Permanent Pacing Indications in Bifascicular Block
Permanent pacing is indicated for patients with syncope and chronic bifascicular block when high-degree AV block is not documented and other causes are excluded. [1]
Permanent pacing is supported by evidence that dual-chamber pacing reduces recurrent syncope in this population (relative risk reduction). [2]
Pacing Strategy
The pacing strategy for bifascicular block with syncope when other causes are excluded is dual-chamber pacing. [1]
For long-term pacemaker programming, minimization of unnecessary right ventricular pacing is recommended in patients receiving ventricular pacing for AV conduction disease. [3]
Mode Selection for Patients Requiring Ongoing Ventricular Pacing
In patients who require permanent pacing for AV block and require frequent ventricular pacing, selection of pacing method should account for ventricular activation physiology.
- If LVEF is 36% to 50% and expected ventricular pacing is >40%, pacing methods that provide more physiologic ventricular activation (including cardiac resynchronization therapy and His bundle pacing) are preferred to right ventricular pacing. [3]
- If LVEF is 36% to 50% and expected ventricular pacing is ≤40%, right ventricular pacing is reasonable compared with methods intended to maintain physiologic ventricular activation. [3]
- If AV block is at the level of the AV node and physiologic ventricular activation is desired, His bundle pacing may be considered. [3]
Clinical Eligibility Criteria Used to Justify Implantation
Implantation is supported when the presentation is consistent with bradyarrhythmic syncope risk in bifascicular block and the following conditions are met:
- Syncope occurs in the setting of chronic bifascicular block. [1]
- High-degree AV block is not documented. [1]
- Other causes of syncope are excluded. [1]
Evidence Base Supporting Dual-Chamber Pacing
Across studies summarized for the syncope guideline, pacing is associated with a reduction in recurrent syncope.
- In a systematic review supporting reflex-syncope pacing guidance, pacing showed a 70% reduction in recurrent syncope (relative risk 0.30, 95% CI 0.15–0.60). [2]
Practical Risk-Reduction in Programming
After implantation, programming should aim to reduce pacing burden that may worsen outcomes.
- Pacemaker programming should be directed to minimize unnecessary chronic right ventricular pacing whenever possible. [3]
Definitions Applied to This Clinical Scenario
Bifascicular block is defined by ECG evidence of impaired conduction in the right bundle branch plus one left fascicle (left anterior or left posterior fascicular block). [4]