Mary Dunlap
Spring 2015
ECG

Electrocardiogram, which can be referred to
as an ECG or EKG, is a graphic
representation of the hearts electrical
activity over time.
Electrocardiography records the electrical
current activity in the heart by electrodes
that are placed on the patients skin.
Electrocardiography

ECG Paper

ECG paper is a grid where time is
measured along the horizontal axis moving
from left to right
Each small square is 1mm in length and
represents 0.04 seconds
Each larger square is 5mm in length and
represents 0.20 seconds
ECG Paper Continue

Hash marks that are located on the top of the
paper mark time.
From one hash mark to the next is 5 large
squares which is 1 second.
Voltage is measured along the vertical
axis(top to bottom) and each small square
represents 1mm or 0.1 millivolt(mV)
ECG Paper

Cells of the Heart

Myocardial cells contract to propel the blood
out of the her chambers
Pacemaker cells and electrical conducting
cells are responsible for generating and
carrying impulses throughout the heart.
Cardiac Electrophysiology

Automaticity, excitability, conductivity, and
contractility are the four characteristics of the
cardiac cells.
Cardiac Electrophysiology

Automaticity is the ability of cardiac
pacemaker cells to generate an electrical
impulse spontaneously and repetitively.
Other muscles in the body require
stimulation from the nervous system.
Excitability the ability of non-pacemaker
cells to respond to an electrical stimulus.
Cardiac Electrophysiology

Conductivity the ability of cardiac cells to
receive an electrical stimulus and then
conduct it to other cardiac cells
Contractility the ability of myocardial
cells to shorten, causing myocardial
contraction in response to an electrical
stimulus.
Nerve Impulse and Muscle
Contraction

A muscle must be electrically stimulated to
contract.
Myocardial cells are bathed in electrolyte
solution
Na+, K+ and Ca++ are the primary
electrolytes responsible for initiating this
process
Nerve Impulse and Muscle
Contraction

Polarized or Ready State- Muscle is relaxed and
ready to receive electrical impulse. The cell has a
high concentration of negatively charged ions
inside the cell and positively charged ions
outside the cell. The difference in the ions inside
and outside the cell is know as a resting
membrane potential (RMP). K+ is inside the cell
& Na+ and Ca++ are found outside the cell.
Nerve Impulse and Muscle
Contraction

Depolarization (P wave)- electrical stimulus
causes the cell membrane to become
permeable allowing the Na+ & Ca++ to inter
the cell while K+ flows into the cell. This
causes shorting of the muscle fibers leading
to myocardial contraction.
The change in electrical charge is referred to
as action potential and is measured in
millivolts (mV)
Nerve Impulse and Muscle
Contraction

Repolarization (The recovery phase)process of restoring the cell to it’s polarized
state. As the K+ flows out of the cell this
process is initiated. The sodium-potassium
pumps move the Na+ & Ca++ out of the cell.
The cell returns to its’ original negative state
Nerve Impulse and Muscle
Contraction

Refractory Period- the time between the
end of the contraction and the return to
ready state. This period is divided into two
phases Absolute Refractory Period and
Relative Refractor Period.
Nerve Impulse and Muscle
Contraction

Absolute Refractory- cells are not
repolarized and can not be stimulated to
conduct an electrical impulse and contract
again. This prevents spasm producing
(tetanic) contractions. This period is
measured from QRS through the 1st 3rd of the
T wave
Nerve Impulse and Muscle
Contraction

Relative Refractor Period- cells have
repolarized to a point that some cells can
again be stimulated to depolarize if the
stimuli is strong enough. The impulse may
be slow and an abnormal pattern may be
noted. This period starts at the end of the
Absolute Refractory Period to the end of
the T wave and is a vulnerable period
Cardiac Conduction System

Cardiac Conduction System

SA node (pacemaker cells) is the hearts primary
pacemaker and generates 60 to 100 impulses per
min. It is located high on the posterior wall of the
right atrium, just below the opening of the
superior vena cava under the epicardium. It
initiates the electrical impulse that travels
downward throughout both the R & L atrium
causing depolarization. The impulse is then
transmitted to the AV node.
Cardiac Conduction System

Atrioventricular (AV) node lies on the floor
of the R atrium above the ventricle. This is the
only pathway for the impulse, generated from
the SA node, to travel from the atrium to the
Bundle of His in the ventricles.
AV node if needed can act as the secondary
pacemaker generating 40 to 60 impulses per
minute
Cardiac Conduction System

