Heart block · Critical
3rd Degree (Complete) AV Block
● Live · lead II25 mm/s · 10 mm/mV
II
10-second rhythm strip · count the boxes
RateAtrial 60–100; ventricular 20–40 (ventricular escape) or 40–60 (junctional)
RegularityP-P regular and R-R regular, but independent
P wavesNormal, marching through the QRS complexes
PR intervalCompletely variable (AV dissociation)
QRSWide if ventricular escape; narrow if junctional
Key features
- Atrial rate > ventricular rate
- P waves land anywhere: before, inside, and after QRS complexes
- No relationship between P and QRS