Frequently
Asked Questions Part I | Part
II | Part III
Electrocardiogram
How Should I Prepare for the Test?
- Avoid
oily or greasy skin creams and lotions the day of the test. They interfere
with the electrode-skin contact.
- Avoid
full-length hosiery, because electrodes need to be placed directly on
the legs.
- Wear a
shirt that can be easily removed to place the leads on the chest.
What
Happens During the Test?
During the procedure, a technician will attach 10 electrodes with adhesive
pads to the skin of your chest, arms and legs. Men may have chest hair
shaved to allow a better connection. You will lie flat while the computer
creates a picture, on graph paper, of the electrical impulses traveling
through your heart. This is called a "resting" EKG. This same
test may also be used to monitor your heart during exercise.
It takes
about 10 minutes to attach the electrodes and complete the test, but the
actual recording takes only a few seconds.
Your EKG
patterns will be kept on file for later comparison with future EKG recordings.
If you have questions, be sure to ask your doctor.
In addition to the standard EKG, your doctor may recommend other specialized
EKG tests, including holter monitor or a signal-averaged electrocardiogram.
What
Is Holter Monitor?
Holter monitor is a portable EKG that monitors the electrical activity
of a freely moving person's heart for one to five days, 24-hours a day.
It is most often used when the doctor suspects an abnormal heart rhythm
or ischemia (not enough blood flow to the heart muscle).
It is a painless test; electrodes from the monitor are taped to the skin.
Once the monitor is in place, you can go home and perform all of your
normal activities (except showering). You will be asked to keep a diary
of your activities and any symptoms you experience and when they occur.
What
Are the Types of Echocardiograms?
- Transthoracic
echocardiogram: This is the standard echocardiogram. It is a painless
test similar to X-ray, but without the radiation. The procedure uses
the same technology used to evaluate a baby's health before birth. High
frequency sound waves (ultrasound) are bounced off the heart structures
(using a device called a transducer) producing images and sounds that
can be used by the doctor to detect heart damage and disease.
- Transesophageal
echocardiogram (TEE): This test requires that the transducer be inserted
down the throat into the esophagus (the swallowing tube that connects
the mouth to the stomach.) Because the esophagus is located close to
the heart, clear images of the heart structures can be obtained without
the interference of the lungs and chest.
- Stress
echocardiogram: This is an echocardiogram that is performed while the
person exercises on a treadmill or stationary bicycle. This test can
accurately visualize the motion of the heart's walls and pumping action
when the heart is stressed; it may reveal a lack of blood flow that
isn't always apparent on other heart tests. The echocardiogram is performed
just prior and just after the exercise.
How
Should I Prepare for the Echocardiogram?
On
the day of the test, eat and drink as you normally would. Take all of
your medications at the usual times, as prescribed by your doctor.
What
Happens During the Echocardiogram
Test?
During the test, you will be given a hospital gown to wear. You will be
asked to remove your clothing from the waist up. A cardiac sonographer
will place three electrodes (small, flat, sticky patches) on your chest.
The electrodes are attached to an electrocardiograph monitor (ECG or EKG)
that charts your heart's electrical activity.
The sonographer
will ask you to lie on your left side on an exam table. He or she will
place a wand (called a sound-wave transducer) on several areas of your
chest. The wand will have a small amount of gel on the end, which will
not harm your skin.
Sounds are
part of the Doppler signal. You may or may not hear the sounds during
the test. You may be asked to change positions several times during the
exam in order for the sonographer to take pictures of different areas
of your heart.
You should
feel no major discomfort during the test. You may feel coolness from the
gel on the transducer and a slight pressure of the transducer on your
chest.
The test
will take about 40 minutes. After the test, you can get dressed and go
about your daily activities.
What
Should I Do to Prepare for a Stress Echo?
On the day of the test, do not eat or drink anything except water for
four hours before the test.
Do not take
the following heart medications on the day of your test unless your doctor
tells you otherwise: Beta-blockers (for example, Tenormin, Lopressor,
Toprol, or Inderal); Isosorbide dinitrate (for example, Isordil, Sorbitrate);
Isosorbide mononitrate (for example, Ismo, Indur, Monoket); Nitroglycerine
(for example, Deponit, Nitrostat, Nitropatches). Your doctor may also
ask you to stop taking other heart medications on the day of your test.
