What Is Excessive Blood Clotting?
Excessive blood clotting is a condition in which
blood clots form too easily or dont dissolve properly.
Normally, blood clots form to seal small cuts or
breaks on blood vessel walls and stop bleeding. Blood clots also can form due
to slow blood flow in the blood vessels. For example, if a blood vessel
narrows, blood flow may slow down as it moves through the vessel.
There are many causes of excessive blood clotting.
The condition may be due to problems with the blood, blood vessel defects, or
other factors. Regardless of the cause, problem blood clots can limit or block
blood flow. This can damage the bodys organs or even cause death.
Overview
Excessive blood clotting can be acquired or genetic.
Acquired causes of excessive blood clotting are more common than genetic
causes.
"Acquired" means that another disease, condition, or
factor triggers the condition. For example,
atherosclerosis
(ath-er-o-skler-O-sis) can damage the blood vessels, which can cause blood
clots to form. Other examples of acquired causes include smoking,
overweight
and obesity, and hospitalization.
"Genetic" means the condition is due to an abnormal
gene. Most genetic defects that cause excessive blood clotting occur in the
proteins needed for blood clotting. Defects also can occur with the substances
that delay or dissolve blood clots.
Although the acquired and genetic causes of the
condition aren't related, a person can have both. People who are at highest
risk for excessive blood clotting have both causes.
Outlook
The outlook and treatment for excessive blood
clotting depend on the cause of the blood clots, how severe they are, and how
well they can be controlled.
Life-threatening blood clots are treated as
emergencies. Medicines that thin the blood are used as routine treatment for
blood clotting problems. Some people must take these medicines for the rest of
their lives.
With medicines and ongoing care, most people who
have excessive blood clotting can successfully manage it.
Other Names for Excessive Blood Clotting
- Thrombophilia. This name is mostly used for
genetic conditions.
- Hypercoagulability.
- Hypercoagulable disorders or states.
- Thrombotic disorders.
- Thromboembolic states.
What Causes Excessive Blood Clotting?
To understand what causes excessive blood clotting,
it helps to understand the bodys normal blood clotting process.
Normally, blood clots form to seal small cuts or
breaks on blood vessel walls and stop bleeding. After the bleeding has stopped
and healing has occurred, the body breaks down and removes the clots.
Blood clotting is a complex process, but it mainly
involves:
- The inner layer of the cells lining the blood
vessels. These cells play a major role in causing blood clots to form.
- Clotting factors. These proteins help create a
network of fibrinanother type of protein. Fibrin acts as glue to hold a
blood clot together.
- Platelets (PLATE-lets). These small blood cell
fragments can stick together to form a clot.
Excessive blood clotting may occur if the
bodys clotting process is altered or wrongly triggered. Blood clots can
form in or travel to the arteries or veins in the brain, heart, kidneys, lungs,
and limbs.
Certain diseases and conditions, genetic mutations,
medicines, or other factors can cause excessive blood clotting.
Diseases and Conditions
A number of diseases and conditions can cause the
blood to clot too much or prevent blood clots from dissolving properly. Certain
diseases and conditions are more likely to cause clots to form in certain areas
of the body.
Antiphospholipid Antibody Syndrome
This condition, also called
APS, is an autoimmune disorder. If you have
APS, your body makes antibodies (proteins) that attack phospholipids
(fos-fo-LIP-ids)a type of fat. Phospholipids are found in all living
cells and cell membranes, including blood cells and the lining of blood
vessels.
In APS, the antibodies trigger blood clots to form
in the bodys arteries and veinsthe vessels that carry blood to your
heart and body. These blood clots can lead to a number of health problems,
including frequent miscarriages.
APS is more common in women and people who have
other autoimmune or rheumatic disorders, such as
lupus.
Bone Marrow Disorders
Some bone marrow disorders can cause your body to
make too many blood cells that can lead to blood clots. Examples of such
disorders include
polycythemia
vera (POL-e-si-THE-me-ah VE-ra), or PV, and
thrombocythemia
(THROM-bo-si-THE-me-ah).
PV is a rare blood disease in which your body makes
too many red blood cells. These extra red blood cells make your blood thicker
than normal. This slows the flow of blood through your small blood vessels and
can lead to blood clots.
Thrombocythemia is a condition in which your body
makes too many platelets. The platelets can stick together to form blood
clots.
