Generation of action potential
ECG Graph paper
Unipolar precordial leads
Normal ECG
Guide in Reading ECG
•
•
•
•
•
•
•
•
•
•
•
•
Standardization & technique
Rhythm
Rate: atrial & ventricular
P wave morphology & duration
P-R interval
QRS complex morphology & duration
ST segment
T-wave
U wave
Q-T interval
Hypertrophy and enlargement
arrhythmias
Standardization
Heart rate
bradycardia
tachycardia
PR interval
QRS
QRS axis
QTc
60 - 100 beats/min
< 60
> 100
0.12 – 0.20 sec
< 0.12 sec
- 30º to + 110º
< 0.47 sec males
< 0.48 sec females
Guide in Reading ECG
•
•
•
•
•
•
•
•
•
•
•
•
•
Standardization & technique
Rhythm
Rate: atrial & ventricular
Axis
P wave morphology & duration
P-R interval
QRS complex morphology & duration
ST segment
T-wave
U wave
Q-T interval
Hypertrophy and enlargement
arrhythmias
Rhythm
SA node – sinus
AV node – junctional
Ventricular rhythm
Rhythm
Are there p waves?
 sinus, atrial fibrillation
Do they look similar?
 MFAT, wandering pacemaker
Are they regular?
 AF
Does a QRS complex follow each p wave?
 SVT, junctional rhythm, ventricular
rhythm
Guide in Reading ECG
•
•
•
•
•
•
•
•
•
•
•
•
•
Standardization & technique
Rhythm
Rate: atrial & ventricular
Axis
P wave morphology & duration
P-R interval
QRS complex morphology & duration
ST segment
T-wave
U wave
Q-T interval
Hypertrophy and enlargement
arrhythmias
Determination of Heart Rate
Heart rate assessment by “rule of 300”
Measurement of Rate
•
Formula 1:
300
# big squares between R-R
•
Formula 2:
1500
# small squares between R-R
Determination of Heart Rate
• Is the atrial rate same as ventricular rate?
– PVC’s, PAC’s, 3rd degree AV block
• Is there normal-looking QRS complex
after each p wave?
• What if there are no p waves?
– Six second strip heart rate
RATE
1. Sinus Bradycardia
2. Sinus Tachycardia
3. AV junctional rhythm
-
Inherent rate of 40-60/min
No p waves
Normal looking QRS complex
4. Ventricular rhythm
-
Inherent rate of 20-40/min
No p waves
Bizaare-looking QRS complex
Guide in Reading ECG
•
•
•
•
•
•
•
•
•
•
•
•
•
Standardization & technique
Rhythm
Rate: atrial & ventricular
Axis
P wave morphology & duration
P-R interval
QRS complex morphology & duration
ST segment
T-wave
U wave
Q-T interval
Hypertrophy and enlargement
arrhythmias
Determination of Axis
Hexaxial System
QRS axis
Vectorial Analysis
Determination of Axis
Axis
=
90 x QRS in AVF
QRS in [ I] + QRS in [AVF]
Special cases:
• negative QRS deflection in I
– Add 90 to result
Guide in Reading ECG
•
•
•
•
•
•
•
•
•
•
•
•
•
Standardization & technique
Rhythm
Rate: atrial & ventricular
Axis
P wave morphology & duration
P-R interval
QRS complex morphology & duration
ST segment
T-wave
U wave
Q-T interval
Hypertrophy and enlargement
arrhythmias
P wave morphology and duration
• No p waves
– Atrial fibrillation
• Multiple p waves
– Multifocal atrial tachycardia
– Wandering pacemaker
• Notched p wave
– Left atrial enlargement
• Peaked p wave
– Right atrial enlargement
Guide in Reading ECG
•
•
•
•
•
•
•
•
•
•
•
•
•
Standardization & technique
Rhythm
Rate: atrial & ventricular
Axis
P wave morphology & duration
P-R interval
QRS complex morphology & duration
ST segment
T-wave
U wave
Q-T interval
Hypertrophy and enlargement
arrhythmias
P-R Interval
P-R interval
• Prolongation
– Hypokalemia
– 1st degree AV block
• Shortening
– Wolff-Parkinson White
Guide in Reading ECG
•
•
•
•
•
•
•
•
•
•
•
•
•
Standardization & technique
Rhythm
Rate: atrial & ventricular
Axis
P wave morphology & duration
P-R interval
QRS complex morphology & duration
ST segment
T-wave
U wave
Q-T interval
Hypertrophy and enlargement
arrhythmias
QRS morphology and duration
• Normal looking
– Supraventricular origin
• Bizarre looking
– Ventricular in origin
– Paced rhythm
Guide in Reading ECG
•
•
•
•
•
•
•
•
•
•
•
•
•
Standardization & technique
Rhythm
Rate: atrial & ventricular
Axis
P wave morphology & duration
P-R interval
QRS complex morphology & duration
ST segment
T-wave
U wave
Q-T interval
Hypertrophy and enlargement
arrhythmias
ST segment
• Elevation
– Infarction
• >1mm in limb leads
• >2 mm in chest leads
• depression
– Ischemia
• >1 mm in all leads from the J point
Guide in Reading ECG
•
•
•
•
•
•
•
•
•
•
•
•
•
Standardization & technique
Rhythm
