This document provides an introduction to EKG interpretation and outlines the systematic approach of evaluating an EKG. It covers the key components to assess, including rate, rhythm, axis, conduction abnormalities, and morphology. Specific conditions are reviewed such as sinus rhythm, bundle branch blocks, AV blocks, ischemia, and infarction. Examples are provided throughout to demonstrate application of the principles. The overall goal is to understand the fundamentals of the EKG and systematically analyze it following the standard approach of rate, rhythm, axis, conduction, morphology.

1. INTRO TO EKG
INTERPRETATION
BRIAN LOCKE, MD
PGY2 INTERNAL MEDICINE
UNIVERSITY OF UTAH
UPDATED APR 18, 2018

2. OBJECTIVES
Understand why ‘the rules’ are what they are.
1. Label the components of an EKG waveform
2. Understand the spatial representation of the different leads
3. Be able to eyeball an estimate of ventricular rate
4. Determine sinus vs. not sinus
5. Determine RBBB vs LBBB vs Neither
6. Identify the morphology of ischemia and infarction

3. SOURCES
Images from:
ecg.utah.edu
En.ecgpedia.org
https://lifeinthefastlane.com/ecg-library/basics/

4. REVIEW:
Normal Cardiac conduction

5. SINGLE LEAD
Name the waves:

6. QRS NAMING
e.g.
qRs
qR
Qr
rS
Rs
rSr’

7. APPROACH TO INTERP
Methodological approach, every time
Numerous variations
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

8. RATE
300 / # big boxes
If Irregular: #QRS in 10 seconds (=the strip) * 6
Eg. 1
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

9. RATE
300 / # small boxes
If Irregular: #QRS in 10 seconds (=the strip) * 6
Eg. 2
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

10. RATE
300 / # small boxes
If Irregular: #QRS in 10 seconds (=the strip) * 6
Eg. 2
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

11. RATE
300 / # small boxes
If Irregular: #QRS in 10 seconds (=the strip) * 6
Closer than 3 boxes = tachycardia.
Spaced more than 5 boxes = bradycardia
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

12. RHYTHM
P-waves?
Regular?
P  QRS?
Every QRS preceded by P?
*P wave upright in II
Eg 1
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

13. RHYTHM
P-waves?
Regular?
P  QRS?
Every QRS preceded by P?
*P wave upright in II
Eg 1
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

14. RHYTHM
P-waves?
Regular?
P  QRS?
Every QRS preceded by P?
*P wave upright in II
Eg 1
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

15. RHYTHM
P-waves?
Regular*?
P  QRS?
Every QRS preceded by P?
*P wave upright in II
Eg 2
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

16. RHYTHM
P-waves?
Regular?
P  QRS?
Every QRS preceded by P?
*P wave upright in II
Eg 2
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

17. RHYTHM
P-waves?
Regular?
P  QRS?
Every QRS preceded by P?
*P wave upright in II
Eg 2
Note: If it’s not sinus, what is it? Another talk: Arrhythmias
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

18. AXIS
Recall limb leads:
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

19. LIMB LEADS
Limb lead I:
+ = an impulse moving R to L
- = an impulse moving L to R
How will a vertical impulse look?

20. LIMB LEADS
Limb leads I, II, and III:

21. LIMB LEADS
Augmented limb leads:

22. PRECORDIAL LEADS
V1 = points toward RV
V6 points toward lateral wall

23. PRECORDIAL LEADS

24. AXIS
Definition of Normal Axis :
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

25. AXIS
Definition of Normal Axis :
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

26. AXIS
E.g. 1
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

27. AXIS
E.g. 1
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

28. AXIS
E.g. 2
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

29. AXIS
E.g. 2
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

30. AXIS
E.g. 3
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

31. AXIS
E.g. 3 LAD
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

32. AXIS
What situation would have a NW / extreme
right / “no-man’s land” axis?
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

