1. EKG Interpretation

2. Objectives Review approach for reading EKGs Keep it simple
Impress preceptors on rounds

3. Resources

4. Interpretation Rate Rhythm Axis Hypertrophy
Ischemia, Injury, Infarction

5. Rate Count # of large boxes between 2 successive R-waves:
1 box = 300 bpm
2 boxes = 150 bpm
3 boxes = 100 bpm
4 boxes = 75 bpm
5 boxes = 60 bpm
6 boxes = 50 bpm
7 boxes = 43 bpm
8 boxes = 37 bpm

7. Irregular rhythms If the R-R Interval is irregular:
Count the number of QRS complexes in a 10 sec span (that is on the entire EKG) and multiply it by 6! {or no. of QRS complexes in a 6 sec span multiplied by 10}

9. Rhythm
Determine whether sinus or non-sinus

10. Sinus Rhythm Every QRS preceded by P-wave P-wave has normal morphology
Duration <0.12 sec (<3 boxes)
Height <2.5 mm
P-wave has normal axis
Upright in lead II
Sinus “arrhythmia”
Rate varies with respiration

11. Arrhythmias Irregular rhythms Escape rhythms Premature beats
Tachy-arrhythmias
Heart blocks

12. Irregular rhythms Wandering atrial pacemaker
P wave shape varies
Atrial rate <100
Irregular ventricular rhythm
Multifocal atrial tachycardia
Same as above, but rate>100
Atrial fibrillation / flutter

13. Escape rhythm Junctional escape Ventricular escape
Originates in AV junction
Narrow QRS (<0.10ms)
Rate 40-60
Ventricular escape
Originates in ventricles
Wide QRS (not normal depolarization)
Rate 20-40

14. Junctional escape

15. Premature beats Irritable focus spontaneously fires a single stimulus
Atrial (PAC)
Ventricular (PVC)

16. Paroxysmal tachycardia
A very irritable focus suddenly paces rapidly
Paroxysmal atrial tachycardia
Paroxysmal junctional tachycardia
Paroxysmal ventricular tachycardia
Look for presence/absence of P waves and ventricular appearance to determine type

18. Supraventricular tachycardia
Often can’t tell between PAT and PJT (both originate above ventricles & produce narrow QRS)
Rapid PAT can be so rapid that P waves not visible
Supraventricular tachycardia (SVT) is umbrella term for both

19. Flutter vs fibrillation
Flutter caused by single ventricular focus firing rapidly ( x/min)
Fibrillation caused by multiple foci firing rapidly ( x/min)

20. Atrial flutter & fibrillation
Atrial fire so rapidly not every impuse triggers ventricular contraction
2:1, 3:1, 4:1 block, etc
Atrial fibrillation
Irregularly irregular

21. Ventricular flutter & fibrillation
Ventricular flutter has smooth sine-wave appearance with no jagged waves
Often degenerates into ventricular fibrillation

22. Heart blocks
AV block
Bundle branch block

23. AV block 1st degree: delay in normal AV conduction
PR >0.20 sec
2nd degree: interruption in normal AV condution
3rd degree: complete dissocation in AV conduction

24. 1st degree AV block
PR >0.20 sec

25. 2nd degree AV block Type I (Mobitz I) aka Wenckebach
PR progressively gets longer with each beat
QRS complex is dropped
Cycle repeats
Type II (Mobitz II)
PR stays constant, then one beat isn’t conducted

27. 2:1 AV block
Sometimes hard to tell Wenckebach vs Mobitz II apart if both have 2:1 conduction (2 P waves then QRS)
Wenckebach
Likely if PR interval lengthened and QRS normal
Mobitz II
Likely if PR interval normal and QRS widened

28. 3rd degree AV block Complete dissocation between atria & ventricles
Atria fire regularly
Ventricles contract independently at either junctional escape (40-60) or ventricular escape (20-40)
If above AV nodal junction, then junctional escape rhythm occurs

30. Bundle branch block Wide QRS (<0.12 sec) Left Right Incomplete
RR’ in V5 & V6
Right
RR’ in V1 & V2
Incomplete
QRS sec

31. Left bundle branch block

32. Right bundle branch block

33. Axis Measures overall electrical activity of heart
Limb leads (I, aVF) used to quickly determine axis
Lead I: 0 degrees
aVF: +90 degrees

