Transcript 03 ECG Leads

ECG LEADS
Chapter 3
introduction
The heart produces electrical currents
The body acts as a conductor of electricity
introduction
An ECG is a recording of the
electrical activity of the heart
Different “views” of the heart
can be recorded using
different electrodes
INtroduction
Electrodes are able to measure the voltages of the
cardiac current
Electrodes
Electrodes
V1: Fourth intercostal space to the right of the
sternum.
V2: Fourth intercostal space to the Left of the
sternum.
V3: Directly between leads V2 and V4.
V4: Fifth intercostal space at midclavicular line.
V5: Level with V4 at left anterior axillary line.
V6: Level with V5 at left midaxillary line. (Directly
under the midpoint of the armpit)
Electrode placement
Electrode and Lead are not the same thing.
Leads
12 possible leads
Six limb (extremity) leads
Bipolar leads: I, II, and III
Unipolar leads: aVR, aVL, aVF
Six chest (precordial) leads
limb leads
Electrodes
Right arm
Left arm
Left leg
Right leg (ground)
lead i
LA = electrical voltages of the
heart that are transmitted to the
left arm
RA = electrical voltages of the
heart that are transmitted to the
right arm
The electrocardiograph
sustracts RA from LA and the
difference appears as lead I.
lead i
Lead one ‘travels’ horizontally.
Its left pole (LA) is postive and
its right pole (RA) is negative.
Therefore, lead I = LA minus
RA
Shows a positive wave when
an impluses moves towards the
left arm, negative wave when
an impuse moves away from
the left arm.
Lead II
Lead II points downward
diagonally
Lower pole (LL) is positive
and upper pole (RA) is
negative.
Lead II = LL minus RA
Lead III
Lead III points downward
diagonally
Lower pole (LL) is positive
and upper pole (LA) is
negative.
Lead III = LL minus LA
Bipolar Leads
Unipolar or Augmented limb
leads
Record the electrical voltages
at one location rather than
relative to the voltage at
another electrode
limb leads
aVR + aVL + aVF = 0
Limb leads
Bipolar leads & Unipolar (or augmented)
leads
Frontal plane
Limb leads
chest leads
V1 to V6
unipolar
horizontal plane
front to back
Chest Leads
ALL 12 leads
Frontal Plane
Horizontal
Plane
Monitor leads
12 leads are not always necessary
Sample of a monitor lead
V1 (positive)
Right shoulder (negative)
Left shoulder (ground)
Holter Monitors