ECG
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Slide Content
Santhiram Medical CollegeSanthiram Medical College
Nandyal Nandyal
ELECTROCARDIOGRAPHYELECTROCARDIOGRAPHY
Lecture By Lecture By
Dr.G.Venkata Swamy M.DDr.G.Venkata Swamy M.D
Nandyal Nandyal
ELECTROCARDIOGRAPHYELECTROCARDIOGRAPHY
Lecture By Lecture By
Dr.G.Venkata Swamy M.DDr.G.Venkata Swamy M.D
HISTORY OF HISTORY OF
ELECTROCARDIOPHYELECTROCARDIOPHY
Agustus – Desire’ Waller was the first Agustus – Desire’ Waller was the first
person to record cardiac electricity in 1887person to record cardiac electricity in 1887
But most comprehensive work on human But most comprehensive work on human
electrocardiography was done by Willem electrocardiography was done by Willem
Einthoven in 1903 Einthoven in 1903
Willem Einthoven was awarded Nobel Willem Einthoven was awarded Nobel
prize for his work in electrocardiography in prize for his work in electrocardiography in
1924 1924
A few years later Wilson and Goldberger A few years later Wilson and Goldberger
developed the unipolar and augmented developed the unipolar and augmented
unipolar systems respectively unipolar systems respectively
ELECTROCARDIOPHYELECTROCARDIOPHY
Agustus – Desire’ Waller was the first Agustus – Desire’ Waller was the first
person to record cardiac electricity in 1887person to record cardiac electricity in 1887
But most comprehensive work on human But most comprehensive work on human
electrocardiography was done by Willem electrocardiography was done by Willem
Einthoven in 1903 Einthoven in 1903
Willem Einthoven was awarded Nobel Willem Einthoven was awarded Nobel
prize for his work in electrocardiography in prize for his work in electrocardiography in
1924 1924
A few years later Wilson and Goldberger A few years later Wilson and Goldberger
developed the unipolar and augmented developed the unipolar and augmented
unipolar systems respectively unipolar systems respectively
DefinitionsDefinitions
Electrocardiogram (ECG) :Electrocardiogram (ECG) :
It is a graphic recording of electricIt is a graphic recording of electric
potentials generated by the heart. potentials generated by the heart.
Electrocardiography Electrocardiography ::
The process of recording ECGThe process of recording ECG
is called electrocardiography is called electrocardiography
Electrocardiograph :Electrocardiograph :
The machine that records the ECG The machine that records the ECG
is called electrocardiograph is called electrocardiograph
Lead :Lead : Electrode placed on the body is Electrode placed on the body is
called a lead called a lead
Electrocardiogram (ECG) :Electrocardiogram (ECG) :
It is a graphic recording of electricIt is a graphic recording of electric
potentials generated by the heart. potentials generated by the heart.
Electrocardiography Electrocardiography ::
The process of recording ECGThe process of recording ECG
is called electrocardiography is called electrocardiography
Electrocardiograph :Electrocardiograph :
The machine that records the ECG The machine that records the ECG
is called electrocardiograph is called electrocardiograph
Lead :Lead : Electrode placed on the body is Electrode placed on the body is
called a lead called a lead
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
• An ECG is a series of waves and deflections recording the
heart’s electrical activity from a certain “view.” Many views,
each called a lead, monitor voltage changes between electrodes
placed in different positions on the body.
• Leads I, II, and III are bipolar leads, which consist of two
electrodes of opposite polarity (positive and negative). The third
(ground) electrode minimizes electrical activity from other
sources.
• Leads aVR, aVL, and aVF are unipolar leads and consist of a
single positive electrode and a reference point (with zero
electrical potential) that lies in the center of the heart’s
electrical field.
• Leads V1–V6 are unipolar leads and consist of a single positive
electrode with a negative reference point found at the electrical
center of the heart.
• An ECG is a series of waves and deflections recording the
heart’s electrical activity from a certain “view.” Many views,
each called a lead, monitor voltage changes between electrodes
placed in different positions on the body.
• Leads I, II, and III are bipolar leads, which consist of two
electrodes of opposite polarity (positive and negative). The third
(ground) electrode minimizes electrical activity from other
sources.
• Leads aVR, aVL, and aVF are unipolar leads and consist of a
single positive electrode and a reference point (with zero
electrical potential) that lies in the center of the heart’s
electrical field.
• Leads V1–V6 are unipolar leads and consist of a single positive
electrode with a negative reference point found at the electrical
center of the heart.
Clinical utility of the ECG :Clinical utility of the ECG :
1.1.It is noninvasive inexpensive and It is noninvasive inexpensive and
highly versatile test highly versatile test
2. Useful in detecting 2. Useful in detecting
a) Arrhythmias a) Arrhythmias
b) Conduction disturbances b) Conduction disturbances
c) myocardial ischemia & infarction c) myocardial ischemia & infarction
and and
d) metabolic disturbances such as d) metabolic disturbances such as
Hyperkalemia and Hypokalemia Hyperkalemia and Hypokalemia
1.1.It is noninvasive inexpensive and It is noninvasive inexpensive and
highly versatile test highly versatile test
2. Useful in detecting 2. Useful in detecting
a) Arrhythmias a) Arrhythmias
b) Conduction disturbances b) Conduction disturbances
c) myocardial ischemia & infarction c) myocardial ischemia & infarction
and and
d) metabolic disturbances such as d) metabolic disturbances such as
Hyperkalemia and Hypokalemia Hyperkalemia and Hypokalemia
ElectrocardiogramElectrocardiogram
1.1.BasicsBasics
2.2. Axis determination Axis determination
3.3.Calculation of Heart Rate Calculation of Heart Rate
4.4.Arrhythmias Arrhythmias
5.5.Bundle Branch Blocks Bundle Branch Blocks
6.6.Myocardial infarction Myocardial infarction
7.7.Cardiac enlargement and Cardiac enlargement and
Hypertrophy Hypertrophy
8.8.AV Blocks AV Blocks
9.9.Metabolic Disturbances Metabolic Disturbances
1.1.BasicsBasics
2.2. Axis determination Axis determination
3.3.Calculation of Heart Rate Calculation of Heart Rate
4.4.Arrhythmias Arrhythmias
5.5.Bundle Branch Blocks Bundle Branch Blocks
6.6.Myocardial infarction Myocardial infarction
7.7.Cardiac enlargement and Cardiac enlargement and
Hypertrophy Hypertrophy
8.8.AV Blocks AV Blocks
9.9.Metabolic Disturbances Metabolic Disturbances
Ctn. Structure and Function of the Normal Heart and Blood Vessels Ctn. Structure and Function of the Normal Heart and Blood Vessels
Conduction System
sinoatrial nodesinoatrial node
located in right atrium inf. to located in right atrium inf. to
opening of SVCopening of SVC
action potential begins hereaction potential begins here
initiates atrial contractioninitiates atrial contraction
atrioventricular nodeatrioventricular node
located in right atrium ant. to located in right atrium ant. to
opening of coronary sinusopening of coronary sinus
main job is to delay the action main job is to delay the action
potential to give atria time to potential to give atria time to
contractcontract
bundle of His (AV bundle)bundle of His (AV bundle)
only site where atrial impulses can only site where atrial impulses can
travel to the ventriclestravel to the ventricles
bundle branchesbundle branches
Purkinje fibers (not shown)Purkinje fibers (not shown)
small branches that travel from small branches that travel from
