What is the management for a patient with a heart rate of 39 beats per minute (bpm) due to escape junctional rhythm on electrocardiogram (EKG), left bundle branch block (LBBB), and complete atrioventricular (AV) block?

Management of Complete AV Block with Junctional Escape Rhythm and LBBB

This patient requires immediate permanent pacemaker implantation. Complete (third-degree) AV block with a heart rate of 39 bpm represents a Class I indication for permanent cardiac pacing, regardless of symptom status 1.

Immediate Management

Acute Stabilization

• Avoid atropine in this patient—atropine is contraindicated (Class III) for AV block occurring at the infranodal level, which is indicated by the wide QRS escape rhythm with LBBB morphology 1. Atropine is only effective for AV nodal-level blocks with narrow QRS escape rhythms 1, 2.

• Apply transcutaneous pacing immediately as a bridge to permanent pacing 1. Transcutaneous pacing is well-suited for patients requiring standby pacing and reduces the need for vascular interventions, particularly important if thrombolytic therapy is being considered 1.

• Assess hemodynamic stability: Monitor for hypotension, altered mental status, chest pain, or heart failure symptoms that would necessitate immediate pacing 1.

Determining Block Location

The combination of complete AV block with LBBB morphology escape rhythm strongly suggests infranodal (His-Purkinje) disease 1. Key distinguishing features:

• Wide QRS escape rhythm (LBBB pattern) = infranodal block with poor prognosis 1
• Narrow QRS escape = AV nodal block with better prognosis 1
• The junctional escape rate of 39 bpm is critically slow and indicates unreliable escape pacemaker function 1

Untreated complete AV block at the infranodal level has extremely poor prognosis, with patients frequently progressing to symptomatic bradycardia, syncope, and sudden cardiac death 1.

Definitive Management: Permanent Pacemaker

Class I Indication (Strongest Recommendation)

Permanent pacing is mandated for complete (third-degree) AV block, as multiple non-randomized studies demonstrate improved survival, particularly in symptomatic patients 1. Even asymptomatic patients with acquired complete AV block are frequently symptomatic regardless of block site and require pacing 1.

Pacemaker Selection

• Dual-chamber pacing (DDD) is preferred to maintain AV synchrony and optimize cardiac output 1
• Consider cardiac resynchronization therapy (CRT) if the patient has:
  • Left ventricular ejection fraction 36-50% with LBBB and QRS >150 ms
  • Class II or greater heart failure symptoms 1

Critical Pitfalls to Avoid

Do Not Delay Pacing

• Complete heart block with wide QRS escape is a medical emergency requiring urgent permanent pacemaker placement 1
• The slow junctional rate (39 bpm) provides inadequate cardiac output and risks asystole 1

Do Not Use Atropine

• Atropine paradoxically worsens infranodal block and may precipitate complete asystole 1, 2
• The FDA label confirms atropine may cause AV block and nodal rhythm in some patients 2

Do Not Perform Extensive Workup Before Pacing

• While electrophysiology studies can localize block site, the presence of complete AV block with wide QRS escape is sufficient for permanent pacing indication without requiring EPS 1
• EPS is reserved for patients with suspected but undocumented high-grade block, not established complete block 1

Prognosis

Without pacing, this patient faces high mortality risk from:

• Sudden progression to asystole 1
• Hemodynamic collapse from inadequate cardiac output 1
• Development of ventricular arrhythmias due to bradycardia 1

With permanent pacing, survival improves dramatically, particularly when pacing is instituted before development of severe symptoms 1.