An electrocardiogram (ECG) records the electrical impulses of the heart, helping to assess cardiac function, diagnose disorders, and evaluate treatment effects. It consists of various leads and components including waves, complexes, segments, and intervals that indicate different heart activities and abnormalities. Proper lead placement and understanding of the ECG paper are essential for accurate interpretation and diagnosing conditions like myocardial infarction and arrhythmias.

1. ECG
- PURVI SHAH
(B.P.T)

3. Electrocardiogram
 An ECG is a permanent record of the electrical impulses
generated in the heart by the depolarization & repolarization
(contraction & relaxation) of the myocardium.
 It is a representation of the electrical events of the cardiac
cycle.
 These impulses are transmitted to the surface of the body
where they are detected & picked up by the electrodes &
measured by electrocardiograph.

5. Clinical use of ECG
 To assess the cardiac functions, e.g. rate, rhythm, &
conduction.
 TO diagnose cardiac rhythm disorders, e.g. heart attack
TO diagnose cardiac diseases, e.g. MI
 To evaluate effects of the treatments, e.g. administration of
cardiac drugs.

6. Rate Rhythm Cardiac
disease
Effect of treatments
Normal = 60
100 beats /
min
Irregular Cardiomyopathy Inotropic effect
Tachycardia Fast Myocardial
infarction
Chonotropic effect
Bradycardia Slow Heart attack Rhythmic effect

7. ECG lead placement
 12. Leads ECG Placement
 3. Standard limbs leads
 3. Augmated limbs leads
 6. Precordial leads

8. Standard limb leads
 LEADS I, II, III
 These are the bipolar leads
that register the voltage
between two electrodes

9. Augmated limb leads
 Leads aVR, aVL, aVF
These are the unipolar leads that register
the activity in the heart which is directed
or located below electrode

10. Precordial lead placement
 V1: 4th intercostal space, right sternal border
 V2: 4th intercostal space, left sternal border
 V3: midway between V2 and V4
 V4: 5th intercostal space, left midclavicular line
 V5: level with V4 anterior axillary line
 V6: level with V4 mid axillary line

13. Leads V1 & aVR- Represent right side of the heart
Leads V2, V3, V4- Represent transition between the right & left
side of the heart
Leads V5, V6. I, aVL- Represent left side of the heart
Leads II, III, aVF- Represent the inferior part of the heart

14. Einthoven’s triangle
It is an imaginary formation of the three
leads in a triangle used in ECG
The heart being a centre of a euilateral
triangle, whose apices are at a right arm,
left leg & left arm.
 The triangle, thus formed is called
Einthoven’s triangle

15. Components of ECG

16. Normal ECG

17. Components of ECG
 ECG consist of waves, complexes, segments & intervals
 Waves Complexes Segments Intervals
P, Q, R, S, T, U QRS P-Q, S-T, T-P P-R, Q-T, R-R

19. P wave
Significance – Depolarization of atria
Time period - <0.12 sec
Abnormalities – Abnormal or absence of SA node
abnormality
P-R Interval
Significance – Time for the impulses to reach the ventricales
Time period - <0.20 sec
Abnormalities – prolonged P-R intervals indicates
conduction of block

20. S-T Segment
Significance – Completion of depolarization of ventricales
Time period - <0.20 sec
Abnormalities – Elevation/Depression represent infarction/ischemia of
myocardium
QRS Complex
Significance – Depolarization of ventricales
Time period - <0.12 sec
Abnormalities – prolonged QRS complex –Abnormal conduction – BBB
T wave
Significance – Complete electrical recovery of the ventricles
Time period - <0.20 sec
Abnormalities – Flat-ischemia/Inverted-infarction

21. Abnormalities of the waves
 Absent of the p wave in atrial fibrillation, atrial flutter, ventricular
tachycardia, hyperkalemia
 Abnormal Q wave - MI
 Abnormal R wave – right ventricular hypertrophy
left ventricular hypertrophy
 Abnormal QRS complex – bundle branch block, intraventricular conduction
defect, ventricular arrhythmias
 Abnormal U wave – left ventricular systolic & diastolic overload (inverted)
hypokalemia, cardiovascular drugs (prominent U wave)

22. Abnormalities of the waves
 Abnormal PR segment – sinus tachycardia, acute pericarditis,
atrial infarction (depression)
 Abnormalities of ST segment – CVA, pulmonary
embolism(depression)
 Abnormalities of P-R interval – coronary artery disease, acute
rheumatic fever (Prolonged P-R interval)
 Abnormalities of Q-T interval – hyperkalemia, hypercalcemia
(shortened Q-T interval)/ mitral valve prolapse, electrolyte
deficiency (prolonged Q-T prolonged)

23. The ECG paper
 Horizontally
One small box – 0.04 sec
One large box – 0.20 sec
Vertically
One large box – 5mm (0.5 mv)

25. Calculating the Heart Rate
 Count the number large square between two consecutive ‘R’
waves then divide the result by 300
 Count number of ‘R’ waves in a 6 sec strip then multiply the result
by 10(this method especially good for irregular heart rates)
 With a rate ruler

26. How to read ECG
 Heart Rate (calculating heart rate with following method)
 Heart Rhythm(regular irregular/irregularly irregular
 Cardiac Axis (describe overall direction of electrical spread
within heart, to determine cardiac axis need to look at leads
I,II,III)
 Look P wave present or absent(check duration, direction&
shape, if P wave are absent indicate irregular rhythm suggest
atrial fibrillation
 PR interval (a prolonged or short indicate certain disease)

28.  QRS complex (width, height, morphology)
 ST segment (elevated or depressed indicate MI)
 T wave
 U wave (>0.5 mm deflection)

29. Causes of poor ECG signal
 oily, dirty & scaly skin
 Dirty electrodes
 Improper application
 Loose electrodes
 Broken cable wire

31. Ventricular Tachycardia

32. Atrial Fibrillation

33. Left Ventricular Hypertrophy

34. Thank You