|
|
Click
topics above to see more information.
To return to Table of Contents click browser Back arrow
or "Return to Top"
|
Introduction
|
Deep
venous thrombosis, also known as DVT, is a blood clot
in a deep vein of the upper (arm or neck) or lower (leg
or pelvic) extremities.
A blood clot from a DVT can break loose (embolize) and
travel to the heart or lungs. An embolus can be life
threatening.
It
is estimated that over half a million hospital patients
in the United States develop a DVT each year, causing
50,000 deaths a year due to pulmonary (lung) emboli.
|
 |
| Superficial
thrombophlebitis is the name for a blood clot in a vein
just below the skin, such as a varicose vein. This is
almost never a life threatening condition. Deep venous
thrombosis is not the same as superficial thrombophlebitis.
Deep veins, in which a DVT occurs, can not be seen or
felt under the skin. |
Top
What
causes a DVT?
Three
factors increase the chance of having a DVT:
- Injury
to a deep vein from trauma or surgery
- Poor
blood circulation in the deep veins
- Conditions
that increase the tendency of blood to clot
Injury
to a deep vein from trauma or surgery causes release of substances
that activate the clotting system.
Blood
that is not moving (stagnant)is much more likely to clot. Conditions
that can cause poor circulation in deep veins include:
- Congestive
heart failure
- Prolonged
immobilization ( not walking or moving)
- Preexisting
small clots
The
body produces a number of clotting factors
(many are made in the liver), maintaining a fine balance between
factors that cause blood to clot and those that either prevent
or dissolve blood clots. Clotting is needed to prevent excessive
bleeding when blood vessels are injured. When clotting is no
longer needed other clotting factors help dissolve clots. When
this balance is disturbed either excessive bleeding or clotting
of blood that serves no useful purpose may occur. Increased
blood clotting (hypercoagulability) may be caused by:
- Hormones
(birth control pills, pregnancy)
- Cigarette
smoking
- Certain
cancers
- Inherited
deficiencies of anticlotting factors
- Certain
autoimmune disorders
Top
Who
gets a DVT?
DVT
is more likely to occur in two different situations:
- Major
surgery, particularly hip and knee replace, increases the
risk of DVT due to venous injury and immobilization. This
is true even in patients without any other risk factors for
DVT. Persons affected are generally older.
- Persons
with inherited deficiencies of anticlotting
factors are at greatly increased risk of DVT. Persons
with such deficiencies often develop DVT at a much younger
age (20's to 40's) without major surgery or leg trauma, suffer
recurrent DVTs, and have family members who have had DVTs.
Factor deficiencies, which can be mild or severe, may include:
- Leiden
factor 5 (most common)
- antithrombin
- protein
C and/ or protein S
Persons
with inherited anticlotting factor deficiency and additional
risk factors (smoking, pregnancy, birth control pills and /or
immobilization) are thought to have a greatly increased risk
of developing DVT.
Top
What
are the symptoms of a DVT?
Symptoms
of a DVT are variable, occurring in less than half of persons
with DVT.
Symptoms,
depending on the size and location of a DVT, can include:
- warmth,
swelling, redness, and /or pain in a leg.
- DVT
of the calf may cause symptoms in the calf while that in the
thigh can cause symptoms in both the thigh and/or calf.
-
The vast majority of DVTs occurs in only one leg at a time
Other
medical conditions can cause pain and/ or welling in the legs.
Persons with pain and/ or swelling of the legs should see their
doctor or go to an emergency department for evaluation, especially
if they have DVT risk factors.
Top
Is
a DVT serious?
A
DVT can be lifethreatening if a large enough blood clot breaks
loose and travels to the heart or lungs. Pulmonary emboli (blood
clots traveling to the lungs) occur in over 300,000 persons
each year in the United States killing at least 50,000 Americans
each year. Pulmonary emboli can disrupt blood flow to the lungs
by directly blocking blood flow to part of the lung and by triggering
certain reflexes that can cause the heat to suddenly stop beating.
Many, although not all, pulmonary emboli are caused by embolization
of DVTs.
