ECGDr Majid Shojaee

Assisstant Professor of Emergency Medicine

Shahid Beheshti university of medical sciences

Leads 1,2,3,aVR,aVL,aVF

Limb leads & colours

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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)

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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)

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0o

30o

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0o

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-30o

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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

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0o

30o

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-120o

90o 120o

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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

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-120o

90o 120o

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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

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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

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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

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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

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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

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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