From the Guidelines
A bifascicular block noted on EKG is indicative of a conduction abnormality, where there is a blockage in two of the three main fascicles of the heart's electrical conduction system.
Implications of Bifascicular Block
Patients with this condition may require close monitoring and potential treatment with medications such as atropine 0.5-1.0 mg IV or transcutaneous pacing, and in some cases, permanent pacemaker implantation may be necessary 1.
Key Considerations
- Syncope: is common in patients with bifascicular block, although it is not associated with an increased incidence of sudden death 1.
- Electrophysiological study: may be helpful to evaluate and direct the treatment of inducible ventricular arrhythmias that are common in patients with bifascicular block 1.
- HV interval: prolongation is a possible predictor of third-degree AV block and sudden death, and patients with an HV interval greater than or equal to 100 milliseconds may be considered for permanent pacing 1.
Treatment Options
Additionally, patients may be started on anti-arrhythmic medications such as amiodarone 200-400 mg orally daily to prevent further conduction disturbances.
- Pacemaker implantation: is considered appropriate in patients who exhibit intermittent second- or third-degree AV block, or signs of a severe conduction disturbance below the level of the AV node 1.
- Close monitoring: is necessary for patients with bifascicular block, as the rate of progression to high-degree AV block is low, but the incidence of sudden death is substantial 1.
From the Research
Implications of Bifascicular Block
The implications of a bifascicular block noted on an Electrocardiogram (EKG) are significant and can have serious consequences for patients. Some of the key implications include:
- Increased risk of progression to complete heart block, particularly if the patient shows a markedly prolonged His-ventricular (HV) interval or evidence of a bifascicular block 2
- Higher risk of sudden cardiac death (SCD) and all-cause mortality, especially in patients with congestive heart failure (CHF) 3
- Increased risk of conduction defects and bradyarrhythmias, especially in patients undergoing anesthesia 4
- Potential need for permanent pacemaker implantation, especially in patients with syncope and bifascicular block 5, 6
Risk Factors and Predictors
Several factors can increase the risk of adverse outcomes in patients with bifascicular block, including:
- Age, with older adults being at higher risk 2, 3
- Presence of CHF, which is an independent predictor of all-cause mortality and SCD 3
- History of myocardial infarction, which can increase the risk of all-cause mortality and SCD 3
- Presence of PR interval prolongation or QRS width, although these factors may not be predictive of major study-related events (MSREs) in all patients 5
Management and Treatment
The management and treatment of patients with bifascicular block depend on several factors, including the presence of symptoms, the severity of the block, and the patient's overall health. Some of the key considerations include:
- Permanent pacemaker implantation, which can reduce the risk of MSREs in patients with syncope and bifascicular block 5, 6
- Implantable loop recorder (ILR) monitoring, which can be used to diagnose and manage patients with syncope and bifascicular block 5, 6
- Anesthesia and monitoring techniques, which can induce conduction defects and bradyarrhythmias in patients with pre-existing bundle branch block 4