From the Guidelines
Patients with bifascicular block who experience syncope, presyncope, or documented high-degree AV block should undergo permanent pacemaker implantation, as it is a Class I recommendation according to the 2018 ACC/AHA/HRS guideline 1. The management of bifascicular block depends on the presence of symptoms and the degree of conduction disturbance.
Asymptomatic Patients
For asymptomatic patients with bifascicular block, no specific treatment is required, but monitoring is recommended with regular ECGs to detect any progression to complete heart block.
Symptomatic Patients
However, for symptomatic patients, the approach is more aggressive:
- Syncope, BBB, and HV >70ms: Permanent pacing is recommended (Class I) 1.
- Alternating BBB: Permanent pacing is recommended (Class I) 1.
- LVEF 36-50%, LBBB, QRS >150 ms, and Class II or greater HF symptoms: Cardiac resynchronization therapy may be considered (Class IIb) 1. The standard pacing system would be a dual-chamber pacemaker programmed to DDD mode.
Special Considerations
Patients with bifascicular block who are undergoing surgery may require temporary pacing during the perioperative period due to increased risk of complete heart block from anesthetics. Bifascicular block occurs because of damage to the conduction system, often due to coronary artery disease, cardiomyopathy, or degenerative fibrosis. The concern with bifascicular block is the potential progression to complete heart block, which can cause Stokes-Adams attacks, syncope, or even sudden cardiac death if not properly managed, as highlighted in the European Society of Cardiology guidelines 1. Some key points to consider in the management of bifascicular block include:
- The role of electrophysiological studies in assessing the risk of progression to complete heart block
- The importance of monitoring asymptomatic patients with regular ECGs
- The need for permanent pacemaker implantation in symptomatic patients
- The potential benefits of cardiac resynchronization therapy in patients with left ventricular dysfunction and LBBB.
From the Research
Bifascicular Block Overview
- Bifascicular block is a condition where there is a blockage in two of the three main electrical pathways of the heart, which can increase the risk of complete heart block 2.
- Studies have shown that patients with bifascicular block and a prolonged PR interval are at risk of developing complete heart block, but the risk is relatively low 2.
Risk of Complete Heart Block
- A study published in 1981 found that none of the 76 patients with bifascicular block and a prolonged PR interval developed complete heart block during a period of 37 general anaesthetics, 32 spinal anaesthetics, and 64 local anaesthetics or endoscopic procedures 2.
- Another study published in 2023 found that pacemaker implantation reduced the risk of major study-related events in patients with bifascicular block and syncope, regardless of the type of bundle branch block or the presence of PR interval prolongation 3.
Management of Bifascicular Block
- Empiric pacemaker implantation has been shown to reduce the risk of syncope recurrence in patients with unexplained, recurrent, traumatic syncope and bifascicular block 4.
- The disopyramide stress test has been found to be a sensitive and specific tool for predicting impending high-degree atrioventricular block in patients with bifascicular block 5.
- A bradycardia-detecting pacemaker can be used to evaluate the risk of atrioventricular block progression in patients with bifascicular block 6.
Predictive Value of Diagnostic Tests
- The sensitivity and specificity of the disopyramide test for predicting high-degree atrioventricular block in patients with bifascicular block have been found to be 71% and 98%, respectively 5.
- The sensitivity and positive predictive values of a positive disopyramide test result and an HV interval > or = 70 ms at baseline have been found to be 75% and 80%, and 47% and 88%, respectively 6.