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The EKG
The electrocardiogram, or EKG, tests the heart's electrical conduction
system and provides a graphic record of the electrical impulses produced during
each heartbeat. The EKG is almost always the first test a patient undergoes as
part of a comprehensive heart evaluation, which is performed
routinely in the doctor's office. Its role in diagnosis is first to establish a
baseline record for comparison with future EKGs. But often the EKG serves as the
quickest route to a diagnosis when a patient is experiencing chest pain or
blackouts that may be the result of heart disease.
Referred to as a "resting" or "baseline"
EKG, the test only requires about 10-15 minutes and is performed with the
patient lying down on a bed or examination table. A 12-lead EKG is the standard
for diagnostic evaluations and requires placement of 10 electrodes. These
electrodes are only sensing devices and cannot generate an electrical shock. The
procedure is painless and the skin may be prepared beforehand with a jelly-like
substance to promote the sending and conveyance of electrical impulses.
The EKG machine translates the electrical signals received from the heart
into tracings on graph paper. These tracings, called waveforms, show how well
the impulses for contraction and relaxation of the heart muscle are generated
and transmitted to reveal the presence or likelihood of certain problems when
the waveforms are abnormal. Abnormalities detected with the standard 12-lead
electrocardiogram are not always definitive. For example, some individuals with
no heart disease may produce an abnormal EKG. Further testing may be required to
rule out heart disease. Additionally, a person with significant heart disease
may produce a normal EKG.
Most often, the EKG is used to obtain:
- Baseline data for comparisons with future EKGs or with findings from other tests
- Rapid evaluation of chest pain for signs of myocardial ischemia or infarction
- Rapid evaluation of heart rate and rhythm abnormalities
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