1. Wolff-Parkinson-White and Atrioventricular (AV) Heart Blocks
Chapters 12 and 17

2. Wolff-Parkinson-White
Chapter 12

3. Artrioventricular Bypass Tract
Accessory pathways form and fail to disappear during fetal development
Formed near the mitral or tricuspid valves or interventricular septum
An AV bypass tract is sometimes referred to as the bundle of Kent

4. Artrioventricular Bypass Tract
From SA node directly to AV node AND to ventricular myocardium
Partially bypassing the bundle of His and purkinje fibers

5. Accessory Pathways

7. 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

12. Wolff-Parkinson-White
F.Y.I.
As a general rule: the initial QRS complex (delta wave) vector will point away from the area of the ventricles that is first to be stimulated by the bypass tract

13. Wolff-Parkinson-White
Bypass Tracts
Left Lateral
negative delta waves in I and/or aVL and positive in V1
Posterior
positive delta waves in most of the precordial (chest) leads and negative in the inferior leads
Right
negative delta waves in V1 and V2 and positive in I and V6
Anteroseptal (anterior)
negative delta waves in leads V1 and V2
F.Y.I.

14. WPW Significance More prone to arrhythmias especially SVT
Often mistaken for RBBB or LBBB or an MI

15. AV Heart Block
Chapter 17 15

16. 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

17. First Degree Block
note the prolonged PR interval

18. Second Degree AV Block
Mobitz type I or Winckebach
Mobitz type II

19. Second Degree AV Block Type I or Wenckebach

20. Second Degree AV Block Type I or Wenckebach
Progressive lengthening of the PR interval from beat to beat until a beat is dropped.
The PR interval after the nonconducted P wave is shorter than the PR interval before the nonconducted P wave.
May be grouping of QRS complexes

22. Second Degree AV Block Type II
Sudden appearance of a single, non- conducted sinus P wave...
...without...
...the progressive prolongation of the PR intervals…
...and the shortening of the PR interval in the beat after the non-conducted P wave.

23. Second Degree AV Block Type II

24. 2:1 AV Blocks Often are type II blocks look for slightly prolonged QRS
But they can be type I blocks
look at long rhythm strip
Sometimes they are labeled a “second degree block” only

25. Advanced Second-Degree AV Block
Two or more consecutive non-conducted sinus P waves
Note the consistent PR intervals

26. Third-Degree (Complete) AV Block

27. Third-Degree (Complete) AV Block
P waves are present, with a regular atrial rate faster than the ventricular rate
QRS complexes are present, with a slow (usually fixed) ventricular rate
The P wave bears no relation to the QRS complexes, and the PR intervals are completely variable
(Some properly timed P waves may be conducted)

28. Third-Degree (Complete) AV Block
QRS can be normal width or wide

29. AV Dissociation SA is pacing the atria AV is pacing the ventricles
Ventricular rate is similar to atria rate
No P wave, even if properly timed, will be conducted.

30. AV Dissociation

31. AV Dissociation

32. Third-Degree (Complete) AV Block

33. 100 b/min
42 b/min No
Complete heart block