The Electrocardiogram:
Basic Concepts and Lead
Monitoring
Chapter 2
Robert J. Huszar, MD
Instructor
Patricia L. Thomas, MBA, RCIS
Electrical Basis of the
Electrocardiogram
 Graphic
record of magnitude and
direction of electrical activities or
current
 Generated by Depolarization and
Repolarization
Components of the Electrocardiogram




P-wave
QRS wave
T wave
Segments
– PR
– ST
– TP

Intervals
– PR
– QT
– R-R

J Point
EKG PAPER

Vertical Lines
– Dark lines are .20 second (5 mm) apart
– Light lines are .04 second (1 mm) apart

Horizontal Lines
– Dark Lines are 5 mm apart
– Light Lines are 1mm apart
Large Square 5 x 5 mm
 One Small Square 1x1 mm

Artifacts
 Tense
or Nervous patients
 Shivering from cold
–Gives EKG finely or coarsely
jagged appearance
 Poor electrical contact with skin
 Dried electrode paste or jelly
Artifacts
 Improperly
grounded
 AC-operated ECG Machine
 Obtained near high tension
wires, transformers or electric
appliances
Artifacts
 Signals
are poorly received over
a biotelemetry system
 When transmitter’s power is
low because or week batteries
Artifacts
During
CPR
Causes regularly spaced,
wide, upright waves
synchronous with the
downward compressions of
the chest
12 Lead ECG

Six Limb or Extremity Leads
– Three standards (bipolar) limb leads
– Leads I, II & III

Three Augmented (unipolar) Leads
– Leads aVR, aVL, & aVF

Six Precordial (unipolar)
– Leads V1, V2, V3, V4, V5 & V6
12 Lead ECG

Lead I
– Left arm (+)
– Right arm (-)

Lead II
– Right arm (-)
– Left leg (+)

Lead III
– Left arm (-)
– Left leg (+)
12 Lead ECG

Central Terminal
– Formed by connecting the extremity electrodes
together which is negative

aVR
– Right arm (+)

aVL
– Left arm (+)

aVF
– Left leg (+)
12 Lead ECG

V1
– Right of sternum in the fourth intercostal space

V2
– Left of sternum in the fourth intercostal space

V3
– Midway between V2 & V4

V4
– Midclavicular line in the fifth intercostal space

V5
– Anterior axillary line at the same level

V6
– Midaxillary line at the same level V5
THE END
OF
CHAPTER 2
Hauszar Robert, Basic Dysrhythmias, Interpretation & Management, Third
Edition, Mosby, Inc. 2002, pp. 1-20.
Bledsoe.Porter.Cherry.”Paramedic Care: Principles & Practice, Prentice-Hall, Inc.
Volume 3. 2001. Pp. 90- 93