Transcript Atrioventricular (AV) Heart Block

Wolff-Parkinson-White and
Atrioventricular (AV) Heart
Blocks
Chapters 12 and 17
Wolff-Parkinson-White
Chapter 12
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
Artrioventricular Bypass
Tract
From SA node directly to
AV node AND to
ventricular myocardium
Partially bypassing the
bundle of His and purkinje
fibers
Accessory Pathways
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
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
Wolff-Parkinson-White
Bypass Tracts
F.Y.I.
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
WPW Significance
More prone to arrhythmias especially
SVT
Often mistaken for RBBB or LBBB or an
MI
AV Heart Block
Chapter 17
15
Classification of AV Heart
Blocks
Degree
1St
Degree Block
2nd Degree, Mobitz Type I
AV Conduction Pattern
Uniformly prolonged PR
interval
Progressive PR interval
prolongation
2nd Degree, Mobitz Type II
Sudden conduction failure
3rd Degree Block
No AV conduction
First Degree Block
note the prolonged PR interval
Second Degree AV Block
Mobitz type I or Winckebach
Mobitz type II
Second Degree AV Block
Type I or Wenckebach
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
Second Degree AV Block
Type II
1. Sudden appearance of a single, nonconducted 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.
Second Degree AV Block
Type II
2:1 AV Blocks
•
Often are type II blocks
•
•
But they can be type I blocks
•
•
look for slightly prolonged QRS
look at long rhythm strip
Sometimes they are labeled a “second
degree block” only
Advanced Second-Degree AV Block
•
•
Two or more consecutive non-conducted sinus P
waves
Note the consistent PR intervals
Third-Degree (Complete) AV Block
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)
Third-Degree (Complete) AV
Block
•
QRS can be normal width or wide
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.
AV Dissociation
AV Dissociation
Third-Degree (Complete) AV Block
100 b/min
42 b/min
No
Complete heart block