Exercise
Electrocardiogram
(Exercise
ECG, Exercise EKG, Stress Test)
What
is an exercise electrocardiogram?
An electrocardiogram
(ECG or EKG) is one of the simplest and fastest
procedures used to evaluate the heart. Electrodes
(small, plastic patches) are placed at certain
locations on the chest, arms, and legs. When the
electrodes are connected to an ECG machine by
lead wires, the electrical activity of the heart
is measured, interpreted, and printed out for
the physician's information and further interpretation.
An exercise
ECG is performed to assess the heart's response
to stress or exercise. The ECG is monitored while
a person is exercising on a treadmill or stationary
bike. While this procedure is seldom used for
young children, it may be very useful in evaluating
adolescents and young adults.
An ECG
tracing will be taken at certain points during
the test in order to compare the effects of increasing
stress on the heart. Periodically, the incline
and treadmill speed will be increased in order
to make exercise more difficult for the person
being tested. If the person is riding a bicycle,
he/she will pedal faster against increased resistance.
In either circumstance, the person will exercise
until reaching a target heart rate (determined
by the physician based on age and physical status)
or until unable to continue due to fatigue, shortness
of breath, chest pain, or other symptoms.
Other
related procedures that may be used to assess
the heart include resting electrocardiogram (ECG),
Holter monitor, signal-averaged ECG, cardiac catheterization,
chest x-ray, computed tomography (CT scan) of
the chest, echocardiography, electrophysiological
studies, magnetic resonance imaging (MRI) of the
heart, myocardial perfusion scans, radionuclide
angiography, and ultrafast CT scan. Please see
these procedures for additional information.
The
heart's electrical conduction system:
The
heart is, in the simplest terms, a pump made up
of muscle tissue. Like all pumps, the heart requires
a source of energy in order to function. The heart's
pumping action comes from an intrinsic electrical
conduction system.
An electrical
stimulus is generated by the sinus node (also
called the sinoatrial node, or SA node), which
is a small mass of specialized tissue located
in the right atrium (right upper chamber) of the
heart.
The
sinus node generates an electrical stimulus regularly
at 60 to 100 times per minute under normal conditions.
This electrical stimulus travels down through
the conduction pathways (similar to the way electricity
flows through power lines from the power plant
to your house) and causes the heart's lower chambers
to contract and pump out blood.
The right and left atria (the two upper chambers
of the heart) are stimulated first and contract
a short period of time before the right and left
ventricles (the two lower chambers of the heart).
The
electrical impulse travels from the sinus node
to the atrioventricular (AV) node, where impulses
are slowed down for a very short period,
then continues down the conduction pathway via
the “bundle of His” into the ventricles.
The “bundle of His” divides into right
and left pathways to provide electrical stimulation
to both ventricles.
This
electrical activity of the heart is measured by
an electrocardiogram. By placing electrodes at
specific locations on the body (chest, arms, and
legs), a graphic representation, or tracing, of
the electrical activity can be obtained. Changes
in an EKG from the normal tracing may indicate
one or more of several heart-related conditions.
Reasons
for your physician to request an exercise ECG
include, but are not limited to, the following:
- to determine limits
for safe exercise in patients who are entering
a cardiac rehabilitation program and/or those
who are recovering from a cardiac event, such
as a heart attack (myocardial infarction, or
MI) or heart surgery
- to assess leg pain
with exercise (also called intermittent claudication)
in patients with suspected occlusion in the
legs' circulatory system
- to evaluate blood pressure
during exercise
- to assess stress or
exercise tolerance in patients with known or
suspected coronary artery disease
There
may be other reasons for your physician to recommend
an exercise ECG.
Because
of the stress the heart incurs during the procedure,
there is a small chance for chest pain, heart
attack, high blood pressure, irregular heartbeats,
dizziness, nausea, and extreme fatigue. Notify
your physician if you have the following conditions:
- aneurysm - a dilation
of a part of the heart muscle or the aorta (the
large artery that carries oxygenated blood out
of the heart to the rest of the body) which
may cause a weakness of the tissue at the site
of the aneurysm
- unstable angina (uncontrolled
chest pain)
- severe heart valve
disease
- severe congestive heart
failure
- recent myocardial infarction
(also called MI, or heart attack)
- severe hypertension
(high blood pressure)
- uncontrolled irregular
heartbeats
- pericarditis (an inflammation
or infection of the sac which surrounds the
heart)
- severe anemia (low
red blood cell count)
If you
are pregnant or suspect that you may be pregnant,
you should notify your physician.