If you have any questions about your medications, ask your doctor. Do
not discontinue any medication without first talking with your doctor.
What
Should I Do if I Have Diabetes?
- If you
take insulin to control your blood sugar, ask your doctor what amount
of your medication you should take the day of the test. Often, your
doctor will tell you to take only half of your usual morning dose and
to eat a light meal four hours before the test.
- If you
take pills to control your blood sugar, do not take your medication
until after the test is complete.
- Do not
take your diabetes medication and skip a meal before the test.
- If you
own a glucose monitor, bring it with you to check your blood sugar levels
before and after your test. If you think your blood sugar is low, tell
the lab personnel immediately.
- Plan to
eat and take your blood sugar medication following your test.
What
Happens During the Test?
First, a technician will gently rub 10 small areas on your chest and place
electrodes (small, flat, sticky patches) on these areas. The electrodes
are attached to an electrocardiograph monitor (ECG or EKG) that charts
your heart's electrical activity during the test.
An intravenous
line (IV) will be inserted into a vein in your arm so dobutamine medication
can be delivered directly into your bloodstream. The technician will perform
a resting EKG, measure your resting heart rate and take your blood pressure.
The doctor or nurse will administer the dobutamine into the IV while the
technician continues to obtain echo images. The medication will cause
your heart to react as if you were exercising.
At regular
intervals, the lab personnel will ask how you are feeling. Please tell
them if you feel chest, arm or jaw pain or discomfort; short of breath;
dizzy; lightheaded or if you have any other unusual symptoms.
The lab personnel
will watch for any changes on the ECG monitor that suggest the test should
be stopped. The IV will be removed from your arm once all of the medication
has entered your bloodstream.
The dobutamine
may cause a warm, flushing feeling and in some cases, a mild headache.
If you begin to notice these symptoms or other symptoms of concern such
as chest discomfort, excessive shortness of breath or irregular heartbeats,
tell the lab personnel immediately.
The appointment
will take about 60 minutes.
What
Happens During the Transesophageal Echo?
Before the test, you will be asked to remove dentures and lie down on
your left side on the exam table. You will be given some intravenous fluids
and a mild sedative (medicine to help you relax). Your heart rate and
blood pressure will be monitored throughout the procedure. Finally, an
anesthetic spray is sprayed into the throat to reduce the gag reflex.
Then a small
transducer attached to along tube is inserted into the esophagus via the
mouth. This won't affect breathing, but swallowing may be temporarily
affected. Next the doctor will perform the test to visualize the heart.
When completed,
the tube is withdrawn. Vital signs will be monitored for about 20-30 minutes.
You cannot eat or drink until the anesthetic spray wears off -- about
an hour.
The test
takes about 90 minutes to perform.
You will
need to arrange transportation home since you may feel groggy from the
sedative.
What
Are the Symptoms of Arrhythmias?
An
arrhythmia can be silent and not cause any symptoms. A doctor can detect
an irregular heartbeat during a physical exam by taking your pulse or
through an electrocardiogram (ECG).
When symptoms
occur, they may include:
- Palpitations
(a feeling of skipped heart beats, fluttering or "flip-flops,"
or feeling that your heart is "running away").
- Pounding
in your chest.
- Dizziness
or feeling light-headed.
- Fainting.
- Shortness
of breath.
- Chest
discomfort.
- Weakness
or fatigue (feeling very tired)
How
Are Arrhythmias Diagnosed?
Tests
used to diagnose an arrhythmia or determine its cause include:
- Electrocardiogram
- Ambulatory
monitors.
- Holter
monitor.
- Transtelephonic
monitor.
- Transtelephonic
monitor with memory loop.
- Stress
test.
- Echocardiogram.
- Cardiac
catheterization.
- Electrophysiology
study (EPS).
- Head-up
tilt table test.
How Are Arrhythmias Treated?
Treatment depends on the type and seriousness of your arrhythmia. Some
people with arrhythmias require no treatment. For others, treatments can
include medication, making lifestyle changes and undergoing surgical procedures.
What
Medications Are Used to Treat Arrhythmias?
A variety of drugs are available to treat arrhythmias. These include:
- Antiarrhythmic
drugs. These drugs control heart-rate, and include beta-blockers.
- Anticoagulant
or antiplatelet therapy. These drugs reduce the risk of blood clots
and include warfarin (a "blood thinner") or aspirin.
