Electrophysiological
Testing of the Heart
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What is the
test?
If you have an arrhythmia (abnormal heart rhythm),
cardiologists can use an electrophysiologic study
(EPS) to find out what part of the heart is causing
this change in rhythm and what medicines will
work best to bring that rhythm back to normal.
Sometimes doctors will recommend a treatment
called ablation that can be done during EPS testing.
Ablation uses electricity to kill the cells in
the heart muscle that seem to cause the abnormal
rhythm.
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How
do I prepare for the test?
You will need to sign a consent form giving
your doctor permission to perform this test.
Tell your doctor if you have ever had an allergic
reaction to lidocaine or the numbing medicine
used at the dentist's office. Also tell your
doctor if you have ever had an allergic reaction
to any heart medicines.
Talk with your doctor ahead of time if you are
taking insulin, or if you take aspirin, nonsteroidal
antiinflammatory drugs, or other medicines that
affect blood clotting. It may be necessary to
stop or adjust the dose of these medicines before
your test. Most people need to have a blood test
done some time before the procedure to make sure
they are not at high risk for bleeding complications.
Your doctor may tell you not to eat anything
for 12 or more hours before the test. A few people
require an anti-anxiety medicine which occasionally
causes nausea, and therefore some doctors prefer
to have you come with an empty stomach. You might
need to plan to spend the night in the hospital
afterwards for recovery.
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What
happens when the test is performed?
The test is done by a specialist using equipment
and cameras in the cardiology department. You
wear a hospital gown and lie on your back during
the procedure. You have an IV (intravenous) line
placed in a vein in case you need medicines or
fluid during the procedure. Your heart is monitored
during the test.
A catheter (a hollow, sterile tube that resembles
spaghetti) is inserted through the skin into
a blood vessel-typically in your groin, but possibly
in the neck or arm. Before the catheter is placed,
medicine through a small needle is used to numb
the skin and the tissue underneath the skin in
that area. The numbing medicine usually stings
for a second. A needle on a syringe is then inserted,
and some blood is drawn into the syringe, so
that the doctor knows exactly where the blood
vessel is located. One end of a wire is threaded
into the blood vessel through the needle and
the needle is pulled out, leaving the wire temporarily
in place. This wire is several feet long, but
only a small part of it is inside your blood
vessel. The catheter can then be slipped over
the outside end of the wire and moved forward
along it like a long bead on a string, until
it is in place with one end inside the blood
vessel. The wire is pulled out of the catheter,
leaving the catheter in place. Now the catheter
can be moved easily forwards and backwards inside
your blood vessel by the doctor, who holds the
outside end of the catheter while using special
controls to point the tip of the catheter in
different directions. The doctor carefully moves
the catheter to the large blood vessels in your
chest and into the chambers of your heart.
As your physician maneuvers the catheter, he
or she watches a live video x-ray to know exactly
where the catheter is. Instruments on the tip
of the catheter allow it to sense electrical
patterns from your heart and also to deliver
small electrical shocks to the heart muscle (or
a stronger electrical burn if you are having
ablation). The electrical shocks, too small for
you to feel, are used to "tickle"
the heart muscle in different places to see if
your abnormal rhythm is triggered by one sensitive
area of your heart. If the rhythm changes, your
doctor gives you small doses of different medicines
through this catheter to see which ones work
best to change the rhythm back to normal. In
some cases the doctor may need to give your heart
some additional mild shocks to get it back into
a normal rhythm. Because this catheter is in
place inside your heart and can give the shocks
directly to the heart muscle, very small amounts
of electricity are used.
After the catheter has been pulled out, a pressure
bandage (basically a thick lump of gauze) is
taped tightly to your groin to reduce bleeding.
The test usually requires one to two hours to
perform.
Many patients are able to feel palpitations
(an irregular or fast heartbeat) from the rhythm
changes. A few patients also experience shortness
of breath or dizziness when they are not in a
normal heart rhythm. Other than the brief sting
of the numbing medicine and some soreness in
your groin area afterward, you are not likely
to feel any pain. For some people, the procedure
provokes anxiety. Some patients also have a difficult
time lying still for the time it takes to perform
this test.
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What
risks are there from the test?
There are significant risks from this procedure.
Most important, some abnormal heart rhythms (arrhythmia)
can be life-threatening, and your doctors will
purposefully cause you to go through a few extra
episodes of arrhythmia during the testing. If
your doctors recommend electrophysiologic testing,
they feel that this is a risk worth taking because
it will allow them to take better care of you
in the future. Because you are right in the lab
and attached to a monitor while you undergo the
rhythm changes, it is easy for them to treat
you should your arrhythmia occur and cause you
symptoms.
Ablation has some additional risks, because
it intentionally causes some scarring of a small
part of the heart muscle. Complications are rare,
but new rhythm changes can occur. A very rare
complication occurs if the ablation instrument
burns a hole through the heart muscle. This causes
bleeding and may require immediate surgery.
There are some more minor risks from the test.
Among them is bleeding from the place where the
catheter was inserted. If bleeding occurs but
the blood collects under the skin, it can form
a large painful bruise called a hematoma. A few
people are allergic to the medicines used in
the procedure, and this can cause a rash or other
symptoms.
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Must
I do anything special after the test is over?
You will need to lie flat for around six hours
after this procedure. If you received anti-anxiety
medicine through your IV during the procedure,
you might feel sleepy at the end of the procedure
and you might not remember much of the test.
You should not drive or drink alcohol for the
rest of the day.
Depending on what happened during your test,
you might need to wear a heart monitor in the
hospital for a few hours or overnight.
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How
long is it before the result of the test is
known?
Your doctors can tell you how the testing went
as soon as it is over. If you had ablation done,
the results will not be certain until you have
had some time to see if your arrhythmia seems
to be under control after the treatment.
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