Thrombotic Thrombocytopenic Purpura and
Disseminated Intravascular Coagulation
Two rare, but serious conditions that can cause
blood clots are
thrombotic
thrombocytopenic purpura (throm-BOT-ik throm-bo-cy-toe-PEE-nick
PURR-purr-ah), or TTP, and disseminated intravascular clotting, or DIC.
TTP causes blood clots to form in the body's small
blood vessels, including vessels in the brains, kidneys, and heart.
DIC is a rare complication of pregnancy, severe
infections, or severe trauma. DIC causes tiny blood clots to form suddenly
throughout the body.
Problems With Blood Clot Breakdown
After a blood clot has done its job, the body
normally breaks down the fibrin that holds the clot together.
Several rare genetic and acquired conditions affect
the fibrin network that holds blood clots together. Thus, the clots don't break
down properly and they remain in the body longer than needed.
In one condition, for example, the body's fibrin is
abnormal and resists being broken down. In another condition, the body has a
decreased amount of plasmin. This protein is needed to break down fibrin.
Excessive Blood Clotting That Mainly Affects the
Heart and Brain
Any condition that damages the smooth inner surface
of the blood vessels can trigger blood clotting. Many of these conditions are
acquired. However, some genetic problems also can damage the blood vessel
walls.
Certain diseases, conditions, or factors may trigger
excessive blood clotting mainly in the arteries and veins of the heart and
brain.
Atherosclerosis.
Atherosclerosis
is a disease in which a fatty material called plaque (plak) builds up on the
insides of your arteries. Over time, the plaque may crack. Platelets clump
together to form blood clots where the cracks are. Atherosclerosis is a major
case of damage to the blood vessel walls.
Vasculitis.
Vasculitis
(vas-kyu-LI-tis) is a disorder that causes the body's blood vessels to become
inflamed. Platelets may stick where the arteries are damaged, and blood clots
can form. Vasculitis also is a major cause of damage to the blood vessel
walls.
Diabetes.
Diabetes increases the risk for plaque buildup in the
arteries. Nearly 80 percent of people who have diabetes die from dangerous
blood clots. (Seventy-five percent of these deaths are due to complications
with the heart and blood vessels.)
Heart failure. Heart
failure is a condition in which the heart is damaged or weakened and can't
pump enough blood to meet the body's needs. This condition slows blood flow,
which can cause blood clots to form.
Atrial fibrillation.
Atrial
fibrillation (A-tre-al fi-bri-LA-shun), or AF, is the most common type of
arrhythmia
(ah-RITH-me-ah). An arrhythmia is a problem with the rate or rhythm of the
heartbeat. AF can cause blood to pool in the upper chambers of the heart. This
can cause blood clots to form.
Overweight and obesity.
Overweight
and obesity refer to a person's overall body weight and where the extra
weight comes from. Overweight is having extra body weight from muscle, bone,
fat, and/or water. Obesity is having a high amount of extra body fat. These
conditions can lead to atherosclerosis, which increases the risk of blood
clots.
Excessive Blood Clotting That Mainly Affects the
Limbs
Blood clots can form in the veins deep in the limbs.
This condition is called
deep
vein thrombosis (DVT). It mostly affects the deep veins of the legs.
A blood clot in a deep vein can break off and travel
through the bloodstream. When the clot travels to the lungs and blocks blood
flow, the condition is called
pulmonary
embolism (PULL-mun-ary EM-bo-lizm), or PE.
Certain diseases, conditions, or factors may trigger
excessive blood clotting mainly in the deep veins of the limbs. These
include:
- Hospitalization for major surgery or serious
medical illness. This causes nearly half of all cases of DVT and PE. If
youre not able to be active for long periods, blood flow in the veins is
slowed and blood clots may form in the legs.
- Hospitalization for serious trauma and broken
bones. This is the cause of about 12 percent of all blood clots that form in
the deep veins of the legs.
- "Coach class." This term refers to a situation in
which you must stay in one position for a long time, such as in a car or on a
plane. This can slow blood flow and lead to blood clots in the legs.
- Cancer growth and cancer treatment. This accounts
for about 20 percent of blood clots that form in the deep veins of the
legs.
Genetic Mutations
Genetic causes of excessive blood clotting are most
often due to gene mutations (changes to a normal gene).
