What is the management for a patient with atrioventricular (AV) block on electrocardiogram (EKG)?

Management of Atrioventricular (AV) Block on EKG

Permanent pacemaker implantation is the definitive treatment for high-grade AV block (Mobitz type II, third-degree) or symptomatic AV block, while observation may be appropriate for asymptomatic first-degree or Mobitz type I AV block. 1

Classification and Initial Assessment

The management of AV block depends on the type, location, symptoms, and underlying etiology:

Types of AV Block:

• First-degree AV block: Prolonged PR interval (>200 ms)
• Second-degree AV block:
  • Mobitz type I (Wenckebach): Progressive PR prolongation until a beat is dropped
  • Mobitz type II: Sudden dropped beats without PR prolongation
• Third-degree (complete) AV block: No atrial impulses reach the ventricles

Key Assessment Points:

• Hemodynamic stability (blood pressure, perfusion)
• Symptoms (syncope, pre-syncope, dizziness, exercise intolerance)
• QRS width (narrow vs. wide complex)
• Ventricular rate
• Underlying structural heart disease
• Reversible causes (medications, electrolyte abnormalities, ischemia)

Management Algorithm

1. Unstable/Symptomatic Patients:

• Immediate interventions for hemodynamically unstable patients:
  • Atropine 0.5 mg IV (may repeat to maximum 2.0 mg) for symptomatic bradycardia 1, 2
  • If no response to atropine, consider transcutaneous pacing 1
  • Beta-adrenergic agonists (isoproterenol) if no response to atropine and low likelihood of coronary ischemia 3
  • Arrange for urgent temporary transvenous pacing if transcutaneous pacing ineffective

2. Stable Patients - Management by AV Block Type:

First-degree AV block:

• Usually no specific treatment required if asymptomatic
• Regular monitoring if PR interval >300 ms
• Evaluate for underlying causes
• Consider permanent pacing if severely prolonged PR interval (>400 ms) with symptoms

Second-degree AV block:

• Mobitz type I (Wenckebach):

  • If asymptomatic: observation and regular follow-up
  • If symptomatic: permanent pacemaker
  • If occurring during inferior MI: atropine may be effective 1

• Mobitz type II:

  • Permanent pacemaker indicated regardless of symptoms due to high risk of progression to complete heart block 1
  • Temporary pacing may be needed while awaiting permanent pacemaker

Third-degree (complete) AV block:

• Permanent pacemaker indicated regardless of symptoms 1
• Temporary pacing as bridge to permanent pacemaker

3. Special Considerations:

• Alternating bundle branch block: Permanent pacing recommended (Class I) 1
• Neuromuscular disorders (Kearns-Sayre syndrome, Emery-Dreifuss, limb-girdle muscular dystrophy): Consider permanent pacing with any degree of AV block due to risk of rapid progression 1
• Anderson-Fabry disease with QRS >110 ms: Consider permanent pacing 1
• Bifascicular block with syncope and HV interval >70 ms: Permanent pacing recommended 1

Pacemaker Selection

• Dual-chamber pacing (DDD) preferred to maintain AV synchrony in patients with preserved left ventricular ejection fraction (>50%) 4
• Cardiac resynchronization therapy (CRT) may be considered in patients with heart failure, mildly to moderately reduced LVEF (36%-50%), and LBBB (QRS ≥150 ms) 1
• Physiologic pacing methods (His bundle pacing) should be considered over right ventricular pacing in patients with reduced LVEF and expected ventricular pacing >40% 4

Common Pitfalls and Caveats

• Do not place permanent pacemakers in asymptomatic patients with isolated conduction disease and 1:1 AV conduction (Class III: Harm) 1
• Avoid negative chronotropic medications (beta-blockers, calcium channel blockers, digoxin) in patients with AV block as they may worsen conduction 4
• Atropine may worsen AV block at infranodal level (type II AV block and third-degree AV block with new wide QRS complex) 1
• Low doses of atropine (<0.5 mg) may paradoxically worsen bradycardia 1
• Temporary pacing should be considered for patients with Lyme carditis and high-degree AV block, as this condition is often transient 5

Follow-up for Patients Without Pacemakers

• Regular ECG monitoring (every 6-12 months)
• Prompt evaluation for any new or worsening symptoms
• Patient education regarding symptoms of bradycardia or heart block
• Annual 24-hour Holter monitoring for patients with first-degree or Mobitz type I AV block to detect progression 4

By following this algorithm, clinicians can effectively manage patients with various types of AV block, minimizing morbidity and mortality while improving quality of life.