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EKG
Reading:
• Klabunde, Cardiovascular Physiology
Concepts
– Chapter 2 (Electrical Activity of the Heart)
pages 27-37
• Dubin, Rapid Interpretation of EKG’s, 6th
Edition.
Check these hyperlinks out!
• http://www.themdsite.com/personal_reference.cfm
• Dubin’s EKG Pocket Guide
Basic Principles
Basic Principles
• The EKG records the electrical activity of
contraction of the heart muscle
• Depolarization may be considered an
advancing wave of positive charges within
the heart’s myocytes
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Depolarization Wave
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Depolarization
Repolarization
Conduction System
SA Node
Right
Atrial
Tracts
Anterior
Internodal
Pathway
AV Node
Middle
Internodal
Pathway
Posterior
Internodal
Pathway
Anterior interatrial
myocardial band
(Bachmann’s Bundle)
Left Atrium
AN Region
N Region
NH Region
Bundle of His
Right Bundle
Branch
Left Bundle
Branch
Anterior
Division
Posterior
Division
Sinus Rhythm
• The SA (Sinus) Node is the heart’s dominant
pacemaker.
• The ability of a focal area of the heart to generate
pacemaking stimuli is known as Automaticity.
• The depolarization wave flows from the SA Node
in all directions.
Atrio-Ventricular (AV) Valves
• Prevent blood backflow to the atria
• Electrically insulate the ventricles from the
atria
AV Conduction
• AV node is situated on right side of
interatrial septum near the ostium of the
coronary sinus
• When the wave of depolarization enters the
AV Node, depolarization slows, producing
a brief pause, thus allowing time for the
blood in the atria to enter the ventricles.
Repolarization
ST
Segment
Plateau
Rapid
Repolarization
Phase
QT
Interval
Ventricular
Systole
Recording the EKG
• Limb Leads
–I
– II
– III
– AVR
– AVL
– AVF
• Chest Leads
– V1
– V2
– V3
– V4
– V5
– V6
Autonomic Nervous System
Check for these on every EKG
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RATE
Rhythm
Axis
Hypertrophy
Infarction
Sinus Rhythm
• The SA (Sinus) Node is the heart’s
dominant pacemaker.
• The generation of pacemaking stimuli is
automaticity.
• The depolarization wave flows from the SA
Node in all directions.
Sinus Rhythm
• The Sinus Node is the heart’s normal
pacemaker
• Normal Sinus Rhythm: 60-100/min.
• Sinus Bradycardia: Less than 60/min.
• Sinus Tachycardia: More than 100/min.
Automaticity Foci
• Level
• Inherent Rate Range
– Atria
– 60-80/min.
– AV Junction
– 40-60/min.
– Ventricles
– 20-40/min.
Overdrive Suppression
SA Node
Overdrive Suppression
Atrial Foci (60-80 bpm)
Junctional Foci (40-60 bpm)
Ventricular Foci (20-40 bpm)
RATE
• Say “300, 150, 100” …“75, 60, 50”
• But for bradycardia: rate = cycles/6 sec.
strip ✕ 10
Check for these on every EKG
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Rate
RHYTHM
Axis
Hypertrophy
Infarction
RHYTHM
• Identify the basic rhythm, then scan tracing
for prematurity, pauses, irregularity, and
abnormal waves.
• Check for: P before each QRS.
• Check for: QRS after each P.
• Check: PR intervals (for AV Blocks).
• Check: QRS interval (for Bundle Branch
Block)
Sinus Rhythm
• Origin is the SA Node (“Sinus Node”)
• Normal sinus rate is 60 to 100/minute
• Rate more than 100/min. = Sinus
Tachycardia
• Rate less than 60/min. = Sinus Bradycardia
Sinus Bradycardia
Sinus Tachycardia
Arrhythmias
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Irregular rhythms
Escape
Premature beats
Tachy-arrhythmias
Irregular Rhythms
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Sinus Arrhythmia
Wandering Pacemaker
Multifocal Atrial Tachycardia
Atrial Fibrillation
Sinus Arrhythmia
• Irregular rhythm that varies with respiration.
• All P waves are identical.
• Considered normal.