Common mutations include Factor V Leiden and
Prothrombin G20210A mutations. Fairly rare genetic mutations include proteins C
and S deficiencies and antithrombin III deficiency.
Medicines
Some medicines can disrupt the bodys normal
blood clotting process. Medicines containing the female hormone estrogen are
linked to an increased risk of blood clots. Examples of medicines that may
contain estrogen include birth control pills and hormone replacement therapy.
Heparin is a medicine commonly used to prevent blood
clots. But, in some people, the medicine can cause blood clots and a low
platelet count. This condition is called heparin-induced thrombocytopenia
(HIT).
HIT rarely occurs outside of a hospital, because
heparin usually is given in hospitals. In HIT, the body's immune system attacks
the heparin and a protein on the surface of the platelets. This attack prompts
the platelets to start forming blood clots.
Other Factors That Can Alter the Blood Clotting
Process
A number of other factors also can alter the
clotting process and lead to excessive blood clotting. Common examples
include:
- Smoking. Smoking greatly raises the risk of
unwanted blood clots. It makes it more likely that platelets will stick
together. Smoking also damages the lining of the blood vessels, which can cause
blood clots to form.
- Increased homocysteine levels. Homocysteine is an
amino acid linked to a high risk of vascular disease. Increased levels of this
substance may damage the inner lining of the arteries.
- Pregnancy. Women are six times more likely to
develop blood clots when theyre pregnant. This is because they have more
platelets and clotting factors in their blood during pregnancy. Also, during
pregnancy, the uterus compresses the veins. This slows blood flow, which can
lead to blood clots.
- HIV and HIV treatment. The risk of blood clots is
highest in HIV patients who have infections, are taking certain medicines, have
been hospitalized, or are older than 45.
- Dehydration. This is a condition in which your
body doesnt have enough fluids. This condition causes your blood vessels
to narrow and your blood to thicken. This increases the chance that clots will
form.
- Organ transplants and implanted devices, such as
central venous catheters and dialysis shunts. Surgery or procedures done on
blood vessels may injure the vessel walls. This can cause blood clots to form.
Also, catheters and shunts have a man-made surface that may trigger blood
clotting.
Who Is At Risk for Excessive Blood Clotting?
People at highest risk for excessive blood clotting
have both acquired and genetic risk factors. For example, if you have the
Factor V Leiden mutation and
atherosclerosis,
and you smoke, you're at higher risk than someone who has only one of these
risk factors.
See "What Causes Excessive
Blood Clotting?" for more information on the diseases, conditions, and
other factors that can lead to this condition.
Genetic Risk Factors
You're more likely to have a genetic cause of
excessive blood clotting if you have:
- Family members who have had dangerous blood
clots
- A personal history of repeated blood clots before
the age of 40
- Had a
heart
attack or
stroke before the age of 50
- Had unexplained miscarriages
Factor V Leiden is one of the more common genetic
mutations that can alter the blood clotting process. It's found in 5 to 15
percent of the general population. This mutation accounts for up to a quarter
of the cases of genetic blood clotting disorders. Factor V Leiden is found
mostly in people who have a European background.
Other Risk Factors
Another risk factor for excessive blood clotting is
antiphospholipid antibody syndrome linked to
lupus. This condition may affect 4 to 14 percent of the U.S.
population.
What Are the Signs and Symptoms of Excessive Blood
Clotting?
Signs and symptoms of excessive blood clotting
depend on where the clots form. For example, symptoms of a blood clot in the
heart or lungs may include chest pain, shortness of breath, and upper body
discomfort in the arms, back, neck, or jaw. These symptoms may suggest
heart
attack or
pulmonary
embolism (PE).
Signs and symptoms of a blood clot in the deep veins
of the leg may include pain, redness, warmth, and swelling in the lower leg.
These signs and symptoms may suggest
deep
vein thrombosis (DVT).
Signs and symptoms of a blood clot in the brain may
include headaches, speech changes, paralysis (an inability to move), dizziness,
and trouble speaking and understanding. These signs and symptoms may suggest a
stroke.
If you have any of these signs or symptoms, call
your doctor right away. The cause of the blood clot(s) needs to be found and
treated as soon as possible. You may need emergency care.
