Electrocardiography (ECG or EKG)

interactive physiology 1
Prof. dr. Milan TaradiProf. dr. Milan Taradi
Department of Physiology and ImmunologyDepartment of Physiology and Immunology
is a method of recording electrical activity of the heart.is a method of recording electrical activity of the heart.
ELECTROCARDIOGRAPHYELECTROCARDIOGRAPHY
(ECG or EKG)(ECG or EKG)

interactive physiologyECG Taradi 2
ELECTROCARDIOGRAPHYELECTROCARDIOGRAPHY
 DefinitionsDefinitions
 Historical overviewHistorical overview
 Transmembrane resting potential and actionTransmembrane resting potential and action
potentialpotential
 Propagation of the depolarization andPropagation of the depolarization and
repolarisation over the membranerepolarisation over the membrane
 Propagation of the waves on the surface of aPropagation of the waves on the surface of a
cardiac muscle mass in volume conductorcardiac muscle mass in volume conductor
 Propagations of waves through atria andPropagations of waves through atria and
ventriculesventricules
 Spreading the impulse through the heartSpreading the impulse through the heart
 Flow of current around the heartFlow of current around the heart
 Recording the standard electrocardiographicRecording the standard electrocardiographic
leadsleads
 Normal ECG recorded in one leadNormal ECG recorded in one lead
 Projection of current in frontal planeProjection of current in frontal plane
 Reconstruction of current in spaceReconstruction of current in space

ECG is a method of recording electrical activity of the heartECG is a method of recording electrical activity of the heart
 ElectrocardiographyElectrocardiography is ais a
science of recording andscience of recording and
interpreting the electricalinterpreting the electrical
activity that precedes and is aactivity that precedes and is a
measure of the action of heartmeasure of the action of heart
muscles.muscles.
 ElectrocardiogphElectrocardiogph is ais a
instrument for recording theinstrument for recording the
changes of electrical potentialchanges of electrical potential
occurring during the heartoccurring during the heart beatbeat
used especially in diagnosingused especially in diagnosing
abnormalities of heart action.abnormalities of heart action.
 ElectrocardiogramElectrocardiogram (EKG or(EKG or
ECG) is a graphical record (onECG) is a graphical record (on
paper or screen) of thepaper or screen) of the
electrical waves of the heart, aselectrical waves of the heart, as
registred on theregistred on the
electrocardiograph.electrocardiograph.

A brief history of electrocardiographyA brief history of electrocardiography
 1843. Carlo Matteucci, professor of Physics at the University of Pisa, shows1843. Carlo Matteucci, professor of Physics at the University of Pisa, shows
that an electric current accompanies each heart beat. He used a preparationthat an electric current accompanies each heart beat. He used a preparation
known as a 'rheoscopic frog' in which the cut nerve of a frog's leg was used asknown as a 'rheoscopic frog' in which the cut nerve of a frog's leg was used as
the electrical sensor.the electrical sensor.
 1856. Rudolph von K1856. Rudolph von Kölliker and Heinrich Muller confirm that an electricallliker and Heinrich Muller confirm that an electrical
current accompanies each heart beat by applying a galvanometer to the basecurrent accompanies each heart beat by applying a galvanometer to the base
and apex of an exposed ventricle.and apex of an exposed ventricle.
 1887. British physiologist Augustus D. Waller of St Mary's Medical School,1887. British physiologist Augustus D. Waller of St Mary's Medical School,
London publishes the first human electrocardiogram. It is recorded with aLondon publishes the first human electrocardiogram. It is recorded with a
capillary electrometer from Thomas Goswell, a technician in the laboratory.capillary electrometer from Thomas Goswell, a technician in the laboratory.
 1893 Dutch physiologist Willem Einthoven introduces the term1893 Dutch physiologist Willem Einthoven introduces the term
'electrocardiogram''electrocardiogram'
 1903. Einthoven invents a new galvanometer for producing1903. Einthoven invents a new galvanometer for producing
electrocardiograms. In this device a fine quartz string is suspended verticallyelectrocardiograms. In this device a fine quartz string is suspended vertically
between the poles of a magnet.between the poles of a magnet.
 1924 Einthoven wins the Nobel prize for inventing the electrocardiograph.1924 Einthoven wins the Nobel prize for inventing the electrocardiograph.
 1932. Wilson defines the unipolar limb leads VR, VL and VF where 'V' stands1932. Wilson defines the unipolar limb leads VR, VL and VF where 'V' stands
for voltage.for voltage.
 1947. Emanuel Goldberger increases the voltage of Wilson's unipolar leads by1947. Emanuel Goldberger increases the voltage of Wilson's unipolar leads by
50% and creates the augmented limb leads aVR, aVL and aVF.50% and creates the augmented limb leads aVR, aVL and aVF.

