Nuclear Stress Tests
There are
four types of cardiolite stress tests:
1. Exercise cardiolite stress test
2. Persantine cardiolite
stress test
3. Adenosine cardiolite stress test
4. Dobutamine cardiolite
stress test
What
is Cardiolite?
Cardiolite is a nuclear radioactive isotope termed
Technetium Tc99m Sestamibi. Cardiolite
is injected through an IV and it travels in the bloodstream and through the
coronary arteries until it is picked up by the heart muscle cells. The
areas of the heart that have an adequate blood supply pick up the tracer
right away and more completely. Areas that do not have adequate blood
supply pick up the tracer very slowly or not at all.
Cardiolite gives off a small amount of radiation that
is detected with a nuclear scanning camera. A computer processes the information
and produces the images of the radioactivity distributed in the heart.
If an area
receives less blood than the rest of the heart (because of a blocked or
narrowed artery), it will pick up a lower level of radioactivity and will
show up as a lighter area, called a "defect."
Cardiolite is injected while you are at rest and while
your heart is under stress. Rest and stress images are taken to allow
doctors to compare how much blood flows through the heart muscle during
stress and at rest.
The amount
of radiation you will be exposed to is comparable to that from an X-ray or
CAT (CT) scan. The half-life of Cardiolite is
6.02 hours. This means that half of the dose you are given will decay in
6.02 hours.
Generally, Cardiolite is cleared from your body in 24 hours by
natural processes. You won't feel any different after you are injected with
Cardiolite. Most patients experience no side
effects. Occasionally patients have a metallic taste in their mouth.
What
is a Cardiolite Stress Test and what does it
show?
A Cardiolite Stress Test is a diagnostic nuclear imaging
study that uses a radioactive tracer, called Cardiolite,
to produce images of the heart muscle. When combined with stress either
through exercise or use of a pharmacological agent, the Cardiolite
scan helps determine if the heart muscle is getting the blood supply it
needs.
As Coronary
Artery Disease (CAD) progresses, the heart muscle may not receive enough
blood when under stress (for example, when exercising). This often results
in chest pain called angina pectoris. On the other hand, there may be no
outward physical signs of the disease. If CAD is limiting blood flow to
part of your heart, the stress test with Cardiolite
may be useful in detecting the presence and significance of CAD.
A Cardiolite Stress Test consists of two parts, rest and
stress:
- Cardiolite will be administered by
injection through your IV while you are at rest, and a special camera
will take pictures of your heart.
- Cardiolite will be administered to you
one other time by an IV injection during the stress portion of the
test, and additional pictures will be taken of your heart.
This allows
the doctor to compare the amount of blood flowing through the heart muscle
during stress and at rest.
Example
of a Nuclear Stress Test Film That Is Read By A Radiologist
How
do I prepare for the test?
- Do not eat or drink for 4
hours prior to the test--this includes caffeine! The pictures of your
heart are clearer when the stomach is not full. If you are diabetic or
need to eat/drink with your medication, get special instructions from
your doctor.
- Avoid any strenuous physical
activity on the day of the test because you will need to exert
yourself maximally if you are doing an exercise test.
- Bring busy material. You
will have periods of waiting throughout the test so bring a book,
newspaper, knitting, etc. to keep you busy.
- No smoking 4 hours prior to
the test. Smoking may interfere with the test results.
- Wear a comfortable two-piece
outfit and comfortable shoes. A hospital gown may be provided and men
may be asked to take off their shirt. Slacks or shorts are preferred
if you are exercising. You should wear comfortable footwear
appropriate for brisk exercise if you are doing an exercise test.
- Do not wear oils or lotions
before your test. Small sticky patches (electrodes) will need to stick
to your chest.
- Do not take the following
heart medications on the day of your test unless your physician tells
you otherwise or if the medication is needed to treat chest
discomfort:
- Isosorbide dinitrate
(for example: Isordil, Sorbitrate)
- Isosorbide mononitrate
(for example: Ismo)
- Nitroglycerin (for example:
Deponit, Nitrostat)
- Your physician 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 physician.
NOTE: Do not discontinue any medication without first talking with
your physician
What
happens during the test?
When you
enter the stress testing room, the Cardiology Tech/Nurse will have you sign
a consent form and he/she will make sure you understand the test. An IV
will be started in a vein in your arm. The Nuclear Medicine Tech will put
your first injection of Cardiolite through the
IV. You will wait in the waiting room for at least 45 minutes to let the Cardiolite circulate to your heart.
Once your
waiting period is over, the Nuclear Medicine Tech will put you under the
camera for about 15 minutes. You will lay on your back on a table with your
hand behind your head. It is important for you to remain very still while
the images are being taken. The camera will move about you but never come
in contact with you during the scan.
Following
the completion of the scan, you will be escorted to a stress testing room.