endocardium into myocadiumendocardium into myocadium
sinoatrial nodesinoatrial node
located in right atrium inf. to located in right atrium inf. to
opening of SVCopening of SVC
action potential begins hereaction potential begins here
initiates atrial contractioninitiates atrial contraction
atrioventricular nodeatrioventricular node
located in right atrium ant. to located in right atrium ant. to
opening of coronary sinusopening of coronary sinus
main job is to delay the action main job is to delay the action
potential to give atria time to potential to give atria time to
contractcontract
bundle of His (AV bundle)bundle of His (AV bundle)
only site where atrial impulses can only site where atrial impulses can
travel to the ventriclestravel to the ventricles
bundle branchesbundle branches
Purkinje fibers (not shown)Purkinje fibers (not shown)
small branches that travel from small branches that travel from
endocardium into myocadiumendocardium into myocadium
Conduction System
ReviewReview
cardiac action potential is initated in cardiac action potential is initated in
the SA nodethe SA node
travels quickly through pathways to travels quickly through pathways to
simultaneously contract the atriasimultaneously contract the atria
the atria and ventricles are insulated the atria and ventricles are insulated
from each other so atrial action from each other so atrial action
potentials can only enter ventricles potentials can only enter ventricles
through one pathwaythrough one pathway
action potential enters AV node where action potential enters AV node where
the impulses are slowed down and the impulses are slowed down and
held momentarilyheld momentarily
this gives the atria time to contractthis gives the atria time to contract
the action potential then travels the action potential then travels
quickly to the rest of the ventricular quickly to the rest of the ventricular
myocardium through the AV bundle, myocardium through the AV bundle,
bundle branches and purkinje fibersbundle branches and purkinje fibers
ReviewReview
cardiac action potential is initated in cardiac action potential is initated in
the SA nodethe SA node
travels quickly through pathways to travels quickly through pathways to
simultaneously contract the atriasimultaneously contract the atria
the atria and ventricles are insulated the atria and ventricles are insulated
from each other so atrial action from each other so atrial action
potentials can only enter ventricles potentials can only enter ventricles
through one pathwaythrough one pathway
action potential enters AV node where action potential enters AV node where
the impulses are slowed down and the impulses are slowed down and
held momentarilyheld momentarily
this gives the atria time to contractthis gives the atria time to contract
the action potential then travels the action potential then travels
quickly to the rest of the ventricular quickly to the rest of the ventricular
myocardium through the AV bundle, myocardium through the AV bundle,
bundle branches and purkinje fibersbundle branches and purkinje fibers
Electrical Flow
resting myocardial cells have a net negative resting myocardial cells have a net negative
charge at restcharge at rest
when an AP reaches a cell it depolarizes when an AP reaches a cell it depolarizes
causing the internal net charge to become causing the internal net charge to become
positivepositive
electrically, the action potential traveling electrically, the action potential traveling
through the heart can be viewed as a wave through the heart can be viewed as a wave
of positive chargeof positive charge
VectorVector
the average direction of all of the positive the average direction of all of the positive
charges as they travel through the charges as they travel through the
myocardiummyocardium
the average vector in a normal heart the average vector in a normal heart
travels to the left and downwardtravels to the left and downward
resting myocardial cells have a net negative resting myocardial cells have a net negative
charge at restcharge at rest
when an AP reaches a cell it depolarizes when an AP reaches a cell it depolarizes
causing the internal net charge to become causing the internal net charge to become
positivepositive
electrically, the action potential traveling electrically, the action potential traveling
through the heart can be viewed as a wave through the heart can be viewed as a wave
of positive chargeof positive charge
VectorVector
the average direction of all of the positive the average direction of all of the positive
charges as they travel through the charges as they travel through the
myocardiummyocardium
the average vector in a normal heart the average vector in a normal heart
travels to the left and downwardtravels to the left and downward
Electrical Flow
Vector InfluencesVector Influences
things that influence the things that influence the
overall amount of charge overall amount of charge
flowing through the flowing through the
myocardium will change the myocardium will change the
average direction the the average direction the the
charge is flowingcharge is flowing
InfarctionInfarction
essentially an area that no essentially an area that no
longer carries chargelonger carries charge
what would happen to the what would happen to the
vector if the posterior wall of vector if the posterior wall of
the l. ventricle infarcted?the l. ventricle infarcted?
Vector InfluencesVector Influences
things that influence the things that influence the
overall amount of charge overall amount of charge
flowing through the flowing through the
myocardium will change the myocardium will change the
average direction the the average direction the the
charge is flowingcharge is flowing
InfarctionInfarction
essentially an area that no essentially an area that no
longer carries chargelonger carries charge
what would happen to the what would happen to the
vector if the posterior wall of vector if the posterior wall of
the l. ventricle infarcted?the l. ventricle infarcted?
Electrical Flow
Vector InfluencesVector Influences
things that influence the overall things that influence the overall
amount of charge flowing through the amount of charge flowing through the
myocardium will change the average myocardium will change the average
direction the the charge is flowingdirection the the charge is flowing
InfarctionInfarction
essentially an area that no longer carries essentially an area that no longer carries
chargecharge
what would happen to the vector if the what would happen to the vector if the
posterior wall of the l. ventricle infarcted?posterior wall of the l. ventricle infarcted?
HypertrophyHypertrophy
essentially an area that carries extra essentially an area that carries extra
chargecharge
how would the vector change with l. how would the vector change with l.
ventricular hypertrophy?ventricular hypertrophy?
vector points towards hypertrophy and vector points towards hypertrophy and
away from infarctionaway from infarction
Vector InfluencesVector Influences
things that influence the overall things that influence the overall
amount of charge flowing through the amount of charge flowing through the
myocardium will change the average myocardium will change the average
direction the the charge is flowingdirection the the charge is flowing
InfarctionInfarction
essentially an area that no longer carries essentially an area that no longer carries
chargecharge
what would happen to the vector if the what would happen to the vector if the
posterior wall of the l. ventricle infarcted?posterior wall of the l. ventricle infarcted?
