cardiolab logocardiolab

2nd Degree AV Block

caution
Lead II
25 mm/s10 mm/mV
Heart rate
72bpm
RR
833ms
QT
358ms
Type

2:1 AV Block

Every other atrial impulse is blocked at the AV node. Only every 2nd P wave conducts to produce a QRS. Cannot be classified as Mobitz I or II from a single strip because there are no consecutive conducted beats to compare PR intervals.

Mechanism

Every other atrial impulse is blocked at the AV node. Only every 2nd P wave conducts to produce a QRS. Cannot be classified as Mobitz I or II from a single strip because there are no consecutive conducted beats to compare PR intervals.

Findings· 3
  • Two P waves for every QRS complex.
  • Regular atrial rate, regular ventricular rate at half the atrial rate.
  • PR interval of conducted beats is constant.
Clinical Impact

Clinical significance depends on the level of block (nodal vs. infranodal). Wide QRS suggests infranodal block (more dangerous). May require pacing.

Differential· 2
Mobitz Type I

Both drop QRS complexes. Mobitz I has progressive PR lengthening; Mobitz II has constant PR.

Complete Heart Block

Mobitz II can progress to complete block. Look for total AV dissociation in 3rd degree.