What are the indications for pacing in patients with bifascicular block?

Indications for Pacemaker Implantation in Bifascicular Block

Permanent pacemaker implantation is indicated for patients with bifascicular block who have intermittent complete heart block with symptomatic bradycardia, or bifascicular/trifascicular block with intermittent type II second-degree AV block, regardless of symptoms. 1, 2

Class I Indications (Definite Indications)

• Bifascicular block with intermittent complete heart block associated with symptomatic bradycardia 1, 2
• Bifascicular or trifascicular block with intermittent type II second-degree AV block 1, 2
• Persistent advanced second-degree AV block or complete heart block after acute myocardial infarction with block in the His-Purkinje system (bilateral bundle branch block) 1
• Transient advanced AV block with associated bundle branch block following myocardial infarction 1, 2
• Syncope in patients with bifascicular block when other causes have been excluded, especially if syncope may have been due to transient third-degree AV block 1, 3

Class IIa Indications (Reasonable to Consider)

• Bifascicular or trifascicular block with syncope not proven to be due to complete heart block, when other causes have been excluded 1, 2
• Markedly prolonged HV interval (≥100 ms) found during electrophysiological study 1
• Intra- or infra-Hisian block demonstrated during incremental atrial pacing at a pacing rate <150 bpm during electrophysiological study 1
• Patients with syncope and bundle branch block with normal HV conduction time (implanting a pacemaker rather than a loop recorder is reasonable due to high short-term incidence of AV block) 1

Not Indicated (Class III)

• Asymptomatic bifascicular block without evidence of intermittent AV block 1
• Acquired left anterior hemiblock in the absence of AV block 1
• First-degree AV block with bundle branch block not previously demonstrated 1, 2

Predictors of Progression to High-Degree AV Block

Several factors have been identified as predictors of progression to advanced AV block in patients with bifascicular block:

• Presence of syncope or presyncope (HR=2.06) 4
• QRS width >140 ms (HR=2.44) 4
• Renal failure (HR=1.86) 4
• HV interval >64 ms (HR=6.6) 4

Efficacy of Pacing in Bifascicular Block

• In patients with bifascicular block and syncope of undetermined origin, dual chamber pacing programmed to DDD60 significantly reduces syncope and symptomatic events compared to backup pacing 5
• Pacing relieves neurological symptoms but has not been shown to reduce the occurrence of sudden death 1
• Patients who receive a pacemaker following a positive electrophysiological study or documentation of paroxysmal AV block have better outcomes with fewer syncope recurrences compared to those who receive empiric pacing 3

Important Considerations

• The rate of progression from bifascicular block to complete heart block is generally slow 1
• No single clinical or laboratory variable, including bifascicular block alone, identifies patients at high risk of death due to future bradyarrhythmia 1
• PR interval prolongation is common in patients with bifascicular block, but the delay is often at the level of the AV node and does not correlate with progression to complete heart block or sudden death 1
• Although HV interval prolongation is associated with increased mortality, death is often due to underlying heart disease rather than AV block 1
• In patients with neuromuscular disease and any degree of fascicular block, cardiac pacing may be indicated due to unpredictable progression of AV conduction disease 1

Pacemaker Mode Selection

• For patients with bifascicular block requiring pacing, suitable modes include VVI, DDD, or single-lead VDD 1
• Devices that maintain synchrony between atria and ventricles (DDD/VDD) are generally preferred, especially in older patients, to maintain the contribution of atrial contraction to ventricular filling 6, 2