What are the treatment options for atrioventricular (AV) block?

Treatment of Atrioventricular (AV) Block

Permanent pacemaker implantation is the definitive treatment for symptomatic third-degree and advanced second-degree AV block at any anatomic level. 1

Classification and Diagnosis

• AV block is classified as first-, second-, or third-degree (complete) block 1:
  • First-degree AV block: PR interval >0.20 seconds
  • Second-degree AV block:
    • Type I (Wenckebach): Progressive PR prolongation before a nonconducted beat
    • Type II: Fixed PR intervals before and after blocked beats, usually with wide QRS
  • Advanced second-degree AV block: Blocking of 2+ consecutive P waves with some conducted beats
  • Third-degree AV block: Complete absence of AV conduction

Treatment Algorithm Based on AV Block Type

Third-Degree and Advanced Second-Degree AV Block

• Permanent pacemaker implantation is indicated when associated with 1:

  • Bradycardia with symptoms (including heart failure)
  • Ventricular arrhythmias presumed due to AV block
  • Medical conditions requiring drug therapy causing symptomatic bradycardia
  • Asystole ≥3.0 seconds or escape rate <40 bpm in awake, symptom-free patients
  • Atrial fibrillation with bradycardia and pauses ≥5 seconds

• For acute management of unstable patients 1:

  • Synchronized cardioversion for hemodynamically unstable patients
  • Atropine can be used in acute situations to improve AV conduction by blocking vagal effects on the AV node 2

First-Degree and Less Advanced Second-Degree AV Block

• No specific treatment required for asymptomatic patients with isolated first-degree AV block 3
• Consider permanent pacing for:
  • Marked first-degree AV block (PR interval ≥300 ms) with symptoms 1, 3
  • Neuromuscular diseases with any degree of AV block due to unpredictable progression 1

Drug-Induced AV Block

• Discontinue or adjust medications that may contribute to AV conduction delay 3, 4
  • Common culprits: beta-blockers, calcium channel blockers, digoxin 4
• Recent evidence suggests permanent pacing may be necessary despite drug discontinuation, as 27% of patients experience recurrence of AV block even after drug withdrawal 4, 5
• Avoid medications that further depress AV conduction in symptomatic patients 3

Special Considerations

• Reversible causes should be corrected first 1:

  • Electrolyte abnormalities
  • Lyme disease
  • Hypervagotonia
  • Perioperative hypothermia
  • Inflammation near AV conduction system after surgery

• Consider permanent pacing despite transient resolution in 1:

  • Sarcoidosis
  • Amyloidosis
  • Neuromuscular diseases
  • Post-valve surgery (physician's discretion)

• Catheter ablation may be considered for specific cases where junctional extrasystoles interfere with otherwise normal AV conduction 6

Pacing Modality Selection

• VDD pacing (single lead system with atrial sensing capabilities) is a viable alternative to DDD pacing in patients with high-degree AV block and normal sinus node function 7

  • Benefits: Lower cost, high reliability, abbreviated implantation time
  • Maintains physiological atrioventricular activation in 94-99% of beats

• Avoid certain medications in pre-excited atrial fibrillation 1:

  • Intravenous digoxin, amiodarone, beta blockers, diltiazem, and verapamil are potentially harmful as they may enhance conduction over accessory pathways

Monitoring and Follow-up

• Consider ambulatory ECG monitoring (Holter) in patients with symptoms suggesting intermittent higher-grade block 3
• Regular follow-up is essential for patients with first-degree AV block with concurrent bundle branch block, as they require closer monitoring 3