Complications of Blood Clots
Blood clots can form in or travel to the arteries or
veins in the brain, heart, kidneys, lungs, and limbs. Blood clots can limit or
block blood flow. This can damage the body's organs and cause a number of
problems. In some cases, blood clots can be fatal.
Stroke
A blood clot in the brain can cause a stroke. A
stroke occurs when blood flow to your brain is cut off. If blood flow is cut
off for more than a few minutes, the cells in your brain start to die. This
impairs the parts of the body that the brain cells control.
A stroke can cause lasting brain damage, long-term
disability, paralysis (an inability to move), or death.
Heart Attack
A blood clot in the heart can lead to a heart
attack. A heart attack occurs when blood flow to a section of heart muscle
becomes blocked. If the flow of blood isn't restored quickly, the section of
heart muscle becomes damaged from lack of oxygen and begins to die.
This heart damage may not be obvious, or it may
cause severe or long-lasting problems such as
heart
failure or
arrhythmias
(irregular heartbeats).
Kidney Problems and Kidney Failure
A blood clot in the kidneys can lead to kidney
problems or
kidney failure. Kidney failure occurs when the kidneys can no
longer remove fluids and waste from your body.
This causes a buildup of these fluids and waste in
your body,
high
blood pressure, and other health problems.
Pulmonary Embolism
If a blood clot travels from a deep vein in the body
to the lungs, it's called a pulmonary embolism, or PE. PE is a serious
condition that can damage your lungs and other organs and cause low oxygen
levels in your blood.
Deep Vein Thrombosis
A blood clot in a vein deep in your arm or leg can
cause pain, swelling, redness, or increased warmth in the affected limb. This
type of clot is called deep vein thrombosis, or DVT. These clots also can break
off, travel to the lungs, and cause PE.
Pregnancy-Related Problems
Blood clots can cause miscarriages, stillbirths, and
other pregnancy-related problems, such as
preeclampsia (pre-e-KLAMP-se-ah). Preeclampsia is high blood
pressure that occurs during pregnancy.
How Is Excessive Blood Clotting Diagnosed?
If your doctor thinks that you have excessive blood
clotting based on your signs and symptoms, he or
she will look for the cause of the condition.
Your doctor will ask about your medical and family
histories and review the results from a physical exam and tests.
Your primary care doctor may refer you to a
hematologist. This is a doctor who is an expert on blood diseases.
Medical and Family Histories
Your doctor may ask you detailed questions about
your medical history and your family's medical history. He or she may ask
whether you or a blood relative:
- Has a history of excessive or abnormal blood
clots before age 40 or had a
heart
attack or
stroke before age 50
- Has had blood clots during pregnancy or while on
birth control pills
- Has had unexplained miscarriages
- Has a history of excessive or unusual blood clots
(such as clots in the veins in the liver or kidneys)
Physical Exam
Your doctor will do a physical exam to see how
severe your blood clotting problem is and to look for its possible causes.
Diagnostic Tests and Procedures
Your doctor may order
blood
tests to look at your blood cells and the clotting process. If he or she
thinks you may have a genetic condition, you may need more blood tests.
Tests to find the cause of excessive blood clotting
may be delayed for weeks or even months while you receive treatment for a
problem blood clot.
Complete Blood Count and Platelet Count
An initial blood test will include a complete blood
count and a platelet count. These tests measure the number of red and white
blood cells and platelets in your blood.
In this situation, your doctor will want to know the
number of platelets in your blood. Platelets are blood cell fragments that
stick together to form clots.
Tests for Clotting Factors and Clotting Time
You also may need blood tests that look at the
proteins active in the blood clotting process and how long it takes them to
form a blood clot.
Clotting proteins or factors react with each other
along two pathways called the intrinsic and extrinsic pathways. (A pathway is a
string of chemical reactions that always occur in a certain order.) The two
pathways join in a common pathway to make a fibrin network that holds blood
clots together.
- PT test. This test looks at the extrinsic and
common pathways to measure how long it takes blood clots to form. People who
have excessive blood clotting may take the medicine warfarin to prolong their
clotting times.
- A PTT test. This test looks at the intrinsic and
common pathways to measure how long it takes blood clots to form. People also
may take blood thinners, like heparin, to slow their clotting times.
