Right Bundle Branch Block on an ECG: What Does It Mean?

Right bundle branch block (RBBB) on an ECG means the electrical signal that makes the heart beat is delayed on its way to the right ventricle, so the right side contracts slightly after the left. It is common, often found by chance on a routine ECG, and in many people it is not serious.

The heart's electrical signal travels down two pathways, the right and left bundle branches. When the right branch conducts slowly, the ECG shows a widened part of the tracing called the QRS complex, often with a typical double-peaked shape in the leads over the right side of the chest.

This guide explains the ECG label. It cannot tell you why RBBB has appeared on your own ECG or whether you need tests. That depends on your symptoms, history, examination and other results.

RBBB itself usually causes no symptoms. Call your local emergency number or go to an emergency department if you have chest pain, sudden or severe shortness of breath, fainting or loss of consciousness, or a feeling that you are about to faint. These can come from other heart or lung problems that need prompt assessment.

Tell the emergency team that you have been told you have RBBB, and bring any earlier ECG if you can. Comparing tracings helps clinicians tell an old finding from a new change. New or worsening dizziness, palpitations or tiredness should be checked soon by your usual clinician.

The difference is how long the delay lasts. Complete RBBB is generally defined by a QRS duration of 120 milliseconds or more. Incomplete RBBB has the same pattern but a shorter delay. The exact lower cut-off for incomplete RBBB varies a little between sources, and readings near the boundary can be interpreted differently by different readers.

Cleveland Clinic describes incomplete RBBB as the more common type and says it does not increase the risk of heart attack or death. Complete RBBB matters more in people who already have heart disease, where it is linked with higher risk. Some people have a rate-dependent form that only appears when the heart beats fast.

Yes. RBBB can occur in people whose hearts otherwise work normally and who have no underlying condition. It becomes more common with age, particularly from about 60 onwards, and is more common in men. Sometimes no cause is ever found.

In people without heart disease, Cleveland Clinic states that RBBB does not change life expectancy and usually needs no treatment. The block tends to be long-lasting; it may stay the same or slowly change over time, and only rarely progresses to complete heart block, a more serious problem where signals from the upper chambers do not reach the lower chambers.

When there is a cause, it may involve the heart or the lungs. Possible causes listed by Cleveland Clinic and NHLBI include:

• Heart conditions such as coronary artery disease or a previous heart attack, heart failure, cardiomyopathy, heart valve disease, myocarditis and congenital heart disease.
• Lung conditions that strain the right side of the heart, such as pulmonary embolism, pulmonary hypertension and COPD.
• High blood pressure and age-related scarring of the conduction system.
• Procedures such as right heart catheterisation.

An echocardiogram is an ultrasound scan of the heart. Alongside the ECG, it is one of the main tests used to look for an underlying heart problem in someone with a bundle branch block, by checking the heart's chambers, valves and pumping.

Whether you need one is a clinical decision. Questions that often shape it include whether you have symptoms such as breathlessness, chest pain or fainting, whether a heart murmur or other abnormal sign was found on examination, whether the block is new compared with earlier ECGs, whether it is complete or incomplete, and whether you have known heart or lung disease. Depending on the answers, a clinician may also consider blood pressure and cholesterol checks, a heart monitor, a stress test or lung function tests.

If you are having an exercise test, an operation or emergency care in future, tell the team you have RBBB, because it can change how they read your ECG.

RBBB on its own is not usually treated. If you have no symptoms and no other heart disease, Cleveland Clinic says treatment is usually not needed, and a bundle branch block generally does not affect work or everyday activities unless symptoms are severe.

When an underlying condition is found, such as high blood pressure, heart failure or a lung condition, treatment is aimed at that condition. A small number of people, for example some with heart failure or fainting linked to the heart's conduction system, may be offered a pacemaker. MedlinePlus also notes that an ECG cannot diagnose a heart condition on its own, which is why the finding is interpreted together with symptoms and other tests.

Bring your ECG report and any earlier tracings. These questions can help:

• Is my RBBB complete or incomplete, and is it new compared with my earlier ECGs?
• Was anything else unusual on the ECG?
• Do my symptoms, if any, fit with RBBB, or could they come from something else?
• Do I need an echocardiogram or other tests to look for an underlying cause, and why or why not?
• Does RBBB affect any treatment I have now or any procedure I am planning?
• Which symptoms should make me seek urgent care?

On SameCase, patients and verified doctors share de-identified cases. Reading how others found RBBB on an ECG, which questions they asked and what follow-up they were offered can help you organise your own history and prepare clear questions.

Similar cases cannot tell you what your own ECG means or whether you need tests. Use them to prepare for a conversation with your clinician, and seek urgent care for any warning symptoms.