Wandering Pacemaker
• Irregular rhythm.
• P waves change shape as pacemaker location
varies.
• Rate under 100/minute
Multifocal Atrial Tachycardia
• Irregular rhythm.
• P waves change shape as pacemaker location
varies.
• Rate greater than 100/minute
Atrial Fibrillation
• Irregular ventricular rhythm.
• Erratic atrial spikes (no P waves) from multiple
atrial automaticity foci.
• Atrial discharges may be difficult to see.
Escape
• Escape Rhythm
– Atrial Escape Rhythm
– Junctional Escape Rhythm
– Ventricular Escape Rhythm
• Escape Beat
– Atrial Escape Beat
– Junctional Escape Beat
– Ventricular Escape Beat
Premature Beats
• Premature Atrial Beat
• Premature Junctional Beat
• Premature Ventricular Contraction (PVC)
Atrial Bigeminy
PVC’s
Bigeminy
Tachyarrhythmias
Paroxysmal Atrial Tachycardia
(Supraventricular Tachycardia)
• An irritable atrial focus discharging at 150250/min. produces a normal wave sequence, if P’
waves are visible.
P.A.T. with block
(Supraventricular Tachycardia)
• Same as P.A.T. but only every second (or more)
P’ wave produces a QRS.
Paroxysmal Junctional Tachycardia
• AV Junctional focus produces a rapid sequence of
QRS-T cycles at 150-250/min.
• QRS may be slightly widened.
Paroxysmal Ventricular Tachycardia
• Ventricular focus produces a rapid (150-250/min)
sequence of (PVC-like) wide ventricular
complexes.
Atrial Flutter
• A continuous (“saw tooth”) rapid sequence of atrial
complexes from a single rapid-firing atrial focus.
• Many flutter waves needed to produce a ventricular
response.
Ventricular Flutter
• A rapid series of smooth sine waves from a single rapidfiring ventricular focus
• Usually in a short burst leading to Ventricular Fibrillation.
Atrial Fibrillation
• Multiple atrial foci rapidly discharging produce a
jagged baseline of tiny spikes.
• Ventricular (QRS) response is irregular.
Ventricular Fibrillation
• Multiple ventricular foci rapidly discharging produce a
totally erratic ventricular rhythm without identifiable
waves.
• Needs immediate treatment.
Block
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Sinus Block
AV Block
Bundle Branch Block
Hemiblock
Sinus (SA) Block
• An unhealthy Sinus (SA) Node misses one or more cycles
(sinus pause)
• The Sinus Node usually resumes pacing
• However, the pause may evoke an “escape” response from
an automaticity focus
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1
AV Block
• PR interval is prolonged to greater than 0.2 sec
(one large square)
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1
AV Block
2° AV Block
(Some P waves without QRS Response)
• Wenkebach
– PR gradually lengthens
with each cycle until
the last P wave in the
series does not produce
a QRS
2° AV Block
(Some P waves without QRS Response)
• Mobitz
– Some P waves don’t
produce a QRS
response.
– Intermittent may cause
an occasional QRS to
be dropped.
– More advanced may
produce a 3:1 pattern
or higher AV ration.
2° AV Block
(Some P waves without QRS Response)
• 2:1 AV Block
– May be Mobitz or
Wenkebach.
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2
AV Block
3° AV Block
(“Complete” Block)
• P waves of SA node origin
• QRS’s if narrow, and if the ventricular rate is 4060/min., then origin is a junctional focus.
3° AV Block
(“Complete” Block)
• P waves of SA node origin
• QRS’s if PVC-like, and if the ventricular rate is
20-40/min., then origin is a ventricular focus.
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3 AV
Block
Bundle Branch Block
• Find R, R' in right or left chest leads
• Always check: Is QRS within 3 tiny squares?
Left Bundle Branch Block
Right Bundle Branch Block
Hemiblock
• Block of Anterior or Posterior Fasicle of the
Left Bundle Branch
• Always check: Has Axis shifted outside
normal range?
