Download How to Read ECG - sha

2/13/2014
Systematic Approach to 12 Lead
ECG Interpretation
Prepared by:
Shadi Kakish
Dr. Halia Al Shahri
How to Read ECG
Understand the
Heart’s Electrical
Message
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How to Read ECG
Your Knowledge is
Vital for Saving Lives
Systematic Approach
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Calibration
Rate
Rhythm
Axis
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P-wave
PR interval
QRS complex
ST segment
QT- Interval
T-wave
U- Wave
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ECG Leads
Impulse Conduction & the ECG
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers
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The “PQRST”
P wave = Atrial depolarization
QRS = Ventricular
depolarization
T wave = Ventricular
repolarization
The ECG Paper
Horizontally
One small box - 0.04 s
One large box - 0.20 s
Vertically
One large box - 0.5 mV
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Calibration
• Check that your ECG is calibrated correctly
• Height
 10mm = 1mV
 Look for a reference; which should be the
rectangular looking wave somewhere near the
left of the paper. It should be 10mm (10 small
squares) tall
• Paper speed
 25mm/ s 25 mm (25 small squares / 5 large
squares) equals one second
How to Read ECG
• Rate
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Rate
Regular :
HR= 300/Nnumber of large squares between 2 Rs
Rate
Irregular :
Count number of complexes in rhythm strip × 6
14 (R waves) x 6 = 84 b/m
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Rhythm
Lead II
P wave= Sinus Rhythm
No P wave= Non sinus
How to Read ECG
Axis
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Axis
• The electrical axis of the heart is the mean
direction of the cardiac impulse during
ventricular depolarization
• Leftward and downward
Axis
• Normal QRS axis between -30o and +90o.
• A QRS axis between -30oand -90o is LAD
• A QRS axis between +90o and +150o is RAD
• A QRS axis between +150o and
-90o is superior RAD
-150o
-90o
-60o
-120o
-30o
180o
0o
30o
150o
120o
90o
60o
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Place your thumb over leads I & aVf
pointing in the direction of the QRS
NORMAL
RAD
LAD
NO MANS LAND
P-wave
• P wave represents atrial depolarization, which
causes atrial contraction.
• Normally a dome-like structure
• Height
a P wave over 2.5mm should arouse suspicion
• Length
a P wave longer than 0.08s (2 small squares)
should arouse suspicion
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Abnormalities of P-wave
• A tall P wave (over2.5mm) can be called P
pulmonale which Occurs due to R atrial
hypertrophy, causes can be:
pulmonary hypertension
Pulmonary stenosis
Tricuspid stenosis
P-pulmonale
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Abnormalities of P-wave
• Length
A P wave with a length>0.08 seconds (2 small
squares) and (M) shape is called P mitrale
which caused by left atrial hypertrophy and
delayed left atrial depolarization, causes can
be:
Mitral valve disease
LVH
P mitrale
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The PR interval
• The PR interval corresponds to the time period
between depolarization of the atria and
ventricular depolarization or its represent the
delay in transmission in AV node
• A normal PR interval is between 0.12 and 0.2
seconds (3-5 small squares)
• The PR interval is measured between the start of
the P wave to the start of the QRS complex
The PR Interval
Atrial depolarization
+
delay in AV junction
(AV node/Bundle of His)
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1 AV Block
• PR Interval > 0.2 seconds (5 small sq)
Second Degree AV Block (2º)
Mobitz Type I (Wenkebach)
Progressive PR prolongation
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Second Degree AV Block (2º)
Mobitz Type II
PR interval is constant
Third Degree AV Block (3º)
(Complete)
P
P
QRS
P
P
QRS
Ps > QRSs
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Q Waves
Non Pathological Q waves
Q waves of less than 2mm are normal
Pathological Q waves
Q waves of more than 2mm
indicate full thickness myocardial
damage from an infarct
Late sign of MI
Pathological Q waves
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QRS
Height
• If the QRS complexes in the chest leads look
very tall, consider left ventricular hypertrophy
(LVH)
• If the depth of the S wave in V1 or V2 added
to the height of the R wave in V5 or V6 comes
to more than 35mm, LVH is present
Left Ventricular Hypertrophy
R in V5 (or V6) + S in V1 (or V2) > 35 mm
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QRS
• Width
• The width of the QRS complex should be less
than 0.12 seconds (3 small squares)
• If the QRS is wider than this, it suggests a
ventricular conduction problem - right or left
bundle branch block (RBBB or LBBB)
LBBB
• If left bundle branch
block is present, the
QRS complex may
look like a (W) shape rS- in V1 and/ or an
(M) shape – RsR
wave- in V 6
• New onset LBBB with
chest pain consider
Myocardial infarction
• Not possible to
interpret the ST
segment
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RBBB
• It is also called rSR pattern
• Terminal R wave in lead V1
• Slurred S wave in leads I and
V6
ST Segment
• The ST segment represents period between
ventricular depolarization and repolarisation.
• The ventricles are unable to receive any
further stimulation
• The ST segment normally lies on the
isoelectric line.
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Ischemia/Infarction
Ischemia/Infarction
II III AVF =Inferior
I AVL = Lateral
V1 V2 = Septal
V3 V4 = Anterior
V5 V6 = High Lateral
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Inferior MI
Anterior MI
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Anterolateral MI
T wave
• T wave generally shouldn’t be taller than half
the size of the preceding QRS
• Hyperacute T waves occur with ST segment
elevation in acute MI or hyperkalemia
• If the T wave is flat, it may indicate
hypokalemia
• If the T wave is inverted it may
indicate ischemia
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QT interval
• The QT interval is measured from the start of
the QRS complex to the end of the T wave
• The QT interval varies with heart rate
• QTc= QT/√RR (Corrected QT interval)
• The normal range for QTc is
0.38 – 0.42
QT interval
Short QTc interval may indicates
hypercalcaemia
Long QTC has many causes;
3 Hypos, Antiarrhythmic drugs and
congenital
Long QTc interval increase the risk of
developing arrhythmia?!!
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U wave
• U waves occur after the T wave and are often difficult
to see
• U waves are thought to represent repolarization of
the papillary muscle or Purkenji fibers
• Prominent U waves can be a sign of hypokalaemia
hyperthyroidism
• could normally be seen in younger,
athletic individuals
References
• The ECG made easy, 6th edition. John R.
Hampton
• Always at your side… ECG Notes interpretation
and management guide. Shirly A.Jones, 2005
• www.thh.nhs.uk/documents/_Departments/U
ndergraduates/.../ECG
• EKG-boken Ylva Lind, Lars Lind, Liber, 2011
• Cardiology Journal 2008, Vol. 15, No. 5, pp.
408–421
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How to read ECG
Hopefully you
understand my Message
Thank You
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