ECG interpretation made easy

1. ECG Basics
Hooman Rowshan M.D. MSc.

2. 12 Lead ECG
 Measures the electrical activity of the heart and produces
normal or pathological waive patterns depending on the
patient’s condition
 It can be viewed as a camera taking pictures of the heart
at different views like anterior, posterior, lateral, and
inferior. These positional references are used to
determined the location of pathology like a patient
presenting with symptoms of MI
 These pictures are transmitted as electrical waives patterns
that are captured on the ECG paper

3. ECG Leads
 Lead I – Lateral view (RA-LA)
 Lead II – Inferior view (RA-LL)
 Lead III – Inferior view (LA-LL)
 aVR – Lateral view (LA+LL – RA)
 aVL – Lateral view (RA+LL – LA)
 aVF – Inferior view (RA+LA – LL )

4. Limb and Augmented leads

5. Chest Leads
 V1 – Septal view of heart
 V2 – Septal view of heart
 V3 – Anterior view of heart
 V4 – Anterior view of heart
 V6 – Lateral view of heart

6. Pericordial Leads

7. Make a Picture of The Heart
These refer to the views of the left ventricles and show the location of MI

8. Picture of the Heart

9. Normal ECG Components

10. Normal Waves
Become Familiar with the normal wave morphology in each lead

11. EKG Paper

12. Approach To ECG
 Rhythm
 Rate
 Wave morphology
 Segments
 Axis Deviation

13. Rhythm
 A normal heart has a sinus rhythm
 There has to be a “P” wave
 “P” waves precede the QRS in every lead
 P-R interval is constant and is between 0 .12 to 0 .2
seconds (3-5 small squares)

14. Heart Rate Calculation
 Select two R waves at random
 Next count the large squares between the two R waves
 Take 300 and divide it by the number of large squares
between the R waves and the result is the heart rate
 Two large squares means we have a HR of 300/2 or 150
 As a general rule, the more large squares you count the
slower the HR. The fewer large squares you count, the
faster the HR—300/4 means a HR of 75

15. Heart Rate Calculation
Example

16. Axis Deviations
The Basics
 A change of the heart axis or a deviation can be an indication
of pathology
 To determine the heart axis you look at the extremity leads only
(not V1-V6)
 focus especially on leads I, and AVF and you can make a good
estimate of the heart axis
 A left heart axis is present when the QRS in lead I is positive
and negative in AVF. (Between -30 and -90 degrees
 A right heart axis is present when lead I is negative and AVF
positive (Between +90 and +180)

17. Axial Interpretation
 The overall direction of depolarization and
repolarization produces a vector that causes positive or
negative deflection on the ECG depending on which
lead it points

18. Vector Basics
How The ECG Produces normal and pathological waves

19. Axis Deviations Cont.

20. Pathology and Axis
Deviation
 Left axis deviation: negative causes: left ventricular
hypertrophy, left anterior fascicular block,
inferior MI, hypertension and emphysema)
 Right axis deviation: causes: right ventricular
hypertrophy, right heart failure

21. MI With S-T Elevation
 Blood flow stops to a region of the heart
 S-T elevation means a total occlusion of the artery supplying the affected
part
 Most often due to athroscrosis of the involved vessel
 Coronary heart disease (CHD) is a leading cause of death among men and
women globally
 Women develop CHD about 10 years later than men, yet the reasons for
this are unclear
 ECG is the most important test and should be done within 10 min of
presentation

22. ECG Of STEMI

23. STEMI
Can You Localize the MI ? Is There An Axis Deviation?

24. STEMI Lateral Leads
Where Do you think the MI is Located?

25. NSTEMI
 NSTEMI stands for Non-ST-elevation myocardial
infarction
 Caused by partial blockage of the affected artery
 It is less serious than the STEMI but it is a heart attack,
nevertheless
 ECG is the most important test and should be done
within 10 min of presentation

26. NSTEMI
ECG Finding

27. STEMI and NSTEMI ECG
comparison

28. Arrhythmia Basics
 Heart arrhythmia is also known as irregular heartbeat
 The heart may be too face
 The heart may be too slow
 Irregular heartbeat: flutter or fibrillation
 It can happen in the atria or the ventricles
 Ventricular fibrillation is one type of arrhythmia that
can be deadly

29. Atrial fibrillation
 Atrial fibrillation is an irregular and often rapid heart rate that
can increase the risk of stroke, heart failure
 During atrial fibrillation, the heart's two upper chambers (the
atria) beat chaotically and irregularly
 Known as “Irregularly Irregular” pattern on ECG and often
used to refer to A-fib
 Commonly Associated with blood clot development
 Anticoagulation is a must

30. Atrial fibrillation On ECG

31. Atrial Flutter

32. Ventricular flutter
 Tachycardia affecting the ventricles with a rate over 250-
350 beats/min
 No clear definition of the QRS and T waves

33. Ventricular fibrillation
 Ventricular fibrillation (v-fib for short) is the most serious
cardiac rhythm disturbance
 The heart's lower (pumping) chambers contract in a rapid,
unsynchronized way
 The ventricles "fibrillate" rather than beat
 The heart pumps little or no blood
 Collapse and sudden cardiac arrest follows
 Shock the heart

34. Ventricular fibrillation

35. Supraventricular
tachycardia (SVT)
 Includes:
 Atrial fibrillation
 Paroxysmal supraventricular tachycardia (PSVT)
 Atrial flutter
 Wolff–Parkinson–White syndrome

36. Paroxysmal supraventricular
tachycardia
 The onset of the rapid heart rate(palpitation)
 Sudden
 While at rest
Key Finding is the Narrow QRS Complex and No discernable P Waves

37. Wolf-Parkinson- White
Syndrome

38. Bradycardia

39. First Degree Heart Block
 P-R interval is more than 0.20 seconds
 Rarely causes symptoms or problems

40. Wenckebach
Second Degree Heart Block
 Second-degree AV block Type I
 P-R interval gets progressively longer until one beat is
dropped

41. Type 2 second-degree AV
block (Mobitz II)
 P-waves are not preceded by PR prolongation as with
second-degree AV block (Type 1)
 Second-degree AV block (Type 2) is clinically significant
because this rhythm can rapidly progress to complete
heart block

42. Third-degree AV block
(complete heart block)
 In complete heart block, there is complete absence of AV
conduction
 None of the supraventricular impulses are conducted to
the ventricles

43. Exercises
 Using an actual patient’s ECG strip do the following:
 Calculate HR
 Check for sinus Rhythm
 Mark off the regions of the heart
 Evaluate the wave morphology for normal and abnormal patterns
 Evaluate for axial deviation (correlate with pathology if axial deviation is noted)
 Localize the MI if present
 Review at least one A Fib strip and detect the “irregularly irregular pattern”
 Review at least one one Paroxysmal SVT strip