- A right bundle branch block, often shortened to RBBB, is an electrical finding on an ECG. It means the signal travelling to the right side of the heart takes a slightly slower route than usual. It is not a blocked artery.
- On its own, in a person who feels well and has a healthy heart, RBBB is common and usually harmless. It is found in roughly 1 in 100 adults, and the figure rises with age.
- What matters is the context. A longstanding RBBB in someone with no symptoms is very different from a brand new RBBB that appears alongside chest pain or breathlessness.
- RBBB becomes more important when it is new, when it occurs with symptoms, or when it appears together with other electrical changes on the same ECG.
- Most people with isolated RBBB need no treatment at all. The block itself is not something that gets fixed, and in the majority of cases it never causes a problem.
Of all the phrases that can appear on an ECG report, “right bundle branch block” is one that sends people straight to a search engine, usually with a rising sense of alarm. The word block sounds ominous. It brings to mind a blocked artery, or something serious going wrong with the heart’s plumbing.
In the great majority of cases, it is neither of those things. This article explains what a right bundle branch block actually is, why it shows up, when it is nothing to worry about, and the smaller number of situations where it genuinely matters.
What the Bundle Branches Actually Do
Your heart has its own electrical wiring. Each beat begins with a signal that spreads across the upper chambers, then passes through a junction box in the centre of the heart and down into the two large lower chambers, the ventricles, which do the heavy pumping work.
From that junction box, the signal travels down two main cables, one to the left ventricle and one to the right. These cables are the bundle branches. They split into ever-finer fibres so that the electrical signal reaches every part of the muscle at almost the same instant, allowing both ventricles to squeeze together in a single coordinated beat.
A right bundle branch block means the cable to the right ventricle is not carrying the signal normally. The impulse is delayed or has to take a detour, reaching the right ventricle a fraction of a second later than it should. The heart still beats. The right ventricle still contracts. It simply gets its instruction by a slightly slower path.
This is quite different from a coronary artery problem, where the issue is blood supply rather than electrical signalling. If you would like to see the wiring for yourself, our interactive guide to your heart’s conduction system shows how the signal travels from the heart’s natural pacemaker down through the bundle branches to the ventricles.
What RBBB Looks Like on an ECG, in Plain Language
An ECG is a recording of the electrical signals that pass through your heart with every beat. Each beat produces a series of waves on the trace, and each wave reflects a different stage of that beat. The first small wave, called the P wave, reflects the upper chambers being activated. The tall central spike, called the QRS, reflects the contraction of the ventricles. The rounded wave that follows, the T wave, reflects those chambers electrically resetting before the next beat.
Because RBBB delays the signal to one ventricle, the two chambers no longer squeeze in perfect unison. The QRS spike, which is normally narrow and sharp, becomes wider and often develops a second bump, giving it a distinctive shape that a cardiologist recognises instantly.
Normal beat
The QRS spike is narrow and sharp. Both ventricles are activated almost together.
Right bundle branch block
The QRS is wider and carries a second bump. This is the delayed right ventricle catching up.
How to read this: the spike in the middle, the QRS, is the part to watch. A normal one is narrow and sharp. In RBBB it is wider and usually has a notch, like an M shape, because the right side of the heart is activated a beat behind the left. The small waves either side are not the focus here.
Why Does a Right Bundle Branch Block Happen?
There are many reasons, and they sit on a wide spectrum from completely benign to clinically important.
A normal variant
In many healthy people, RBBB is simply how their wiring is built. It can be present for life, cause no symptoms, and never lead to any trouble.
Age and the wiring itself
The conduction fibres can slow gradually with age, in the same way other tissues change over time. This is why RBBB becomes more common in later decades.
Strain on the right heart
Conditions that make the right side of the heart work harder, such as some lung conditions, can be associated with RBBB. Here the block is a signpost, not the problem itself.
Heart muscle conditions
Some conditions affecting the heart muscle or its valves can disturb the conduction system and produce RBBB along the way.
After a heart procedure
RBBB can appear after certain cardiac procedures or surgery. When expected, it is usually monitored rather than treated, and most people do well.
A sign during a heart attack
A brand new RBBB that appears during chest pain can be an important warning sign. This is the context that needs urgent assessment, not a routine finding.
The Question That Really Matters: Is It New?