33. AXIS
What situation would have a NW / extreme right
/ “no-man’s land” axis?
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

34. CONDUCTION
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology
Check intervals
PR (?AV Block)
QRS duration (?BBB)
QTc

35. CONDUCTION
AV Block
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology
1st Degree Prolonged PR
2nd Degree Type 1
(Wenkebock)
PR lengthens, until a QRS is not
conducted
2nd Degree Type 2 No PR lengthening prior to non
conducted QRS
High Degree So many non-conducted QRS that
you can’t tell (<2:1)
3rd Degree No conducted QRS complexes (both
P-P and QRS-QRS are regular and
different)

36. CONDUCTION
AV Block: At or below the level of the AV-node = risk of
becoming complete heart block
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology
1st Degree Prolonged PR
2nd Degree Type 1
(Wenkebock)
PR lengthens, until a QRS is not
conducted
2nd Degree Type 2 No PR lengthening prior to non
conducted QRS
High Degree So many non-conducted QRS that
you can’t tell (<2:1)
3rd Degree No conducted QRS complexes (both
P-P and QRS-QRS are regular and
different)

37. CONDUCTION
Bundle Branch (and fascicle) Blocks – wide QRS (120+ms)
Remember the precordial leads
V1 = toward RV, V6 = Toward lateral wall
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

38. CONDUCTION
Bundle Branch (and fascicle) Blocks
RBBB = delayed positive deflection in V1 1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

39. CONDUCTION
Bundle Branch (and fascicle) Blocks
LBBB = Positive Deflection in V6
(Remember, LV size > RV size)
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

40. CONDUCTION
Bundle Branch (and fascicle) Blocks
Meets neither criteria?
IVCD (Intraventricular conduction delay)
Ventricular Ectopic Beat (e.g. PVC, VT)
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

41. MORPHOLOGY
Check for:
LAA, RAA, RVH / Strain Pattern, LVH, Hypo/hyperkalemia and
ischemia
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

42. MORPHOLOGY
STEMI = Transmural ischemia from occlusion
NSTEMI = Subendocardial ischemia (further from
the blood vessel
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

43. MORPHOLOGY
An Evolving Infarct
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

44. MORPHOLOGY
Ischemia: ST deviation, T-wave inversion
Infarct: q-waves (ST Elevation will be)
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

45. MORPHOLOGY
Ischemia: ST deviation, T-wave inversion
Infarct: q-waves (ST Elevation will be)
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

46. MORPHOLOGY
Ischemia: ST deviation, T-wave inversion
Infarct: q-waves (ST Elevation will be)
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

47. MORPHOLOGY
Ischemia: ST deviation, T-wave inversion
Infarct: q-waves (ST Elevation will be)
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology

48. EXAMPLE

49. EXAMPLE

50. EXAMPLE

51. MORPHOLOGY
A note about LBBB
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology
6. Check Prior

52. MORPHOLOGY
A note about LBBB:
Always have STE – when is it pathologic? Sgarbossa
1. Rate
2. Rhythm
3. Axis
4. Conduction
5. Morphology
6. Check Prior

53. PRACTICE

54. PRACTICE

55. PRACTICE

56. PRACTICE

57. OBJECTIVES
Understand why ‘the rules’ are what they are.
1. Label the components of an EKG waveform
2. Understand the spatial representation of the different leads
3. Be able to eyeball an estimate of ventricular rate
4. Determine sinus vs. not sinus
5. Determine RBBB vs LBBB vs Neither
6. Identify the morphology of ischemia and infarction

58. NEXT STEPS
Arrythmias
ACS management
Heart Failure

59. RESOURCES
Tutorials
• http://en.ecgpedia.org
• https://lifeinthefastlane.com/ecg-library/basics/
• Also with links to many resources
Practice EKGs
• https://ecg.bidmc.harvard.edu/
• https://ecg.utah.edu/
• Questions? Brian.locke@hsc.utah.edu