From the Guidelines
Left bundle branch block (LBBB) is a cardiac conduction abnormality that requires careful management, particularly in patients with heart failure, and cardiac resynchronization therapy (CRT) may be recommended for those with a QRS duration of ≥150 milliseconds and LBBB morphology, as evidenced by the 2019 acc/aha guidelines on heart failure 1.
Diagnosis and Treatment
LBBB is diagnosed through an electrocardiogram (ECG), which shows a QRS complex duration of ≥120 milliseconds, along with specific patterns including a broad, notched R wave in leads I and V6, and absence of Q waves in leads I, V5, and V6. The management of LBBB focuses on identifying and treating the underlying cause, which may include coronary artery disease, hypertension, cardiomyopathy, or valvular heart disease.
Cardiac Resynchronization Therapy (CRT)
For patients with heart failure and LBBB, CRT may be recommended, especially if the QRS duration is ≥150 milliseconds, as shown in the EchoCRT trial and individual patient data meta-analysis 1. However, the evidence for CRT in patients with a QRS duration between 130 and 150 ms, or non-LBBB morphology, is less clear, with differences in recommendations between the ACC/AHA and ESC guidelines 1.
Key Considerations
- LBBB itself doesn't require specific treatment, but management focuses on identifying and treating the underlying cause.
- Regular cardiac follow-up is essential as LBBB can be associated with increased risk of cardiovascular morbidity and mortality.
- Patients should report any symptoms like chest pain, shortness of breath, dizziness, or fainting, which might indicate worsening of the underlying cardiac condition.
- The 2018 acc/aha/hrs guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay also provides recommendations for the management of conduction disorders, including LBBB 1.
Recommendations
- CRT is recommended for patients with LVEF <35%, markedly prolonged QRS duration (>150 ms), left bundle branch block (LBBB) morphology, and in sinus rhythm, as evidenced by the 2019 acc/aha guidelines on heart failure 1.
- Patients with LBBB and heart failure should be closely monitored and managed according to the underlying cause and severity of symptoms.
- Further research is needed to clarify the role of CRT in patients with LBBB and a QRS duration between 130 and 150 ms, or non-LBBB morphology.
From the Research
Definition and Pathophysiology
- Left bundle branch block (LBBB) is a condition where there is a blockage in the left bundle branch of the heart's conduction system, leading to abnormal electrical activity in the heart 2.
- LBBB can be due to conduction system degeneration or a reflection of myocardial pathology, and may also develop following aortic valve disease or cardiac procedures 3.
Diagnosis and Treatment
- Patients with heart failure with reduced ejection fraction and LBBB may respond positively to cardiac resynchronization therapy (CRT) 4, 3.
- CRT is the therapy of choice in symptomatic patients with heart failure with reduced ejection fraction and a broad QRS complex with a LBBB morphology 4.
- Left bundle branch pacing (LBBP) has been reported to be effective in heart failure patients with LBBB, with significant improvements in QRS duration, left ventricular ejection fraction, and clinical outcomes 5, 6.
Clinical Outcomes
- LBBP has been shown to be safe and effective in heart failure patients with LBBB, with a success rate of 93.2% and significant improvements in clinical and echocardiographic outcomes 5.
- LBBP has been compared to biventricular pacing (BVP), with some studies suggesting that LBBP may be more effective in improving QRS duration, left ventricular ejection fraction, and clinical outcomes 5, 6.
- Baseline LBBB and left ventricular end-diastolic diameter have been identified as independent predictors of echocardiographic response to LBBP 6.