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2nd Degree AV Block

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

3:1 AV Block

Only every 3rd atrial impulse conducts to the ventricles. A high-grade AV block indicating severe conduction disease.

Mechanism

Only every 3rd atrial impulse conducts to the ventricles. A high-grade AV block indicating severe conduction disease.

Findings· 2
  • Three P waves for every QRS complex.
  • Very slow ventricular rate (typically one-third of the atrial rate).
Clinical Impact

High-grade block with significant hemodynamic compromise. Almost always requires permanent pacemaker implantation.

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.