From the Guidelines
A bundle branch block is a cardiac conduction abnormality where electrical impulses are delayed or blocked as they travel through the bundle branches, affecting how the heart's electrical system coordinates the contraction of the ventricles. This condition can be explained in simpler terms as a problem with the heart's electrical system, where the signals that control the heartbeat are delayed or blocked in the bundle branches, which are specialized fibers that carry these signals. There are two main types of bundle branch blocks: right bundle branch block (RBBB) and left bundle branch block (LBBB), depending on which pathway is affected. According to the 2019 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1, bundle branch blocks can be detected on an electrocardiogram (ECG) by characteristic patterns, including widened QRS complexes and specific morphology changes in different leads.
Some key points to consider about bundle branch blocks include:
- They can be asymptomatic, or they can indicate underlying heart disease such as coronary artery disease, heart failure, or cardiomyopathy
- The presence of a bundle branch block on an ECG can be a predictor for abnormal conduction properties, as noted in the 2019 guideline 1
- Alternating bundle branch block implies unstable conduction disease in both conduction bundles, as discussed in the 2008 ACC/AHA/HRS guidelines for device-based therapy of cardiac rhythm abnormalities 1
- Regular cardiac monitoring is important for those diagnosed with bundle branch blocks to track any progression or development of related heart conditions
In terms of management, the 2019 guideline recommends permanent pacing for patients with syncope and HV intervals ≥70 ms or frank infranodal block 1. Additionally, cardiac resynchronization therapy with a specialized pacemaker might be recommended for patients with LBBB and significant ventricular dyssynchrony leading to heart failure symptoms. Overall, the management of bundle branch blocks should be individualized based on the patient's symptoms, underlying heart disease, and other factors, with a focus on reducing morbidity, mortality, and improving quality of life.
From the Research
What is a Bundle Branch Block
A bundle branch block is a condition where there is a delay or obstruction in the electrical conduction system of the heart, specifically in the bundle branches that carry electrical impulses from the atrioventricular node to the ventricles [ 2 ].
Types of Bundle Branch Blocks
There are two main types of bundle branch blocks:
- Left Bundle Branch Block (LBBB): This occurs when there is a delay or blockage in the left bundle branch [ 2 ].
- Right Bundle Branch Block (RBBB): This occurs when there is a delay or blockage in the right bundle branch [ 3 ].
Causes and Associations
Bundle branch blocks can be caused by various factors, including:
- Conduction system degeneration [ 2 ]
- Myocardial pathology [ 2 ]
- Aortic valve disease [ 2 ]
- Cardiac procedures [ 2 ]
- Chronic coronary syndromes [ 4 ]
Clinical Implications
Bundle branch blocks can have significant clinical implications, including:
- Increased risk of heart failure [ 4, 3 ]
- Increased risk of pacemaker implantation [ 4, 3 ]
- Increased risk of cardiovascular death [ 3 ]
Key Points to Consider
Some key points to consider about bundle branch blocks include: