1. ECG Interpretation
Chapter 22

2. ECG Interpretation Rate Atrial rate: PP interval
Ventricular rate: RR interval
Rhythm
P wave
PR interval
QRS
voltage (height)
width
Axis
Hypertrophy
Blocks
Infarct
Ischemia

3. Standardization Standardization mark
10 mm vertical deflection = 1 mVolt

4. Rate Ventricular rate (heart rate) Atrial rate 3rd degree AV block
RR interval
Atrial rate
PP interval
3rd degree AV block

5. Heart Rate Calculation
1500 divided by the number of small boxes between two R waves
most accurate
take time to calculate
only use with regular rhythms
1 lg sq = 300 bpm
2 lg sq = 150 bpm
3 lg sq = 100 bpm
4 lg sq = 75bpm
5 lg sq = bpm
6 lg sq = bpm
300 divided by the number of large boxes between two R waves
quick
not too accurate
only use with regular rhythm
10 multiplied by the number of R waves in 6 seconds
less precise
use with irregular rhythms
very quick

6. Rhythm Sinus rhythm - consistent P waves
Atrial rhythm - irregular P waves
Junctional/Nodal rhythm - no P waves, late P waves, or inverted P waves
Ventricular rhythm - no P waves, wide QRS

7. AV Junctional Rhythms
Retrograde P waves immediately preceding the QRS complexes in aVR and II.
Retrograde P waves immediately following the QRS complexes
Absent P waves

8. ECG Waves P wave atrial depolarization ≤ 2.5 mm in amplitude
< 0.12 sec in width
PR interval ( sec.)
time of stimulus through atria and AV node
prolonged interval = first-degree heart block

9. P wave
Tall = RAE
Wide = LAE

10. PR Interval Long PR interval = first degree AV block
Short PR interval = WPW
Short PR interval with inverted P waves = ectopic atrial or junctional pacemaker

11. Classification of AV Heart Blocks
Degree
AV Conduction Pattern
1St Degree Block
Uniformly prolonged PR interval
2nd Degree, Mobitz Type I
Progressive PR interval prolongation
2nd Degree, Mobitz Type II
Sudden conduction failure
3rd Degree Block
No AV conduction

12. Wolff-White-Parkinson
Wide QRS
due to early depolarization
not due to a delay in depolarization
Shortened PR interval
Upstroke QRS complex is slurred; delta wave

13. ECG Waves
QRS
width 0.12 second or less

14. Normal QRS
V6?
V6?
V1?
V1?
Fig. 4-6

15. Normal Q waves
Septal r wave
Septal q wave

16. Q Waves Abnormal if wider than 0.04 sec Greater than 25% of the R wave
Leads I, II, III, aVf or leads V3 - V6.
Greater than 25% of the R wave
Note: Not all Q waves are abnormal, Not all Q waves are the result of MI.

17. QRS Width
Wide
RBBB or LBBB
Premature ventricular beats
WPW

18. QRS Voltage
RVH
LVH

19. Mean QRS Axis

20. Axis Deviation (or Lead II or III) LEAD I LEAD aVF LEAD aVR Normal
Positive
LAD
Negative
RAD
(or Negative)
Intermediate axis

21. R Wave Progression

22. Transmural MI Pathalogical Q waves ST segment elevation.
Ischemia
Tall T waves
(and/or reciprocal T wave inversion)
Injury
ST segment elevation.
T wave inversion of the previously tall T waves
Infarct
Pathalogical Q waves
(at least one small box wide or 11/3 the entire QRS height)

23. Posterior (reciprocal)
Overview
LEAD
AREA OF THE HEART
V1-V2
Anterior/Septum
V3-V4
Anterior Wall
V5-V6
Anterior/Lateral
II, III, aVF
Inferior
I and aVL
Lateral
Posterior (reciprocal)

24. ST Segments J point: end of QRS wave beginning of ST segment
beginning of ventricular repolarization
normally isoelectric (flat)
changes, elevation or depression, may indicate pathological condition

25. Subendocardial Ischemia
ST segment depression criteria
1 mm or more
horizontal or downward
lasts 0.08 seconds
depression of only the J point with rapid upward sloping are considered normal.