From the Guidelines
Fascicular block is associated with increased cardiovascular risk, and patients with this condition should undergo comprehensive cardiac evaluation and regular ECG monitoring to detect any progression of conduction disease. The risk of developing complete heart block, which can lead to syncope, cardiac arrest, or sudden cardiac death, is particularly elevated in patients with underlying heart disease such as coronary artery disease, cardiomyopathy, or valvular heart disease 1.
Key Considerations
- Bifascicular block affects two of the three major fascicles of the cardiac conduction system, leaving only one functioning fascicle to maintain atrioventricular conduction 1.
- The prevalence of bundle branch block increases with age, and syncope is usually seen in patients with bundle branch blocks who often have other cardiac diseases 1.
- In patients with neuromuscular disease and any degree of fascicular block, with or without symptoms, cardiac pacing may have a place, in view of the unpredictable progression of AV conduction disease 1.
Management
- Comprehensive cardiac evaluation including echocardiography and possibly stress testing to assess for ischemic heart disease is recommended for patients with fascicular block 1.
- In symptomatic patients with documented progression to intermittent complete heart block, permanent pacemaker implantation may be necessary 1.
- Regular cardiac follow-up with ECG monitoring is recommended for asymptomatic patients with fascicular block to detect any progression of conduction disease 1.
Prognosis
- The risk of sudden cardiac death is higher in patients with fascicular block, especially those with underlying heart disease 1.
- The HV interval has been identified as a possible predictor of third-degree AV block and sudden death, and patients with a prolonged HV interval should be considered for permanent pacing 1.
From the Research
Associated Cardiovascular Risks for Fascicular Block
- Fascicular heart blocks can progress to complete heart blocks, and the risk has been evaluated in a large general population 2.
- Patients with fascicular block have an increased risk of incident higher degree atrioventricular block (AVB), syncope, pacemaker implantation, and death 2.
- The risk of cardiovascular outcomes increases with the complexity of fascicular block, with isolated left anterior fascicular block (LAFB) associated with a 0%-2% increased 10-year risk of developing third-degree AVB 2.
- Right bundle branch block combined with LAFB and first-degree AVB is associated with up to 23% increased 10-year risk of developing third-degree AVB, depending on age and sex group 2.
- Except for left posterior fascicular block, there is no significant association between fascicular block and death 2.
Relation to Coronary Artery Disease
- Left Anterior Fascicular Block (LAFB) is correlated with coronary artery disease (CAD), but the clinical significance is still controversial 3.
- LAFB subjects have more pathological CAD and myocardial infarction (MI), but LAFB is not an independent relevant factor of CAD 3.
- LAFB lowers the accuracy to clinically diagnose CAD and is associated with increased risk of death and cardiac death 3.
Management and Treatment
- Beta-blockers are proven to improve survival among patients with heart failure with reduced ejection fraction, and their efficacy in patients with heart failure and pacemaker devices has been demonstrated 4.
- Beta-blocker therapy is associated with improved survival among patients with heart failure and a pacemaker rhythm on ECG 4.
- The use of beta-blockers in patients with an implantable cardioverter defibrillator (ICD) is recommended, but the actual use is lower than optimal 5.