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
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
8.
9.
10.
11.
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
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.
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
20. Second Degree AV Block
Type I or Wenckebach
1.Progressive lengthening of the PR
interval from beat to beat until a beat is
dropped.
2.The PR interval after the nonconducted
P wave is shorter than the PR interval
before the nonconducted P wave.
3.May be grouping of QRS complexes
21.
22. Second Degree AV Block
Type II
1. Sudden appearance of a single, non-
conducted sinus P wave...
2. ...without...
1. ...the progressive prolongation of the PR
intervals…
2. ...and the shortening of the PR interval in
the beat after the non-conducted P wave.
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
27. Third-Degree (Complete) AV Block
1. P waves are present, with a regular atrial
rate faster than the ventricular rate
2. QRS complexes are present, with a slow
(usually fixed) ventricular rate
3. The P wave bears no relation to the QRS
complexes, and the PR intervals are
completely variable
4. (Some properly timed P waves may be
conducted)
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.