AVBs (copy)

First Degree AVB

Rate: can occur at any rate

Regularity: depends on underlying rhythm

P waves: upright, matching, 1:1

PR: prolonged (> 0.20 secs)

QRS: < 0.12 secs

Type 1 Second Degree AVB (Wenckebach)

Rate: atrial 60 – 100, ventricular – varies

Regularity: irregular. Group of beats, then a pause

P waves: upright, matching, one blocked

PR: gradually prolonging PR intervals until a QRS is dropped

QRS: < 0.12 secs

Type 2 Second Degree AVB

Rate: atrial 60 – 100; ventricular – varies 

Regularity: regular, irregular, or regular but interrupted

P waves: upright, matching, some blocked

PR: constant on the conducted beats

QRS: < 0.12 secs if no bundle branch block, > = 0.12 secs if bundle branch block

2:1 AV Block

Rate: atrial 60 – 100; ventricular — half the atrial rate

Regularity: regular

P waves: upright, matching, 2 per QRS

PR: constant on the conducted beats

Qrs: < 0.12 secs

Third Degree AVB

Rate: atrial 60 – 100; ventricular usually 20 – 60

Regularity: regular

P waves: upright, matching, dissociated from QRSs

PR: varies

QRS: < 0.12 secs if AV junction is pacemaker; > 0.12 secs if ventricle is pacemaker