Atrioventricular (AV) Heart Block

Chapter 17

Classification of AV Heart Blocks

DegreeAV Conduction

Pattern

1St Degree BlockUniformly prolonged

PR interval2nd Degree, Mobitz

Type IProgressive PR interval

prolongation2nd Degree, Mobitz

Type IISudden conduction

failure

3rd Degree Block No AV conduction

First Degree Block

•prolonged PR interval

Second Degree AV Block

•Mobitz type I or Winckebach

•Mobitz type II

Mobitz Type I

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.

Mobitz Type II

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.

Advanced Second-Degree AV Block

Two or more consecutive nonconducted sinus P waves

Third-Degree (Complete) AV

Block

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