What is the treatment for 3rd degree heart block?

Treatment for 3rd Degree Heart Block

Permanent pacemaker implantation is the definitive treatment for third-degree heart block in nearly all cases, regardless of symptoms or ventricular rate. 1

Indications for Permanent Pacemaker Implantation

The ACC/AHA/HRS guidelines provide clear recommendations for managing third-degree (complete) heart block. Permanent pacemaker implantation is indicated in the following scenarios:

Class I Indications (Definite Benefit):

1. Symptomatic patients:

   • Third-degree AV block with symptoms (including heart failure) or ventricular arrhythmias 1
   • Bradycardia with symptoms due to AV block 1

2. Asymptomatic patients with any of the following:

   • Documented periods of asystole ≥3.0 seconds 1
   • Any escape rate <40 bpm 1
   • Escape rhythm below the AV node 1
   • AF with bradycardia and pauses ≥5 seconds 1
   • Cardiomegaly or LV dysfunction with ventricular rates ≥40 bpm 1

3. Special circumstances:

   • After catheter ablation of the AV junction 1
   • Postoperative AV block not expected to resolve 1
   • Associated with neuromuscular diseases 1
   • Second or third-degree AV block during exercise (non-ischemic) 1

Class IIa Indications (Reasonable):

• Persistent third-degree AV block with escape rate >40 bpm in asymptomatic adults without cardiomegaly 1
• First or second-degree AV block with symptoms similar to pacemaker syndrome 1

Acute Management Before Pacemaker Implantation

For unstable patients with third-degree heart block awaiting permanent pacemaker implantation:

1. Pharmacologic interventions:

   • Atropine (may be ineffective if block is below AV node) 2
   • Isoproterenol infusion 3
   • Dopamine or dobutamine for hemodynamic support 3, 4

2. Temporary pacing:

   • Transcutaneous pacing for immediate stabilization 2
   • Transvenous temporary pacing for bridge to permanent pacemaker 5, 3, 6

Pacemaker Selection

Once the decision for permanent pacing is made, device selection should consider:

• Chamber configuration: Single vs. dual-chamber vs. biventricular devices
• Pacing/sensing configuration: Unipolar vs. bipolar
• Rate response capability: Particularly important for patients with chronotropic incompetence
• Additional features: Automatic capture verification, remote monitoring capabilities 1

Special Considerations

• Pediatric patients: Different rate criteria apply for congenital third-degree AV block:

  • Infants: Pacing indicated if ventricular rate <55 bpm (or <70 bpm with congenital heart disease) 1
  • Children beyond first year: Consider pacing if average heart rate <50 bpm 1

• Reversible causes: Pacemaker implantation is not indicated for AV block expected to resolve (e.g., drug toxicity, Lyme disease, transient vagal tone increases) unless recurrence is expected 1

Common Pitfalls

1. Delaying pacemaker implantation in asymptomatic patients: Even asymptomatic patients with third-degree AV block generally require pacing, especially with escape rates <40 bpm or infranodal block location 1

2. Misinterpreting the escape rhythm location: The site of origin of the escape rhythm (AV node, His bundle, or infra-His) is more critical for prognosis than the actual escape rate 1

3. Overlooking exercise-induced block: Second or third-degree AV block during exercise (when not due to ischemia) indicates disease in the His-Purkinje system and requires pacing 1

4. Inadequate temporary support: Unstable patients may require temporary pacing while awaiting permanent pacemaker implantation 2, 3