ECG - easy to read. the above presentation helps in having a perspective of ECG

1. ECG INTERPRETATION
Gowtham Krishna J.

2. • Introduction
• Physiology
• Knowing the ECG – Calibrations,Components,Terminologies and
tracings
• ECG interpretation
• Identifying arrhythmias

3. Introduction
• An electrocardiogram is a picture of the electrical conduction of the
heart.
• By examining changes from normal on the ECG, clinicians can identify
a multitude of cardiac disease processes.
• Electrocardiograph (or) Electrocardiogram

5. Conduction System of the heart
(Atrial syncytium,
junctional fibres)

6. The cardiac cycle Total duration – 0.8 sec for a
heart beating at 72/min

9. From electrode to Paper
• The electric waves in the heart are recorded in millivolts by the
electrocardiograph by electrodes controlling an ink needle.
• A standard 12-lead ECG report shows a 2.5 second tracing of each of
the twelve leads.
• The whole ECG is a 10 second recording.

10. • The tracings are most commonly arranged in a grid of four columns
and three rows.
• The first column is the limb leads (I,II, and III), the second column is
the augmented limb leads (aVR, aVL, and aVF), and the last two
columns are the precordial leads (V1-V6).

11. Knowing the ECG paper/Calibrations
Vertical calibration
Horizontal calibration
decrease
increase
decrease

12. The Normal ECG-Terminolgies
• Wave:
A positive or negative deflection from baseline that indicates a specific
electrical event. The waves on an ECG include the P wave, Q wave, R wave, S
wave, T wave and U wave.
• Interval:
The time between two specific ECG events. The intervals commonly measured
on an ECG include the PR interval, QRS interval (also called QRS duration), QT
interval and RR interval.

13. • Segment:
The length between two specific points on an ECG that are supposed to be at
the baseline amplitude (not negative or positive). The segments on an ECG
include the ST segment and TP segment.
• Complex:
The combination of multiple waves grouped together. The only main complex
on an ECG is the QRS complex.
• Point:
There is only one point on an ECG termed the J point, which is where the QRS
complex ends and the ST segment begins.

15. Parts of the ECG
• 10 electrodes are used for a 12 – lead ECG
• The term “lead” refers to 12 different vectors along which the along
which the hearts depolarisation is measured and recorded.
Left leg
right arm
Right leg
Left arm

16. HEXAXIAL REFERENCE SYSTEM

17. Contiguity of leads

19. ECG interpretation
• There are two ways to learn ECG interpretation —
• pattern recognition (the most common) and
• understanding the exact electrical vectors recorded by an ECG as they relate
to cardiac electrophysiology.

20. Approach to interpretation of ECG
• Rhythm
• Rate
• Axis
• P-wave
• PR interval
• Q wave
• QRS complex
• QT interval
• ST segment
• T wave

21. Rhythm
• Check R-R interval
• Check for P wave before every QRS complex
1. Regularly regular

22. • Irregularly Irregular

23. Regularly irregular

24. Rate
• If Regular rhythm- 300/(no:of large box between R-R)
• If irregular rhythm- Number of R in 6 second * 10

25. Axis
• Normal axis is -30 to +110
• Plot on perpendicular leads

27. Left leaves
Right returns
I
aVF

28. P wave
• See for presence
• Look for p wave in lead II and v1
• Height - <2.5 mm – (lead II)
• <1.5 mm – (V1)
• Width - <0.12 sec

30. PR interval
• Start of P-wave to start of Q wave
• 0.12 – 0.2 sec
• Prolonged:

31. Reduced

32. Depressed-Pericarditis

33. Q wave
• Pathological if >2 small squares deep or wider than 1 small squares.
• And must be seen in two anatomically contiguous leads.
• Indicative of old infarctions

35. QRS complex
• 0.08-0.12 sec

37. • Spontaneous action potentials generated by individual cells-Ectopic
• They can give single or multiple impulses-when it’s a single impulse it
is a ventricular ectopic and multiple- can be any ventricular rhythm

38. QT interval(start of Q to end of T)
• Normal is <1/2 of preceding RR interval
• Increased QT intervals-Ventricular arrythmias-Torsades de pointes
• SEE QTc - >440-460 -tdp

39. ST segment(End of Swave and start of T wave)
• ST segment deviations(elevations or depressions) are calculated by the
height difference from the baseline(PR segment).
• Changes in ST segment and T wave are related.

40. ST Depressions

42. T wave
• Upright in all leads except avR & V1
Not significant

44. • T wave inversions without ST
segment changes are not
ischemic

45. Left Ventricular Hypertrophy

46. Right ventricular Hypertrophy
• Right axis deviation
R/S >1(V1)
R/S < 1(V1)
R > 7 mm(V1)

47. Identifying Arrythmias
• Phase I : Assesment
• Phase II : Examine ECG
• Phase III : Determine the arrythmia
• Phase IV : Action

48. Assesment
• Assess patient symptoms, and vital signs.
• Assess leads to the patient (leads must be in proper placement).
• Assess obvious abnormalities of ECG (rate, rhythm).

49. Examine ECG
• 10 step process

50. Determine the Arrhythmia

51. Heart blocks

52. Questions

53. Rhythm - regular-
Rate - 75/min