Rate: atrial & ventricular
Axis
P wave morphology & duration
P-R interval
QRS complex morphology & duration
ST segment
T-wave
U wave
Q-T interval
Hypertrophy and enlargement
arrhythmias
T and U waves
• T wave
– Hypokalemia
– 1st degree AV block
• Shortening
– Wolff-Parkinson White
Guide in Reading ECG
•
•
•
•
•
•
•
•
•
•
•
•
•
Standardization & technique
Rhythm
Rate: atrial & ventricular
Axis
P wave morphology & duration
P-R interval
QRS complex morphology & duration
ST segment
T-wave
U wave
Q-T interval
Hypertrophy and enlargement
arrhythmias
Determination of QT interval
Corrected QT interval = QT (actual)
R-R
QT interval
• prolongation
– hypocalcemia
• shortening
– hypercalcemia
Chamber Enlargement
Atrial Enlargement (due to chronic lung disease or
pulmonay embolus
Atrial Enlargement (commonly seen in mitral valve
disease)
B
V1
II
V1
Ventricular Enlargement
Ventricular Enlargement
Right Ventricular Hypertrophy
R in V1 + S in V5-V6 >11 mm
R in V1 >7mm
R:S in V1 >1
RAD > +90 degrees
Ischemic Heart Disease
Anatomy of Myocardial Infarction
Infarction
area
ECG leads
Coronary
Artery
Branch
Extensive
anterior
Anteroseptal
Anterolateral
Inferior
A, AVL, V1 – V6
Left, LM
LAD, LCX
V1 – V4
I, AVL, V3 – V6
II, III, AVF
LAD
LCX
PDA
True posterior
V1 – V2
(reciprocal)
V3 – V4
Left
Left
Right 80%
Left 20%
Variable
left/right
Left
Anterior
LCX
PL
LAD
*LAD = left anterior descending aretery; LCX = left circumflex artery
LM = left main artery; PDA = posterior descending artery;
PL = posterolateral branches
Evolution of Infarct
1.
2.
3.
4.
5.
ST segment elevation
Progressive decrease in ST segment elevation
Q wave formation
T wave flattening/inversion
Q wave with upright T wave
Significant Q wave
RULES on Q waves
• Not significant in aVR
• Ignored in V1 unless with abnormalities in
other precordial leads
• Ignored in III unless with abnormalities in
II, AVF
more reliable if with St-T segment changes
• Not significant if located in V1-V3 in LBBB
• Significant in V1-V2 in the presence of
RBBB
• Pathologic if >= 0.04 sec and >25% of R
wave amplitude
RHYTHM DISORDERS
ATRIAL Arrhythmias
1.
2.
3.
4.
Atrial fibrillation
Atrial flutter
Wandering Pacemaker
Multifocal Atrial tachycardia
ATRIAL FIBRILLATION
-
-
-
Most common sustained arrhythmia
associated with increased CV mortality
and morbidity
Prevalence increasing with age, doubling
with each successive decade, 70% in
ages 65-85
Multiplier effect on risk
-
-
3-5x stroke
3x CHF
1.5-3x death
Associated with heart disease but ~30%
are without underlying heart disease
ATRIAL FIBRILLATION
-
Rapid and irregular atrial fibrillatory waves
at a rate of 350 to 600/minute
CRITERIA
-
-
Absent P waves
F waves vary in amplitude, morphology and
intervals
R-R intervals are irregularly irregular
Ventricular rate usually ranges from 90-170
QRS complexes are narrow unless AV
conduction is abnormal
Hypothesized to be due to multiple wavelets in
the atrium competing for the conduction to the
AV node
ATRIAL FIBRILLATION
ATRIAL FLUTTER
-
Atrial rate of 220 to 350/minute
CRITERIA
-
Absent p waves
Biphasic saw-toothed flutter waves, fairly
regular
F waves vary in amplitude, morphology and
intervals
R-R intervals are irregularly irregular
Ventricular rate usually ranges from 90-170
QRS complexes are narrow unless AV
conduction is abnormal
Hypothesized to be due to multiple wavelets in
the atrium competing for the conduction to the
AV node
ATRIAL FLUTTER
Escape Rhythm/Beat
1. Atrial
-
Sinus arrest causing escape rhythm
With p’ waves
2. Junctional
-
No P waves
40-60/min inherent rate
Produces a series of lone QRS complexes
3. Ventricular
- may occur in complete AV block
Escape Rhythm/Beat
Sinoatrial block
-
Complete failure of a P wave to appear
A cycle appears which is twice the
anticipated P-P interval
Transient doubling of P-P interval
-
SA exit block
-
No visible P-QRST complex for more than 1
cycle
Normal P wave morphology, before and after
the pause
Pause is preceded and followed by a normal PP cycle
P-P interval is a mutliple of the normal P-P
interval
SA block
SINUS ARREST vs SINUS PAUSE
Wandering Pacemaker
-
-
Impulses originate from different foci in the
atrium and even AV node
Sinus node may still be dominant
