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ECG
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ECGDr Majid Shojaee
Assisstant Professor of Emergency Medicine
Shahid Beheshti university of medical sciences
Leads 1,2,3,aVR,aVL,aVF
Limb leads & colours
?
Euro & Iran Rt Lt
Precordial Leads= V1-V6
Precordial Leads Measure potentials close to the heart, V1-
V6
Unipolar leads
ECG Chest Leads
Precardial (chest) Lead Position V1 = 4th ICS, right sternal border V2 = 4th ICS, left sternal border V3 = between V2 and V4 V4 = 5th ICS, left Mid clavicular Line V5 = 5th ICS Left anterior axillary line V6 = 5th ICS Left mid axillary line
Calibration, or standardization refers to the amplitude of the waveforms
on the tracing. It is usually set at a default value of 10 mm/mV
Increasing the calibration to 20 mm/mV is helpful when trying to decipher P wave morphology.
Decreasing the calibration to 5 mm/mV is helpful in cases wherein the amplitude of the QRS complex (usually in the precordial leads) is so large
Paper speed
usually is set at a default of 25 mm/sec. It may be manipulated for purposes of deciphering a dysrhythmia,
It is important that the clinician examine all ECG tracings for standardization and speed parameters before attempting clinical interpretation.
ADDITIONAL lEADS
15 lead ECG Posterior leads Right leads Invasive procedural leads
15 leads: V7-V8-V9V7: post. Axillary linev8: tip of Lt scapulav9: near the border of paraspinal m.
Posterior leads
V8-V9
Right side leads; V4R (Rt 5th intercostal space mid-clavicular line) is the most useful lead for detecting STE in RV MI
Lewis leads RA &LLVertical sternal (Barker) leads RA &LLModified bipolar chest leads (MCL)MCL1: RA & LAMCL6: RA & LL
Alternative leads
WHY?
Rhythm assessment often requires ECGmonitoring over continuous periods of time,
making the standard 12-lead ECG (requiring 10 electrodes), and
even unipolar precordial V1 monitoring (requiring 5 electrodes), not feasible.
A number of alternative lead systems requiring fewer electrodes have been described.
& vertical sternal leads produce a larger P wave than other systems
Einthoven’s triangle
Lewis, Barker & MCL6 : lead 2MCL1: lead 1
Einthoven’s triangle
Lead misplacement
Normal ECG Signal
P – atrial depolarization
QRS complex – ventricular depolarization
T – ventricular repolarization
Reading 12-Lead ECGs
The best way to read 12-lead ECGs is : 6-step approach:
1. Calculate RATE2. Determine RHYTHM3. Determine QRS AXIS4. Calculate INTERVALS5. Assess for HYPERTROPHY6. Look for evidence of INFARCTION
Rate Determination300/RR(large square)
40
Next
QRS
QRS
Rhythm
Sinus? Each P followed by QRS, R-R
constant
Dr Majid Shojaee 42
Rate Rhythm Axis Intervals Hypertrophy Infarct
We can quickly determine whether the QRS axis is normal by looking at leads I and II.
If the QRS complex is overall positive (R > Q+S) in leads I and II, the QRS axis is normal.
