What is the diagnosis and treatment for bifascicular block (a type of heart block involving two fascicles of the electrical conduction system)?

From the Guidelines

Asymptomatic patients with bifascicular block do not require permanent pacemaker implantation, but regular cardiac monitoring is recommended to detect progression to complete heart block, whereas symptomatic patients with syncope, presyncope, or documented high-degree AV block should undergo pacemaker implantation, as supported by the most recent guidelines 1.

Key Considerations

• Bifascicular block is a cardiac conduction abnormality involving two of the three fascicles of the His-Purkinje system, typically presenting as a right bundle branch block (RBBB) combined with either left anterior fascicular block (LAFB) or left posterior fascicular block (LPFB) 1.
• The decision for pacemaker placement should be based on symptoms and evidence of intermittent complete heart block, not solely on the ECG finding of bifascicular block, with a focus on preventing morbidity and mortality 1.
• Patients with bifascicular block should avoid medications that can further impair cardiac conduction, such as beta-blockers, calcium channel blockers, and certain antiarrhythmics, to minimize the risk of progression to complete heart block 1.
• The risk of progression to complete heart block is relatively low (about 1-2% per year), but requires vigilance, especially in patients with underlying heart disease, and regular monitoring can help identify those at higher risk 1.

Management Approach

• For asymptomatic patients, regular cardiac monitoring is recommended to detect progression to complete heart block, with a focus on preventing sudden cardiac death and improving quality of life 1.
• For symptomatic patients, permanent pacemaker implantation is the standard treatment, with the goal of preventing further syncopal episodes and reducing the risk of mortality 1.
• The use of implantable loop recorders (ILRs) may be considered in patients with syncope and bifascicular block, especially if the cause of syncope is unclear, to help diagnose the underlying mechanism and guide treatment 1.
• Electrophysiological studies (EPS) may also be helpful in evaluating patients with bifascicular block and syncope, particularly if there is evidence of significant His/infra-His disease, to inform treatment decisions and improve outcomes 1.

From the Research

Bifascicular Block Overview

• Bifascicular block is a condition characterized by the presence of two or more fascicular blocks in the heart, which can lead to syncope and other cardiac complications 2.
• The incidence of bifascicular block is estimated to be around 0.0033% (3.3 per thousand) in the general population, with males being more affected than females at a rate of 2.4 to 1 2.

Clinical Characteristics and Prognosis

• Patients with bifascicular block often have underlying cardiovascular conditions such as high blood pressure, coronary heart disease, and diabetes mellitus 2.
• The prognosis of bifascicular block is generally good, with a low mortality rate, but patients may experience syncope and other cardiac complications 2, 3.
• Studies have shown that permanent pacing can reduce the risk of syncope and other major adverse events in patients with bifascicular block and syncope of unexplained origin 3, 4, 5.

Treatment and Management

• Permanent pacing is often considered for patients with syncope and bifascicular block, particularly those with a high risk of cardiac complications 3, 4, 5.
• The type of bundle branch block morphology does not seem to affect the outcome of patients with syncope and bifascicular block, and pacemaker implantation can reduce adverse events regardless of the type of bundle branch block 6.
• The use of implantable cardiac monitors (ICMs) can also be beneficial in patients with bifascicular block and syncope, particularly in those with a low risk of cardiac complications 3.

Outcomes and Complications

• Patients with bifascicular block and syncope who receive permanent pacing may still experience syncope recurrence, particularly those who receive empiric pacing without a clear indication for pacing 5.
• The progression to high-degree atrioventricular block is a common complication in patients with bifascicular block, and permanent pacing can reduce the risk of this complication 5.
• The annual incidence of rhythm disease development in patients with bifascicular block is estimated to be around 7.4% 4.