Followup Tests
If your doctor thinks your blood clotting condition
is genetic, you may need other blood tests. These may include tests that
check:
- For gene mutations that can cause excessive blood
clotting
- For antibodies related to
antiphospholipid antibody syndromea
cause of excessive blood clotting
- Your homocysteine levels (if youre at risk
for vascular disease)
How Is Excessive Blood Clotting Treated?
Excessive blood clotting is treated with medicines.
Depending on the size and location of the clot(s), you may need emergency
treatment and/or routine treatment.
Emergency Treatment
Blood clots can be dangerous. They can damage the
body and lead to serious problems, such as
stroke,
heart
attack,
kidney failure,
deep
vein thrombosis, or
pulmonary
embolism. Blood clots also can cause miscarriages, stillbirths, or
pregnancy-related problems.
Emergency treatment to prevent these problems often
consists of medicines that can quickly break up clots.
These medicines, called thrombolytics or "clot
busters," are used to treat large clots that cause severe symptoms. These
medicines can cause sudden bleeding. Thus, they're only used in
life-threatening situations.
Routine Treatment
Blood Thinners
Anticoagulants, or "blood thinners," are used as
routine treatment for excessive blood clotting. These medicines prevent blood
clots from forming. They also keep existing blood clots from getting
larger.
Warfarin and heparin are two types of blood
thinners. Warfarin is given in pill form. (Coumadin® is a common
brand name for warfarin.) Heparin is injected into a vein.
Your doctor may treat you with both heparin and
warfarin at the same time. Heparin acts quickly. Warfarin takes 2 to 3 days
before it starts to work. Once the warfarin starts to work, the heparin is
stopped.
Pregnant women will be treated with heparin, because
warfarin can harm the fetus.
Sometimes aspirin is used with warfarin. In other
cases, aspirin may be used alone. Aspirin also thins the blood and helps
prevent blood clots.
Some people must take blood thinners for the rest of
their lives if their risk for forming blood clots remains high.
Side effects. The most common side
effect of blood thinners is bleeding. This happens if the medicine thins your
blood too much. This side effect can be life threatening. Bleeding can occur
inside your body (internal bleeding) or on its surface.
Know the warning signs of internal bleeding, so you
can get help right away. They include:
- Unexplained bleeding from the gums and nose
- Increased menstrual flow
- Bright red vomit or vomit that looks like coffee
grounds
- Bright red blood in your stools or black, tarry
stools
- Pain in your abdomen or severe pain in your
head
- Sudden changes in vision
- Sudden loss of movement in your arms and
legs
- Memory loss or confusion
A lot of bleeding after a fall or injury or easy
bruising or bleeding also may mean that your blood is too thin. Call your
doctor right away if you have any of these signs.
People who are treated with blood thinners usually
need regular
blood
tests, called PT and PTT tests, to check how well their blood is clotting.
These tests also show whether you're taking the
right amount of medicine. Your doctor will check to make sure that you're
taking enough medicine to prevent clots, but not so much that it causes
bleeding.
Other Treatments
Short-term treatments may include treatment with
antithrombin factor and protein C. Antithrombin factor may be helpful for
people who have known antithrombin deficiencies. This treatment is used in
special situations, such as before surgery, when there's a very serious blood
clot or repeat blood clots.
Some people who have antithrombin deficiencies may
need this treatment because heparin doesn't work for them.
Protein C may be given to people who have protein C
deficiencies before they receive warfarin. Protein C is given to protect them
from skin necrosisa serious side effect of warfarin. (Skin necrosis
destroys and damages the skin cells.)
How Can Excessive Blood Clotting Be Prevented?
You can't prevent genetic causes of excessive blood
clotting. However, you can take steps to control or avoid some acquired risk
factors.
- Treat conditions that can lead to excessive blood
clotting, such as
diabetes or heart and vascular diseases.
- Make lifestyle changes, such as quitting smoking
or losing weight, if needed.
- Avoid medicines that contain the female hormone
estrogen. Talk to your doctor about other, safer options.
- Stay active if you can. Move your legs, flex, and
stretch during long trips. This helps blood flow in your calves.
- Talk to your doctor about ways to lower your
homocysteine level if it's high. You may need more vitamin B6, vitamin B12, or
folate.
Living With Excessive Blood Clotting
If you have excessive blood clotting, you
should:
- Know the signs and symptoms of problem blood
clots.