This is the single most useful thing to understand about a right bundle branch block. The pattern itself tells a cardiologist relatively little until it is placed in context, and the most important piece of that context is whether the block is new or longstanding.
A right bundle branch block that has been present on previous ECGs for years, in someone who feels well, is reassuring. It is part of that person’s normal electrical signature. Research consistently shows that isolated RBBB in people without other heart disease carries an excellent outlook.
A right bundle branch block that has appeared for the first time, particularly alongside symptoms such as chest pain, breathlessness, or fainting, is a different matter. Here the new block may be a clue that something is happening in the heart right now, and it deserves prompt evaluation. This is why your cardiologist will often be very interested in finding an old ECG to compare against.
RBBB and LBBB Are Not the Same Story
It is natural to assume that a block on the right and a block on the left are mirror images of each other, equally significant. In practice, they tend to carry different weight.
A left bundle branch block more often prompts a closer look at the heart muscle and its pumping function, because the left ventricle is the heart’s main pump. An isolated right bundle branch block, by contrast, is more frequently a benign finding in an otherwise healthy person.
This is a generalisation rather than a rule, and the context still governs everything. But it helps explain why a patient might be told their RBBB is nothing to worry about while a friend with an LBBB was sent for more tests.
Will I Have Symptoms?
Most people with a right bundle branch block have no symptoms from it whatsoever. They feel completely normal, and the finding is picked up by chance on an ECG done for an unrelated reason, such as a routine check, a pre-operative assessment, or an insurance examination.
Because RBBB itself rarely causes symptoms, any symptoms that are present, such as breathlessness, palpitations, or fainting, usually point to whatever underlying condition is present rather than to the block on its own. That is part of why your cardiologist treats the symptoms and the whole clinical picture, not the line on the ECG report.
What Happens Next, and What Tests Might Be Done
If an isolated RBBB is found and you feel well, often the answer is simply that nothing further is needed beyond noting it on your record. Knowing it is there is valuable in itself, because it gives every future ECG a baseline to compare against.
When the context suggests a closer look is worthwhile, your cardiologist may arrange an echocardiogram, an ultrasound scan that shows the heart’s structure and how well it is pumping. This helps confirm whether the heart muscle and valves are normal. Depending on the situation, blood tests or a period of heart rhythm monitoring may also be suggested.
The point of these tests is not the block itself, which generally cannot and need not be reversed. It is to make sure there is nothing else going on that the RBBB might be pointing to.
When RBBB Sits Alongside Other Findings
One situation deserves a mention because it changes the picture. Sometimes RBBB appears on an ECG together with other conduction delays. When the heart’s electrical pathways show several areas of slowing at once, cardiologists pay closer attention, because the wiring is showing wear in more than one place.
In a small number of people, particularly those who also have symptoms such as fainting, this combination may eventually lead to a conversation about a pacemaker. This is the exception rather than the rule, and it applies to a minority of cases. The great majority of people with a simple, isolated RBBB never approach this territory.
Heart Matters Resource
When in Doubt, Get Checked Out
A new finding on an ECG, or one that comes with chest pain, breathlessness, or fainting, is always worth discussing promptly with your GP or cardiologist rather than worrying about alone.
Read: When in Doubt, Get Checked Out →Conclusion
A right bundle branch block is an electrical finding, not a blocked artery, and for most people who carry one it is a harmless quirk of their heart’s wiring that will never cause a problem. The word block makes it sound far more alarming than it usually is.
What turns a routine finding into one worth investigating is context: whether it is new, whether it comes with symptoms, and whether it sits alongside other changes. If your ECG shows a right bundle branch block and you feel well, the most likely explanation is the most reassuring one. If it is new or you have symptoms, it is worth discussing with your cardiologist promptly, who can place that single line on the report into the bigger picture of your heart.
Related Reading
- What Does a Left Bundle Branch Block (LBBB) Mean on an ECG?
- The Electrocardiogram (ECG / EKG): What It Shows
- First-Degree AV Block on Your ECG: What Does It Really Mean?
- Understanding Your Heart: Anatomy, Valves and the Conduction System
- The Echocardiogram: What It Shows and Why It Matters
- What You Need to Know About Pacemakers
- When a Slow Heart Rate Is Not Normal: Understanding Bradycardia