>= 3 P wave morphologies, with varying
P-R intervals, resulting in varying R-R
intervals
Heart rate <100
May be seen in
-
Increased vagal tone
Digitalis effect
Organic heart disease
Wandering Pacemaker
Multifocal Atrial Tachycardia
-
Irregular atrial rate > 100
P wave shows >= 3 different morphologic
patterns and varying PR intervals
Varying P-P and P-R intervals result in
avrying R-R intervals
Multifocal Atrial Tachycardia
HEART BLOCKS
1. 1st degree
2. 2nd degree
-
Type 1 Wenkeboch
Type 2 Mobitz II
3. Complete AV block
4. Bundle Branch Block
-
Right bundle branch block
Left bundle branch block
5. Hemiblocks
-
Left anterior hemiblock
Left posterior hemiblock
• 1st degree
– PR interval > 0.20s
• 2nd degree (type1 and 2)
– Type 1 – PR interval becomes longer until depolarization is
not conducted anymore
– Type 2 – AV conduction is blocked
• 3rd degree
– AV dissociation
– Variable PR and RP intervals
– QRS rate is usually constant and lies within the range of 1570 beats /min
Trifascicular Conduction System
Right Bundle Branch Block
• Lead V1
pattern)
• Lead V6
• Lead I
late intrinsicoid, M-shaped QRS (RSR
early intrinsicoid, wide S wave
wide S wave
Right Bundle Branch Block
• Associated with
–
–
–
–
–
–
–
RHD
Cor pulmonale/RVH
Myocarditis
IHD
Degenerative disease of the conduction system
Pulmonary embolus
ASD
Right Bundle Branch Block
Left Bundle Branch Block
• Lead V1
• Lead V6
R
• Lead I
QS or rS
late intrinsicoid, no Q waves, monophasic
monophasis R, no Q wave
Left Bundle Branch Block
• Associated with
– CAD
– HHD
– Dilated cardiomyopathy
-- unusual for LBBB to exist in the absence of organic disease
Left Bundle Branch Block
Left Anterior Hemiblock
•
•
•
•
•
LAD (usually -30 to -60 degrees)
Small Q in leads I and aVL, small R in II, III and aVF
Usually normal QRS duration
Late intrinsicoid deflection in aVL
Increased QRS voltage in limb leads
Left Anterior Hemiblock
• Usually benign in the absence of apparent organic
heart disease and not associated with block in the
other fascicles
• Can also occur in
–
–
–
–
–
CAD
Chagas disease
Infiltrative and inflammatory diseases
CHDs
Sclerodegenerative disorder
Left Anterior Hemiblock
Left Posterior Hemiblock
•
•
•
•
•
•
RAD (usually + 120 degrees)
Small R in leads I and aVL, small Q in II, III and aVF
Usually normal QRS duration
Late intrinsicoid deflection in aVF
Increased QRS voltage in limb leads
No evidence of RVH
Left Posterior Hemiblock
• Can occur in
–
–
–
–
–
Cardiomyopathies
Myocarditis
Hyperkalemia
Acute cor pulmonale
chronic degeneerative and fibrotic processes of the
conducting system
– Aretriosclerotic cardiovascular disease
Left Posterior Hemiblock
Bifascicular Block
• Complete LBBB
• RBBB with either LAHB or LPHB
• Duration of QRS complex is prolonged to 0.12s
Bifascicular Block
Trifascicular Block
• Bifascicular block associated with 1st degree AV
block
Trifascicular Block
Premature Complexes
1. Premature Atrial Complex
2. Junctional Premature Beats
3. Ventricular Premature Beats
Premature Complexes - PACs
-
Premature atrial activation arising from a
site other than the sinus node
P wave occuring relatively early in the
cardiac cyle
- with a different morphology from the sinus P
wave
-
PR interval different from that during the
sinus rhythm
Premature Complexes - PACs
-
Not life-threatening by themselves
But may also start a VT
May be asymptomatic or cause a
sensationof “skipping” or palpitations
May be associated with normal conduction
or aberrant conduction
Premature Complexes - PACs
Premature Complexes –
Junctional Premature Beats
-
Arise from the AV node or in the His
bundle
A premature normal QRS complex is
closely accompanied by an “upside down”
P wave
Premature Complexes –
Ventricular Premature Beats
-
Duration of more than 0.12s
Bizarre morphology T wave in the
opposite direction from the QRS vector
A fully compensatory pause
Ventricular bigeminy, trigeminy,
quadrigeminy, couplet
Premature Complexes –
Ventricular Premature Beats
-
May be present in
-
Normal individuals
MVP
Hypertension and LVH
Chronic HD
Acute MI
cardiomyopathy
Miscellaneous
• Poor R wave progression
– < 3mm R wave in V3
• Low QRS
– < 5mm QRS amplitude in limb leads
– <10mm QRS amplitude in chest leads