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Holter monitoring is a
continuous recording of the ECG, usually for 24 hours, while the
patient goes about his or her usual daily activities. The test is
useful for detecting arrhythmias that may not appear during a resting
ECG at the doctor's office.
The event recorder is carried over a period
of days or weeks, and is used to record arrhythmias that occur infrequently.
When symptoms occur, the patient activates the recorder; the device
records and stores up to several minutes of heart rhythm.
The exercise ECG test (or treadmill test)
allows doctors to record the ECG during the stress of exercise.
It can help bring on arrhythmias that may not occur during a resting
ECG.
During an electrophysiology (EP) study,
special electrode catheters (long, flexible wires) are inserted
into veins and guided into the heart. Once inside, the catheters
can sense electrical impulses in various areas of the heart. The
study allows doctors to locate abnormal sites inside the heart that
may be causing serious arrhythmias.
Rapid Heart Rhythms
Rapid heart rhythms (tachycardias) may originate in the
atria, AV node, or ventricles. Because the ventricles do most of
the pumping, rapid rhythms in the ventricles are generally more
serious.
The ICD is used for treating life-threatening
rapid heart rhythms, such as VT and VE.
Ventricular Tachycardia (VT)
With VT, abnormal electrical pathways exist in the ventricles,
usually in an area of the heart muscle that has been damaged by
heart attack or disease. If an electrical signal enters such a pathway,
it may start traveling in a circular pattern. This may cause the
ventricles to contract with each cycle, and may result in a very
rapid heartbeat.
During VT, there is not enough time for the heart
to fill with blood between beats. As a result, the heart does not
pump blood as efficiently as it does during a normal rhythm.
If this rapid heartbeat continues, the brain and
body may not receive enough blood and oxygen. This may cause dizziness,
shortness of breath, chest pain or discomfort, or a fainting spell.
VT sometimes tends not to stop by itself. What's
worse, it may progress into ventricular fibrillation and cardiac
arrest.
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