محاضرات دورة ECG COURSE 3

1. AV Heart Blocks
Rami AL-Khatib

2. AV Heart Blocks

3. Causes
• Drug therapy
• IHD (MI)
• Degeneration (age)
• Sclerosis (Aortic)
• Cardiac surgery

4. AV Node
• AV nodal conduction time is represented on
the ECG as the PR segment.
• P

5. First Degree Heart Block (1º)
• SA Node – normal
•Normal P wave
• AV Node conducts more slowly than
normal
•Prolonged constant PR Interval
• Rest of conduction is normal
•Normal QRS

6. First Degree Heart Block (1º)
• PR Interval > 0.2 seconds (5 small sq)
• Note – the PR Interval is constant

8. Significance
• Clinical significance
• None
• Treatment
• None
• Note – this can progress to 2º or 3º
heart block

9. Second Degree Heart Block (2º)
Types
• Mobitz Type I (Wenkebach)
• Mobitz Type II

10. Second Degree Heart Block (2º)
Mobitz Type I
(Wenkebach)
• Conduction through the AV Node –
progressively delayed until a drop beat
is seen
• Karl Wenkebach

11. Second Degree Heart Block (2º)
Mobitz Type I
(Wenkebach)
• PR Interval prolongs with each beat
until a dropped beat is seen.
• The PR Interval is NOT constant
• After each dropped beat, the PR
interval may be normal and the cycle
starts again.

12. Second Degree Heart Block (2º)
Mobitz Type I
(Wenkebach)
PR PR PR DROPPED BEAT

13. 2nd Degree AV block Mobitz 1

14. Significance
• Clinical Significance
•Slight symptoms
e.g. Lethargy, Confusion
• Treatment
•Pacemaker
• Note – this can progress to 3º Heart Block

15. Second Degree Heart Block
(2º)
Mobitz Type II
• Conduction through the AV node is
constant.
• PR interval is constant
• Occasionally more than one a dropped
beat is seen

16. Second Degree Heart Block
(2º)
Mobitz Type II
PR PR DROPPED BEAT PR

18. Significance
• Clinical significance – this is more
significant disease
• Treatment – pacemaker
• Note – this can progress to 3º Heart
Block

19. Third Degree Heart Block (3º)
(Complete)
• Complete failure of the AV Node
• No impulses from Sinus Node will pass
through to the ventricles
• Some part if the conducting system will
take over as pacemaker of the heart
(even a myocardial cell 10-15 bpm)

20. Third Degree Heart Block (3º)
(Complete)
• P wave rate – normal
• Ventricular rate – slow
• Ventricular complex may be broad
•Idioventricular rhythm
• Complete dissociation between P
waves & QRS

21. Third Degree Heart Block (3º)
(Complete)
P P P P P
QRS QRS

22. 3rd degree AV block

23. Significance
• clinical significance
•Symptoms LOC, Confusion,
Dizziness, Low BP
•Can lead to standstill, VT or VF
• Treatment - pacemaker

24. Summary
• 1º - prolongation of PR Interval & costant
• 2º - Mobitz I – Increasing PR Interval until dropped
beat is seen
• Mobitz II – Constant PR Interval with more P
waves to QRS
• 3º - Complete dissociation between P waves & QRS

25. References
• Hampton, J. R. (2013). The ECG made
easy. Elsevier Health Sciences.
• Hampton, J. R. (2013). 150 ECG problems.
Elsevier Health Sciences.
• O'Keefe Jr, J. H., Hammill, S. C., Freed,
M. S., & Pogwizd, S. M. (2010). The
complete guide to ECGs. Jones & Bartlett
Publishers.

26. Thank You