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Module title = Tutorial: Basic Electric Stuff
Lesson title = The Precordial leads
This is lesson 4 of 7 in this module
In the last lesson, we discussed the limb leads. In this lesson, we will discuss the precordial leads.
The precordial leads function in the exact same manner as do the limb leads. There are 2 primary differences, however:
The first difference is
location
. See the diagram below to see how they are arranged.
The second difference is that these leads
only use 1 electrode
.
The limb leads are called
bipolar
leads. Because precordial leads have only 1 electrode, they are called
unipolar
leads.
However, the precordial leads do have a second electrode: it is the sum of the 3 electrodes used for limb leads and functions like an electrical "ground". Think of this other lead as existing in the middle of the chest. In the diagram above, this is represented by the
blue dotted circle
. Each black arrow represents each of the 6 precordial leads and the direction of the arrow indicates the positive direction.
As a result of the "location" of the ground lead being in the center of the chest, the precordial leads measure electrical activity that is moving in a
front-back
(or back-front) direction and/or a
right-left
(or left-right) direction. Unlike the limb leads, they
do not
measure any signals in the up-down (head-toe) direction. This is called the axial plane, shown in image below.
To summarize the
limb leads
(previous lesson) vs. the
precordial leads
:
-
limb leads
: up-down and right-left directions
-
precordial leads (V
1
to V
6
)
: front-back and right-left directions
Note that "right-left" direction means right to left, or left to right, in both diections. The same applies for "front-back".
Lesson 4 of 7
That was the last lesson!