- Take all your medicines as prescribed.
- Get ongoing medical care.
Signs and Symptoms
Knowing the signs and
symptoms of problem blood clots is important. You should call your doctor
right away if you have any of these signs or symptoms. The cause of the blood
clots needs to be found and treated as soon as possible. You may need emergency
care.
Medicines
You may need to take anticoagulants, or blood
thinners, to prevent blood clots or to keep them from getting larger. You
should take these medicines exactly as your doctor prescribes.
Tell your doctor about all other medicines
youre taking, including over-the-counter medicines. Some medicines can
thin your blood. Taking two medicines that thin your blood may increase your
risk of bleeding.
Sexually active women who take warfarin (a type of
blood thinner) should use birth control measures. This is because warfarin can
cause birth defects.
If you need surgery, your doctor may adjust the
amount of medicines you take before, during, and after the surgery to prevent
bleeding. This also may happen for dental work, but its less common.
If you take blood thinners, let everyone on your
health care team know.
Ongoing Care
Have
blood
tests done as your doctor directs. These tests help track how well your
blood is clotting.
The medicines used to treat excessive blood clotting
may cause bleeding. Bleeding can occur inside your body (internal bleeding) or
on its surface. Know the warning signs of internal bleeding, so you can get
help right away. They include:
- Unexplained bleeding from the gums and nose
- Increased menstrual flow
- Bright red vomit or vomit that looks like coffee
grounds
- Bright red blood in your stools or black, tarry
stools
- Pain in your abdomen or severe pain in your
head
- Sudden changes in vision
- Sudden loss of movement in your arms and
legs
- Memory loss or confusion
A lot of bleeding after a fall or injury or easy
bruising or bleeding also may mean that your blood is too thin. Call your
doctor right away if you have any of these signs.
Talk to your doctor about lifestyle changes that can
help you stay healthy. Ask him or her whether your diet may interfere with your
medicines. If you take warfarin, some foods or drinks can increase or decrease
the effect of the medicine.
Discuss with your doctor what amount of alcohol is
safe for you to drink if you're taking medicine. If you smoke, ask your doctor
about programs and products that can help you quit.
Key Points
- Excessive blood clotting is a condition in which
blood clots form too easily or don't dissolve properly.
- Normally, blood clots form to seal small cuts or
breaks on blood vessel walls and stop bleeding. Blood clots also can form due
to slow blood flow in the blood vessels.
- There are many causes of excessive blood
clotting. The condition may be due to problems with the blood, blood vessel
defects, or other factors. Regardless of the cause, problem blood clots can
limit or block blood flow. This can damage the bodys organs or even cause
death.
- Excessive blood clotting can be acquired or
genetic. "Acquired" means that another disease, condition, or factor triggers
the condition. "Genetic" means the condition is due to an abnormal gene.
- People at highest risk for excessive blood
clotting have both genetic and acquired risk factors.
- Signs and symptoms of excessive blood clotting
depend on where the clots form. Signs and symptoms may include chest pain;
shortness of breath; upper body discomfort; pain, redness, warmth, and swelling
in the lower leg; ongoing headaches; speech changes; paralysis (an inability to
move); dizziness; and trouble speaking and understanding.
- If your doctor thinks that you have excessive
blood clotting based on your signs and symptoms, he or she will look for the
cause of the condition. Your doctor will ask about your medical and family
histories and review the results from a physical exam and tests.
- Excessive blood clotting is treated with
medicines. Depending on the size and location of the clot(s), you may need
emergency treated and/or routine treatment. Long-term control of problem blood
clotting is treated with blood-thinning medicines over time. Some people must
take blood thinners for the rest of their lives.
- You can't prevent genetic causes of excessive
blood clotting. However, you can take steps to control or avoid some acquired
risk factors. (For more information, see "How Can
Excessive Blood Clotting Be Prevented?")
- If you have excessive blood clotting, you should
know the signs and symptoms of problem blood clots, take all of your medicines
as prescribed, and get ongoing medical care.
- The outcome for people who have excessive blood
clotting depends on the underlying cause of the condition. With medicines and
ongoing care, most people who have the condition can successfully manage
it.
Links to Other Information About Excessive Blood
Clotting
NHLBI Resources
Non-NHLBI Resources
Clinical Trials
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