Symptoms
of a pulmonary embolus may include:
- Shortness
of breath
- Chest
pain
- Increased
heart and breathing rate.
 |
If
these symptoms occur, especially with DVT symptoms, call
911 immediately! |
Another
complication of DVT, particularly recurrent DVTs, is postphlebitic
syndrome. Chronic stretching and injury to deep veins may cause
blood to pool and stagnate in the lower legs. This can cause
chronic swelling and pain in the affected leg. Leg sores may
also develop. Although not life threatening this condition can
be unpleasant.
Top
How
does a Doctor diagnose a DVT?
Your
doctor or an emergency physician may order certain tests if
he/she suspects, based on symptoms and risk factors, you might
have a DVT. Several different tests can be used to diagnose
or exclude a DVT.
Doppler
ultrasound is most commonly used. This tests, using sound
waves to create a picture of the veins, is very accurate and
noninvasive. It is able to reliably detect DVTs in either
below or above the knee.
Venogram
uses dye injected into the veins followed by a series
of x-rays. Although this test is extremely accurate it has
largely been replaced by ultrasound because a venogram is
more difficult to perform, more expensive, and is somewhat
invasive.
Impedance
plethsmography (IPG) is very accurate for excluding DVT
above the knee( the kind that can embolize to the lungs).
It measures volume and pressure changes that occur in the
thigh with DVT. IPG is much less accurate in detecting clots
below the knee. This limitation is not as important because
DVTs below the knee almost never embolize. This test, although
inexpensive and accurate, has largely been replaced by ultrasound
in most hospitals.
Top
How
is a DVT treated?
Treatment
of a DVT may depend on both its location and underlying cause.
Anticoagulants (blood thinners), which keep
the clot from getting larger, are the mainstay of DVT treatment.
In certain circumstances clot dissolving (thrombolytic) medications
may be used.
Location
of DVT
DVT
occurring in only the calf (below the knee) rarely embolize.
Treatment consists of bedrest at home and anti-inflammatory
medications. Anticoagulants are not needed unless the DVT
continues to spread (propagate) into the veins of the knee
or thigh. Clot propagation occurs in 10 percent to 30 percent
of DVTs below the calf. For this reason your doctor will follow
you closely and want to know if pain or swelling occur at
or above the knee.
Your
doctor may hospitalize you if there are risk factors for propagation
such as previous DVTs, being bedridden, or having a hypercoagulable
disorder.
DVT
occurring in deep knee or thigh veins, known as proximal DVT,
require hospitalization and anticoagulation because of increased
risk of pulmonary embolus.
Medication
Once
proximal DVT is diagnosed you will be hospitalized for 7 to
10 days and treated with anticoagulants
(blood thinning medications). Anticoagulants stop the formation
of new clots but do not dissolve already formed clots. Naturally
occurring thrombolytic proteins are responsible for slowly
dissolving blood clots.
Heparin
Is
an anticoagulant that is given through an IV for the first
5 to 7 days. Heparin works immediately and stops working
quickly after being stopped. Unfortunately, heparin cannot
be taken by mouth, requires very frequent monitoring, and
must be given in a hospitalized setting. Heparin must be
continued until a second anticoagulant, coumadin, is working
properly.
Coumadin
Coumadin
(warfarin) is an anticoagulant that can be taken by mouth.
It is started on the first or second day that heparin is
started. Coumadin takes about one week to adequately inhibit
clotting factors. Heparin must be taken until coumadin is
fully effective. Coumadin cannot be used in pregnancy because
it crosses the placenta and can cause fetal malformations.
Your
doctor will measure certain blood tests, called a PT and
a PTT to see how well coumadin and heparin are working.
Low
Molecular Weight Heparin
Newer
forms of heparin can be self administered under the skin
and do not require constant monitoring. Enoxaprin is currently
approved by the FDA in the United States
for treatment of DVT. Used in Europe for over 10 years,
low molecular weight heparins have been shown to be as effective
as traditional heparin in DVT prevention and treatment.
Because frequent monitoring is not needed hospital stays
can be reduced to 2 or 3 days compared to 7 to 10 days currently
needed. Benefits include lower health care costs and patient
convenience. Larger studies will be needed before Enoxaprin
and other low molecular weight heparins gain wider acceptance
in the United States.