QRS negative (R < Q+S)
QRS equivocal (R = Q+S)
Rate Rhythm Axis Intervals Hypertrophy Infarct
Now using what you just learned fill in the following table. For example, if the QRS is positive in lead I and negative in lead II what is the QRS axis? (normal, left, right or right superior axis deviation)
44
0o
30o
-30o
60o
-60o-90o
-120o
90o 120o
150o
180o
-150o
0o
30o
-30o
60o
-60o-90o
-120o
90o 120o
150o
180o
-150o
QRS Complexes
I
Axis I II
+ + normal
II
Dr Majid Shojaee
Rate Rhythm Axis Intervals Hypertrophy Infarct
Now using what you just learned fill in the following table. For example, if the QRS is positive in lead I and negative in lead II what is the QRS axis? (normal, left, right or right superior axis deviation)
45
0o
30o
-30o
60o
-60o-90o
-120o
90o 120o
150o
180o
-150o
0o
30o
-30o
60o
-60o-90o
-120o
90o 120o
150o
180o
-150o
QRS Complexes
I
Axis I II
+ +
+ -
normal
left axis deviation
II
Dr Majid Shojaee
Rate Rhythm Axis Intervals Hypertrophy Infarct
… if the QRS is negative in lead I and positive in lead II what is the QRS axis? (normal, left, right or right superior axis deviation)
46
0o
30o
-30o
60o
-60o-90o
-120o
90o 120o
150o
180o
-150o
0o
30o
-30o
60o
-60o-90o
-120o
90o 120o
150o
180o
-150o
QRS Complexes
I
Axis I II
+ +
+ -
- +
normal
left axis deviation
right axis deviation
II
Dr Majid Shojaee
0o
30o
-30o
60o
-60o-90o
-120o
90o 120o
150o
180o
-150o
Rate Rhythm Axis Intervals Hypertrophy Infarct
… if the QRS is negative in lead I and negative in lead II what is the QRS axis? (normal, left, right or right superior axis deviation)
47
QRS Complexes
I
Axis I II
+ +
+ -
- +
- -
normal
left axis deviation
right axis deviation
right superior axis deviation
0o
30o
-30o
60o
-60o-90o
-120o
90o 120o
150o
180o
-150o
II
Dr Majid Shojaee
Rate Rhythm Axis Intervals Hypertrophy Infarct
Is the QRS axis normal in this ECG?
No, there is left axis deviation.
The QRS is positive in I and negative in II.
Axis Determination
49
NORMAL RIGHT LEFT
ALL UPRIGHT
Intervals
QT= 0.33”-0.42” (<0.47”) QTcQT/√RR
QRS <0.12” PR =0.10”-0.20”
P duration < 0.12 sec P amplitude < 2.5 mm
Hyperthrophy / Enlargement
Right Atrial Enlargement
Always examine Lead 2 for RAE Tall Peaked P Waves, Arrow head P waves Amplitude is 4 mm ( 0.4 mV) - abnormal Pulmonary Hypertension, Mitral Stenosis Tricuspid Stenosis, Regurgitation Pulmonary Valvular Stenosis Pulmonary Embolism Atrial Septal Defect with L to R shunt
Right Atrial Enlargement
53
P wave voltage is 4 boxes or 4 mm
Left Atrial Enlargement
Always examine V 1 and Lead 1 for LAE Biphasic P Waves, Prolonged P waves P wave 0.16 sec, ↑ Downward
component Systemic Hypertension, MS and or MR Aortic Stenosis and Regurgitation Left ventricular hypertrophy with
dysfunction Atrial Septal Defect with R to L shunt
Left Atrial Enlargement
55
P wave duration is 4 boxes-0.04 x 4 = 0.16
Atrial Hypertrophy: Enlarged Atria
RIGHT ATRIAL HYPERTROPHYTall, peaked P wave in leads I and II
LEFT ATRIAL HYPERTROPHYWide, notched P wave in lead IIDiphasic P wave in V1
Ventricular Hypertrophy
Ventricular Muscle Hypertrophy
QRS voltages in V1 and V6, L1 and aVL
We may have to record to ½ standardization
T wave changes opposite to QRS direction
Associated Axis shifts Associated Atrial hypertrophy
57
Marriott's Practical Electrocardiography: Galen S. Wagner
Normal Variations in ECG May have slight left axis due to rotation of heart
May have high voltage QRS – simulating LVH
Mild slurring of QRS but duration < 0.09
J point depression, early repolarization
T inversions in V2, V3 and V4 – Juvenile T ↓
Similarly in women also T↓
Low voltages in obese women and men
Non cardiac causes of ECG changes may
occur
S.A.H. ECG changes
60
?
61
Pediatric ECG
This is the ECG of a 6 year old child -Heart rate is 100 – Normal for the age -See )V1 + V5( R >> 35 – Not LVH –
Normal -T↓ in V1, V2, V3 – Normal in child -Base line disturbances in V5, V6 due to
movement by child
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