A left bundle branch block, or an LBBB, is the interruption or delay in the conduction of electrical impulses on the left side of the heart. It can lead to a prolongation of the QRS interval on an ECG.
A left bundle branch block generally does not cause symptoms. It may be related to other heart conditions, although the cause is sometimes unknown.
Treatment for a left bundle branch block may vary depending on the underlying cause and whether or not the patient presents with symptoms. Patients with an LBBB that have no symptoms and no confirmed heart conditions may just require regular monitoring with a cardiologist.
Main symptoms
A left bundle branch block usually does not cause symptoms and many people only discover they have one after completing a regular ECG.
Patients with symptoms from an LBBB usually experience them as a result of another, pre-existing heart condition. Some symptoms may include fainting or a slow heart beat.
Patients who have an LBBB and have a history of angina, for example, may experience chest pain, while other patients with a known arrhythmia may faint or experience shortness of breath.
Confirming a diagnosis
A left bundle branch block diagnosis is usually confirmed through an ECG (electrocardiogram), when the QRS interval is above 120 ms.
If an LBBB is noted in the ECG, your doctor may order additional tests, like bloodwork or an echocardiogram, to determine the underlying cause.
Possible causes
Having a left bundle branch block may be a sign of heart damage, which can be caused by:
- Coronary artery disease
- Heart attack
- High blood pressure
- Enlarged heart
- Heart failure
- Myocarditis
- Problems with the heart valves
- Cardiomyopathy
- Cardiac arrhythmias
If the patient does not have any history of these conditions, the doctor may order further testing to investigate for other causes. However, it is also possible for a left bundle branch block to appear for no apparent reason.
Treatment options
Most people who suffer from a left bundle branch block do not require any specific treatment. However, if the LBBB is related to heart disease, targeted treatment (with medication, for example) may be advised to treat the condition.
Depending on the severity of the heart disease and the patient's symptoms, the doctor may recommend the use of a pacemaker to ensure optimal heart functioning. Read more about what a pacemaker is and what it's for.
Lifestyle changes to promote heart health may also be advised like maintaining balanced diet, exercising regularly, reducing or eliminating alcohol intake, smoking cessation, and stress management.