HypertrophyHypertrophy
essentially an area that carries extra essentially an area that carries extra
chargecharge
how would the vector change with l. how would the vector change with l.
ventricular hypertrophy?ventricular hypertrophy?
vector points towards hypertrophy and vector points towards hypertrophy and
away from infarctionaway from infarction
ECG PAPER ECG PAPER
•The horizontal scale represents time,
such that, at a standard paper speed
of 25 mm/sec, each small box (1 mm)
represents 0.04 second and each large
box (5 mm) represents 0.20 second.
•The vertical scale represents amplitude
(10 mm = 1 mV). The heart rate can be
estimated by dividing the number of
large boxes between complexes (R-R
interval) into 300.
•The horizontal scale represents time,
such that, at a standard paper speed
of 25 mm/sec, each small box (1 mm)
represents 0.04 second and each large
box (5 mm) represents 0.20 second.
•The vertical scale represents amplitude
(10 mm = 1 mV). The heart rate can be
estimated by dividing the number of
large boxes between complexes (R-R
interval) into 300.
ECG graph paper ECG graph paper
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
In the ECG each wave has a height In the ECG each wave has a height
(positive deflection ) (positive deflection )
or depth (negative deflection and or depth (negative deflection and
width)width)
When current flows towards When current flows towards
an electrode a tall positive deflectionan electrode a tall positive deflection
is recorded is recorded
When current flows away from the When current flows away from the
electrode a deep negative deflection electrode a deep negative deflection
is recorded is recorded
When current flows at 90When current flows at 90
0 0
to to
thethe
electrode a small ½ positive and electrode a small ½ positive and
½ negative deflections are recorded ½ negative deflections are recorded
In the ECG each wave has a height In the ECG each wave has a height
(positive deflection ) (positive deflection )
or depth (negative deflection and or depth (negative deflection and
width)width)
When current flows towards When current flows towards
an electrode a tall positive deflectionan electrode a tall positive deflection
is recorded is recorded
When current flows away from the When current flows away from the
electrode a deep negative deflection electrode a deep negative deflection
is recorded is recorded
When current flows at 90When current flows at 90
0 0
to to
thethe
electrode a small ½ positive and electrode a small ½ positive and
½ negative deflections are recorded ½ negative deflections are recorded
When current flows towards When current flows towards
an electrode a tall positive deflectionan electrode a tall positive deflection
is recorded fig. – Eis recorded fig. – E
1 1 electrode electrode
When current flows towards When current flows towards
an electrode a tall positive deflectionan electrode a tall positive deflection
is recorded fig. – Eis recorded fig. – E
1 1 electrode electrode
When current flows away from the When current flows away from the
electrode a deep negative deflection electrode a deep negative deflection
is recorded fig – Eis recorded fig – E
22 electrode electrode
When current flows away from the When current flows away from the
electrode a deep negative deflection electrode a deep negative deflection
is recorded fig – Eis recorded fig – E
22 electrode electrode
When current flows at 90When current flows at 90
0 0
to to
thethe
electrode a small ½ positive and electrode a small ½ positive and
½ negative deflections are recorded½ negative deflections are recorded
fig – Efig – E
3 3 electrode electrode
When current flows at 90When current flows at 90
0 0
to to
thethe
electrode a small ½ positive and electrode a small ½ positive and
½ negative deflections are recorded½ negative deflections are recorded
fig – Efig – E
3 3 electrode electrode
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
Standard Limb LeadsStandard Limb Leads
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
Standard Limb Leads
Standard Limb Electrode Placement
Standard Limb Leads
Standard Limb Electrode Placement
Standard Limb LeadsStandard Limb Leads
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
Augmented Limb Leads
Standard Limb Electrode Placement
Augmented Limb Leads
Standard Limb Electrode Placement
Augmented Limb LeadsAugmented Limb Leads
All Limb LeadsAll Limb Leads
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
Standard Chest Lead Electrode Placement
The Right-Sided 12-Lead ECG The 15-Lead ECG
Standard Chest Lead Electrode Placement
The Right-Sided 12-Lead ECG The 15-Lead ECG
ECG AXIS DETERMINATION ECG AXIS DETERMINATION
Direction of Direction of LEAD – 1LEAD – 1 LEAD-2 LEAD-2
AXIS AXIS
QRS compels DOMINANTLY DOMINANTY QRS compels DOMINANTLY DOMINANTY
NORMAL NORMAL
POSITIVE POSITIVE POSITIVE POSITIVE
AXIS AXIS
QRS compels DOMINANTLY DOMINANTY QRS compels DOMINANTLY DOMINANTY
NORMAL NORMAL
POSITIVE POSITIVE POSITIVE POSITIVE
DIRECTION DIRECTION LEAD – 1LEAD – 1 LEAD – 2LEAD – 2
AXIS AXIS
OF QRS DOMINANTLY DOMINANTLY LAD OF QRS DOMINANTLY DOMINANTLY LAD
COMPLEX POSITIVE NEGATIVE COMPLEX POSITIVE NEGATIVE
1.1.NORMAL VARANT 2. LVH NORMAL VARANT 2. LVH
3. LEFT ANTERIOR FASCICULAR BLOCK 3. LEFT ANTERIOR FASCICULAR BLOCK
