From the Guidelines
Asymptomatic left bundle branch block (LBBB) should be evaluated with a comprehensive cardiac workup, starting with a thorough history and physical examination, followed by an electrocardiogram (ECG) to confirm the LBBB, and then an echocardiogram to assess cardiac structure and function, as recommended by the 2019 ACC/AHA/HRS guideline 1.
Evaluation of Asymptomatic LBBB
The evaluation of asymptomatic LBBB is crucial to rule out underlying heart disease, as LBBB can be a marker of cardiac pathology, including coronary artery disease, cardiomyopathy, or valvular heart disease. The diagnostic yield of transthoracic echocardiography in patients without clinical evidence of heart disease is low, but it is still recommended in patients with asymptomatic LBBB to assess cardiac structure and function 1.
Recommended Testing
The following tests are recommended in the evaluation of asymptomatic LBBB:
- Electrocardiogram (ECG) to confirm the LBBB
- Echocardiogram to assess cardiac structure and function, particularly left ventricular function
- Cardiac biomarkers to rule out cardiac injury or disease
- Stress test (preferably with imaging such as nuclear perfusion or stress echocardiography) to evaluate cardiac function under stress
- Cardiac MRI or coronary CT angiography may be considered depending on clinical suspicion of underlying cardiac disease 1
Management
If significant cardiac disease is identified, appropriate treatment should be initiated based on the specific diagnosis. For patients with normal cardiac function and no evidence of structural heart disease, no specific treatment is required for the LBBB itself, but regular cardiac follow-up every 1-2 years is recommended to monitor for development of cardiac dysfunction 1.
Key Considerations
- Asymptomatic LBBB can be a marker of underlying cardiac disease, and early detection allows for timely intervention to prevent progression of cardiac dysfunction
- The presence of LBBB in patients referred for echocardiography in evaluation of suspected congestive heart failure confers nearly a 4-fold increased likelihood of left ventricular systolic dysfunction 1
- Transthoracic echocardiography can identify various structural cardiac abnormalities underlying bradycardia or conduction disturbance, including cardiomyopathy, valvular heart disease, congenital anomalies, tumors, infections, infiltrative processes, immunologically mediated conditions, and diseases of the great vessels and pericardium 1
From the Research
Asymptomatic Left Bundle Branch Block (LBBB)
- Asymptomatic LBBB is a condition where the left bundle branch of the heart's electrical conduction system is blocked, but the patient does not exhibit any symptoms 2.
- Studies have shown that asymptomatic LBBB can be a predictor of new-onset congestive heart failure and death from cardiovascular diseases 2.
- The prevalence of LBBB at baseline was 2.5% in a community-based cohort study, and the incidence of congestive heart failure was higher in patients with LBBB than in those without LBBB 2.
Diagnosis and Treatment
- LBBB can be diagnosed using electrocardiogram (ECG) criteria, and strict LBBB criteria have been proposed to identify patients with greater mechanical dyssynchrony 3.
- Cardiac magnetic resonance imaging (MRI) can be used to identify patterns of dyssynchrony and implications for late gadolinium enhancement imaging in patients with LBBB 4.
- Patients with LBBB may benefit from cardiac resynchronization therapy, which can improve symptoms and reduce mortality 5.
Prognosis and Outcome
- Asymptomatic LBBB is associated with a higher risk of cardiovascular morbidity and mortality, and patients with LBBB are at high risk of morbidity and mortality 2, 6.
- Mortality rates for patients with LBBB have decreased over the years, but there may be room for further improvement in treatment strategies 6.
- Additional studies are needed to better identify patients with LBBB who may maximally benefit from an early invasive treatment strategy 6.