Thoracic
Aortic Aneurysm
A thoracic
aortic aneurysm, also called TAA, 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.
An aneurysm
can be characterized by its location, shape, and
cause. A thoracic aortic aneurysm is located in
the chest area. The thoracic aorta can be divided
into segments: ascending aorta, aortic arch, and
descending aorta, as described above. An aneurysm
may be located in one of these areas and/or may
be continuous throughout the aorta. An aneurysm
called a thoracoabdominal aneurysm involves a
thoracic aortic aneurysm extending down to the
abdominal aorta.
Thoracic
aneurysms do not occur as often as abdominal aneurysms.
The descending thoracic aorta is the most common
location of a thoracic aneurysm, followed by the
ascending segment, then the arch. The location
of an aneurysm is distinctly connected with the
cause, course, and treatment of a thoracic aneurysm.
The
shape of an aneurysm is described as being fusiform
or saccular which helps to identify a true aneurysm.
A true aneurysm involves all three layers of the
arterial blood vessel wall. 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 prior surgery or
trauma. Sometimes, a tear may occur on the inside
layer of the vessel resulting in blood entering
the layers of the blood vessel wall, creating
a pseudoaneurysm.
The
aorta is under constant pressure from blood being
ejected from the heart. With each heartbeat, the
walls of the aorta expand and 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 thoracic aortic wall), which
may cause life-threatening hemorrhage (uncontrolled
bleeding) and, potentially, death.
Once
formed, an aneurysm will gradually increase in
size and there will be a progressive weakening
of the aneurysm wall. Treatment for a thoracic
aneurysm may include surgical repair or removal
of the aneurysm to prevent rupture.
Thoracic
aortic aneurysms may be caused by different disease
processes, especially in respect to their location.
Examples
of different locations of thoracic aortic aneurysms
and their causes may include, but are not limited
to, the following:
| Location
of Thoracic Aortic Aneurysm |
Causes
Associated with Aneurysm Type |
| Ascending
Thoracic Aneurysm |
- cystic medial
degeneration (necrosis) - breaking down
of the tissue of the aortic wall. This
is the most common cause of this type
of thoracic aortic aneurysm.
- genetic disorders
which affect the connective tissue,
such as Marfan syndrome and Ehlers-Danlos
syndrome
- family history
of thoracic aortic aneurysm with no
incidence of Marfan syndrome
- atherosclerosis
- hardening of the arteries caused by
a build-up of plaque in the inner lining
of an artery. This is a rare cause of
ascending thoracic aortic aneurysm.
- infection,
syphilis (rare causes of thoracic aortic
aneurysm)
|
| Aortic
Arch Thoracic Aneurysm |
- Takayasu's
arteritis - a type of vasculitis that
causes inflammation of the arteries
- atherosclerosis
- continuation
of an ascending and/or descending aortic
aneurysm
|
| Descending
Thoracic Aortic Aneurysm |
Atherosclerosis
is most often associated with descending
thoracic aneurysms, and is thought to
play an important role in aneurysmal disease,
including the risk factors associated
with atherosclerosis such as:
- age (greater
than 55)
- male gender
- family history
(first-degree relatives such as father
or brother)
- genetic factors
- hyperlipidemia
(elevated fats in the blood)
- hypertension
(high blood pressure)
- smoking
- diabetes
|
Thoracic
aortic aneurysms may be asymptomatic (without
symptoms) or symptomatic (with symptoms). Symptoms
of a thoracic aneurysm may be related to the location,
size, and growth rate of the aneurysm.
Severe
onset of pain associated with a thoracic aneurysm
may be a sign of a life-threatening medical emergency.
Symptoms
of an ascending thoracic aneurysm may include,
but are not limited to, the following:
- pain in the chest,
neck, and/or back
- swelling of head, neck,
and arms as a result of pressure on large blood
vessels
- heart failure - an
ascending aneurysm may affect the heart valves,
causing blood to back up into the heart
Symptoms
of an aortic arch aneurysm or a descending thoracic
aneurysm may include, but are not limited to,
the following:
- wheezing, coughing,
or shortness of breath as a result of pressure
on the trachea (windpipe)
- coughing up blood (hemoptysis)
- hoarseness as a result
of pressure on the vocal cords
- difficulty swallowing
(dysphagia) due to pressure on the esophagus
- pain in the chest and/or
back
The
symptoms of a thoracic aortic aneurysm may resemble
other conditions. Consult your physician for a
diagnosis.
In addition
to a complete medical history and physical examination,
diagnostic procedures for a thoracic aortic 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 standard 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.
- echocardiogram (Also
called echo.) - a procedure that evaluates the
structure and function of the heart by using
sound waves recorded on an electronic sensor
that produce a moving picture of the heart and
heart valves, as well as the structures within
the chest, such as the lungs, mediastinum (area
in the chest containing the heart, aorta, trachea,
esophagus, thymus, and lymph nodes), and pleural
space (space between the lungs and the interior
wall of the chest).
- transesophageal echocardiogram
(TEE) - a diagnostic procedure that uses echocardiography
to assess the presence of an aneurysm, the condition
of heart valves, and/or presence of a dissection
(tear) of the lining of the aorta. TEE is performed
by inserting a probe with a transducer on the
end down the throat.
- chest x-ray - a diagnostic
test which uses invisible electromagnetic energy
beams to produce images of internal tissues,
bones, and organs onto film.
- 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.
The dye makes the blood vessels visible on an
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 for
specific medications, procedures, or therapies
- expectations for the
course of the disease
- your opinion or preference
Treatment
may include:
- routine MRI or CT
- 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
- medication - to control
factors such as hyperlipidemia (elevated levels
of fats in the blood) and/or high blood pressure
- surgery
- thoracic aortic
aneurysm open repair
The type of surgical repair of a thoracic
aortic aneurysm will depend on several factors:
the location of the aneurysm, the type of
aneurysm, and the patient's tolerance
for the procedure. For an ascending or aortic
arch aneurysm, a large incision may be made
through the breastbone (median sternotomy).
If an ascending aneurysm involves damage
to the aortic valve of the heart, the valve
may be repaired or replaced during the procedure.
For a descending aneurysm, a large incision
may extend from the back under the
shoulder blade around the side of the rib
cage to just under the breast (thoracotomy).
These approaches allow the surgeon to visualize
the aorta directly to repair the aneurysm.
- endovascular aneurysm
repair (EVAR)
EVAR is a procedure which requires only
small incisions in the groin, along with
the use of x-ray guidance and specially-designed
instruments, to repair the aneurysm by inserting
a tube, called a stent-graft, inside the
aorta. At this time, the only thoracic aneurysms
repaired by means of EVAR are descending
thoracic aneurysms.
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 5.5 to 6 centimeters (greater than two
inches)
- aneurysm growth rate
0.5 centimeters (slightly less than one-fourth
inch) over a period of six months to one year
- presence of genetic
disorders or familial history of thoracic aneurysms
- 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, usually in the ascending or
descending thoracic aorta. 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, there are several risk factors associated
with aortic dissection, such as:
- 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 chest and/or upper
back pain, sometimes described as "ripping"
or "tearing." The pain may be "migratory,"
moving from one place to another, according to
the direction and extent of the dissection.
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.
- 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, such as
surgery, is usually performed.
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