Electrocardiogram(ECG) Recording
Electrocardiogram (ECG or EKG)
The ECG is the basis for all arrhythmia diagnosis. The ECG tracing is a series of
waves that represent the electrical events of the various chambers and conduction
pathways within the heart. The small initial wave, called the P wave, represents the
electrical activation of the atria. Next comes the QRS complex, the tallest wave on
the ECG, representing the stimulation of the ventricles. Finally, the T wave
represents the period when the ventricles recover their electrical forces so they may
be stimulated again.
Long-Term ECG Recording
Patients with heart rhythm irregularities or heart rhythms which are not documented
on the routine electrocardiogram will usually require some type of home or ambulatory
monitoring. Quite often the person's symptoms occur only once a day, once a week,
once a month, or even less often. There are recording methods that allow such
infrequent event to be captured and analyzed. The electrophysiologist might use any
or all of these methods and techniques. The methods are 24-hour Holter recording,
loop continuous recording and transtelephonic event recording.
 Holter monitoring is a
continuous recording of the ECG for 24 hours. Ideally the patient goes about his
her usual daily activities. The patient should keep a diary to allow the doctors to
correlate activities and symptoms with the ECG recording. The monitor itself is a
small, portable recorder worn on a strap over the shoulder or around the waist.
Several electrodes are placed on the patient's chest and connected by wires to
the recorder. The patient is instructed to keep a diary while wearing the recorder
so that correlations can be made between the symptoms and the rhythm. The ECG is
recorded continuously on tape (or on computer chips). The tape recording will be
analyzed by a computer and a summary will be prepared with tracing of the recording
of selected times for interpretation by the doctor.
When symptoms presumed to be due to a rhythm disturbance occur less frequently than
once during a single 24- or 48-hour period, an event recorder may be used. Event
recorders are small devices capable of recording short episodes of ECG which are
not worn at all times. When you have symptoms, you attach the device to your body
temporarily, usually by putting on bracelets that attach to the recorder or by
pressing the device itself against your chest. You then press a button on the
device to start a recording of your heart rhythm. The recording lasts for up to a
minute. The electrocardiogram that is recorded is transmitted over the telephone to
the electrophysiologist's office for interpretation. The event monitor is lent
to patients for one month at a time with instructions regarding its use. Event
monitors are ideal for recording sustained rhythms that allow the patient the time
and the capacity to capture the event.
This is an ECG recorder which records only a few minutes worth of the
electrocardiogram at a time on a computer chip. It continuously records new
information and discards the oldest information, so that at any time it has in
memory only the last few minutes of your electrocardiogram. When you have symptoms,
you can "freeze" the recording in the device's memory. The frozen
recording can then be transmitted over the telephone to the physician's office
for him or her to review. Since the loop recorder is continuously refreshing its
memory, the loop recorder can be carried for long periods. Loop recorders are ideal
for capturing brief episodes when it takes too long to apply an event recorder or
for capturing ECG recordings of episodes that are associated with incapacitating
symptoms such as syncope.
Implantable Loop Recorder (ILR)
The ILR is a continuous loop recorder that is implanted in the body under the skin.
Like a continuous loop recorder applied to the body surface, the ILR is useful for
diagnosing infrequent rhythm problems associated with incapacitating symptoms, such
as syncope. No external electrodes or power source is required. The patient or a
bystander uses a small hand-held activator which communicates through the skin with
the ILR to "freeze" the ECG surrounding the event. The stored data is
then retrieved by the physician using a second computer to communicate with the ILR
through the skin. The device can be reset to record subsequent events. Minimally
invasive subcutaneous placement of the ILR in the chest area can be performed with
local anesthesia, sometimes even in the doctor's office.
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