This document provides a template for systematically interpreting electrocardiograms (ECGs). It outlines 13 sections to analyze, including ECG type and recording, rate, rhythm and axis, P wave, PR interval, QRS complex, ST segment, T wave, and U wave. Additional features like delta waves are also addressed. Various abnormalities are defined and associated diagnoses are provided. The template aims to help clinicians make accurate ECG interpretations through a standardized approach.

1. ECG: Systematic
Analysis
Dr Nola McPherson CME SCGH 2014

2. ECG Interpretation Overview
1. ECG type &recording
2. Rate, Rhythm, Axis
3. P wave
4. PR interval + segment
5. Q Waves, R waves
6. QRS complex
7. ST segment
8. T wave
9. U wave
10. QT interval

3. ECG Interpretation Overview
11. Additional waves (D O E)
12. Chamber hypertrophy
13. Other
- T oxicology
- I schaemia
- E lectrolytes
- sudden death ECG
Q B R A D W H
- dextrocardia
- lead reversals
- artefacts
- pacing spikes

4. Putting it all together…
Diagnosis
Differential diagnoses
Life threats

5. ECG Interpretation Template
1. ECG type & recording

6. ECG TYPE & RECORDING
 12 lead vs rhythm strip
 Paper rate (N= 25mm/s)
 Calibration (5mm wide, 10mm
high = 1mV)
 Unusual leads
- right
- posterior

11. ECG Interpretation Template
1. ECG type &recording
2. Rate, Rhythm, Axis

12. Rate, Rhythm, Axis
RATE
Normal 60-100/min (tachy/bradycardia)
Method: 300/RR(large squares)
OR 1500/RR(small squares)
OR number of QRS x 6 (if 25mm/s)
RHYTHM
Pattern: regular or irregular (reg irreg or irreg irreg)
7 STEP APPROACH

13. Rate, Rhythm, Axis
AXIS
Normal (-30 to +90)
RAD
LAD
NW axis

14. NORMAL SINUS RHYTHM
12 Lead ECG

15. ECG Interpretation Template
1. ECG type &recording
2. Rate, Rhythm, Axis
3. P wave

16. P Wave
 ?present or absent
 Amplitude & duration (LAE/RAE/BAE)
<2.5mm amp limb leads, <1.5mm amp chest leads
<3mm duration
 Contour
monophasic lead II, biphasic lead V1
inverted aVR, upright I, II, V2-6

17. Left Atrial Enlargement

18. Left Atrial Enlargement

19. Right Atrial Enlargement

20. Right Atrial Enlargement

21. ECG Interpretation Template
1. ECG type &recording
2. Rate, Rhythm, Axis
3. P wave
4. PR interval +
segment

22. PR Interval
 Duration (N= 120-200ms)
Short (<120ms)
1. Preexcitation Syndrome
eg WPW, Lown - Ganong- Levine (LGL)
2. AV (nodal) junctional Rhythm
Long (>200ms)
1. 1 HB (alone or with other blocks)
Varying (blocks)

23. Short PR Interval - WPW
 Short PR interval (<120ms)
 Prolonged QRS (>110ms) + early slurred upstroke (delta wave)
 Dominant R in V1-3
 ST seg & T wave discordant changes

24. Short PR Interval - LGL

25. Short PR – AV (nodal)
Junctional Rhythm

26. Long PR Interval

27. PR Segment
 Elevation or Depression
1. pericarditis
2. atrial ischaemia
- Liu’s Criteria

28. ECG Interpretation Template
1. ECG type &recording
2. Rate, Rhythm, Axis
3. P wave
4. PR interval + segment
5. Q Waves, R waves

29. Q waves
 NORMAL
<1mm wide, <2mm deep
 PATHOLOGICAL
Criteria:
- >40ms (>1mm wide)
- > 2mm deep
- >25% depth of QRS complex
- seen in lead V1- V3
DDX:
1. Myocardial infarction
2. Cardiomyopathies
Hypertrophic
Infiltrative disease

30. Pathological Q Waves

31. R waves
 NORMAL
Transition point V3-V4
 ABNORMAL
Dominant R wave in aVR
Dominant R wave in V1
Poor R wave progression (Ht ≤ 3 mm in V3)

32. Dominant R Wave in aVR
CAUSES
1. Poisoning with Na channel blocking medications
(Criteria: R wave height > 3 mm, R/S ratio > 0.7)
2. Dextrocardia
3. Incorrect lead placement (L & R arms reversed)

33. Dominant R Wave in V1
CAUSES
1. RVH (PE, L to R shunt)
2. RBBB
3. POSTERIOR MI (+ STE in leads V7,8,9)
4. WPW TYPE A
5. Hypertrophic Cardiomyopathy
6. Dextrocardia
7. Normal in children and young adults

35. Poor R Wave Progression
CAUSES
1. Prior anteroseptal infarction
2. LVH
3. Dilated cardiomyopathy
4. Transpositioin of leads V1 & V3
5. May be normal

