produce detailed images of
organs and structures within the body.
- ultrasound - uses
high-frequency sound waves and a computer to
create images of blood vessels, tissues, and
organs. Ultrasounds are used to view internal
organs as they function, and to assess blood
flow through various vessels.
- arteriogram (angiogram)
- an x-ray image of the blood vessels used to
evaluate various conditions, such as aneurysm,
stenosis (narrowing of the blood vessel), or
blockages. A dye (contrast) will be injected
through a thin flexible tube placed in an artery.
This dye makes the blood vessels visible on
x-ray.
Specific
treatment will be determined by your physician
based on:
- your age, overall health,
and medical history
- extent of the disease
- your signs and symptoms
- your tolerance of specific
medications, procedures, or therapies
- expectations for the
course of the disease
- your opinion or preference
Treatment
may include:
- routine ultrasound
procedures - to monitor the size and rate of
growth of the aneurysm
- controlling or modifying
risk factors - steps such as quitting smoking,
controlling blood sugar if diabetic, losing
weight if overweight or obese, and controlling
dietary fat intake may help to control the progression
of the aneurysm
- Asymptomatic aneurysms may
not require surgical intervention until they
reach a certain size or are noted to be increasing
in size over a certain period of time. Parameters
considered when making surgical decisions include,
but are not limited to, the following:
- aneurysm size greater than
5 centimeters (about two inches)
- aneurysm growth rate 0.5
centimeters (slightly less than one-fourth inch)
over a period of six months to one year
- patient’s ability to
tolerate the procedure
For
symptomatic aneurysms, immediate intervention
is indicated.
An aortic
dissection begins with a tear in the inner layer
of the aortic wall. The aortic wall is made up
of three layers of tissue. When a tear occurs
in the innermost layer of the aortic wall, blood
is then channeled into the wall of the aorta,
separating the layers of tissues. This generates
great pressure in the aortic wall with a potential
to rupture (burst). Aortic dissection can be a
life-threatening emergency.
The
cause of aortic dissection is still under investigation.
However, several risk factors associated with
aortic dissection include, but are not limited
to, the following:
- hypertension (high
blood pressure)
- connective tissue disorders,
such as Marfan’s disease, Ehlers-Danlos
syndrome, and Turner’s syndrome
- cystic medial disease
(a degenerative disease of the aortic wall)
- aortitis (inflammation
of the aorta)
- atherosclerosis
- existing thoracic aneurysm
- bicuspid aortic valve
(presence of only two cusps, or leaflets, in
the aortic valve, rather than the normal three
cusps)
- trauma
- coarctation of the
aorta (narrowing of the aorta)
- hypervolemia (excess
fluid or volume in the circulation)
- polycystic kidney disease
(a genetic disorder characterized by the growth
of numerous cysts filled with fluid in the kidneys)
The
most commonly reported symptom of an acute aortic
dissection is severe, constant pain, sometimes
described as “ripping” or “tearing,”
and located in the chest, the middle of the abdomen,
the lower back, or the pelvis area. The pain may
be “migratory,” moving from one place
to another, according to the direction and extent
of the dissection.
The
symptoms of aortic dissection may resemble other
medical conditions or problems. Always consult
your physician for more information.
In addition
to a complete medical history and physical examination,
diagnostic procedures for an aortic dissection
may include any, or a combination, of the following:
- computed tomography
scan (Also called a CT or CAT scan.) - a diagnostic
imaging procedure that uses a combination of
x-rays and computer technology to produce cross-sectional
images (often called slices), both horizontally
and vertically, of the body. A CT scan shows
detailed images of any part of the body, including
the bones, muscles, fat, and organs. CT scans
are more detailed than general x-rays.
- transesophageal echocardiogram
(TEE) - a diagnostic procedure that uses echocardiography
to assess the heart’s function and structures.
A transesophageal echocardiogram is performed
by inserting a probe with a transducer down
the esophagus. By inserting the transducer in
the esophagus, TEE provides a clearer image
of the heart because the sound waves do not
have to pass through skin, muscle, or bone tissue.
The
physician will determine the most appropriate
examination. When a diagnosis of aortic dissection
is confirmed, immediate intervention is necessary.
Medical intervention or surgery will be required
depending on the location of the aortic dissection.
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