Wolff-Parkinson-White and Atrioventricular (AV) Heart Blocks

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 • 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 F.Y.I.

13. Wolff-Parkinson-White F.Y.I. • 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

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

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 BlockType 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 BlockType 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