Second degree AV block type II

Background

2nd degree AV Block Type 2 (4:3 conduction)

• A disturbance of atrial impulse conduction through the AV node
• Significant risk of hemodynamic instability, symptomatic bradycardia, and decompensation into Third Degree AV Block
• Risk of asystole 35% per year

Clinical Features

• Most patients are asymptomatic
• Chest pain
• Hypotension
• Bradycardia
• Altered mental status
• Syncope, weakness

Differential Diagnosis

• Anterior MI
• Rheumatic fever
• Myocarditis
• Lyme disease
• Lenegre's disease
• Lev's disease
• SLE
• Systemic sclerosis
• Amyloidosis
• Hemachromatosis
• Sarcoidosis
• Hyperkalemia
• Toxicology
  • Beta blocker toxicity
  • Calcium channel blocker toxicity
  • Digoxin toxicity
  • Amiodarone

AV blocks

• First degree AV block
• Second degree
  • Second degree AV block type I (Wenkebach)
  • Second degree AV block type II
• Third degree AV block
• AV dissociation without complete heart block

Evaluation

2nd degree AVB, 2:1 conduction, LBBB with buried p-waves in t-waves

• ECG findings
  • Fixed PR interval for conducted QRS complexes
  • Intermittent non-conducted P-waves
  • P waves march through (beware of p-waves consistently buried in T-waves)

Management

• If symptomatic, standard ACLS guidelines for symptomatic bradycardia to include
  • Atropine 0.5mg IV q3-5min PRN
  • Transcutaneous pacing, followed by transvenous pacing
• Treat underlying etiology
• Avoid AV nodal blocking agents (e.g. β-blockers)

Disposition

• Admission for pacing and monitoring
• Subsequent permanent pacemaker
• 2:1 and 3:1 blocks
  • May be unable to determine if Second Degree AV Block Type I or type II
  • Admit to cardiology and assume type II

See Also

• AV blocks