4. INFERIOR M I 4. INFERIOR M I
AXIS AXIS
OF QRS DOMINANTLY DOMINANTLY LAD OF QRS DOMINANTLY DOMINANTLY LAD
COMPLEX POSITIVE NEGATIVE COMPLEX POSITIVE NEGATIVE
1.1.NORMAL VARANT 2. LVH NORMAL VARANT 2. LVH
3. LEFT ANTERIOR FASCICULAR BLOCK 3. LEFT ANTERIOR FASCICULAR BLOCK
4. INFERIOR M I 4. INFERIOR M I
DIRECTION DIRECTION LEAD1 LEAD1 LEAD2LEAD2
AXIS AXIS
OF QRS OF QRS DOMINANTLY DOMINANTLY DOMINANTLY DOMINANTLY
RAD RAD
COMPLEX COMPLEX NEGATIVE POSITIVE NEGATIVE POSITIVE
1.1. NORMAL VARIENT 2. DEXTROCARDIA NORMAL VARIENT 2. DEXTROCARDIA
3. SPURIOUS FINDING DUE TO REVERSAL OF 3. SPURIOUS FINDING DUE TO REVERSAL OF
RIGHT AND LEFT ARM ELECTRODES RIGHT AND LEFT ARM ELECTRODES
4.4. RVH 5. LATERAL WALL M I 6. LEFT PNEUMOTHORAX RVH 5. LATERAL WALL M I 6. LEFT PNEUMOTHORAX
7. LEFT POSTERIOR FASCICULAR BLOCK7. LEFT POSTERIOR FASCICULAR BLOCK
AXIS AXIS
OF QRS OF QRS DOMINANTLY DOMINANTLY DOMINANTLY DOMINANTLY
RAD RAD
COMPLEX COMPLEX NEGATIVE POSITIVE NEGATIVE POSITIVE
1.1. NORMAL VARIENT 2. DEXTROCARDIA NORMAL VARIENT 2. DEXTROCARDIA
3. SPURIOUS FINDING DUE TO REVERSAL OF 3. SPURIOUS FINDING DUE TO REVERSAL OF
RIGHT AND LEFT ARM ELECTRODES RIGHT AND LEFT ARM ELECTRODES
4.4. RVH 5. LATERAL WALL M I 6. LEFT PNEUMOTHORAX RVH 5. LATERAL WALL M I 6. LEFT PNEUMOTHORAX
7. LEFT POSTERIOR FASCICULAR BLOCK7. LEFT POSTERIOR FASCICULAR BLOCK
AXIS DETERMINATION AXIS DETERMINATION
TO DETERMINE THE AXIS, LOCATE THE FRONTAL PLANE TO DETERMINE THE AXIS, LOCATE THE FRONTAL PLANE
LEAD WHICH SHOWS SMALL EQUIPHASIC QRS DEFLETION LEAD WHICH SHOWS SMALL EQUIPHASIC QRS DEFLETION
ITS PERPENDICULAR LEAD FORMS THE ELECTRICAL AXIS ITS PERPENDICULAR LEAD FORMS THE ELECTRICAL AXIS
OF THEHEART WHICH SHOWS MAXIMUM QRS DEFLECTION OF THEHEART WHICH SHOWS MAXIMUM QRS DEFLECTION
IF THE DEFLECTION IS POSITIVE THE AXIS IS THE AXIS IF THE DEFLECTION IS POSITIVE THE AXIS IS THE AXIS
OF THE POSITIVE POLE OF THAT LEAD OF THE POSITIVE POLE OF THAT LEAD
IF THE DEFLECTION IS NEGATIVE THE AXIS IS THE AXIS IF THE DEFLECTION IS NEGATIVE THE AXIS IS THE AXIS
OF THE NEGATIVE POLE OF THAT LEAD OF THE NEGATIVE POLE OF THAT LEAD
TO DETERMINE THE AXIS, LOCATE THE FRONTAL PLANE TO DETERMINE THE AXIS, LOCATE THE FRONTAL PLANE
LEAD WHICH SHOWS SMALL EQUIPHASIC QRS DEFLETION LEAD WHICH SHOWS SMALL EQUIPHASIC QRS DEFLETION
ITS PERPENDICULAR LEAD FORMS THE ELECTRICAL AXIS ITS PERPENDICULAR LEAD FORMS THE ELECTRICAL AXIS
OF THEHEART WHICH SHOWS MAXIMUM QRS DEFLECTION OF THEHEART WHICH SHOWS MAXIMUM QRS DEFLECTION
IF THE DEFLECTION IS POSITIVE THE AXIS IS THE AXIS IF THE DEFLECTION IS POSITIVE THE AXIS IS THE AXIS
OF THE POSITIVE POLE OF THAT LEAD OF THE POSITIVE POLE OF THAT LEAD
IF THE DEFLECTION IS NEGATIVE THE AXIS IS THE AXIS IF THE DEFLECTION IS NEGATIVE THE AXIS IS THE AXIS
OF THE NEGATIVE POLE OF THAT LEAD OF THE NEGATIVE POLE OF THAT LEAD
In this figure small equiphasic QRS In this figure small equiphasic QRS
deflection is AVR THE LEAD WHICH deflection is AVR THE LEAD WHICH
IS AT 90IS AT 90
O O
IS LIS L
IIIIII. IN L. IN L
IIIIII THE THE
DEFLECTION IS POSTIVE SO THE DEFLECTION IS POSTIVE SO THE
AXIS IS +120AXIS IS +120
00
deflection is AVR THE LEAD WHICH deflection is AVR THE LEAD WHICH
IS AT 90IS AT 90
O O
IS LIS L
IIIIII. IN L. IN L
IIIIII THE THE
DEFLECTION IS POSTIVE SO THE DEFLECTION IS POSTIVE SO THE
AXIS IS +120AXIS IS +120
00
IN THIS FIGUER SMALL EQUIPHASIC IN THIS FIGUER SMALL EQUIPHASIC
QRS DEFLECTION IS LQRS DEFLECTION IS L
II. II. THE LEAD ATTHE LEAD AT
9090
0 0
TO LTO L
IIII LEAD IS AVL LEAD IS AVL
. .
IN THIS LEAD IN THIS LEAD
THE DEFLECTION IS NEGATIVE SO THE DEFLECTION IS NEGATIVE SO
THE AXIS IS +150THE AXIS IS +150
00
QRS DEFLECTION IS LQRS DEFLECTION IS L
II. II. THE LEAD ATTHE LEAD AT
9090
0 0
TO LTO L
IIII LEAD IS AVL LEAD IS AVL
. .
IN THIS LEAD IN THIS LEAD
THE DEFLECTION IS NEGATIVE SO THE DEFLECTION IS NEGATIVE SO
THE AXIS IS +150THE AXIS IS +150
00
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
Methods for Calculating Heart Rate
•Method 1: Count Large Boxes : Regular rhythms
can be quickly determined by counting the number of large
graph boxes between two R waves. That number is divided
into 300 to calculate bpm.
Methods for Calculating Heart Rate
•Method 1: Count Large Boxes : Regular rhythms
can be quickly determined by counting the number of large
graph boxes between two R waves. That number is divided
into 300 to calculate bpm.
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
•Method 2: Count Small Boxes: Sometimes it is
necessary to count the number of small boxes
between two R waves for fast heart rates. That
number is divided into 1500 to calculate bpm.
•Method 2: Count Small Boxes: Sometimes it is
necessary to count the number of small boxes
between two R waves for fast heart rates. That
number is divided into 1500 to calculate bpm.
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
•Method 3: Six-Second ECG Rhythm
Strip: The best method for measuring
irregular rates with varying R-R intervals is
to count the
•number of R waves in a 6-sec strip and
multiply by 10. This gives the average
number of bpm.
•Method 3: Six-Second ECG Rhythm
Strip: The best method for measuring
irregular rates with varying R-R intervals is
to count the
•number of R waves in a 6-sec strip and
multiply by 10. This gives the average
number of bpm.
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
Electrocardiogram Electrocardiogram
ArrhythmiasArrhythmias
ArrhythmiasArrhythmias
Normal Sinus Rhythm
(NSR)
Rate: Normal (60–100 bpm)
Rhythm: Regular
P Waves: Normal (upright and uniform)
PR Interval: Normal (0.12–0.20 sec)
QRS: Normal (0.06–0.10 sec)
(NSR)
Rate: Normal (60–100 bpm)
Rhythm: Regular
P Waves: Normal (upright and uniform)
PR Interval: Normal (0.12–0.20 sec)
QRS: Normal (0.06–0.10 sec)
Asystole
Rate: None
Rhythm: None
P Waves: None
PR Interval: None
QRS: None
Rate: None
Rhythm: None
P Waves: None
PR Interval: None
QRS: None
Sinus Bradycardia
Rate: Slow (<60 bpm)
Rhythm: Regular
P Waves: Normal (upright and
uniform)
PR Interval: Normal (0.12–0.20
sec)
QRS: Normal (0.06–0.10 sec)
Rate: Slow (<60 bpm)
Rhythm: Regular
P Waves: Normal (upright and
uniform)
PR Interval: Normal (0.12–0.20
sec)
QRS: Normal (0.06–0.10 sec)
Sinus Tachycardia
Rate: Fast (>100 bpm)
Rhythm: Regular
P Waves: Normal (upright and
uniform)
PR Interval: Normal (0.12–0.20
sec)
QRS: Normal (0.06–0.10 sec)
Rate: Fast (>100 bpm)
Rhythm: Regular
P Waves: Normal (upright and
uniform)
PR Interval: Normal (0.12–0.20
sec)
QRS: Normal (0.06–0.10 sec)
Sinus Arrhythmia
Rate: Usually normal (60–100 bpm);
frequently increases with inspiration
and decreases with expiration
Rhythm: Irregular; varies with respiration
P Waves: Normal (upright and uniform)
PR Interval: Normal (0.12–0.20 sec)
QRS: Normal (0.06–0.10 sec)
Rate: Usually normal (60–100 bpm);
frequently increases with inspiration
and decreases with expiration
Rhythm: Irregular; varies with respiration
P Waves: Normal (upright and uniform)
PR Interval: Normal (0.12–0.20 sec)
QRS: Normal (0.06–0.10 sec)
Sinus Pause (Sinus Arrest)
Rate: Normal to slow; determined by
duration and frequency of sinus pause
Rhythm: Irregular whenever a pause (arrest)
occurs
P Waves: Normal (upright and uniform)
except in areas of pause (arrest)
PR Interval: Normal (0.12–0.20 sec)
QRS: Normal (0.06–0.10 sec)
Rate: Normal to slow; determined by
duration and frequency of sinus pause
Rhythm: Irregular whenever a pause (arrest)
occurs
P Waves: Normal (upright and uniform)
except in areas of pause (arrest)
PR Interval: Normal (0.12–0.20 sec)
QRS: Normal (0.06–0.10 sec)
Sinoatrial (SA) Block
Rate: Normal to slow; determined by duration and frequency
of SA block
Rhythm: Irregular whenever an SA block occurs
P Waves: Normal (upright and uniform) except in areas of
dropped beats
PR Interval: Normal (0.12–0.20 sec)
QRS: Normal (0.06–0.10 sec)
•The block occurs in some multiple of the P-P interval.
•After the dropped beat, cycles continue on time.
Rate: Normal to slow; determined by duration and frequency
of SA block
Rhythm: Irregular whenever an SA block occurs
P Waves: Normal (upright and uniform) except in areas of
dropped beats
PR Interval: Normal (0.12–0.20 sec)
QRS: Normal (0.06–0.10 sec)
•The block occurs in some multiple of the P-P interval.
•After the dropped beat, cycles continue on time.
Supraventricular Tachycardia (SVT)
Rate: 150–250 bpm
Rhythm: Regular
P Waves: Frequently buried in preceding T waves and
difficult to see
PR Interval: Usually not possible to measure
QRS: Normal (0.06–0.10 sec) but may be wide if
abnormally conducted through ventricles
•This arrhythmia has such a fast rate that the P
waves may not be seen.
Rate: 150–250 bpm
Rhythm: Regular
P Waves: Frequently buried in preceding T waves and
difficult to see
PR Interval: Usually not possible to measure
QRS: Normal (0.06–0.10 sec) but may be wide if
abnormally conducted through ventricles
•This arrhythmia has such a fast rate that the P
waves may not be seen.
Atrial Flutter (A-flutter)
Rate: Atrial: 250–350 bpm; ventricular: slow or fast
Rhythm: Usually regular but may be variable
P Waves: Flutter waves have a saw-toothed
appearance
PR Interval: Variable
QRS: Usually normal (0.06–0.10 sec), but may
appear widened if flutter waves are buried in QRS
Rate: Atrial: 250–350 bpm; ventricular: slow or fast
Rhythm: Usually regular but may be variable
P Waves: Flutter waves have a saw-toothed
appearance
PR Interval: Variable
QRS: Usually normal (0.06–0.10 sec), but may
appear widened if flutter waves are buried in QRS
Atrial Fibrillation (A-fib)
Rate: Atrial: 350 bpm or greater; ventricular: slow or
fast
Rhythm: Irregular
P Waves: No true P waves; chaotic atrial activity
PR Interval: None
QRS: Normal (0.06–0.10 sec)
•Rapid, erratic electrical discharge comes from
multiple atrial ectopic foci.
•No organized atrial contractions are detectable.
Rate: Atrial: 350 bpm or greater; ventricular: slow or
fast
Rhythm: Irregular
P Waves: No true P waves; chaotic atrial activity
PR Interval: None
QRS: Normal (0.06–0.10 sec)
•Rapid, erratic electrical discharge comes from
multiple atrial ectopic foci.
•No organized atrial contractions are detectable.
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
Premature Ventricular Contraction (PVC)
Ventricular Tachycardia (VT)
Premature Ventricular Contraction (PVC)
Ventricular Tachycardia (VT)
Ctn. Electrocardiogram (ECG)Ctn. Electrocardiogram (ECG)
Torsade de Pointes
Ventricular Fibrillation (VF)
Torsade de Pointes
Ventricular Fibrillation (VF)
Myocardial infarction Myocardial infarction
The 12-Lead ECGThe 12-Lead ECG
The 12-Lead ECG sees the heart The 12-Lead ECG sees the heart
from 12 different views.from 12 different views.
Therefore, the 12-Lead ECG Therefore, the 12-Lead ECG
helps you see what is happening helps you see what is happening
in different portions of the in different portions of the
heart.heart.
The rhythm strip is only 1 of The rhythm strip is only 1 of
these 12 views.these 12 views.
The 12-Lead ECG sees the heart The 12-Lead ECG sees the heart
from 12 different views.from 12 different views.
Therefore, the 12-Lead ECG Therefore, the 12-Lead ECG
helps you see what is happening helps you see what is happening
in different portions of the in different portions of the
heart.heart.
