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ECG

M.BayatPh.D

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Galvanometer

Willem Einthoven (1860–1927), known as the creator of the electrocardiograph, won a Nobel Prize in 1924 for his contributions to the field of electrocardiography.

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string galvanometer

Willem Einthoven (1860–1927), known as the creator of the electrocardiograph, won a Nobel Prize in 1924 for his contributions to the field of electrocardiography.

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The location of 10 electrodes

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Summary of Leads

Limb Leads Precordial Leads

Bipolar I, II, III(standard limb leads)

-

Unipolar aVR, aVL, aVF (augmented limb leads)

V1-V6

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The 12-Lead view• Leads are electrodes which measure the difference in

electrical potential between either• Each limb lead I, II, III, AVR, AVL, AVF records from a

different angle• All six limb leads intersect and visualize a frontal

plane• The six chest leads (precordial) V1, V2, V3, V4, V5, V6

view the body in the horizontal plane to the AV node• The 12 lead ECG forms a camera view from 12 angles

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Limb leads I, II, III are bipolar and have a negative and positive pole

Electrical potential differences are measured between the poles

++

+I

II III

Right

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+ +

+

Augmented voltage

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Voltage wilson=Vw

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Views from Augmented and Limb Leads- Frontal

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Precordial Leads

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Right ventricleLeft ventricle

septal

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Precordial lead snapshots

• Think of each precordial lead as a horizontal view of the heart at the AV node

• With the limb leads and the precordial leads you have a snapshot of heart portions

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I and AVL

II, III and AVF

V3 & v4

V1 & v2

V5 & v6

Where the positive electrode is positioned, determines what part of the heart is seen!

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V5,V6

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http://en.wikipedia.org/wiki/Myocardial_infarction

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II, III, AVF

Inferior MI

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Lateral MI

I, AVL, V5, V6

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Septal wall MI

V2,v3

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Posterior MI

V1, V2

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Anterior MI

V3,V4

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Anatomic Groups(Summary)

Right ventricle Apex

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The ECG Tracing: Waves

• P- wave– Marks the beginning of the cardiac cycle and measures the

electrical impulse that causes atrial depolarization and mechanical contraction

• QRS- Complex– Measures the impulse that causes ventricular depolarization

• Q-wave- the first downward deflection following the P-wave• R-wave- first upward deflection following P wave• S-wave- the first downward deflection following the R-wave

• T- wave– Marks ventricular repolarization that ends the cardiac cycle

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BASIC TERMINOLOGY

• Arrhythmia: Abnormal rhythm• Baseline: Flat, straight, isoelectric line• Waveform: Movement away from the

baseline, up or down• Segment: A line between waveforms• Interval: A waveform plus a segment• Complex: Combination of several waveforms

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-+

Why do Recorded waves by various types of leads have different shape ?

I

aVL

V3

aVR

V1,V2

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II

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1 2

3 4

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Depolarization and repolarization in ventricles

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+

+

-

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Views from Augmented and Limb Leads- Frontal

III

III

III

III

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r

R

S

s Q

R

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V5,V6

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I+III=II

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r

S

R

s Q

R

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r

S

r

S

R

S

R

s

R

s

R

s

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• Do you know determining the Heart Rate by ECG recording?

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Determining the Heart Rate

• Rule of 300

• 10 Second Rule• 60/RR interval sec

Lead V1,I,II are the best lead for evaluation of P wave and heart rate

Large square in RR1500

Small square in RR

300

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What is the heart rate?

(300 / 6) = 50 bpm

www.uptodate.com

If paper speed is 25 mm/s each small square is 0.04 s

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What is the heart rate?

(300 / ~ 4) = ~ 75 bpm

www.uptodate.com

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What is the heart rate?

(300 / 1.5) = 200 bpm

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The Rule of 300

It may be easiest to memorize the following table:

# of big boxes

Rate

1 300

2 150

3 100

4 75

5 60

6 50

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10 Second Rule

As most EKGs record 10 seconds of rhythm per page, one can simply count the number of beats present on the EKG and multiply by 6 to get the number of beats per 60 seconds.

This method works well for irregular rhythms.

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The QRS AxisDo you know determining the QRS axis by ECG recording?

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http://en.ecgpedia.org/wiki/Heart_axis

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The QRS Axis

the normal QRS axis is defined as ranging from +20° to +100°.

+20° to -90° is referred to as a left axis deviation (LAD)

+100° to +180° is referred to as a right axis deviation (RAD)

+20

+100

LAD

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The Quadrant Approach1. Examine the QRS complex in leads I and aVF to determine if they are predominantly

positive or predominantly negative. The combination should place the axis into one of the 4 quadrants below. In the event that LAD is present, examine lead II to determine if this deviation is pathologic. If the QRS in II is predominantly positive, the LAD is non-pathologic (in other words, the axis is normal). If it is predominantly negative, it is pathologic.

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Quadrant Approach: Example 1

Negative in I, positive in aVF RAD

The Alan E. Lindsay ECG Learning Center http://medstat.med.utah.edu/kw/ecg/

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Quadrant Approach: Example 2

Positive in I, negative in aVF Predominantly positive in II

Normal Axis (non-pathologic LAD)

The Alan E. Lindsay ECG Learning Center http://medstat.med.utah.edu/kw/ecg/

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The Equiphasic Approach1. Determine which lead contains the most equiphasic QRS

complex. The fact that the QRS complex in this lead is equally positive and negative indicates that the net electrical vector (i.e. overall QRS axis) is perpendicular to the axis of this particular lead.

2. Examine the QRS complex in whichever lead lies 90° away from the lead identified in step 1. If the QRS complex in this second lead is predominantly positive, than the axis of this lead is approximately the same as the net QRS axis. If the QRS complex is predominantly negative, than the net QRS axis lies 180° from the axis of this lead.

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Determining the Axis

Predominantly Positive

Predominantly Negative

Equiphasic

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Equiphasic Approach: Example 1

Equiphasic in aVF Predominantly positive in I QRS axis ≈ 0°

The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/

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Equiphasic Approach: Example 2

Equiphasic in II Predominantly negative in aVL QRS axis ≈ +150°

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Equiphasic Approach: Example 2

150

II 60

aVL

III

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aVR

aVF

Please calculate Net potential

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LAD

Left ventricular hypertrophy