Because
everyone is different, it may take trials of several medications and doses
to find the one that works best for you.
What
Is Electrical Cardioversion?
If drugs are not able to control a persistent irregular heart rhythm (such
as atrial fibrillation), cardioversion may be required. After administration
of a short-acting anesthesia, an electrical shock is delivered to your
chest wall that synchronizes the heart and allows the normal rhythm to
restart.
What
Is Heart Surgery?
Heart surgery may be needed to correct heart disease that may be causing
the arrhythmia. The Maze procedure is a type of surgery used to correct
atrial fibrillation. During this procedure, a series of incisions are
made in the right and left atria to confine the electrical impulses to
defined pathways.
Why
Would I Need a Pacemaker?
Your heart is normally regulated by the heart?s natural pacemaker. This
natural pacemaker is called the SA (sino-atrial) node. The SA node automatically
increases your heart rate in response to your body?s needs -- for example,
during exercise, when a faster heart rate is required. Sometimes, the
SA node stops working properly. It may improperly speed up or slow down
the rate at which it sends out electrical signals. If the signal rate
is too slow, the chambers of the heart do not contract often enough to
supply the proper amount of blood to your body.
What
Is Heart Block?
Problems may also occur with the electrical pathway between the upper
heart and the lower heart. The natural pacemaker signals sent out by the
SA node may be delayed in the AV (atrioventricular node) or may fail all
together. This condition is called "heart block." Heart block
often means that the ventricles pump too slowly even though the SA node
may be sending out faster signals in an effort to increase the heart rate.
What
Is a Pacemaker System?
Your pacemaker alters your heart rate to help meet your body?s needs.
It does this by providing pacing signals that are much like the heart?s
normal signals. Depending on your particular situation, your pacemaker
may:
- Replace
the function of the heart?s natural pacemaker or SA node.
- Help
maintain a normal timing sequence between the upper and lower heart.
- Make
sure critical lower chambers of the heart always contract at an adequate
rate.
What
Makes Up a Pacemaker?
A pacemaker is roughly the size of a silver dollar and about as thick
as 2 silver dollars together. The pacemaker system is powered by a small
battery sealed inside the pulse generator. The battery cannot be recharged.
For this reason, the pulse generator must be replaced when the battery?s
energy is used up. The pacemaker also includes several electronic circuits.
These circuits control the pacemaker?s functions, including the way it
monitors your heart?s activity. Replacement of the device usually occurs
in 4-8 years.
Pacemaker
Types
There are two basic kinds of pacemakers: single-chamber and dual-chamber.
A single-chamber pacemaker has one lead to carry signals to and from one
chamber of your heart --either the right atrium or the right ventricle.
A dual-chamber pacemaker has two leads, with the tip of one lead positioned
in the right atrium and the tip of the other lead located in the right
ventricle
How
Is a Pacemaker Implanted?
The lead(s) are positioned in the right ventricle and also in the right
atrium (when needed). A pocket is formed under the skin of the upper chest.
The pacemaker is then connected to its leads. Most pacemaker surgery is
done under local anesthesia. Additional medicine may be given in an IV
to help the patient relax. The procedure typically takes 1 to 1 ? hours.
What
Are the Complications of having a Pacemaker?
All surgical procedures contain risks. These should be discussed with
a physician.
What
Happens After a Pacemaker Is Implanted?
Once the pacemaker is implanted, it is important that the patient be followed
by a pacemaker clinic or a commercial group that specializes in pacemaker
follow-up. The physician implanting the pacemaker should help the patient
arrange appropriate follow-up. Pacemaker follow-up is usually done on
a defined schedule. The schedule may vary depending on who is in charge
of following or checking the pacemaker. Some physicians will prefer that
the patient be seen in the office on a regular basis to have the pacemaker
checked. Others will arrange a pacemaker check to be done by telephone,
called transtelephonic monitoring, with periodic visits in the office
or clinic. In many offices, the pacemaker check will be performed by a
nurse or technician that is specially trained in management of pacemakers.
Pacemakers
are checked with a special device called a programmer. A portion of the
programmer is simply held over the pacemaker and is able to communicate
with the pacemaker. It can obtain information about the function of the
pacemaker. It can also change certain functions of the pacemaker to whatever
the doctor, nurse, or technician feels is most appropriate. A special
magnet may also be used during the pacemaker evaluation, and if transtelephonic
monitoring is part of the follow-up, a magnet will probably be given to
the patient to use during the telephone evaluations.
