Left Bundle Branch Block (LBBB) is a cardiac conduction abnormality seen on the electrocardiogram (ECG). It occurs when there’s a delay or blockage in the electrical pathway that stimulates the left side of the heart. This causes the left ventricle to contract later than the right ventricle.

How is it Diagnosed?
LBBB is primarily diagnosed through an ECG. Key features on the ECG include:

• Wide QRS Complexes: Typically wider than 120 milliseconds.
• Bizarre and Notched R waves: Particularly in leads V5, V6, I, and aVL.
• Absent Q waves: In leads V5 and V6, which are usually present in normal ECGs.
• ST and T waves: Often show compensatory changes opposite to the direction of the main QRS complex.

Causes of LBBB
LBBB can occur due to various conditions, some of which include:

• Coronary artery disease
• Hypertension leading to cardiac hypertrophy
• Aortic valve disease
• Cardiomyopathies
• Congenital heart defects
• As a result of cardiac procedures or surgeries

Clinical Significance

• Symptoms: While LBBB itself may not cause symptoms, the underlying condition responsible for LBBB often does. Symptoms might include breathlessness, fatigue, and signs of heart failure or cardiac ischemia.
• Risk Assessment: LBBB can be an indicator of underlying heart disease, particularly in the presence of symptoms or significant cardiovascular risk factors. It is associated with a higher risk of cardiac events, especially in older adults or those with other cardiac abnormalities.
• Management Implications: Treatment of LBBB involves addressing the underlying cause. In symptomatic severe cases, especially those associated with heart failure, cardiac resynchronization therapy (CRT) or a pacemaker might be needed to help coordinate the timing of the ventricular contractions.

Management of LBBB

• Monitoring: Regular follow-up and monitoring of heart function through ECG and possibly echocardiography.
• Medications: Treatment may include medications to manage heart failure or ischemic heart disease if these conditions are present.
• Lifestyle Changes: Lifestyle modifications, including diet and exercise, are recommended to reduce cardiovascular risk factors.