Bundle of His is located below the AV node and
continues transmitting the impulse to the bundle
branches.
The bundle passes through an opening in the
fibrous skeleton to the interventricular septum
where it divides into the L & R bundle branches
(BB). The R branch goes to the R ventricle, while
the L branch goes to the L ventricle.
Cardiac Conduction System

Purkinje fibers is where the R & L bundle
branches transmit their impulses to as well
as terminate. The countless number of
Purkinje Fibers extend into the muscle walls
of the ventricles, where they transmit the
impulses.
Purkinje fibers and BB can initiate an
impulse at a rate of 20 to 40 beats per min.
Cardiac Conduction System

 http://www.youtube.com/watch?v=qiIUrCe2Sxs
 http://www.youtube.com/watch?v=te_SY3MeWys
Basic ECG Complex

P wave
PR segment
PR interval
Q wave
QRS complex
J point
ST segment
T wave
U wave
QT interval
Basic ECG Complex

Basic ECG Complex

P wave indicates SA node function and atrial
depolarization and preparation for contraction.
First positive upward defection,
Normal length 0.06 to 0.10 sec
Amplitude 0.5 to 2.5 mm
PR segment time required for the impulse to
travel through the AV node (where it is
delayed), bundle of His, BB, & Purkinje fibers,
just prior to ventricular depolarization
Basic ECG Complex

PR interval time it takes an impulse to be
conducted through the Atria & AV node, until
the impulse begins to cause ventricular
depolarization. It is measured from the
beginning of the P wave to the end of the PR
segment. Normal length 0.12 to 0.20 sec
Q wave is the first negative (downward)
deflection
Basic ECG Complex

QRS Complex ventricular depolarization
and conduction of impulse from AV node
through ventricular muscle. It is measured
from the beginning of the Q wave to the J
point. Normal length 0.04-0.10 sec.
J point the junction where the QRS complex
ends and the ST segment begins
Basic ECG Complex

ST segment early ventricular repolarization
and measured from end of S to beginning f T
wave can flat(normal), elevated, or depressed
T wave ventricular repolarization. The wave
may be above or below the isoelectric line. T
wave depressed frequently indication of
previous cardiac ischemia. Wave greater than
½ the height of QRS complex
Basic ECG Complex

U wave (not always present)late
ventricular repolarization, may indicate
hypokalemia
QT interval total time required for
ventricular depolarization & repolarization.
Measured from QRS complex to end of T
wave
ECG Complex Video

 http://www.youtube.com/watch?v=4vkbywows-o
ECG Rhythm Analysis

The Nine Step Process
assesses the main elements of
an ECG tracing
ECG Rhythm Analysis

Determine the heart rate
Is it normal, fast or slow?
Count the Number of R waves during a 6
sec period and then multiply by 10 to
determine the number of beats per min
Normal rate is 60 to 100 beats/min
ECG Rhythm Analysis

Determine the heart rhythm
Is it regular or irregular?
Is the distance the same between consecutive
P waves & QRS complexes?
ECG Rhythm Analysis

Analyze the P wave
Are they present?
Do they occur regularly?
Amplitude 0.5 to 2.5 mm
Duration 0.06 to o.10 sec
Is there a P wave for each QRS complex?
Are the P waves smooth, round, upright?
Do they all look similar?
ECG Rhythm Analysis

Measure the PR interval
Are they identifiable?
Are they within normal limits (0.12-0.20 sec)?
Are they constant across the tracing?
ECG Rhythm Analysis

Measure the QRS duration
Are they within normal limits (0.04-0.10sec) ?
Are the complexes of equal duration ?
Do thy all look alike ?
ECG Rhythm Analysis

Assess ST segment;
Duration 0.08 to 0.12 sec. or less
Is it a flat, elevated or depressed line?
Elevated segment of 1 mm or more above the
baseline may indicate myocardial injury
ECG Rhythm Analysis

Asses T waves; is it upright and normal
height, inverted, peaked or flattened?
Should follow ST segment
Configuration upright
Amplitude no higher than 5mm
Deflection same direction as the preceding
QRS complex
ECG Rhythm Analysis

Assess QT intervals; normal duration
0.36 to 0.44 sec.
U waves; are they present?
ECG Rhythm Analysis

 ECG ANALYSIS you tube VIDEO
 Basic ECG interpretation
 Understanding an ECG
 Mechele Kuntz basic overview
Power Point Recourses

Fast & Easy ECG’s (2e) Bruce Shade
Medical Surgical Nursing 6th ed
Ignatavicius & Workman
Medical Surgical Nursing 5th ed LeMone, Burke,
& Bauldoff
Linda Ball, RN, BSN, CCRN, CEN
Educator for Central Florida Health Alliance