• Anterior Hemiblock:
– Axis shifts leftward > L.A.D. Look for Q1S3
• Posterior Hemiblock:
– Axis shifts rightward > R.A.D. Look for S1Q3
Left Anterior Hemiblock
Check for these on every EKG
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Rate
Rhythm
AXIS
Hypertrophy
Infarction
Using Vectors to Represent
Electrical Potentials
• A vector is an arrow that points in the direction of
the electrical potential generated by current flow
• The arrowhead of the vector is in the positive
direction
• The length of the arrow is drawn proportional to
the voltage of the potential
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RV
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Lead I
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Axis
• QRS above or below baseline for Axis
Quadrant (Normal vs. R or L Axis Dev.)
– For Axis in degrees, find isoelectric QRS in a
limb lead
• Axis rotation in the horizontal plane (chest
leads) find “transitional” (isoelectric) QRS
Causes of Axis Deviation
• Change of the position of the heart in the
chest
• Hypertrophy of one ventricle
• Myocardial infarction
• Bundle branch block
Check for these on every EKG
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Rate
Rhythm
Axis
HYPERTROPHY
Infarction
Hypertrophy
• P wave for Atrial hypertrophy
• R wave for Right Ventricular Hypertrophy
• S wave depth in V1 + R wave height in V5
for Left Ventricular Hypertrophy
Right Atrial Hypertrophy
• Large, diphasic P wave with tall initial component
• Seen in lead V1
Left Atrial Hypertrophy
• Large, diphasic P wave with wide terminal
component
• Seen in lead V1
Right Ventricular Hypertrophy
• R > S wave in V1
– R wave gets progressively smaller from V1-V6
• S wave persists in V5-V6
• RAD with slightly widened QRS
• Rightward rotation in the horizontal plane
Left Ventricular Hypertrophy
mm of S in V1
+
mm of R in V5
Total:
If more than 35 mm there is LVH
Left Ventricular Hypertrophy
• LAD with slightly widened QRS
• Leftward rotation in the horizontal plane
• Inverted T wave
– Slants downward gradually, but up rapidly
Hypertrophy
Left Ventricle and Left Atrium
Check for these on every EKG
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Rate
Rhythm
Axis
Hypertrophy
INFARCTION (and Ischemia)
Infarction
• Scan all leads for:
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Q waves
Inverted T waves
ST segment elevation or depression
Find the location of the pathology and then
identify the occluded coronary artery
Necrosis
= Q wave (significant Q’s only)
• Significant Q wave:
– One mm wide (0.04
sec in duration) or
– 1/3 the amplitude (or
more) of the QRS
• Omit lead AVR when
looking for significant
Q’s
• Old infarcts: Q waves
remain for a lifetime
Injury
= ST elevation
• Signifies an acute process
• ST elevation associated
with significant Q waves
indicates an acute (or
recent) infarct
• ST depression (persistent)
may represent a
“subendocardial
infarction”
Ischemia
= T wave inversion
• Inverted T wave (of
ischemia) is symmetrical
– Normally T wave is upright
when QRS is upright, and
vice versa
• Usually in the same leads
that demonstrate signs of
acute infarction (Q waves
and ST elevation)
Inferior Infarction
Inferior Infarction
(+ LBBB)
Anterior Infarction
Postero-Lateral Infarction
Miscellaneous
Digitalis
• EKG appearance with
digitalis
– Salvador Dali
mustache
– T waves depressed or
inverted
– QT interval shortened
Digitalis
• Digitalis Excess
• (Blocks)
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SA Block
P.A.T. with Block
AV Blocks
AV Dissociation
• Digitalis Toxicity
• (Irritable foci firing
rapidly)
– Atrial Fibrillation
– Junctional or
Ventricular
Tachycardia
– Multiple PVS’s
– Ventricular Fibrillation
Calcium
Decreased Potassium
(Hypokalemia)
Hyperkalemia
Pulmonary Embolism
• S1Q3T3
– Wide S in I, large Q and inverted T in III
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Acute Right Bundle Branch Block
R.A.D. and clockwise rotation
Inverted T waves in V1 – V4
ST depression in II
Pulmonary Embolism
Pacemakers
Wolf-Parkinson-White Syndrome
Wolf-Parkinson-White Syndrome
Review the 12-lead EKG on top
in the next slide (EKG b).
Anything unusual about it?
The End