The rhythm strip is only 1 of The rhythm strip is only 1 of
these 12 views.these 12 views.
The 12-LeadsThe 12-Leads
The 12-leads The 12-leads
include:include:
–3 Limb leads
(I, II, III)
–3 Augmented leads
(aVR, aVL, aVF)
–6 Precordial leads
(V
1
- V
6
)
The 12-leads The 12-leads
include:include:
–3 Limb leads
(I, II, III)
–3 Augmented leads
(aVR, aVL, aVF)
–6 Precordial leads
(V
1
- V
6
)
Views of the HeartViews of the Heart
Some leads get Some leads get
a good view of a good view of
the:the:
Anterior portion
of the heart
Lateral portion
of the heart
Inferior portion
of the heart
Some leads get Some leads get
a good view of a good view of
the:the:
Anterior portion
of the heart
Lateral portion
of the heart
Inferior portion
of the heart
ST ElevationST Elevation
One way to One way to
diagnose an diagnose an
acute MI is to acute MI is to
look for look for
elevation of elevation of
the ST the ST
segment.segment.
One way to One way to
diagnose an diagnose an
acute MI is to acute MI is to
look for look for
elevation of elevation of
the ST the ST
segment.segment.
ST Elevation (cont)ST Elevation (cont)
Elevation of the Elevation of the
ST segment ST segment
(greater than 1 (greater than 1
small box) in 2 small box) in 2
leads is leads is
consistent with consistent with
a myocardial a myocardial
infarction.infarction.
Elevation of the Elevation of the
ST segment ST segment
(greater than 1 (greater than 1
small box) in 2 small box) in 2
leads is leads is
consistent with consistent with
a myocardial a myocardial
infarction.infarction.
Anterior View of the HeartAnterior View of the Heart
The anterior portion of the heart is The anterior portion of the heart is
best viewed using leads Vbest viewed using leads V
11- V- V
44..
The anterior portion of the heart is The anterior portion of the heart is
best viewed using leads Vbest viewed using leads V
11- V- V
44..
Anterior Myocardial InfarctionAnterior Myocardial Infarction
If you see changes in leads VIf you see changes in leads V
11 - V - V
44
that are consistent with a that are consistent with a
myocardial infarction, you can myocardial infarction, you can
conclude that it is an anterior wall conclude that it is an anterior wall
myocardial infarction.myocardial infarction.
If you see changes in leads VIf you see changes in leads V
11 - V - V
44
that are consistent with a that are consistent with a
myocardial infarction, you can myocardial infarction, you can
conclude that it is an anterior wall conclude that it is an anterior wall
myocardial infarction.myocardial infarction.
Putting it all TogetherPutting it all Together
Do you think this person is having a Do you think this person is having a
myocardial infarction. If so, where?myocardial infarction. If so, where?
Do you think this person is having a Do you think this person is having a
myocardial infarction. If so, where?myocardial infarction. If so, where?
InterpretationInterpretation
YesYes, this person is having an acute , this person is having an acute
anterior wall myocardial infarction.anterior wall myocardial infarction.
YesYes, this person is having an acute , this person is having an acute
anterior wall myocardial infarction.anterior wall myocardial infarction.
Other MI LocationsOther MI Locations
Now that you know where to look for Now that you know where to look for
an anterior wall myocardial infarction an anterior wall myocardial infarction
let’s look at how you would determine let’s look at how you would determine
if the MI involves the lateral wall or if the MI involves the lateral wall or
the inferior wall of the heart.the inferior wall of the heart.
Now that you know where to look for Now that you know where to look for
an anterior wall myocardial infarction an anterior wall myocardial infarction
let’s look at how you would determine let’s look at how you would determine
if the MI involves the lateral wall or if the MI involves the lateral wall or
the inferior wall of the heart.the inferior wall of the heart.
Other MI LocationsOther MI Locations
First, take a First, take a
look again at look again at
this picture of this picture of
the heart.the heart.
Anterior portion
of the heart
Lateral portion
of the heart
Inferior portion
of the heart
First, take a First, take a
look again at look again at
this picture of this picture of
the heart.the heart.
Anterior portion
of the heart
Lateral portion
of the heart
Inferior portion
of the heart
Other MI LocationsOther MI Locations
Now, using these 3 diagrams let’s figure Now, using these 3 diagrams let’s figure
where to look for a lateral wall and where to look for a lateral wall and
inferior wall MI.inferior wall MI.
Limb Leads Augmented Leads Precordial Leads
Now, using these 3 diagrams let’s figure Now, using these 3 diagrams let’s figure
where to look for a lateral wall and where to look for a lateral wall and
inferior wall MI.inferior wall MI.
Limb Leads Augmented Leads Precordial Leads
Anterior MIAnterior MI
Remember the anterior portion of the Remember the anterior portion of the
heart is best viewed using leads Vheart is best viewed using leads V
11- V- V
44..
Limb Leads Augmented Leads Precordial Leads
Remember the anterior portion of the Remember the anterior portion of the
heart is best viewed using leads Vheart is best viewed using leads V
11- V- V
44..
Limb Leads Augmented Leads Precordial Leads
Lateral MILateral MI
So what leads do you So what leads do you
think the lateral think the lateral
portion of the heart is portion of the heart is
best viewed? best viewed?
Limb Leads Augmented Leads Precordial Leads
Leads I, aVL, and V
5
- V
6
So what leads do you So what leads do you
think the lateral think the lateral
portion of the heart is portion of the heart is
best viewed? best viewed?
Limb Leads Augmented Leads Precordial Leads
Leads I, aVL, and V
5
- V
6
Inferior MIInferior MI
Now how about the Now how about the
inferior portion of the inferior portion of the
heart? heart?
Limb Leads Augmented Leads Precordial Leads
Leads II, III and aVF
Now how about the Now how about the
inferior portion of the inferior portion of the
heart? heart?
Limb Leads Augmented Leads Precordial Leads
Leads II, III and aVF
Putting it all TogetherPutting it all Together
Now, where do you think this person Now, where do you think this person
is having a myocardial infarction?is having a myocardial infarction?
Now, where do you think this person Now, where do you think this person
is having a myocardial infarction?is having a myocardial infarction?
Inferior Wall MIInferior Wall MI
This is an inferior MI. Note the ST This is an inferior MI. Note the ST
elevation in leads II, III and aVF.elevation in leads II, III and aVF.
This is an inferior MI. Note the ST This is an inferior MI. Note the ST
elevation in leads II, III and aVF.elevation in leads II, III and aVF.
Putting it all TogetherPutting it all Together
How about now?How about now?
How about now?How about now?