34. Axis

35. If lead I is positive, the green zone reveals the
area of electrical activity
Lead I
-90 _ + I
aVF

36. red zone reveals the area of electrical activity
aVF
If aVF is positive, the
red zone reveals the area
of electrical activity –
-90 + I
aVF

37. If we superimpose these onto one another we find the axis to be
-90 I
If we superimpose these
onto one another we
find the axis to be
between 0° & +90°
aVF
+90

38. Left axis deviation
Usually caused by HTN, aortic valvular disease & cardiomyopathies
aVF: negative
Lead I: positive

39. If lead I is positive then
the blue zone is the area of electrical activity
Lead I _
-90 + I
aVF
+90

40. If aVF is negative, the green zone is the area of electrical activity_
aVF
If aVF is negative, the green zone is the area of electrical activity
-90 + I
aVF
+90

41. If we superimpose these onto one another we find the axis to be
between 0° & –90°
-90 I
aVF
+90

43. Right axis deviation
Usually secondary to enlarged right ventricle or pulmonary disease
Pulmonary HTN
COPD
Acute pulmonary embolism

44. If lead I is negative the green zone encompasses
the area of electrical activity
Lead I _
-90 + I
180
aVF
+90

45. red zone reveals the area of electrical activity aVF_
If aVF is positive, the
red zone reveals the area
of electrical activity
aVF
-90 + I
180
aVF
+90

46. If we superimpose these onto one another, we find the axis to be
-90 I
180
If we superimpose these
onto one another, we
find the axis to be
between 90° & 180°
aVF
+90

48. Right atrial enlargement

50. Left atrial enlargement

52. Left ventricular hypertrophy
Large S in V1
Large R in V5
S in V1 + R in V5 >35mm = LVH
aVL > 11-13mm = LVH

54. Right ventricular hypertrophy
Normally S > R in V1
Large R in V1 = RVH
Large R in V1 will get smaller V2V4

56. Ischemia, Injury, Infarction
T wave inversions or ST depression
Injury
ST segment elevation
>1mm in 2 or more contiguous leads
Infarction
Q waves
1mm wide or 1/3 height of QRS

57. Ischemia

58. Injury

59. Infarction

60. Location Anterior = V1-V4 Inferior = II, III, aVF Lateral = I, aVL
Posterior = Large R wave, ST depression in V1 or V2

61. Anterior MI

62. Inferior MI

63. Anterolateral

64. Posterior MI

65. Tips for rounds
Review EKG silently (don’t talk though method unless asked to)
Ignore interpretation at top of 12-lead
Intervals usually ok
Summarize findings
Rate
Rhythm
Axis
Hypertrophy
Ischemia, infarction

66. Example
This is a normal sinus rhythm, rate 60, normal intervals, no hypertrophy, no ischemic or infarctive changes
This is normal sinus rhythm, rate 75, 1st degree AV block, left ventricular hypertrophy, possible old inferior MI
This is atrial fibrillation with a rapid ventricular response

68. NSR
Rate 80
Normal axis
Normal intervals, no block
No hypertrophy
No ischemic or infarctive changes

70. NSR (sinus tachycardia)
Rate 111
Normal axis
Normal intervals
One premature ventricular contraction
No hypertrophy
No ischemic or infarctive changes

72. NSR, rate 100
1st degree AV block
Normal axis
Borderline LVH by voltage
No ischemic or infarctive changes

74. NSR, rate 100
LAD
Normal intervals
No hypertrophy
Acute anterior wall MI with reciprocal ST depression inferiorly

76. NSR, rate ~60
Normal axis
Right bundle branch block
No hypertrophy
No ischemic or infarctive changes

78. NSR, rate ~90
Normal axis
Normal intervals
No hypertrophy
Old inferior wall MI with ?inferior ischemia

80. Atrial flutter with variable block
Normal QRS (no BBB)
No hypertrophy
No ischemic or infarctive changes

82. NSR, rate 75
Left axis deviation
Left bundle branch block
Left ventricular hypertrophy
Can’t tell infarction because of LBBB repolarization changes

84. Ventricular tachcardia
Rate ~170
Don’t really care about anything else

86. Accelerated junctional
Normal axis
LVH by voltage
No ischemic or infarctive changes

87. Interpretation Rate Rhythm Axis Hypertrophy
Ischemia, Injury, Infarction