The Cardio Tech/Nurse will have you lay on a stretcher while he/she hooks
you up to equipment. A bag of normal saline will be attached to your IV.
The chest will be abraded with alcohol and a cloth. If you have a hairy
chest, patches will be shaven. Ten electrode patches are placed on your
chest and torso. Wires will be attached to the electrodes in order to
monitor your heart rate and EKG. A resting EKG and blood pressure are
recorded. Once the Cardiologist arrives in the room, your test will begin.
Persantine Cardiolite
Stress Test
 For patients who are unable to exercise
adequately on the treadmill, the drug Persantine
may be given to produce an effect on the heart similar to exercise. During
the test, you will be lying on the stretcher. A line of normal saline will
be connected to your IV. The drug Persantine will
be infused through your IV. The Persantine dosage
you will be given is based on your body weight. Persantine
is a vasodilator so you may feel warm, flushed, experience chest pressure,
headache, dizziness, nausea or shortness of breath. These symptoms are
perfectly normal, but make sure to let the Cardiologist know how you feel.
The Persantine is infused over 4 minutes. Two
minutes will lapse. Then you will be given another injection of Cardiolite. After the Cardiolite
injection, you will be given the drug Aminophylline
if you are experiencing any symptoms from the Persantine.
In some cases, the Cardiologist will have you perform hand squeezing
exercises to help get more accurate test results.
What
is Persantine?
Persantine is a coronary vasodilator that is used as a
diagnostic agent in nuclear stress testing. Persantine
works by increasing the blood vessel circumference of the coronary arteries
(arteries that feed the heart) in order to increase blood flow to the
heart. Persantine causes a 20% increase in heart
rate and a mild but significant decrease in systolic and diastolic blood
pressure. Persantine is metabolized in the liver.
The amount of Persantine you will be given is
based on your body weight.
Side effects
include: chest pain/pressure, dizziness, headache, nausea, dizziness,
shortness of breath, or a warm and flushed feeling. Some patients
experience a burning or stinging sensation at their IV site because Persantine is more acidic than your blood. Persantine is contraindicated in patients who have a
hypersensitivity to this drug. Persantine can
also cause bronchospasm so your doctor may order
a different test for you if you have a lung condition that will be
exacerbated by using Persantine.
If you do develop side effects to Persantine, the
Cardiologist will use the antidote Aminophylline
to reverse your side effects.
Adenosine
Cardiolite Stress Test
An adenosine
cardiolite stress test is identical to a Persantine cardiolite stress
test, using a different dilating medication, Adenosine.
What
is Adenosine?
Adenosine is
an antiarrhythmic agent that is used as a diagnotic agent in nuclear stress testing. Adenosine
acts as a vasodilator and its actions are similar to that of Persantine. It also increases the blood vessel
circumference of the coronary arteries (arteries that feed the heart) in
order to increase blood flow to the heart. Adenosine has a short half-life
(less than 10 seconds). This means, any side effects you may experience
will be generally predictable, short lives, and easily tolerated. Side
effects include: chest pressure, dizziness, shortness of breath, flushing, headache,
lightheadedness, nausea, or numbness. Adenosine is contraindicated in
patients who have a hypersensitivity to this drug and in patients who have
a known or suspected bronchospastic or bronchoconstrictive lung disease (e.g., asthma).
If you do
develop side effects to Adenosine that do not disappear quickly, the
Cardiologist will use the antidote Aminophylline
to reverse your side effects.
Dobutamine Cardiolite
Stress Test
For patients
who are unable to exercise adequately on the treadmill, the drug Dobutamine may be given to produce an effect on the
heart similar to exercise. During the test, you will be lying on the
stretcher. A line of normal saline will be connected to your IV. The drug Dobutamine will be infused through your IV. The Dobutamine dosage you will be given is based on your
body weight. Dobutamine is infused slowly through
your IV, and the dose is increased every 3 minute. The Dobutamine
infusion is turned off after it is infused for about 12 minutes. The Dobutamine may be turned off early if:
- You exceed a
"target" heart rate based on your age
- The Cardiologist or Cardio
Tech/Nurse detects abnormal changes on your EKG
- You experience significant
symptoms, such as shortness of breath, chest pain, chest tightness,
dizziness, etc. that do not permit you to exercise any longer.
- Your blood pressure goes up
too high
The dobutamine is infused longer than the 12 minutes if
your heart rate has not reached the predicted "target" heart
rate. Sometimes the Cardiologist will have the Nurse give you a drug called
Atropine through your IV if your heart rate has not sufficiently increased.
You will be given one more injection of Cardiolite
once your heart rate is at or has exceeded your "target" heart
rate. Sometimes the Cardiologist will have the Nurse give you a drug called
Lopressor through your IV if your heart rate is
taking a long time to decrease.
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