Anterolateral MIAnterolateral MI
This person’s MI involves This person’s MI involves bothboth the anterior the anterior
wall (Vwall (V
22-V-V
44) and the lateral wall (V) and the lateral wall (V
55-V-V
66, I, , I,
and aVL)!and aVL)!
This person’s MI involves This person’s MI involves bothboth the anterior the anterior
wall (Vwall (V
22-V-V
44) and the lateral wall (V) and the lateral wall (V
55-V-V
66, I, , I,
and aVL)!and aVL)!
Right Ventricular Infarction Right Ventricular Infarction
R.V infarction is associated withR.V infarction is associated with
inferoposterior infarcation inferoposterior infarcation
RV infarcation causes signs of sever RV RV infarcation causes signs of sever RV
failure failure
( JVP , Kussmaul’s sign , tender ( JVP , Kussmaul’s sign , tender
hepatomegaly with or without hypotension )hepatomegaly with or without hypotension )
ST segment elevation is present in ST segment elevation is present in
V1 V2 and V4 R V1 V2 and V4 R
R.V infarction is associated withR.V infarction is associated with
inferoposterior infarcation inferoposterior infarcation
RV infarcation causes signs of sever RV RV infarcation causes signs of sever RV
failure failure
( JVP , Kussmaul’s sign , tender ( JVP , Kussmaul’s sign , tender
hepatomegaly with or without hypotension )hepatomegaly with or without hypotension )
ST segment elevation is present in ST segment elevation is present in
V1 V2 and V4 R V1 V2 and V4 R
Bundle branch blocksBundle branch blocks
Left Bundle Branch BlockLeft Bundle Branch Block
CriteriaCriteria
QRS duration ≥ 120msQRS duration ≥ 120ms
Broad R wave in I and VBroad R wave in I and V
66
Prominent QS wave in VProminent QS wave in V
11
Absence of q waves (including Absence of q waves (including
physiologic q waves) in I and Vphysiologic q waves) in I and V
66
CriteriaCriteria
QRS duration ≥ 120msQRS duration ≥ 120ms
Broad R wave in I and VBroad R wave in I and V
66
Prominent QS wave in VProminent QS wave in V
11
Absence of q waves (including Absence of q waves (including
physiologic q waves) in I and Vphysiologic q waves) in I and V
66
Right Bundle Branch BlockRight Bundle Branch Block
CriteriaCriteria
QRS duration ≥ 110msQRS duration ≥ 110ms
rSR’ pattern or notched R wave in VrSR’ pattern or notched R wave in V
11
Wide S wave in I and VWide S wave in I and V
66
CriteriaCriteria
QRS duration ≥ 110msQRS duration ≥ 110ms
rSR’ pattern or notched R wave in VrSR’ pattern or notched R wave in V
11
Wide S wave in I and VWide S wave in I and V
66
Chamber Enlargement And Chamber Enlargement And
Hypertrophy Hypertrophy
Hypertrophy Hypertrophy
Left Atrial EnlargementLeft Atrial Enlargement
Criteria
P wave duration in II ≥120ms
or
Negative component of
biphasic P wave in V
1
≥ 1 “small
box” in area
Criteria
P wave duration in II ≥120ms
or
Negative component of
biphasic P wave in V
1
≥ 1 “small
box” in area
Right Atrial EnlargementRight Atrial Enlargement
Criteria
P wave height in II ≥ 2.4mm
or
Positive component of
biphasic P wave in V
1
≥ 1
“small box” in area
Criteria
P wave height in II ≥ 2.4mm
or
Positive component of
biphasic P wave in V
1
≥ 1
“small box” in area
Left Ventricular HypertrophyLeft Ventricular Hypertrophy
Many sets of criteria for diagnosing LVH Many sets of criteria for diagnosing LVH
have been proposed:have been proposed:
SensitivitySensitivitySpecificitySpecificity
The sum of the S wave in VThe sum of the S wave in V
11
and the R wave in either Vand the R wave in either V
55
or Vor V
66 > 35 mm > 35 mm
43%43% 95%95%
Sum of the largest precordial Sum of the largest precordial
R wave and the largest R wave and the largest
precordial S wave > 45 mmprecordial S wave > 45 mm
45%45% 93%93%
Romhilt-Estes Point SystemRomhilt-Estes Point System 50-54%50-54% 95-97%95-97%
Many sets of criteria for diagnosing LVH Many sets of criteria for diagnosing LVH
have been proposed:have been proposed:
SensitivitySensitivitySpecificitySpecificity
The sum of the S wave in VThe sum of the S wave in V
11
and the R wave in either Vand the R wave in either V
55
or Vor V
66 > 35 mm > 35 mm
43%43% 95%95%
Sum of the largest precordial Sum of the largest precordial
R wave and the largest R wave and the largest
precordial S wave > 45 mmprecordial S wave > 45 mm
45%45% 93%93%
Romhilt-Estes Point SystemRomhilt-Estes Point System 50-54%50-54% 95-97%95-97%
Left Ventricular HypertrophyLeft Ventricular Hypertrophy
Right Ventricular HypertrophyRight Ventricular Hypertrophy
Right axis deviationRight axis deviation
Right atrial enlargementRight atrial enlargement
Downsloping ST depressions in VDownsloping ST depressions in V
11-V-V
33 (a.k.a. (a.k.a.
RV strain pattern)RV strain pattern)
Tall R wave in VTall R wave in V
11
Right axis deviationRight axis deviation
Right atrial enlargementRight atrial enlargement
Downsloping ST depressions in VDownsloping ST depressions in V
11-V-V
33 (a.k.a. (a.k.a.