How
is the battery replaced in the pacemaker?
The battery is sealed inside the pacemaker case, or can, which also contains
the electronic circuitry. When the battery?s energy is depleted, a new
pacemaker must be implanted. The surgery needed to remove the old pacemaker
and implant the new one may require only a local anesthetic and is generally
a very brief operation. In most cases, your original pacemaker lead(s)
will not need to be replaced.
Is
there a chance that my pacemaker will fail?
Yes, there is a remote possibility that any electronic device can fail,
but technical advances in recent years have made it possible to make pacemakers
very reliable.
What
happens if my pacemaker does fail?
If your pacemaker should fail to function properly, you may experience
the same symptoms that you had before you received the pacemaker. If you
ever have these symptoms, contact you doctor as soon as possible.
Can
I use my cellular phone?
Yes. In certain cases, a cellular phone could affect your pacemaker?s
operation if it is closer than six inches. This interaction is temporary,
and moving the phone away from the pacemaker will return it to proper
function. To reduce the chance of interaction, maintain a distance of
at least six inches between the cellular phone and your pacemaker; hold
the cellular phone on the opposite side of your body from your pacemaker;
do not carry a cellular phone in a breast pocket or on a belt if that
places the phone within 6 inches of your pacemaker.
Will
microwave ovens interfere with my pacemaker?
Microwave ovens will not interfere with pacemakers that are manufactured
today or in recent years. Patients with pacemakers may use microwaves
without concern.
Is
there other electronic equipment that will interfere with my pacemaker?
Certain types of welding equipment could interfere with a pacemaker and
should be discussed with your physician prior to using. There are other
industrial sources of potential interference. If you work in an environment
where heavy equipment is used, it is worthwhile discussing it with your
physician to be certain there is no concern.
Certain types
of hospital equipment may cause interference. MRI or magnetic resonance
imaging equipment is capable of interference and is generally not performed
in patients with pacemakers. MRI has been done in special circumstances
in patients with pacemakers. If an MRI was felt to be critical, this would
require discussion between you and the doctor ordering the MRI.
Why
is an angiogram done?
Angiography is done to:
- Evaluate
possible problems with blood vessels that affect blood flow, such as
a tear that can cause blockage or internal bleeding, aneurysms that
indicate a weakness in the blood vessel wall, narrow areas, and blockage
caused by blood clots or the buildup of fatty deposits.
- Detect
changes in the blood vessels that lead to injured or damaged organs.
- Investigate
the pattern of blood flow to a tumor. This can help determine the extent
of the tumor and guide treatment.
Occasionally,
interventional radiology may be used during angiography to treat diseases
through blood vessels. For example, a catheter can be used to open a blocked
blood vessel, to deliver medication to a tumor, or to stop intestinal
bleeding caused by diverticular disease. To stop intestinal bleeding,
the catheter is moved into the small artery where the bleeding is occurring,
and medication that constricts the artery or causes the blood to clot
is injected through the catheter.
How
to prepare or
an angiogram
Before the angiography procedure, tell your doctor if you:
- Are
or might be pregnant.
- Are
allergic to the iodine dye used in the contrast material or any other
substance that contains iodine.
- Have
ever had a serious allergic reaction (anaphylaxis) from any substance
(such as the venom from a bee sting or from eating shellfish).
- Have
asthma.
- Are
allergic to any medications.
- Have
any bleeding problems or are taking blood-thinning medication.
- Have
a history of kidney problems or diabetes, especially if you take metformin
(Glucophage) to control your diabetes. The contrast material used during
angiography can cause kidney damage in people who have poor kidney function.
If you have a history of kidney problems, blood tests (creatinine, blood
urea nitrogen) may be done before angiography to confirm that your kidneys
are functioning properly. For more information, see the medical tests
Creatinine and Creatinine Clearance and Blood Urea Nitrogen.
Do not eat
or drink for 4 to 8 hours before the test.
If you are
not spending the night in the hospital after having this test, you should
arrange to have someone take you home. Check with your doctor ahead of
time to find out when you will be able to go home.
The test
may take several hours, so you may want to go to the bathroom just before
it begins.