Inductive or deductive?Inductive or deductive?
 Forward problemForward problem
 Inverse problemInverse problem

Membrane Potentials Caused by DiffusionMembrane Potentials Caused by Diffusion
 The membrane isThe membrane is
permeable to thepermeable to the
potassium ions but notpotassium ions but not
for anions.for anions.
 Because of the largeBecause of the large
potassiumpotassium
concentration gradientconcentration gradient
from the inside towardfrom the inside toward
outside, there is aoutside, there is a
strong tendency forstrong tendency for
extra numbers ofextra numbers of
potassium ions topotassium ions to
diffuse outward.diffuse outward.

The Resting Membrane PotentialThe Resting Membrane Potential
 The potentialThe potential
inside the cell isinside the cell is
more negativemore negative
than thethan the
potential in thepotential in the
extracelularextracelular
fluid on thefluid on the
outside of theoutside of the
cell.cell.

Membrane Potentials Caused by DiffusionMembrane Potentials Caused by Diffusion
 The membrane is semipermeable for the ions.The membrane is semipermeable for the ions.
 Concentration gradients exist.Concentration gradients exist.
 The stady state of gradients is maintained by the pump.The stady state of gradients is maintained by the pump.
 There is a lot of nondiffusible anions inside the cell.There is a lot of nondiffusible anions inside the cell.
diffusion of Na+
diffusion of K+
3 Na3 Na++
2 K+
ATP
Mg++
ADP + Pi
ICT

Contributions of the NaContributions of the Na++
-K-K++
PumpPump
 NaNa++
-K-K++
pump ispump is
electrogenic.electrogenic.
 There isThere is
continuouscontinuous
pumping of 3 Napumping of 3 Na++
to outside forto outside for
each 2 Keach 2 K++
pumpedpumped
to the inside ofto the inside of
the membrane.the membrane.

interactive physiologyECG
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Recording Membrane Potentials and ActionRecording Membrane Potentials and Action
PotentialsPotentials
0
-
 The micropipetteThe micropipette
(active electrode)(active electrode)
is inserted intois inserted into
the interior of thethe interior of the
cell.cell.
 The otherThe other
electrode is onelectrode is on
infinite distance,infinite distance,
on potential 0 V.on potential 0 V.
 MonophasicMonophasic
potential ispotential is
recorded on therecorded on the
one spot of theone spot of the
membrane.membrane.

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Recording Biphasic PotentialRecording Biphasic Potential
 TwoTwo
electrodes areelectrodes are
placed outsideplaced outside
the cell.the cell.
 BiphasicBiphasic
potential ispotential is
recorded.recorded.
 BothBoth
electrodes areelectrodes are
active.active.
0

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Monophasic Action Potential ofMonophasic Action Potential of
myocytemyocyte

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Monophasic Action Potential of Ventricular CellMonophasic Action Potential of Ventricular Cell

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Pacemaker Potentials in Sinus NodePacemaker Potentials in Sinus Node

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Propagations of action potentialsPropagations of action potentials
 The action potentialThe action potential
elicited at any pointelicited at any point
excites adjacentexcites adjacent
portions of theportions of the
membrane in allmembrane in all
directions.directions.
 Depolarization waveDepolarization wave
 Repolarization waveRepolarization wave
 No potential is recordedNo potential is recorded
when the cell is eitherwhen the cell is either
completely polarized orcompletely polarized or
depolarized.depolarized.
- +
- +
- +
- +
- +
+++++++++++++++++++++
----------------------
---------+++++++++++++
++++++++--------------
---------------------- ++++++++++
+++++++++++
+++++++++-------------
----------++++++++++++
++++++++++++++++++++
----------------------

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Principles of Vectorial AnalysisPrinciples of Vectorial Analysis
 Resultant vector depends on the length of the vector andResultant vector depends on the length of the vector and
the angle between the lead axis and the vector (projectedthe angle between the lead axis and the vector (projected
vector = length x cos of an angle)vector = length x cos of an angle)
 Also, resultant vector is diminish with the square of axisAlso, resultant vector is diminish with the square of axis
distance.distance.

