From the Guidelines
Left Bundle Branch Block (LBBB) on an electrocardiogram (ECG) is a conduction abnormality that requires further cardiac evaluation, particularly if it's new-onset, as it may indicate underlying heart disease. When LBBB is identified, management focuses on identifying and treating the underlying cause rather than the LBBB itself. Patients with LBBB should undergo echocardiography to assess cardiac structure and function, and depending on clinical context, stress testing or coronary angiography may be warranted 1. While LBBB itself doesn't typically require specific treatment, patients should be monitored regularly for progression of any underlying heart condition and potential development of heart failure or arrhythmias. Some key points to consider in patients with LBBB include:
- The presence of LBBB can make it difficult to interpret ischemic electrocardiographic changes, and an imaging component may be necessary 1
- Exercise-induced LBBB has been associated with increased risk of death and cardiac events 1
- Patients with LBBB and suspected acute myocardial infarction (AMI) should be evaluated using the Sgarbossa criteria, which include ST-segment elevation of 1 mm or more and concordant with the QRS complex, ST-segment depression of 1 mm or more and concordant with the QRS in one or more precordial leads V1 through V3, and ST-segment elevation of 5 mm or more in discordant leads 1
- The use of high-sensitivity cardiac troponin (hs-cTn) assays can help diagnose MI in patients with LBBB, and the result of the hs-cTn measurement at presentation should be integrated into the decision regarding immediate coronary angiography 1. Overall, the management of LBBB should focus on identifying and treating the underlying cause, as well as monitoring for progression of any underlying heart condition and potential development of heart failure or arrhythmias.
From the Research
Left Bundle Branch Block (LBBB) on ECG
- LBBB is a condition where the left bundle branch of the heart's electrical conduction system is blocked, causing the left ventricle to contract later than the right ventricle 2, 3.
- On an electrocardiogram (ECG), LBBB is characterized by a prolonged QRS duration, typically greater than 120 milliseconds, and a specific pattern of electrical activity in the heart 4, 5.
- LBBB can be caused by a variety of factors, including coronary artery disease, cardiomyopathy, and conduction system disease 3, 6.
Clinical Significance of LBBB
- LBBB can cause symptoms such as chest pain, shortness of breath, and fatigue, and can increase the risk of heart failure and cardiac arrhythmias 2, 3.
- LBBB can also make it more difficult to diagnose coronary artery disease using stress testing or echocardiography 6.
- Cardiac resynchronization therapy (CRT) is a treatment option for patients with LBBB and heart failure, and can help to improve symptoms and reduce the risk of complications 4.
Diagnosis and Evaluation of LBBB
- The diagnosis of LBBB is typically made using ECG, and can be confirmed using echocardiography or other imaging modalities 4, 5.
- Stress echocardiography can be used to evaluate patients with LBBB and suspected coronary artery disease, but has a poor positive predictive value for identifying significant angiographic disease 6.
- Electrophysiology studies can be used to evaluate the conduction system and identify the underlying cause of LBBB 3.
Treatment and Management of LBBB
- Treatment of LBBB depends on the underlying cause and severity of symptoms, and may include medications, CRT, or conduction system pacing 2, 3, 4.
- Patients with LBBB and heart failure may benefit from CRT, which can help to improve symptoms and reduce the risk of complications 4.
- Conduction system pacing is a newer treatment option that involves pacing the left bundle branch directly, and may be effective for patients with LBBB and heart failure 5.