You may have
a routine blood test done before the angiography. You may also be given
a sedative to help you relax and to prevent pain about an hour before
the test.
You may be
asked to sign a consent form before the procedure. Take this opportunity
to discuss any final concerns you may have about the need for the test,
the risks of the test, or how it will be done.
You will
be observed for several hours after the test, so you may want to bring
some reading materials or a project (such as knitting) to pass the time
during this period.
How
is an angiogram
done?
Angiography is usually done by a doctor who specializes in evaluating
imaging tests (radiologist). The doctor is often assisted by a radiology
technologist and a nurse.
You will
need to remove jewelry that might interfere with the X-ray picture. You
will need to take off all or most of your clothes, depending on which
area is being examined (you may be allowed to keep on your underwear if
it does not interfere with the test). You will be given a cloth or paper
covering to use during the test.
An intravenous
(IV) needle may be inserted into the back of your hand or the inside of
your elbow. This allows the doctor to give you medication or additional
fluids quickly, if needed, during the procedure. A device (called a pulse
oximeter) that measures oxygen levels in your blood and monitors your
pulse may be clipped to your finger. Electrodes that monitor your heart
are usually taped to your arms, chest, or legs.
During the
test, you will lie on your back on an X-ray table. You may want to ask
for a pad or blanket to make yourself more comfortable before the procedure
begins. The area of your body to be studied will be placed in the correct
position and may be held in place with a strap, tape, or sandbags. A lead
shield or apron may be placed over your genitals and pelvic area to protect
them from X-ray exposure.
A round
cylinder or rectangular box that produces the X-rays (fluoroscope) will
be moved directly above you. The fluoroscope will move up and down during
the test.
The contrast
material is injected into a blood vessel through a catheter. The place
where the catheter will be inserted (in the groin or above the elbow)
will be shaved and cleaned. The doctor then injects a small amount of
local anesthetic to numb the area and a needle is inserted into the blood
vessel. A guide wire will be inserted into the blood vessel through the
needle, and the needle is removed. The catheter will be placed over the
guide wire and inserted into the blood vessel. Then it is guided through
the blood vessels until the catheter tip is in the area to be studied.
The catheter location will be checked using the fluoroscope.
When the
catheter is in place, the contrast material is injected through it. During
the injection you may be asked to take a breath and hold it for several
seconds. A rapid series of X-ray pictures will be taken, developed, and
reviewed immediately. You need to lie very still to avoid blurring the
pictures. Depending on the results, more contrast material may be injected
so more X-rays can be taken.
The catheter
is kept open by flushing it with a salt solution containing a medication
(heparin) that keeps blood from clotting. Your pulse, blood pressure,
and breathing rate are usually monitored throughout the test.
Angiography
usually takes between 1 and 3 hours, depending on how long it takes to
position the catheter and how many X-ray pictures are needed. When the
test is over, the catheter is removed and pressure is applied to the needle
site for 10 to 15 minutes to stop any bleeding. A bandage is then applied.
You will be given medication for pain if you need it.
If the catheter
was inserted into your arm, you should not have any blood drawn from that
arm or your blood pressure measured in that arm for several days. If the
catheter was placed in the groin area, try to keep that leg straight for
12 hours if an artery was used or 8 hours if a vein was used. Your doctor
will give you specific instructions following the test. You can apply
an ice pack to the puncture site to help relieve pain. Beyond the first
day after the test, occasional warm soaks can help relieve pain and speed
healing of the puncture site.
How do you feel after an angiogram?
The injection of pain medication may sting briefly. You may feel a brief,
sharp pain when the catheter is inserted into the vessel. You may also
feel pressure within the artery as the catheter is moved. Let your doctor
know if you are uncomfortable. Your discomfort may be relieved by additional
injections of pain medication.
When the
contrast material is injected, you will probably feel warmth in the area
of your body that is being examined. This sensation lasts only a few seconds.
Ask your doctor to tell you in advance where and when you will feel the
heat. For some people, the sensation of heat is strong and for others
it is very mild.
You may also
have a brief headache, flushing of the face, or a salty or metallic taste
in your mouth. These sensations will also pass quickly. Some people may
feel nauseated or may vomit, but this is uncommon.
After the
test, you may notice some tenderness and bruising at the site where the
catheter was inserted.
