1. Atrioventricular (AV) Heart Block
Chapter 17

2. 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

3. First Degree Block
prolonged PR interval

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

5. Mobitz Type I

6. Mobitz Type I
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.

7. Mobitz Type II

8. Mobitz 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 nonconducted P wave.

9. Advanced Second-Degree AV Block
Two or more consecutive nonconducted sinus P waves

10. Third-Degree (Complete) AV Block

11. 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 flow (usually fixed) ventricular rate
The P wave bears no relation to the QRS complexes, and the PR intervals are completely variable