Prolonged
application of the adhesive electrode patches
may cause tissue breakdown or skin irritation
at the application site.
There
may be other risks depending upon your specific
medical condition. Be sure to discuss any concerns
with your physician prior to the procedure.
Certain
factors or conditions may interfere with or affect
the results of the test. These include, but are
not limited to, the following:
- intake of a heavy meal,
caffeine, and/or smoking prior to the procedure
- high blood pressure
- electrolyte abnormalities,
such as too much or too little potassium, magnesium,
and/or calcium in the blood
- certain medications
- heart valve disease
- enlarged left ventricle
- Your physician or the
technician will explain the procedure to you
and offer you the opportunity to ask any questions
that you might have about the procedure.
- You will be asked to
sign a consent form that gives your permission
to do the procedure. Read the form carefully
and ask questions if something is not clear.
- You will be asked to
fast for a few hours before the procedure. You
should not smoke for two hours prior to the
procedure.
- If you are pregnant
or suspect that you may be pregnant, you should
notify your physician.
- Notify your physician
of all medications (prescription and over-the-counter)
and herbal supplements that you are taking.
- Wear flat shoes that
are comfortable for walking and loose-fitting
pants or shorts. Women should wear a short-sleeved
top that fastens in the front for ease of attaching
the ECG electrodes to the chest.
- The area(s) where the
electrodes are to be placed may be shaved.
- Based upon your medical
condition, your physician may request other
specific preparation.
An exercise
ECG may be performed on an outpatient basis or
as part of your stay in a hospital. Procedures
may vary depending on your condition and your
physician’s practices.
Generally,
an exercise ECG follows this process:
- You will be asked to
remove any jewelry or other objects that may
interfere with the procedure.
- You will be asked to
open your blouse or shirt in the front (men
may be asked to remove their shirts). The technician
will ensure your privacy by covering you with
a sheet or gown and exposing only the necessary
skin.
- If your chest, arms,
or legs are very hairy, the technician may shave
small patches of hair, as needed, so that the
electrodes will stick closely to the skin.
- Electrodes will be
attached to your chest, arms, and legs.
- The lead wires will
be attached to the skin electrodes.
- Once the leads are
attached, the technician may key in identifying
information about you into the machine's computer.
- A blood pressure cuff
will be attached to your arm while you are sitting
down. Initial, or baseline, ECG and blood pressure
readings will be taken while you are sitting
down and standing up.
- You will be instructed
on how to walk on the treadmill. Alternately,
you may exercise on a bicycle. You will be told
to let the technician, physician, or nurse know
if you begin to have any chest pain, dizziness,
lightheadedness, extreme shortness of breath,
nausea, headache, leg pains, or other symptoms
during exercise.
- You will begin to exercise
at a minimal level. The intensity of the exercise
will be gradually increased on the treadmill
by increasing the incline and speed of the treadmill
every few minutes.
- ECG and blood pressure
readings will be taken periodically during the
exercise to measure how well your heart and
body are responding to the exercise.
- The exercise will end
once you have reached a target heart rate (determined
by the physician based on your age and physical
condition). The test may also be stopped if
you develop severe symptoms such as chest pain,
dizziness, nausea, severe shortness of breath,
severe fatigue, or elevated blood pressure.
- Once you have reached
your target heart rate, the rate of exercise
will be slowed for a "cool down" period to help
avoid any nausea or cramping from sudden stopping
of exercise.
- You will sit in a chair
and your ECG and blood pressure will be monitored
until they return to normal or near-normal.
This may take 10 to 20 minutes.
- Once your ECG and blood
pressure readings are acceptable to the physician,
the ECG electrodes and blood pressure cuff will
be removed. You may then put on your shirt or
blouse.
You
should be able to resume your normal diet and
activities, unless your physician instructs you
differently.
Generally,
there is no special care following an exercise
ECG.
You
may feel tired for several hours or longer after
the procedure, particularly if you do not normally
exercise. Otherwise, you should feel normal within
a few hours after the procedure, if not sooner.
If your fatigue lasts longer than a day, you should
notify your physician.
Notify
your physician if you develop any signs or symptoms
you had prior to the test (e.g., chest pain, shortness
of breath, dizziness, or fainting).
Your
physician may give you additional or alternate
instructions after the procedure, depending on
your particular situation.
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