1. Fundamentals of ECG
interpretation
Part I
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PART II

2. Electrocardiogram (ECG)
 Provides representation of the electrical activity of the heart
 Extremely important diagnostic tool for various cardiac dysfunctions
 Used extensively in healthcare systems
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3. WILLIAM ENTHOVAN.
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4. Dr. Nagel developed the first telemetry unit for transmitting
E.C.G.recordings via radio waves from the field to the
hospital.
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5. v1 v2
v3
v4
v5
v6
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6. 6
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7. 7
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8. 8
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9. 9
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10. Summary of events of cardiac cycle
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11. 11
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12. 12
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13. ECG Reported as:
1.Standardisation 9.QRS Complex
2.Voltage 10.QRS Duration
3.Rate 11.ST Segment
4.Rhythm 12.T Wave
5.Axis 13.QT Interval
6.Position 14.U Waves
7.P Waves 15. Conclusion
8.PR Interval
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14. Step - Rate
Method
Count the number of R waves for a six second interval and
multiply by ten
3 sec 3 sec
6 sec
(can be used for regular & irregular)
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15. Step - Rate
Method :
Count the number of 5mm squares in R-R interval and divide into 300
300
150
100
75
60
50
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37
33
30 … slow
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16. Step 1 - Rate
RATE:
 Tachycardia exists if the rate is greater than
100 beats/min.
 Bradycardia exists if the rate is less than 60
beats/min.
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17. Step : Rhythm
RHYTHM:
 Determine if the ventricular rhythm is regular
or irregular (pattern to irreg.?)
 R-R intervals should measure the same
 P-P intervals should also measure the same
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18. STEP - Rhythm
IRREGULAR
REGULAR
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19. STEP - Rhythm Example
• Irregularly Irregular
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20. STEP 3 – Is the P Wave Normal?
Relation to QRS?
Appearance ?
Consistency?
Identify and examine P waves:
Present?
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21. 22
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22. 23
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23. STEP 3 - Is the P Wave Normal ?
Normal P wave with no QRS
complex
Normal
Same Shape
Associated with a QRS Complex?
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24. STEP 4 –PR Interval/Relationship
Consistent PRI of <0.20 secs is normal, lengthened or variant
PRIs could indicate an AV block
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25. STEP 5 –QRS DURATION
• A narrow QRS complex (< 0.12), indicates the impulse has
followed the normal conduction pathway
• A widened QRS complex (> 0.12), may indicate the impulse was generated
somewhere in the ventricles
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26. 26
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27. 27
BARKUL HOSPITAL

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29. STEP 6 – ST segment & T wave
• Ventricular repolarization characterized on ECG as ST
segment and T wave
• Changes in ST segment and T wave often seen in
ischemic heart disease
ST depression T wave inversion ST elevation
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30. Identifying ST segment changes
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31. Regional association with ECG
Area of
infarction
Leads associated Vessels involved
Inferior Leads II, III, and aVF; ST elevations Right coronary artery, left
circumflex
Posterior Leads V1, V2, V3 ST depression;
large R wave
Proximal right coronary artery,
left circumflex
Anterior Leads V1, V2, V3, V4; ST elevation Left anterior descending
Lateral Leads V1, AVL, V5, V6; ST elevation Left circumflex
Right
ventricular
Elevations in leads II, III, aVF, and
V1; elevation greater in III than
II; large R wave V4
Proximal right coronary artery
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32. ST elevation myocardial
infarction (STEMI)
ST elevation 1 mm or more in 2 contiguous leads
ST elevation in II, III & aVF
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33. Evolving infarction:
ECG progression
A. Normal ECG prior to MI
B. Ischemia from coronary artery
occlusion results in ST depression
(not shown) and peaked T-waves
C. Infarction from ongoing ischemia
results in marked ST elevation
D/E. Ongoing infarction with
appearance of pathologic Q-waves
and T-wave inversion
F. Fibrosis (months later) with
persistent Q- waves, but normal ST
segment and T- waves
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34. Sequence of changes seen during
evolution of MI
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35. Clinical implications of ECG
changes…
 Peaked T waves
◦ Present only for 5-30
mins after onset of
MI
◦ Intervention at this
stage may prevent
infarction; improved
outcomes than
initiating therapy at
later stages
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36. Clinical implications of ECG
changes …
 ST segment elevation
◦ Injury to myocardium
◦ Patients with largest
ST deviation benefit
most from fibrinolysis
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37. Clinical implications of ECG
changes …
 Pathological Q waves
◦ May develop within 1-2 hrs of onset
of symptoms of acute MI, though
often they take 12 hrs to appear
◦ If ST segment elevation and Q waves
evident on ECG and chest pain is of
recent onset, patient may benefit
from thrombolysis or direct
intervention
◦ Absence of Q waves post fibrinolysis
may serve as favorable prognostic
indicator
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38. Clinical implications of ECG
changes…
 T wave inversion
◦ Late sign of evolving MI; occurs in
3/4th patients with completed MI
◦ May persist for months and
occasionally remains a permanent
sign of infarction
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39. Clinical implications of ECG
changes
 Normalization of ST segment
◦ Last ECG change during MI; occurs when
transmural MI progresses to completed
infarction
◦ ST elevation with an inferior MI may take up
to two weeks to resolve, may persist even
longer with anterior MI and may persist
indefinitely if left ventricular aneurysm
develops
◦ Role of reperfusion therapy limited
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40. Evolving ECG in STEMI
Middle-aged male presents to emergency medical service with chest
pain; initial ECG demonstrates nonspecific abnormalities; within 15
minutes during transport, ECG demonstrates significant inferior ST
segment elevation, consistent with inferior wall STEMI
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41. Inferior Wall STEMI
ST elevation in II, III & aVF
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42. Anterior Wall STEMI
ST elevation in V1-V5
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43. Anterolateral MI
This person’s MI involves both the anterior wall (V2-V4) and the lateral wall
(V5-V6, I, and aVL)!
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44. Unstable angina/NSTEMI
 ECG ST-segment depression or prominent T-
wave inversion and/or positive biomarkers
of necrosis in absence of ST-segment
elevation and appropriate clinical setting
(chest discomfort or anginal equivalent)
 NSTEMI if elevated biomarkers present
(Troponin T, Troponin I or Creatine Kinase-
MB [CK-MB])
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45. UA vs. NSTEMI
T wave inversion in II, III, aVF, V1-V6
If biomarkers normal, Unstable angina
If biomarkers elevated, NSTEMI
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46. Angina
Patient complained of chest pain
A.ST depression
B.5 minutes later, after nitroglycerin, ST segments
revert to normal with relief of angina
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47. Prinzmetal’s angina with transient
ST elevation
Patient with history of
exertional and rest
angina
A. Baseline resting ECG
shows non-specific
inferior ST-T changes
B. With chest pain, ST
elevations in II, III, aVF
and reciprocal ST
depression in I and aVL
C. Return of ST segments
to baseline after
nitroglycerin
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48. Summary
 ECG an essential adjunct to clinical history
& physical examination in patients with
chest pain
 ECG adds considerable information for risk
stratification and clinical decision support
for treatment strategies in ACS
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49. Ecg.exe
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50. Consulting
Physician,Beed
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