Pulmonary
Embolism
A pulmonary
embolism (PE) is a blood clot that develops in
a blood vessel elsewhere in the body (most commonly
from the leg), travels to an artery in the lung,
and forms an occlusion (blockage) of the artery.
A blood
clot (thrombus) that forms in a blood vessel in
one area of the body, breaks off, and travels
to another area of the body through the bloodstream
is called an embolus. An embolus can lodge itself
in a blood vessel, blocking the blood supply to
a particular organ. This blockage of a blood vessel
by an embolus is called an embolism.
An embolism
to the lung may cause serious life-threatening
consequences and, potentially, death. Most commonly,
a PE is the result of a condition called deep
vein thrombosis (blood clot in the deep veins
of the leg).
The
heart, arteries, capillaries, and veins make up
the body's circulatory system. Blood is pumped
with great force from the heart into the arteries,
then into the capillaries (small blood vessels
in the tissues) and returns to the heart through
the veins. Much of the force of the heartbeat
is lost when the blood enters the veins and results
in the slowing down of the blood flow through
the veins back to the heart. Under certain conditions,
decreased blood flow may contribute to clot formation.
Blood
clotting is a normal process that occurs in the
body to prevent bleeding. The body makes blood
clots and then breaks them down. Under certain
circumstances, the body may be unable to break
down a clot, which may result in a serious health
condition.
Abnormal
blood clotting in the veins is related to a combination
of several problems such as "sluggish"
blood flow through the veins, an over-increase
in clot forming factors, and/or an injury to the
blood vessel wall.
Blood
clots can form in arteries and/or veins. Clots
formed in veins are called venous clots. Veins
of the legs can be classified as superficial veins
(close to the surface of the skin) or deep veins
(located near the bone and surrounded by muscle).
Venous
clots most often occur in the deep veins of the
legs. This condition is called deep vein thrombosis
(DVT), or deep vein clot. Once a clot has formed
in the deep veins of the leg, there is a potential
for part of the clot to break off and travel (embolize)
through the bloodstream to another area of the
body. Deep vein thrombosis is the most common
cause of a pulmonary embolism. Therefore, the
term venous thromboembolism (VTE) may refer to
deep vein thrombosis and/or the complication,
pulmonary embolism.
Other
less frequent sources of pulmonary embolism are
a fat embolus, amniotic fluid embolus, air bubbles,
and a deep vein thrombosis in the upper body.
Clots may also form on the end of an indwelling
intravenous (IV) catheter, break off, and travel
to the lungs.
Risk
factors that are associated with the processes
that may increase the risk of a venous thromboembolism
include:
- genetic conditions
that increase the risk of blood clot formation
- surgery or trauma (especially
to the legs)
- situations in which
mobility is limited, such as extended bed rest,
flying or riding long distances, or paralysis
- previous history of
clots
- older age
- cancer and cancer
therapy
- certain medical conditions,
such as heart failure, chronic obstructive pulmonary
disease (COPD), hypertension (high blood pressure),
stroke, and inflammatory bowel disease (chronic
inflammation of the digestive tract)
- certain medications,
such as oral contraceptives (birth control pills)
and hormone replacement therapy (estrogen pills
for postmenopausal women)
- pregnancy (during and
after pregnancy, including cesarean section)
- obesity
- varicose veins (enlarged
veins in the legs)
- cigarette smoking
A risk
factor is anything that may increase a person's
chance of developing a disease. It may be an activity,
such as smoking, diet, family history, or many
other things. Different diseases have different
risk factors.
Although
these risk factors increase a person's risk,
they do not necessarily cause the disease. Some
people with one or more risk factors never develop
the disease, while others develop disease and
have no known risk factors. Knowing your risk
factors to any disease can help to guide you into
the appropriate actions, including changing behaviors
and being clinically monitored for the disease.
The
following are the most common symptoms for pulmonary
embolism. However, each individual may experience
symptoms differently:
- sudden shortness of
breath (most common)
- chest pain (usually
worse with breathing)
- a feeling of anxiety
- a feeling of dizziness,
lightheadedness, or fainting
- palpitations (heart
racing)
- coughing up blood (hemoptysis)
- sweating
- low blood pressure
- symptoms of deep vein
thrombosis, such as:
- pain in the affected
leg (may occur only when standing or walking)
- swelling in the
leg
- soreness, tenderness,
redness, and/or warmth in the leg(s)
- redness and/or
discolored skin
You
may or may not have these symptoms should a pulmonary
embolism occur. Usually, if a PE is suspected,
the physician will check your legs for evidence
of a deep vein thrombosis.
The
type and extent of symptoms of a pulmonary embolism
will depend on the size of the embolism and whether
the person already has existing heart and/or lung
problems.
The
symptoms of a pulmonary embolism may resemble
other medical conditions or problems. Always consult
your physician for a diagnosis.