RV strain pattern)RV strain pattern)
Tall R wave in VTall R wave in V
11
Right Ventricular HypertrophyRight Ventricular Hypertrophy
ExamplesExamples
Left Ventricular Hypertrophy
Right Bundle Branch Block
Right Atrial Enlargement
Left Bundle Branch Block
Left Atrial Enlargement
Right Ventricular Hypertrophy
Left Ventricular Hypertrophy
(with frequent PVCs)
(with frequent PVCs)
A-V BLOCKSA-V BLOCKS
Interruption/delay in the conduction Interruption/delay in the conduction
of electrical impulses between the of electrical impulses between the
atria & ventriclesatria & ventricles
Classified site of block/severity of Classified site of block/severity of
conduction abnormality conduction abnormality
11
stst
degree, 2 degree, 2
ndnd
degree Mobitz I degree Mobitz I
(Wenkebach), 2(Wenkebach), 2
ndnd
degree Mobitz II, 3 degree Mobitz II, 3
rdrd
degree (Complete heart block)degree (Complete heart block)
Interruption/delay in the conduction Interruption/delay in the conduction
of electrical impulses between the of electrical impulses between the
atria & ventriclesatria & ventricles
Classified site of block/severity of Classified site of block/severity of
conduction abnormality conduction abnormality
11
stst
degree, 2 degree, 2
ndnd
degree Mobitz I degree Mobitz I
(Wenkebach), 2(Wenkebach), 2
ndnd
degree Mobitz II, 3 degree Mobitz II, 3
rdrd
degree (Complete heart block)degree (Complete heart block)
11
stst
Degree AV Block Degree AV Block
Characterized by PR Interval > 0.20 Characterized by PR Interval > 0.20
secondsseconds
Delay in conduction AV NodeDelay in conduction AV Node
Prolonged PR Interval constantProlonged PR Interval constant
Usually asymptomaticUsually asymptomatic
Least concerning of the blocksLeast concerning of the blocks
stst
Degree AV Block Degree AV Block
Characterized by PR Interval > 0.20 Characterized by PR Interval > 0.20
secondsseconds
Delay in conduction AV NodeDelay in conduction AV Node
Prolonged PR Interval constantProlonged PR Interval constant
Usually asymptomaticUsually asymptomatic
Least concerning of the blocksLeast concerning of the blocks
22
ndnd
Degree Mobitz I Degree Mobitz I
(Wenkebach)(Wenkebach)
Successive impulses from SA node delayed Successive impulses from SA node delayed
slightly longer than the previous impulseslightly longer than the previous impulse
Characterized by prolonged PR interval that Characterized by prolonged PR interval that
continues until the P wave is dropped (impulse continues until the P wave is dropped (impulse
doesn’t reach ventricle)doesn’t reach ventricle)
May have hypotension or lightheadednessMay have hypotension or lightheadedness
ndnd
Degree Mobitz I Degree Mobitz I
(Wenkebach)(Wenkebach)
Successive impulses from SA node delayed Successive impulses from SA node delayed
slightly longer than the previous impulseslightly longer than the previous impulse
Characterized by prolonged PR interval that Characterized by prolonged PR interval that
continues until the P wave is dropped (impulse continues until the P wave is dropped (impulse
doesn’t reach ventricle)doesn’t reach ventricle)
May have hypotension or lightheadednessMay have hypotension or lightheadedness
22
ndnd
Degree Mobitz II Degree Mobitz II
Less common, more seriousLess common, more serious
Impulses from SA node fail to conduct to Impulses from SA node fail to conduct to
ventriclesventricles
Hallmark PR Interval constant normal or Hallmark PR Interval constant normal or
prolonged, doesn’t prolong before dropping, not prolonged, doesn’t prolong before dropping, not
followed by QRS, can have > 1 dropped in a rowfollowed by QRS, can have > 1 dropped in a row
Precursor to 3Precursor to 3
rdrd
Degree Heart Block Degree Heart Block
ndnd
Degree Mobitz II Degree Mobitz II
Less common, more seriousLess common, more serious
Impulses from SA node fail to conduct to Impulses from SA node fail to conduct to
ventriclesventricles
Hallmark PR Interval constant normal or Hallmark PR Interval constant normal or
prolonged, doesn’t prolong before dropping, not prolonged, doesn’t prolong before dropping, not
followed by QRS, can have > 1 dropped in a rowfollowed by QRS, can have > 1 dropped in a row
Precursor to 3Precursor to 3
rdrd
Degree Heart Block Degree Heart Block
33
RDRD
DEGREE “COMPLETE DEGREE “COMPLETE
HEART BLOCK”HEART BLOCK”
Indicates complete absence of impulse between Indicates complete absence of impulse between
the atria & ventriclethe atria & ventricle
Atrial rate > or = ventricular rateAtrial rate > or = ventricular rate
Occur @ AV node 40-60 bpmOccur @ AV node 40-60 bpm
Occur @ bundle branches < 40 bpm wide QRS Occur @ bundle branches < 40 bpm wide QRS
complexcomplex
Decreased C.O., P-P & R-R disassociated Decreased C.O., P-P & R-R disassociated
RDRD
DEGREE “COMPLETE DEGREE “COMPLETE
HEART BLOCK”HEART BLOCK”
Indicates complete absence of impulse between Indicates complete absence of impulse between
the atria & ventriclethe atria & ventricle
Atrial rate > or = ventricular rateAtrial rate > or = ventricular rate
Occur @ AV node 40-60 bpmOccur @ AV node 40-60 bpm
Occur @ bundle branches < 40 bpm wide QRS Occur @ bundle branches < 40 bpm wide QRS
complexcomplex
Decreased C.O., P-P & R-R disassociated Decreased C.O., P-P & R-R disassociated
HypokalemiaHypokalemia
Clinical consequences of hypokalemia Clinical consequences of hypokalemia
usually goes unnoticed. Common usually goes unnoticed. Common
findings include weakness, fatigue, findings include weakness, fatigue,
constipation, ileus, and respiratory constipation, ileus, and respiratory
muscle dysfunction.muscle dysfunction.
Thus, most of the time K+ gets Thus, most of the time K+ gets
replaced out of habit or to please the replaced out of habit or to please the
consultants. (e.g. Cardiology likes a consultants. (e.g. Cardiology likes a
K+ of 4.0 or above in MI patients.)K+ of 4.0 or above in MI patients.)
Clinical consequences of hypokalemia Clinical consequences of hypokalemia
usually goes unnoticed. Common usually goes unnoticed. Common
findings include weakness, fatigue, findings include weakness, fatigue,
constipation, ileus, and respiratory constipation, ileus, and respiratory
muscle dysfunction.muscle dysfunction.
Thus, most of the time K+ gets Thus, most of the time K+ gets
replaced out of habit or to please the replaced out of habit or to please the
consultants. (e.g. Cardiology likes a consultants. (e.g. Cardiology likes a
K+ of 4.0 or above in MI patients.)K+ of 4.0 or above in MI patients.)
Don’t Forget about EKGDon’t Forget about EKG
ST depressions with prominent U waves and prolonged ST depressions with prominent U waves and prolonged
repolarizationrepolarization
ST depressions with prominent U waves and prolonged ST depressions with prominent U waves and prolonged
repolarizationrepolarization
DefinitionDefinition
Normal serum potassium 3.5-5.5 Normal serum potassium 3.5-5.5
mEq/LmEq/L
Hyperkalemia is a serum Hyperkalemia is a serum
potassium greater than 5.5 potassium greater than 5.5
mEq/LmEq/L
Normal serum potassium 3.5-5.5 Normal serum potassium 3.5-5.5
mEq/LmEq/L
Hyperkalemia is a serum Hyperkalemia is a serum
potassium greater than 5.5 potassium greater than 5.5
mEq/LmEq/L
EKG ChangesEKG Changes
Peaked T WavesPeaked T Waves
Peaked T WavesPeaked T Waves
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