What you as the
medic needs to
SPC Farrar, Shawna
Task, Conditions, Standards
• Task: To instruct 68W in understanding
and recognizing specific cardiac rhythms
• Conditions: Classroom setting full of
highly motivated Lifeline Medics
• Standard: Ensure all personnel in
attendance understand the basic rhythms
and can identify basic components on an
EKG vs ECG
• Electrocardiogram (EKG) measures the
electrical activity of the heart
• Echocardiogram (ECG) uses sounds
waves to generate images of the heart,
similar to an ultra sound of the heart
Electrical Conduction System
EKG is recorded at a speed of 25 mm/sec, and the voltages are
calibrated so that 1 mV = 10 mm in the vertical direction. Therefore,
each small 1-mm square represents 0.04 sec (40 ms) in time and 0.1
mV in voltage.
P Wave represents the wave of depolarization that spreads from the
SA node throughout the atria. Shape of the wave can change if the
“pacemaker” of the heart moves from the SA node.
QRS complex represents ventricular depolarization.
Isoelectric Period (ST segment) following the QRS is the time at
which the entire ventricle is depolarized and roughly corresponds to
the plateau phase of the ventricular action potential.
T wave represents ventricular repolarization and is longer in duration
than depolarization (i.e., conduction of the repolarization wave is
slower than the wave of depolarization).
Sometimes a small positive U wave may be seen following the T
wave It represents the last remnants of ventricular repolarization.
Q-T interval represents the time for both ventricular depolarization
and repolarization to occur.
No distinctly visible wave representing atrial repolarization because
it occurs during ventricular depolarization. Because the wave of
atrial repolarization is relatively small in amplitude it is masked by
the much larger ventricular-generated QRS complex.
You can calculate the heart rate by counting the small squares and
dividing the number by 1500. (i.e., 21 small squares. 21/1500 =
.014. Heart beats ONCE every 1.4 seconds, or roughly 43 bpm)
P wave rate 60-100 bpm with <10%
Height of wave < 2.5 mm in lead II
Width <.11 s in lead II
PR Interval 0.12 0.20 s (3-5 small
QRS Complex < 0.12 s duration (3 small
QT interval (QTc) = dividing QT interval
by square root of preceeding R-R interval.
Normal = .42 s (380-420 ms)
ST segment = no elevation/depression
Artifacts in the EKG Reading
Artifact occurs when something causes a disruption in
monitoring. Some common causes are:
•AC interference -causes 60 cycle artifact
•Respiratory artifact-wandering baseline
•Broken lead wire
•Faulty Wiring in the EPTF
• Every cell in the heart can act as a
• The SA node has an intrinsic heart beat
generation of 60-80 bpm. “Pacemaker” of
• The AV node has a rate of 40-60 bpm.
Responsible for “holding” the impulse until
the ventricles are ready to receive them.
• The ventricles generate rates of 20-40
The Heart (con’t)
• The ventricles may kick in if the cells of the
upper chambers fail or if the electrical
signals to the ventricle are blocked.
• A normal heart pushes at least 50-60% of
the blood in the ventricle out to the body
when it beats
• Heart has 2 types of cells, electrical
(conductive) and mechanical (contracting)
• EKG evaluates the electrical cells.
Pulse/BP evaluates the mechanical cells.
• Premature Atrial Contractions (PACs) –
when the atrium beats early
• Premature Ventricular Contraction (PVCs)
– when the ventricle beats early
• Everyone has the occasional palpitation,
PAC, PVC. It becomes an issue when it
begins to occur regularly
Rate normal or accelerated
usually have a different morphology than sinus
P wave P waves because they originate from an ectopic
normal, however the ectopic beats may have a
different P-R interval.
PAC's occur early in the cycle and they usually
do not have a complete compensatory pause.
P wave usually obscured by the QRS, PST or T wave of the PVC
wide > 0.12 seconds; morphology is bizarre with the ST segment and the T wave
opposite in polarity. May be multifocal and exhibit different morphologies.
the impulse originates below the branching portion of the Bundle of His; full
compensatory pause is characteristic.
irregular. PVC's may occur in singles, couplets or triplets; or in bigeminy,
trigeminy or quadrigeminy.
PVCs can occur in healthy hearts. For example, an increase in
circulating catecholamines can cause PVCs. They also occur in
diseased hearts and from drug (such as digitalis) toxicities
Rhythm disturbances are classified
according to whether they arise from the
atrium or the ventricle, whether they are
fast or slow, and whether they are regular
Rapid heart rates can originate from either
the atrium or the ventricle. Rhythms from
the ventricle are more often considered life
• Usually due to heart blockage and the
aging of the electrical wiring of the heart.
Can be treated utilizing a pacemaker
• (Sinus = from SA node, Tachy=rapid,
Cardia=heart) Rapid Regular Heartbeat
• Occurs when the body asks the heart to
pump more blood, or when the electrical
system is stimulated by chemicals
• Occurs most frequently during times of
physiologic stress, exercise, dehydration,
ingestion of medications/drugs, hormones
within the body
P wave sinus
Rhythm regular or slightly irregular
The clinical significance of this dysrhythmia depends on
the underlying cause. It may be normal. Underlying
causes include: increased circulating catecholamines,
CHF, hypoxia, physical exercise, increased temperature,
stress, response to pain .
