Holter
Monitor
(Continuous
Electrocardiogram, Continuous ECG, Ambulatory
ECG Monitoring)
What
is a Holter monitor?
The
Holter monitor is a type of electrocardiogram
(ECG or EKG) used to monitor the ECG tracing continuously
for a period of 24 hours or longer. An ECG 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.
When
symptoms such as dizziness, fainting, low blood
pressure, prolonged fatigue, and palpitations
continue to occur without a definitive diagnosis
obtained with a resting ECG, an exercise ECG,
or a signal-averaged ECG, your physician may request
an ECG tracing to be run over a long period of
time, using the Holter monitor.
Certain
dysrhythmias/arrhythmias (abnormal heart rhythms),
which can cause the symptoms noted above, may
occur only intermittently, or may occur only under
certain conditions, such as stress. Dysrhythmias
of this type are difficult to obtain on an ECG
tracing that only runs for a few minutes. Thus,
the physician will request a Holter monitor to
allow a better opportunity to capture any abnormal
beats or rhythms that may be causing the symptoms.
The Holter monitor records continuously for the
entire period of 24 to 48 hours. Some Holter monitors
may record continuously but also have an event
monitor feature that you activate when symptoms
begin to occur.
You
will receive instructions regarding how long you
will need to wear the recorder (usually 24 to
48 hours), how to keep a diary of your activities
and symptoms during the test, and personal care/activity
instructions.
What
is an event monitor?
Event
monitoring is very similar to Holter monitoring,
and is often ordered for the same reasons. With
an event monitor, you wear ECG electrode patches
on your chest, and the electrodes are connected
by wire leads to a recording device. Unlike the
Holter monitor, however, which records continuously
throughout the testing period of 24 to 48 hours,
the event monitor does not record until you feel
symptoms and trigger the monitor to record your
ECG tracing at that time.
When
you feel one or more symptoms, such as chest pain,
dizziness, or palpitations, you push a button
on the event monitor recorder. Some monitors have
a feature (memory loop recorder) which captures
a short period of time prior to the moment you
triggered the recording and afterwards. This feature
can help your physician determine more details
about the possible change in your ECG at the time
the symptoms started, and what was happening with
your ECG just before you triggered the recorder.
Other monitors, called "post-event recorders,"
simply start recording your ECG from the moment
you trigger it.
Post-event
recorders are quite small - some may even be worn
on the wrist (similar to a wristwatch). Memory-loop
recorders are about the size of a pager.
After
you experience symptoms and record them, you will
send the recording of the event to your physician
or to a central monitoring center. This transmission
is done over the telephone. You will be instructed
regarding how to do this on the recorder. You
will also keep a diary of your symptoms and corresponding
activities (as done during the Holter monitoring
procedure).
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 ECG from the normal tracing may indicate
one or more of several heart-related conditions.
Some
reasons for your physician to request a Holter
monitor recording or event monitor recording include,
but are not limited to, the following:
- to evaluate chest pain
not reproduced with exercise testing
- to evaluate other signs
and symptoms which may be heart-related, such
as fatigue, shortness of breath, dizziness,
or fainting
- to identify irregular
heartbeats or palpitations
- to assess risk for
future heart-related events in certain conditions,
such as idiopathic hypertrophic cardiomyopathy
(enlarged heart due to unknown reasons), post-heart
attack with dysfunction of the left side of
the heart, or Wolff-Parkinson-White syndrome
(a condition in which an additional electrical
pathway carries an impulse from the atria to
the ventricles, causing rhythm problems)
- to assess the function
of an implanted pacemaker
- to determine the effectiveness
of therapy for complex arrhythmias
There
may be other reasons for your physician to recommend
the use of a Holter monitor.
The
Holter monitor is a noninvasive method of assessing
the heart’s function. Risks associated with
the Holter monitor are rare.
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 wearing the monitor.
Certain
factors or conditions may interfere with or affect
the results of the Holter monitor reading. These
include, but are not limited to, the following:
- close proximity to
magnets, metal detectors, high-voltage electrical
wires, and electrical appliances such as shavers,
toothbrushes, and hair dryers
- smoking, certain medications
- excessive perspiration,
which may cause the leads to loosen or detach
- Your physician will
explain the procedure to you and offer you the
opportunity to ask any questions that you might
have about the reading.
- Fasting is not required.
- 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.
A Holter
monitor recording is generally performed on an
outpatient basis. Procedures may vary depending
on your condition and your physician’s practices.
Generally,
a Holter monitor recording follows this process:
- You will be asked to
remove any jewelry or other objects that may
interfere with the reading.
- You will be asked to
remove clothing from the waist up in order to
attach the electrodes to your chest. 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 and the
Holter monitor will be attached to the electrodes
with lead wires. The monitor box may be worn
over the shoulder like a shoulder bag, or it
may clip to a belt or pocket.
- Once you have been
hooked up to the monitor and given instructions,
you can return to your usual activities, such
as work, household chores, and exercise, unless
your physician instructs you differently. This
will allow your physician to identify problems
that may only occur with certain activities.
- You will be instructed
to keep a diary of your activities during the
recording period. You should write down the
date and time of your activities, particularly
if any symptoms, such as dizziness, palpitations,
chest pain, or other previously-experienced
symptoms, occur.
You
should be able to resume your normal diet and
activities, unless your physician instructs you
differently.
Generally,
there is no special care following a Holter monitor
recording.
Notify
your physician if you develop any signs or symptoms
you had prior to the recording (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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