37. ECG Interpretation Template
1. ECG type &recording
2. Rate, Rhythm, Axis
3. P wave
4. PR interval + segment
5. Q Waves, R waves
6. QRS complex

38. QRS Complex
 Duration
N = 70-100ms
narrow (Supraventricular)
wide (ventricular or SVT
with aberrant
conduction)
 Amplitude
High voltage eg LVH
Low voltage
Alternans eg
pericardial effusion
 Morphology
Notched
RBBB
LBBB
 Spot Diagnoses
Brugada Syndrome
WPW Syndrome (delta
waves)
Tricyclic poisoning (wide
QRS + dom R in aVR

40. ECG Interpretation Template
1. ECG type &recording
2. Rate, Rhythm, Axis
3. P wave
4. PR interval + segment
5. Q Waves, R waves
6. QRS complex
7. ST segment

41. ST Segment
 Displacement
Elevation
Depression
 ST Depression Morphology
Horizontal
Up sloping
Down sloping

42. ST Segment Elevation

43. ST Segment Depression

44. ECG Interpretation Template
1. ECG type &recording
2. Rate, Rhythm, Axis
3. P wave
4. PR interval + segment
5. Q Waves, R waves
6. QRS complex
7. ST segment
8. T wave

45. T Wave
Normal
= < 5mm height in limb leads
= < 15mm height in precordial leads
= < 2/3 R

46. T Wave Amplitude &
Morphology
Peaked eg hyperkalaemia
Flat eg myocardial ischaemia, hypoK
Hyperacute eg early STEM, Prinzmetal angina
Inverted eg ischaemia & infarction, increased ICP
Biphasic eg Myocardial ischaemia, hypoK, Wellens

47. T Wave Morphology

48. ECG Interpretation Template
1. ECG type &recording
2. Rate, Rhythm, Axis
3. P wave
4. PR interval + segment
5. Q Waves, R waves
6. QRS complex
7. ST segment
8. T wave
9. U wave

49. U Wave
 Normal
= 0.5 mm (max 2mm)
= 10% TW (max 25% TW)
 Prominent
 Inverted

50. U Wave
 Prominent
> 1-2mm or > 25% ht TW
CAUSES
Bradycardia
HypoK
HypoCa, HypoMg
Hypothermia
Increased ICP
LVH
Hypertrophic cardiomypy
Digoxin
 Inverted
abnormal if in leads with upright
T waves
CAUSES
Heart disease
**HIGHLY SPECIFIC FOR HEART
DISEASE**
**Predicts >75% stenosis of
LAD/LMCA and suggests LV
dysfn**

51. ECG Interpretation Template
1. ECG type &recording
2. Rate, Rhythm, Axis
3. P wave
4. PR interval + segment
5. Q Waves, R waves
6. QRS complex
7. ST segment
8. T wave
9. U wave
10. QT interval

52. QT Interval
 Normal QTc
= 390-440ms M/460 ms
F
< ½ preceding RR
inversely prop to HR
Measure in lead II or V5-6
Large U waves (>1 mm) fused
to T included in measurement
Small, separate U waves
excluded in measurement
 Long (>440/460 ms)
 Short (<350ms)

53. QT Interval

54. ECG Interpretation Template
11. Additional waves (D O E)

55. Additional Waves (D O E)
 Delta Wave
WPW
= slurred upstroke to QRS
Additional Features:
Short PR interval (<120ms)
Broad QRS (>100ms)

56. Additional Waves (D O E)
 Osborn Wave (J waves)
= positive deflection at J point
Most prominent in precordial leads
Causes
Hypothermia
Hyper Ca
Medications
Raised ICP
Normal varient

57. Additional Waves (D O E)
 Epsilon Wave
Arrythmogenic RV dysplasia (in
30% patients)
= pos deflection buried in end of
QRS
Additional Features
TWI V1-3
Prolonged S Wave upstroke V1-3

59. ECG Interpretation Template
11. Additional waves (D O E)
12. Chamber hypertrophy
13. Other
- T oxicology
- I schaemia
- E lectrolytes
- sudden death ECG
- dextrocardia
- lead reversals
- artefacts
- pacing spikes

60. Lethal Causes Syncope
Q BRAD W H
1. QT syndrome (Long/short)
2. Brugada Syndrome
3. RV infarction
4. Arrythmogenic RV Dysplasia
5. Dilated Cardiomyopathy
6. WPW
7. Hypertrophic Cardiomyopathy

61. Questions & Comments

62. References
 What-When-How In Depth Tutorials and Information:
http://what-when-how.com/paramedic-care/diagnostic-
ecgthe-12-lead-clinical-essentials-paramedic-care-
part-5/
 ECG Basics-Parts of the ECG:
http://www.emergsource.com/?page_id=90
 Academic Life in Emergency Medicine:
http://www.aliem.com/posterior-myocardial-infarction-
how-accurate-is-the-flipped-ecg-trick/

63. References
 ECG PEDIA.ORG:
http://en.ecgpedia.org/wiki/QRS_axis
 Life in the Fast Lane ECG Library