Risks
of an angiogram?
Although the risk of any major problem caused by angiography is extremely
small, there are a number of complications that can occur. In most cases,
the complications occur within 2 hours after the test.
- There
is a slight risk of developing an allergic reaction to the iodine contrast
material. The reaction can be mild (itching, rash) or severe (difficulty
breathing or sudden shock). Death resulting from an allergic reaction
is rare. Most reactions can be controlled using medication. Be sure
to tell your doctor if you have allergies of any kind (such as hay fever,
iodine allergy, asthma, hives, or food allergies).
- There
is a small risk that the catheter may damage an artery or dislodge a
piece of clotted blood or fatty deposit from the artery wall. The dislodged
object can block blood flow and cause damage to the brain (stroke),
arm, leg, or intestine (bowel).
- Excessive
bleeding from the needle site in the artery is rare but possible. In
addition, a blood clot can form where the catheter was inserted. This
may cause partial blockage of a blood vessel to the arm or leg.
- Damage
to the kidneys is a possible risk that may lead to kidney failure. Contrast
material used during the test can cause excessive water loss or direct
damage to the kidneys. This is a special concern for people who have
kidney problems, diabetes, or dehydration. Special precautions are usually
taken during the test to prevent problems for people with these conditions.
- There
is always a slight risk of damage from being exposed to any radiation,
including the low levels of X-rays used for this test. However, if this
test is really needed, the risk of damage from the X-rays is usually
very low compared with the potential benefits of the test.
If you notice
weakness in the muscles of your face, vision problems, or slurred speech,
or if your leg or arm becomes cool, pale, or numb during or after the
procedure, notify your doctor immediately.
What
are the test results of an angiogram?
The doctor may be able to discuss some results immediately after the test.
Full results should be ready within 2 days.
Angiography
Normal:
- The contrast
material flows evenly through the blood vessels.
- No narrowing,
blockage, bulging, or other abnormality of the blood vessels is seen.
Abnormal:
- A narrow
spot in an artery may indicate a fatty deposit, clot, or other narrowing
that reduces blood flow through the blood vessel.
- Blood
vessels that are not in their normal position may indicate that a tumor
or other growth is pushing against them.
- A bulge
in a blood vessel may indicate a weakness in the blood vessel wall (aneurysm).
- An unusual
pattern of blood vessels may indicate the presence of a tumor.
- Contrast
material that leaks out of a blood vessel may indicate a bleeding blood
vessel.
What are the affects of an angiogram?
- Angiography
is not usually done for pregnant women because the X-rays could damage
the developing fetus.
- The
results of angiography may not be accurate if you cannot remain still
or hold your breath during the test.
- Blockage
of the blood vessels through which the catheter is guided may make it
difficult to position the catheter in the proper location for injecting
the contrast material.
What
to think about before you have
an angiogram?
- Magnetic
resonance angiography (MRA) and CT angiography are replacing conventional
angiography in many situations because these tests are less invasive
and easier to perform than conventional angiography. Results obtained
from MRA and CT angiography may sometimes be just as accurate as the
results obtained from conventional angiography (see the medical tests
Magnetic Resonance Angiography and CT Scan of the Body). However, some
surgeons may prefer having the results from a conventional angiogram
before proceeding with surgery to repair a damaged or abnormal blood
vessel.
- For
people with kidney problems, diabetes, or dehydration, steps may be
taken to prevent kidney damage. Less contrast material may be used,
and additional fluids may be provided before, during, and after the
test.
- In
the rare event that excessive bleeding occurs from the puncture in the
artery where the catheter is inserted, surgery may be necessary. There
is also a substance (called Angio-Seal) that can be used to help plug
the artery and stop the bleeding. The substance used to plug the artery
is normally absorbed by the body within several months.
- Digital
subtraction angiography (DSA) combines the X-ray techniques of angiography
with a high-speed computer to improve the X-ray pictures of blood flow
through the arteries. During DSA, two X-ray pictures are taken: one
before the contrast material is injected into a blood vessel, and a
second one after the contrast material is injected. A computer then
subtracts images of bone, tissues, and other interfering structures
that appear in the first picture from the second picture. The resulting
X-ray picture, displayed on a video monitor, shows only the blood vessels.
DSA requires less contrast material than standard angiography, but the
technique is more sensitive to movement of the person being tested.
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