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Depolarization waveDepolarization wave
 Depolarizations has extended over the entireDepolarizations has extended over the entire
muscle cell.muscle cell.

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Cardiac muscle is a functional syncycium.Cardiac muscle is a functional syncycium.
 The cardiac muscle cells are joined end toThe cardiac muscle cells are joined end to
end by specialized cell junction calledend by specialized cell junction called
intercalated discs.intercalated discs.

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Depolarization wave in the muscle massDepolarization wave in the muscle mass
 The potentials developed on the surface of cardiacThe potentials developed on the surface of cardiac
muscle mass.muscle mass.

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The genesis of theThe genesis of the
electrocardiogramelectrocardiogram
 Propagation of thePropagation of the
action potential inaction potential in
the group ofthe group of
myocytesmyocytes

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Activation frontActivation front
 The signal producedThe signal produced
by the propagatingby the propagating
activation frontactivation front
between a pair ofbetween a pair of
extracellularextracellular
electrodes.electrodes.

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Propagation of action potentials in cardiac musclePropagation of action potentials in cardiac muscle
 vectorsvectors
 resultant vectorresultant vector
 depolarizationdepolarization
wavewave

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The Hart is in Volume ConductorThe Hart is in Volume Conductor
 Flow of electrical currents in the chest aroundFlow of electrical currents in the chest around
the heart.the heart.

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The record depends on the locations of electrodesThe record depends on the locations of electrodes
 It is crucialIt is crucial
where towhere to
placeplace
electrode.electrode.

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Standard Axes of the three bipolar leadsStandard Axes of the three bipolar leads

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Cardiac Conductive SystemCardiac Conductive System
 sinus node (sinoatrialsinus node (sinoatrial
node)node)
 internodal pathwaysinternodal pathways
 anterior interatrial
band (Bachman)
 anterior, middle and
posterior internodal
pathways
 atrioventricular nodeatrioventricular node
 transitional fibers
 A-V node
 AV-bundle (His)AV-bundle (His)
 penetrating portion
 distal portion
 Purkinje systemPurkinje system
 left bundle branch
 right bundle branch

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Summary of the Spread of Cardiac Impulse TroughSummary of the Spread of Cardiac Impulse Trough
the Heartthe Heart

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The P wave – Depolarization of the AtriaThe P wave – Depolarization of the Atria
 Depolarization of the atria andDepolarization of the atria and
generation of the P wavegeneration of the P wave
6
1
2
3
4
5
1
2 3
4
5
6
1 6

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The cathode ray tubeThe cathode ray tube
 produces theproduces the
vectorcardiogramvectorcardiogram
in the frontalin the frontal
plane from theplane from the
Einthoven limbEinthoven limb
leads.leads.

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Vectorial Analysis of the Normal ECGVectorial Analysis of the Normal ECG
(Vectorcardiograms)(Vectorcardiograms)
P QRS
T

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The P wave - Depolarization of the AtriaThe P wave - Depolarization of the Atria
Lead I.

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Transmission of the cardiac impulse from the atriaTransmission of the cardiac impulse from the atria
to the ventricleto the ventricle

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The QRS complex – Depolarization of the VentriclesThe QRS complex – Depolarization of the Ventricles
 The QRS complex is often composed of three separateThe QRS complex is often composed of three separate
waves.waves.
Lead I.

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The R waveThe R wave
Lead I.

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The J Point – The Zero Reference PotentialThe J Point – The Zero Reference Potential
 The damaged part of the heart muscle is partially or totally depolarized all the time.The damaged part of the heart muscle is partially or totally depolarized all the time.
Lead I.
0

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The T Wave – Repolarization of the VentriclesThe T Wave – Repolarization of the Ventricles
 The septum and the other endocardial areas have a longer period ofThe septum and the other endocardial areas have a longer period of
contraction and therefore are slower to repolarize then the most of the externalcontraction and therefore are slower to repolarize then the most of the external
surfaces of the heart.surfaces of the heart.
 The reason is the high blood pressure inside the ventricules during sistole.The reason is the high blood pressure inside the ventricules during sistole.
Lead I.

