1. ECG PERFORMANCE AND INTERPRETATION
DR FRANCIS AGYEKUM
CARDIOLOGIST

2. OBJECTIVES TO DESCRIBE HOW TO PERFORM ECG
TO DESCRIBE THE ECG NOMENCLATURE
TO INTRODUCE THE NORMAL ECG
TO DESCRIBE THE STEP-WISE APPROACH TO ECG INTERPRETATION

3. What is ECG
An electrocardiogram (ECG) is a recording of cardiac electrical activity made from the body surface and displayed on graph paper
Each millimeter on the horizontal axis represents 40 ms (0.04 s) of elapsed time and each millimeter on the vertical axis represents 0.1 mV of electrical force.
Each 5 millimeter mark on the paper is scored with a heavier line representing 200 ms or 0.20 s on the horizontal axis or time line and 0.5 millivolt on the vertical axis or amplitude line.

5. Leads placement 6 Limb leads: 6 horizontal or chest leads (unipolar)
3 bipolar
3 unipolar (augmented leads)
6 horizontal or chest leads (unipolar)
V1 – 4th ICS RSB
V2 – 4th ICS LSB
V4 – 5th ICS MCL
V3 – between V2 and V4
V5, 6 – 5th ICS anterior and mid axillary line respectively.

6. Conventional electrode placement

7. WHICH PART OF THE HEART?

8. Einthoven’s triangle

10. THE HEXAXIAL REFERENCE SYSTEM

11. Cardiac events on the ECG

12. NOMENCLATURE
Complexes and intervals. a: P wave amplitude, b: R wave amplitude, c: Q wave amplitude, d: T wave amplitude, e: S wave amplitude.

13. ECG and the Cardiac Cycle

14. NOMENCLATURE

16. 12-Lead Shows 2.5 Sec View of Each Lead
The 12-lead ECG only provides a 2.5-second view of each lead. When first introduced to the 12-lead ECG, these 2.5 seconds may seem prohibitively short. However, when looking for evidence of infarction, most of the information is obtained from analyzing a single, representative complex in each lead. It is assumed that 2.5 seconds is long enough to capture at least one representative complex. A 2.5-second view is not long enough to properly assess rate and rhythm, so at least one continuous rhythm strip is usually included at the bottom of the tracing.

17. SYSTEMATIC INTERPRETATION
Systematic approach with careful examination of each of the 12 leads.
9-step approach

18. 9-STEP APPROACH 1. Calibration 2. Rate 3. Rhythm 4. Axis
5. Waves and segments
6. Chamber enlargement
7. Ischaemia and infarction
8. Miscellaneous
9. Synthesis

19. The ECG Paper

20. RATE 300/BIG BOXES 1500/SMALL BOXES
IRREGULAR RHYTHMS: RHYTHM STRIP (10secs) then multiply by 6
Note: each big box = 0.2secs; small box = 0.04 secs

21. What is the heart rate?

22. RHYTHM Start from rhythm strip then look at all 12:
What is the rate: tachy; brady?
QRS: Narrow or wide complexes?
Do you see P waves?
Is it regular, regularly irregular or irregularly irregular?
What is the relationship b/n P and QRS?
Vagal maneuvers (CSM, Valsalva)

23. AXIS DETERMINATION QRS axis: normal = -30 to +90
Shortcut and approximate axis

24. QUICK LOOK METHOD NORMAL: positive in leads I, II and/or aVF, aVL
LAD: Positive in I but negative in II and aVF
RAD: negative in I but positive in II and aVF
If negative in both I and II = extreme RAD

29. ISOELECTRIC LEAD METHOD the hexa-axial system
Identify the most isoelectric lead
Axis is perpendicular to this lead

30. QRS AXIS

32. WAVES AND SEGMENTS P WAVE PR INTERVAL QRS COMPLEX Q WAVE R WAVE
ST SEGMENT
J POINT
U WAVE
QT INTERVAL

33. P WAVE Represents atrial depolarization
Best seen in leads II, aVF and V1
Normal: 120msec and 0.25mV
Sinus P wave: Upright in I, II, aVF and V2-6
Biphasic in V1
Variable in III and aVL
P-pulmonale and P-mitrale

34. P MITRALE

35. P-Pulmonale

36. PR INTERVAL
Represents the time interval between the onset of atrial depolarization and the onset of ventricular depolarization
Normal: 120 – 200msec
Prolonged and short PR
PR depression: normal variant, pericarditis, COPD.

37. 24 yo lady, routine ECG during med screening

39. QRS complex Represents ventricular depolarization
Measured in the lead with the widest QRS complex
Normal duration: msec
Widening: BBB, Aberrancy, Ventricular source, severe hyperkalaemia
Amplitude: large or low voltages

40. RBBB

41. LBBB

42. Large voltages Ventricular hypertrophy Thin chest wall
Alternating QRS height (electrical alternans) is highly suggestive of pericardial effusion, when it occurs in sinus rhythm.

43. Low voltages Cardiomyopathy Myocarditis Pericardial effusion Obesity
Pneumothorax
Hypothyroidism

44. Q WAVES Pathological Q wave defined as
>0.02s in leads V2-3 or QS complex in leads V2-V3
>0.03s and >0.1mV deep or QS complex in leads I, II, aVL or V4-6

45. RVH Frontal plane leads:
• Right axis deviation of at least +110 degrees.
Horizontal plane leads:
• R:S ratio in V1 greater than 1.0
• R wave in V1 = 7 mm
• S wave in V1 is less than 2 mm
• qR or qRS pattern in V1
• S wave in V5 or V6 = 7 mm
• rSR′ in V1 with R′ wave greater than 10 mm
• R in V1 + S in V5 or V6 greater than 10.5 mm (SOKOLOW-LYON)

46. RVH

47. LVH Many criteria; all are specific but insensitive
Sokolow-Lyon index: SV1 + RV5 or 6 > 3.5mV
RaVL > 1.1mV
Cornell Voltage Criteria: RaVL + SV3 > 2.0mV (women) or 2.8mV (men)
Romhilt-Estes : 5-points or 4-points score
Other criteria

48. OTHER LVH CRITERIA R wave in aVL = 11 mm R wave in aVF = 20 mm.
Horizontal plane leads:
S wave in V1 + R wave in V5 or V6 = 35 mm
R wave in V5 or V6 = 26 mm
Largest S wave + largest R wave = 45 mm
Secondary ST segment and T wave abnormalities
Prolonged QR interval in V6.

49. LVH

50. TO BE CONTINUED
THANK YOU