What is the treatment for third-degree atrioventricular (AV) heart block?

Treatment for Third-Degree Atrioventricular Block

Permanent pacemaker implantation is the definitive treatment for third-degree atrioventricular block. 1

Initial Management of Third-Degree AV Block

• For patients with symptomatic third-degree AV block and hemodynamic instability, immediate interventions should include:
  • Establishing IV access, administering supplemental oxygen, and placing on continuous cardiac monitoring 2
  • Initiating transcutaneous pacing immediately while preparing for transvenous pacing in unstable patients 2, 3
  • Considering atropine administration (0.5 mg IV every 3-5 minutes, maximum 3 mg) while preparing for pacing, though it may be ineffective in infranodal blocks 2, 4
  • Using vasopressor support (dopamine or epinephrine infusion) if hypotension persists despite pacing 2

Definitive Treatment

Class I Indications for Permanent Pacemaker Implantation (Strongest Recommendations):

• Third-degree AV block at any anatomic level with:
  • Bradycardia with symptoms (including heart failure) or ventricular arrhythmias 1
  • Symptomatic bradycardia due to required drug therapy 1
  • Asystole ≥3.0 seconds or escape rate <40 bpm in awake, symptom-free patients 1
  • AF with bradycardia and pauses ≥5 seconds 1
  • Post-catheter ablation of AV junction 1
  • Postoperative AV block not expected to resolve 1
  • Neuromuscular diseases with AV block (e.g., myotonic muscular dystrophy, Kearns-Sayre syndrome) 1, 3
  • Asymptomatic persistent third-degree AV block with cardiomegaly or LV dysfunction 1
  • Second or third-degree AV block during exercise in absence of ischemia 1

Class IIa Indications (Reasonable to Perform):

• Persistent third-degree AV block with escape rate >40 bpm in asymptomatic adults without cardiomegaly 1
• Alternating bundle-branch block 1

Special Considerations

• Reversible causes of AV block should be identified and corrected before permanent pacing, including:

  • Electrolyte abnormalities 1
  • Drug toxicity 1
  • Lyme disease 1
  • Transient increases in vagal tone 1

• Some conditions may warrant pacemaker implantation despite transient resolution of AV block due to risk of disease progression:

  • Sarcoidosis 1
  • Amyloidosis 1
  • Neuromuscular diseases 1, 3

• In acute myocardial infarction, the approach differs based on location:

  • Inferior MI often causes transient AV block at supra-Hisian level that may respond to atropine 3, 5
  • Anterior MI usually causes infra-Hisian AV block with worse prognosis, often requiring permanent pacing 3, 5

Temporary Pacing as a Bridge

• For patients with sepsis or infection where permanent device implantation is temporarily contraindicated:
  • Temporary transvenous pacing can serve as a bridge until infection is controlled 6
  • VDD pacing mode may be preferable to VVI in patients with normal sinus function to maintain AV synchrony 6

Common Pitfalls and Caveats

• Not all third-degree AV blocks require immediate permanent pacing; asymptomatic patients with narrow QRS and adequate escape rhythm may be observed 7
• Failure to recognize the anatomical level of block may lead to inappropriate treatment; infranodal blocks typically respond poorly to atropine 4, 5
• Overlooking potentially reversible causes before proceeding to permanent pacemaker implantation 1, 2
• Delaying pacemaker implantation in high-risk patients (elderly with comorbidities) can lead to sudden death 8