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Making Waves
33
Making Waves
Electrodes can be placed anywhere on the surface of the body to
record the heart’s electrical activity. If we do this, we quickly discover
that the waves recorded by a positive electrode on the left arm look
very different from those recorded by a positive electrode on the right
arm (or right leg, left leg,
etc.
).
It’s easy to see why. A wave of depolarization moving
toward
a
positive electrode causes a
positive
deflection on the EKG. A wave
of depolarization moving
away
from a positive electrode causes a
negative
deflection.
Look at the figure below. The wave of depolarization is moving left
to right,
toward
the electrode. The EKG records a positive deflection.
Now look at the following figure. The wave of depolarization is
moving right to left,
away
from the electrode. The EKG therefore
records a negative deflection.
Depolarization
EKG
Positive
electrode
A wave of depolarization moving toward a positive electrode records a
positive deflection on the EKG.