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Principles of ECGPrinciples of ECG
Ecg.swf

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 The normalThe normal
electrocardiogramelectrocardiogram
Principles of ECGPrinciples of ECG

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Normal ECGNormal ECG

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The J PointThe J Point
 The zero referenceThe zero reference
potential for analyzingpotential for analyzing
current of injurycurrent of injury
 The damaged part ofThe damaged part of
the heart muscle isthe heart muscle is
partially or totallypartially or totally
depolarized all thedepolarized all the
time.time.

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Waves, complexes, intervals, segmentsWaves, complexes, intervals, segments

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Intervals of the ECGIntervals of the ECG

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The Determination of the Rate of HeartbeatThe Determination of the Rate of Heartbeat

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TachycardiaTachycardia

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The standard bipolar Leads are in frontal plane.The standard bipolar Leads are in frontal plane.

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Standard Bipolar LeadsStandard Bipolar Leads
 The system is threeaxial.The system is threeaxial.

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Einthoven´s triangleEinthoven´s triangle
Einthoven´s lawEinthoven´s law
I + III = III + III = II

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Standard leadsStandard leads

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Augmented Unipolar Limb LeadsAugmented Unipolar Limb Leads

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Augmented Unipolar Limb LeadsAugmented Unipolar Limb Leads
 Axes of the unipolar leadsAxes of the unipolar leads

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The Standard Limbs LeadsThe Standard Limbs Leads
 The ECG is very similar in all leads .The ECG is very similar in all leads .

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The axes of three standard bipolar leadsThe axes of three standard bipolar leads

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The axis deviationThe axis deviation

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Normal range of the mean electrical axisNormal range of the mean electrical axis

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Normal ECG (left-sided axis)Normal ECG (left-sided axis)

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Normal ECG (vertical axis)Normal ECG (vertical axis)

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Standard LimbStandard Limb

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The body planesThe body planes

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Precordial leadsPrecordial leads
 UnipolarUnipolar
chest leadschest leads

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Precordial Leads AxisPrecordial Leads Axis

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Precordial LeadsPrecordial Leads

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All Leads and AxisAll Leads and Axis
 Lead I.Lead I. STANDARDSTANDARD
 Lead II. (3)Lead II. (3)
 Lead III.Lead III.
 aVRaVR AUGMENTEDAUGMENTED
 aVL (3)aVL (3)
 aVFaVF
 VV11 PRECORDIALPRECORDIAL
 VV22 (6)(6)
 VV33
 VV44
 VV55
 VV66
 total (12)total (12)

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Complete ECG in 12 LeadsComplete ECG in 12 Leads

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The relationship of ECG and Heart CycleThe relationship of ECG and Heart Cycle

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Relationship of ECG and Heart CycleRelationship of ECG and Heart Cycle

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SummarySummary
 P waveP wave
 P-Q segmentP-Q segment
 QRS complexQRS complex
 J pointJ point
 S-T segmentS-T segment
 T waveT wave
 T-P segmentT-P segment
 U waveU wave
 P-R (P-Q) intervalP-R (P-Q) interval
 Q-T intervalQ-T interval
 R-R intervalR-R interval

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QuestionsQuestions

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Sinus rhythmSinus rhythm
 Normal sinusNormal sinus
rhythm (Raterhythm (Rate
60 - 100/min )60 - 100/min )
 SinusSinus
bradycardiabradycardia
(Rate <(Rate <
60/min)60/min)
 SinusSinus
tachycardiatachycardia
(Rate >(Rate >
100/min100/min ))
1.1. RHYTHM DIAGNOSISRHYTHM DIAGNOSIS

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ArrhythmiaArrhythmia
 Sinus arrhythmiaSinus arrhythmia
 Longest R-R interval exceeds shirtest > 0.16 sLongest R-R interval exceeds shirtest > 0.16 s

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Wandering pacemakerWandering pacemaker
 Impuses originate from varying points in atriaImpuses originate from varying points in atria
 Variation in P-wave contour, P-R and P-P intervalVariation in P-wave contour, P-R and P-P interval
and therefore in R-R intervalsand therefore in R-R intervals

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Ectopic beatEctopic beat

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Ectopic beatEctopic beat

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Atrial flutterAtrial flutter
 Impulses travel in circular course in atriaImpulses travel in circular course in atria
 Rapid flutter waves, ventricular responseRapid flutter waves, ventricular response
irregularirregular

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Atrial fibrillationAtrial fibrillation
 Impuses have chaotic, random pathways in atriaImpuses have chaotic, random pathways in atria
 Baseline irregular, ventricular response irregularBaseline irregular, ventricular response irregular