Coumadin
is taken the same way as with IV heparin.
Thrombolytic
Medications
Thrombolytic
(clot busting) medications, unlike anticoagulants,
are able to dissolve blood clots that have already formed.
Several types of thrombolytic medications, including TPA
and streptokinase, are used to dissolve blood clots that
cause heart attacks and DVT.
Use
of thrombolytics in DVT has more limited benefit than with
heart attack. These medications have increased risk of serious
bleeding and are not likely to significantly benefit most
persons with DVT because most persons do quite well with
proper use of anticoagulants.
Early
use of thrombolytics may decrease the incidence of postphlebitic
syndrome in persons with massive or recurrent DVT. Clear
cut indications for thrombolytic therapy in DVT are still
investigation.
Side
effects of anticoagulant and thrombolytic medications
Anticoagulants
can cause both minor and serious side effect- most related
to bleeding. Persons taking anticoagulants must notify their
doctor if the following occur:
- Back
or stomach pain
- Black
tarry stools or obvious blood in stools (bowel movements)
- Vomiting
or coughing up blood
- Blood
in the urine
- Nose
bleeds
- Unusual
bruising of the skin , mouth, lips or gums
- Very
heavy menstrual bleeding
- Cold,
blue or painful hands or feet.
Small
amounts of blood in the urine and nose bleeds are relatively
common when starting anticoagulant therapy. Treatment is
not usually stopped for these two problems but your doctor
may check blood tests to make sure you are not receiving
too much anticoagulant.
Vomiting
or passing blood in the stool is potentially a very serious
problem and will require immediate evaluation by your doctor
or emergency department.
Thrombolytic
medications may be used to treat an initial DVT but are
not given on an ongoing basis. Side effects are similar
to anticoagulants except there is an even higher risk of
initial hemorrhage (severe life threatening bleeding) including
stroke.
If
you are taking anticoagulants it is extremely important
you discuss side effects and other medications you may be
taking with your doctor in more detail!
Top
How
long are anticoagulants taken after a DVT?
DVTs
of the knee, thigh and groin (proximal DVTs) are initially treated
with intravenous heparin for the first 5 to 10 days in conjunction
with coumadin (taken be mouth). How long coumadin is taken will
depend on how much risk there is of developing another DVT.
If
you have no major risk factors, have not had a DVT and are about
to undergo hip or knee replacement you may be anticoagulated
for 6 to 12 weeks.
Persons
having a DVT are typically anticoagulated for 3 to 6 months.
Persons with recurrent DVT, multiple risk factors or severe
anticlotting factor deficiency(s) may require lifelong anticoagulation.
Top
How
can DVT be prevented?
Prevention
of DVT depends on recognizing and eliminating preventable risk
factors, such as smoking and extreme obesity, with use of anticoagulants
in high risk situations.
Anticoagulation
with heparin and coumadin should be used in all persons (not
having absolute contraindications) undergoing hip or knee replacement
because of the high risk of DVT (30 to 50 percent) when anticoagulation
is not used.
Persons
who are bedridden, in the hospital or at home, are at increased
risk for DVT. The risk is not as high as it is for persons undergoing
hip or knee replacement. Injection of subcutaneous heparin (traditional
heparin) is effective in preventing (not treating) DVT in this
situation. Properly fitted compression stockings (not pantyhose)
may also help but are inconvenient and must be used properly.
Persons
with recurrent DVTs may require lifelong anticoagulation with
coumadin.
All
persons taking anticoagulants must be under the care of a physician
and undergo routine monitoring.
Top
Glossary
| Anticoagulant |
a
substance that prevents blood from clotting |
| Anticlotting
factors |
proteins
made by the body that, when activated, inhibit blood
from clotting |
| Clotting
factors |
proteins
made by the body that, when activated, cause blood
to clot. |
| FDA |
Food
and Drug Administration- a branch of the federal
government regulating the licensing and use of medications
in the United States. |
| Thrombolytic |
a
substance that dissolves existing blood clots |
|
Top
Other
Sites & Resources
Top
|