• (sinus=sa node, brady=slow, cardia=heart)
• Heart beat generated by SA node at rate
slower than 60 bpm.
• May be normal for people who are
active/athletic, or pt’s taking medications
designed to slow heart rate (beta blockers
or Ca channel blockers)
Rate 40-59 bpm
P wave sinus
QRS normal (.06-.12)
P-R normal or slightly prolonged at slower
Rhythm regular or slightly irregular
This rhythm is often seen as a normal
variation in athletes, during sleep, or in
response to a vagal maneuver.
• Episode of profound sinus bradycardia
associated with noxious stimulus where
the vagal system of the body kicks in.
• Sympathetic system of the body is
mediated by adrenaline.
• Parasympathetic system is mediated by
vagus nerve and chemical acetylcholine;
promotes opposite body reaction than
• Rapid heart rhythm that originates from
the lower chambers (ventricles) of the
• Prevents heart from filling adequately with
blood; less blood is able to pump through
usually between 100 to 220/bpm, but can be as rapid as
P wave obscured if present and are unrelated to the QRS complexes.
QRS wide and bizarre morphology
Conduction as with PVCs
three or more ventricular beats in a row; may be regular or
Ventricular tachycardia almost always occurs in diseased hearts.
Some common causes are CAD, acute MI, digitalis toxicity, CHF,
Patients are often symptomatic with this dysrhythmia.
Ventricular tachycardia can quickly deteriorate into ventricular
Ventricular Fibrillation (V Fib)
• Heart has ceased to beat, ventricles do
not have a coordinated electrical pattern.
Ventricles do not beat, but “jiggle”
P wave may be present, but obscured by ventricular waves
QRS not apparent
Conduction chaotic electrical activity
Rhythm chaotic electrical activity
This dysrhythmia results in the absence of cardiac output.
Almost always occurs with serious heart disease, especially
Atrial Fibrillation (A Fib)
• Atrium has lost ability to beat in a
• SA node fails to generate single electrical
signal; numerous areas of atrium become
irritated and produce electrical impulses.
• Atrium “jiggles” rather than beat; causes
ventricles to fire irregularly, often quickly
Rate atrial rate usually between 400-650/bpm.
P wave not present; wavy baseline is seen instead.
variable AV conduction; if untreated the ventricular response
is usually rapid.
irregularly irregular. (This is the hallmark of this
Atrial fibrillation may occur suddenly, but often becomes chronic.
It is usually associated with COPD, CHF or other heart disease
• When involving ventricles, often
asymptomatic and of little consequence
• When involving atrium, classified as first,
second, and third degree
• Heart beats slowly, causing decreased
Rate normal or bradycardia
P wave those present are normal
Rhythm basic rhythm is regular*.
In a type I SA block, the P-P interval shortens until one P
wave is dropped.
In a type II SA block, the P-P intervals are an exact multiple
of the sinus cycle, and are regular before and after the
dropped P wave.
1st Degree Heart Block
• Common and of little significance
• Slight delay in getting the electrical signal
from the SA node to the AV node
• Heart functions normally
P wave normal
impulse originates in the SA node but has prolonged
Conduction conduction in the AV junction; P-R interval is > 0.20
This is the most common conduction disturbance. It occurs
in both healthy and diseased hearts. Causes include
inferior MI, digitalis toxicity, hyperkalemia, increased vagal
tone, acute rheumatic fever, myocarditis.
2nd Degree Heart Block
• Two Types: Mobitz I & Mobitz II
• Mobitz II can be precursor to life
threatening rhythm problem
P wave normal morphology with constant P-P interval
the P-R interval is progressively longer until one P wave is
blocked; the cycle begins again following the blocked P wave.
Second degree AV block type I occurs in the AV node above the
Bundle of His. It is often transient and may be due to acute inferior
MI or digitalis toxicity. Often asymptomatic.
P wave normal with constant P-P intervals
usually widened because this is usually associated with a bundle
P-R interval may be normal or prolonged, but it is constant until
one P wave is not conducted to the ventricles.
Rhythm usually regular when AV conduction ratios are constant
This block usually occurs below the Bundle of His and may
progress into a higher degree block. It can occur after an acute
anterior MI due to damage in the bifurcation or the bundle
branches. More serious than the type I block.
3rd Degree Heart Block
• Describes complete loss of connection
between electrical activity of the atrium
and the ventricle
• 2nd & 3rd Degree heart blocks are
diagnosed by analyzing heart rhythm
strips and EKGs
atrial rate is usually normal; ventricular rate is usually less than 70/bpm. The
atrial rate is always faster than the ventricular rate.
P wave normal with constant P-P intervals, but not "married" to the QRS complexes.
may be normal or widened depending on where the escape pacemaker is
located in the conduction system
atrial and ventricular activities are unrelated due to the complete blocking of
the atrial impulses to the ventricles.
Complete block of the atrial impulses occurs at the A-V junction,
common bundle or bilateral bundle branches. Another pacemaker
distal to the block takes over in order to activate the ventricles or
ventricular stand still will occur. May be caused by digitalis toxicity,
acute infection, MI, and degeneration of the conductive tissue