Pulmonary
embolism is often difficult to diagnose because
the signs and symptoms of PE mimic those of many
other conditions and diseases.
In addition
to a complete medical history and physical examination,
diagnostic procedures for a pulmonary embolism
may include any, or a combination, of the following:
- chest x-ray - a type
of diagnostic radiology procedure used to assess
the lungs, as well as the heart. Chest x-rays
may provide important information regarding
the size, shape, contour, and anatomic location
of the heart, lungs, bronchi, great vessels
(aorta and pulmonary arteries), and mediastinum
(area in the middle of the chest separating
the lungs).
- ventilation-perfusion
scan (V/Q scan) - a type of nuclear radiology
procedure in which a tiny amount of a radioactive
substance is used during the procedure to assist
in the examination of the lungs. A ventilation
scan evaluates ventilation, or the movement
of air into and out of the bronchi and bronchioles.
A perfusion scan evaluates blood flow within
the lungs.
- pulmonary 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.
- spiral computed tomography
(Also called CT or CAT scan.) - a diagnostic
procedure that uses a combination of x-rays
and computer technology to produce cross-sectional
images (often called slices). CT with contrast
enhances the image of the blood vessels in the
lungs. Contrast refers to a substance injected
into an intravenous (IV) line that causes the
particular organ or tissue under study to be
seen more clearly.
- 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.
- duplex ultrasound
- a type of vascular ultrasound procedure done
to assess blood flow and the structure of the
blood vessels in the lungs. The term "duplex"
refers to the fact that two modes of ultrasound
are used - Doppler and B-mode. The B-mode transducer
(like a microphone) obtains an image of the
vessel being studied. The Doppler probe within
the transducer evaluates the velocity and direction
of blood flow in the vessel.
- laboratory tests -
blood tests to check the blood's clotting
status. Other blood work may include testing
for genetic (inherited) disorders that may contribute
to abnormal clotting of the blood. In addition,
arterial blood gases may be checked to determine
the amount of oxygen in the blood.
- electrocardiogram
(ECG or EKG) - one of the simplest and fastest
procedures used to evaluate the heart. Electrodes
(small, plastic patches) are placed at certain
locations on the chest, arms, and legs. When
the electrodes are connected to an ECG machine
by lead wires, the electrical activity of the
heart is measured, interpreted, and printed
out for the physician's information and
further interpretation.
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
options for pulmonary embolism include:
- anticoagulants - also
described as "blood thinners," these
medications decrease the ability of the blood
to clot. Examples of anticoagulants include
warfarin (Coumadin®) and heparin.
- fibrinolytic therapy
- also called "clot busters," these
medications are given intravenously (IV) to
break down the clot.
- vena cava filter -
a small metal device placed in the vena cava
(the large blood vessel that returns blood from
the body to the heart) may be used to prevent
clots from traveling to the lung. These filters
are generally used in patients who cannot receive
anticoagulation treatment (for medical reasons),
who develop additional clots even with anticoagulation
treatment, or who develop bleeding complications
from anticoagulation.
- pulmonary embolectomy
- surgical removal of a pulmonary embolism.
This procedure is generally performed only in
severe situations in which the PE is very large,
the patient either cannot receive anticoagulation
and/or thrombolytic therapy due to other medical
considerations or has not responded adequately
to those treatments, and the patient's condition
is unstable.
- percutaneous thrombectomy
- insertion of a catheter (long, thin, hollow
tube) to the site of the embolism, using X-ray
guidance. Once the catheter is in place, the
catheter is used to break up the embolism, extract
it (pull it out), or dissolve it by injecting
thrombolytic medication.
An important
aspect of treatment of pulmonary embolism is prophylactic
(preventative) treatment to prevent formation
of additional embolisms.
Because
pulmonary embolism is caused by an embolus formed
elsewhere in the body (generally in the legs),
and because it is often difficult to detect presence
of a venous embolus prior to the onset of complications
such as a pulmonary embolism, the prevention of
these emboli is necessary in the prevention of
PE.
In order
to prevent pulmonary embolism, the only effective
way is to prevent deep vein thrombosis. Prophylactic
treatment to prevent DVT includes:
- non-invasive mechanical
measures
Mechanical measures to prevent DVT include:
- compression stockings
(elastic stockings that squeeze or compress
the veins and prevent blood from flowing
backward)
- pneumatic compression
devices (sleeves on the legs that are connected
to a machine that provides alternating pressure
on the legs)
- getting up and
moving as soon as possible after surgery
or illness, as movement can help to prevent
clots from forming by stimulating blood
circulation
- medication
Anticoagulants and/or aspirin are often given
prophylactically to prevent DVT.
Many
patients remain at risk for development of DVT
for a period of time after they are either discharged
from the hospital or transferred to a different
type of care facility. It is important that prophylactic
treatment for DVT continue until the risk for
DVT development has been resolved.
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