1. ECG interpretation

2. Overview
Rate
Rhythm
Intervals
QRS
ST-T wave

3. ECG

4. P- QRS- T waves

5. Overview
Rate
Rhythm
Intervals
QRS
ST-T wave

6. Rate Normal heart rate 60-100 beats per minute
Tachycardia is > 100 beats per minute
Bradycardia is < 60 beats per minute

7. What is the heart rate?

8. Rate Method 1: Count squares
300 / # of big squares between QRS complexes

9. Rate Method 2: Count seconds 60 ÷ Seconds between QRS complexes
60 ÷ 0.92 seconds = 65 beats per minute
Because 60 seconds/ min ÷ ___ seconds/ beat = ___ beats/ minute

10. Overview
Rate
Rhythm
Intervals
QRS
ST-T wave

11. Rhythm Sinus Rhythm Are the complexes regular or irregular?
P wave in every lead (upright in I, II, III)
Every P wave is followed by a QRS complex
1 p wave for every 1 QRS
Are the complexes regular or irregular?
Regularly irregular vs irregularly irregular

12. Rhythm AFIB P wave? P wave before QRS in 1:1 ratio? Regular?
Is this sinus rhythm?

13. Rhythm A FLUTTER 4:1 P wave? P wave before QRS in 1:1 ratio? Regular?
Is this sinus rhythm?

14. Rhythm JUNCTIONAL RHYTHM P wave? P wave before QRS in 1:1 ratio?
Regular?
Is this sinus rhythm?

15. Overview
Rate
Rhythm
Intervals
QRS
ST-T wave

16. Intervals

17. Intervals: PR PR interval
Normal is seconds
1st degree AV block: PR interval > 0.20 seconds
2nd degree AV block has 2 types
Type 1: PR interval gets longer under QRS drops
Type 2: PR interval doesn’t change. QRS drops suddenly
3rd degree AV block: No association between p and QRS

18. 1st degree AV block

19. 2nd degree AV block

20. 3rd degree AV block

21. Intervals

22. Intervals: QRS QRS complex Left bundle branch block
Normal: less than 0.10 seconds
Left bundle branch block
QRS > 0.12 seconds
No q wave in V5 and V6
Broad notched R wave in V5 and V6

23. Intervals: QRS Right bundle branch block QRS > 0.12 seconds
Deep slurred s in leads I and V6
“Rabbit ears” (rsR’) in V1 or V2

24. LBBB or RBBB?

25. LBBB or RBBB?

26. Intervals: QT QT should be less than half of R-R interval
The time for ventricular repolarization and therefore the QT (or JT) interval is dependent upon the heart rate; it is shorter at faster heart rates and longer when the rate is slower.

27. Overview
Rate
Rhythm
Intervals
QRS
ST-T wave

28. QRS Is there a pathologic Q wave? (sign of previous MI)
More than 1 box wide and
More than 1/3 of the height of the R wave

29. QRS Are the QRS complexes normal, too small, or too tall?
Too small (low voltages)
<5mm in leads I, II, III and <10mm in leads V1-V6

30. QRS Too tall: (left ventricular hypertrophy)
Most common criteria: S in V1 + R in V5 or V6 ≥ 35mm

31. Overview
Rate
Rhythm
Intervals
QRS
ST-T wave

32. ST segment-T wave Is there ST depression or elevation ?
>1mm in 2 “contiguous leads” (2 leads that are in the same area of the heart)
Is there T wave inversion?
What parts of the heart (leads) are involved?

33. What part of the heart is affected?

34. ST elevation

35. ST depression

36. T waves Are they inverted? (Can suggest ischemia)
Are they peaked (Such as in hyperkalemia)?

37. Peaked T waves
While no frequently-used criteria have been validated, they may be generally >10 mm in height as measured in the precordial leads, and >5 mm in height in the limb leads, or only relatively tall compared with baseline. This appearance is in contrast to the normal T wave which is asymmetric (the initial upstroke is slow while the end or downstroke is rapid) regardless of its amplitude. Tall T waves may be seen with left ventricular hypertrophy or even in normal subjects who have tall QRS complex amplitude.
In addition to hyperkalemia, prominent (so-called ”hyperacute”) T waves may be seen in the early phases of an acute myocardial infarction or with myocardial ischemia (possibly related in part to localized extracellular hyperkalemia). (See "Electrocardiogram in the diagnosis of myocardial ischemia and infarction".) Tall T waves may also be seen in the presence of left ventricular hypertrophy or left bundle branch block, in which the amplitude of the QRS complex is increased, or may even be a normal variant; in these cases, the T waves are not peaked and still have an asymmetric morphology, often as part of the benign early repolarization variant.

38. Hyperkalemia Peaked T waves occurs early in hyperkalemia
As hyperkalemia gets more severe
PR widens
QRS widens
P wave
disappears
This is called a
“sine wave”

39. Summary Rate Rhythm Intervals Sinus rhythm or not?
PR <0.20 seconds?
QRS <0.12 seconds?
QT less than ½ of RR interval?

40. Summary QRS ST- T wave Is there a pathologic (big) Q wave?
Are the QRS intervals too big/tall?
R in V1/2 + S in V5/6 >35mm?
Are the QRS intervals too small?
<5mm in limb leads and <10mm in V1-V6
ST- T wave
Is there ST elevation or depression? What part of the heart?
Are the T waves inverted or peaked?

41. Quiz: Interpret ECG-1

42. Quiz: Interpret ECG-1 Rate: 150 bpm Rhythm: Sinus tachycardia
Intervals: PR, QRS, QT intervals all normal
QT interval looks long, but this is because HR is fast. When we calculate QT corrected for HR, it is normal.
QRS: No pathologic Q waves, Normal size QRS
ST-T: No ST depression/elevation, No T wave changes

43. Quiz: Interpret ECG-2

44. Quiz: Interpret ECG-2 Rate: 52 bpm Rhythm: Sinus bradycardia
Intervals:
PR long: 1st degree AV block
QRS normal
QT long
QRS: No pathologic Q wave, Normal size QRS
ST-T: No ST depression/elevation. No T wave changes

45. Quiz: Interpret ECG-3

46. Quiz: Interpret ECG-3 Rate: 70 bpm Rhythm: Sinus rhythm
Intervals: PR, QRS, QT all normal
QRS: No pathologic Q waves. Normal size QRS
ST-T:
No ST depression or elevation
T waves are peaked