Why
look to the EKG?
The electrocardiogram (EKG) is a device that receives electric impulses
from the body and changes them into a monitor tracing that can be
analyzed to find problems with electrical conduction in the heart.
The EKG simply picks up electrical impulses; it does not read mechanical
activity. When a patient has ischemia, injury or necrosis to the
heart muscle, the electrical impulses change in the area involved.
Nurses can analyze the electrical changes
and determine if they indicate mechanical dysfunction.
Why
use 12-Leads?
Traditional EKG monitoring is done with a single lead to assess
for arrhythmias. However, a single lead provides only a single view
of the heart. Consider the following analogy: if you were buying
a house and wanted to show your friends what it looked like, a picture
would give them some idea of the size and shape of the house. One
picture wouldn’t show the sides or the back of the house,
nor would it represent the layout of the house on the land it is
on. Several pictures would do a much better job.
If you
were to walk around the house and take pictures, you could show
the back and sides of the house. How about an aerial photo? That
would really show the lay of the land! These are the concepts behind
the 12-lead EKG: the limb leads walk around the house, while the
chest leads give the aerial view. By using twelve different views,
many different parts of the heart can be assessed.
Changes
on the 12-lead
The EKG is simply a volt meter that picks up electrical signals.
Therefore, anything that interferes with electrical conduction can
cause changes in the EKG. These variables can be divided into three
main categories: 1) physiological variables not specific to the
heart (ie. pulmonary embolism, increased intracranial pressure),
2) electrical interference (ie. poorly placed lead), or 3) ischemia,
injury, or infarction.
The
5 Steps to 12-Lead Interpretation will help you differentiate between
non-specific causes of EKG changes and actual cardiac problems by
applying five simple rules:
5
Steps to 12 Lead Interpretation
1. Assess regularity and speed
2. Look for signs of infarction
3. Present in >1 lead, but not all?
4. Assess associated conditions
5. Correlate with clinical condition
To learn
more about the “5-steps”, see level
2.
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