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Junctional rhythmJunctional rhythm
 Impuses originate at AV node with retrograde andImpuses originate at AV node with retrograde and
antegrade directionantegrade direction
 P-wave is often inverted, may be under or afterP-wave is often inverted, may be under or after
QRS complex, Heart rate is slowQRS complex, Heart rate is slow

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ArrhythmiaArrhythmia
 Premature ventricular contractionPremature ventricular contraction
 A single impulse originates at right ventricleA single impulse originates at right ventricle
 Time interval between normal R peaks is aTime interval between normal R peaks is a
multiple of R-R intervalsmultiple of R-R intervals

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Ventricular tachycardiaVentricular tachycardia
 Impulse originate at ventricular pacemakerImpulse originate at ventricular pacemaker
 Wide ventricular complexes, rate > 120/minWide ventricular complexes, rate > 120/min

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Ventricular fibrillationVentricular fibrillation
 Chaotic ventricular depolarizationChaotic ventricular depolarization
 Rapid, wide, irregular ventricular complexesRapid, wide, irregular ventricular complexes

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Ventricular DefibrillationVentricular Defibrillation

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Pacer rhythmPacer rhythm
 Impulses originate at transvenous pacemakerImpulses originate at transvenous pacemaker
 Wide ventricular complexes preceded byWide ventricular complexes preceded by
pacemaker spike. Rate is the pacer rhythmpacemaker spike. Rate is the pacer rhythm

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A-V blockA-V block
 First-degreeFirst-degree
(A-V(A-V
conductionconduction
lengthened )lengthened )
 Second-degreeSecond-degree
(Sudden(Sudden
dropped QRS-dropped QRS-
complex )complex )
 First-degreeFirst-degree
(Impulses(Impulses
originate at AVoriginate at AV
node andnode and
proceed toproceed to
ventricles)ventricles)
2.2. ACTIVATION SEQUENCEACTIVATION SEQUENCE

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Four Types of AV blockFour Types of AV block

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WPW syndromeWPW syndrome

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Right bundle-branch blockRight bundle-branch block
 QRSQRS
durationduration
greater thangreater than
0.12 s0.12 s
 Wide SWide S
wave inwave in
leads I, V5leads I, V5
and V6and V6

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Left bundle-branch blockLeft bundle-branch block
 QRS durationQRS duration
greater thangreater than
0.12 s0.12 s
 Wide S waveWide S wave
in leads V1in leads V1
and V2, wideand V2, wide
R wave in V5R wave in V5
and V6and V6

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Right atrial hypertrophyRight atrial hypertrophy
 Tall, peaked P wave inTall, peaked P wave in
leads I and IIleads I and II
3.3. HYPERTROPHYHYPERTROPHY

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Right ventricular hypertrophyRight ventricular hypertrophy
 Large R wave in leads V1 and V3Large R wave in leads V1 and V3
 Large S wave in leads V5 and V6Large S wave in leads V5 and V6

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Left ventricular hypertrophyLeft ventricular hypertrophy
 Large S wave inLarge S wave in
leads V1 and V2leads V1 and V2
 Large R wave inLarge R wave in
leads V5 and V6leads V5 and V6

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Left ventricular hypertrophyLeft ventricular hypertrophy

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Myocardial InfarctionMyocardial Infarction
 A. Normal ECG prior to MIA. Normal ECG prior to MI
 B. Hyperacute T wave changes -B. Hyperacute T wave changes -
increased T wave amplitude andincreased T wave amplitude and
width; may also see ST elevationwidth; may also see ST elevation
 C. Marked ST elevation withC. Marked ST elevation with
hyperacute T wave changeshyperacute T wave changes
(transmural injury)(transmural injury)
 D. Pathologic Q waves, less STD. Pathologic Q waves, less ST
elevation, terminal T waveelevation, terminal T wave
inversion (necrosis) (Pathologic Qinversion (necrosis) (Pathologic Q
waves are usually defined aswaves are usually defined as
duration >0.04 s or >25% of R-waveduration >0.04 s or >25% of R-wave
amplitude)amplitude)
 E. Pathologic Q waves, T waveE. Pathologic Q waves, T wave
inversion (necrosis and fibrosis)inversion (necrosis and fibrosis)
 F. Pathologic Q waves, upright TF. Pathologic Q waves, upright T
waves (fibrosis)waves (fibrosis)

Electrocardiography (ECG or EKG)

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Editor's Notes