What is Right Bundle Branch Block?
Right bundle branch block (RBBB) is a condition detected using an electrocardiogram, a test that measures the electrical activity of your heart. It happens when the heart’s natural electrical system – specifically a part of the heart’s electrical conduction system called the His-Purkinje system – is disrupted or changes in some way. This results in an irregular heartbeat and different patterns on the electrocardiogram.
The His-Purkinje system divides into two pathways – the right and left bundle branches. The right bundle branch first travels close to the inner lining of the heart, then goes deeper into the heart muscle, before moving closer to the inner lining again. The blood supply for the right bundle branch comes mainly from a blood vessel known as the anterior descending coronary artery. It also gets additional blood supply from either the right or left circumflex coronary arteries, depending on the individual layout of the heart.
Right bundle branch block can be linked to physical changes in the heart caused by stretching or inadequate blood supply. It can also occur as an unintended consequence of certain heart procedures, like right heart catheterization – a procedure where a thin plastic tube is guided through your blood vessels into your heart. Even though there is no strong relationship with risk factors for heart vascular disease, having a right bundle branch block increases the risk of death from a heart attack, heart failure, and certain types of irregular heartbeat. If someone has no symptoms and right bundle branch block is their only heart abnormality, they typically don’t need further evaluation.
What Causes Right Bundle Branch Block?
The right bundle branch, part of your heart’s electrical system, can get damaged in three main areas. The area closest to the inner layer of the heart is usually the most susceptible. Damage to the farthest part of the right bundle branch usually only happens during specific surgeries. And the terminal part of the right bundle branch can get injured via certain surgical procedures.
A condition called right bundle branch block typically occurs when diseases or conditions alter the heart muscles of the right bundle branch. These could include structural changes, trauma, or infiltrative processes, which means that other substances or cells have invaded this part of the heart. Sometimes, high potassium levels in the blood, or hyperkalemia, can change the way electrical impulses move through the heart, causing right bundle branch block. Infections or heart attacks could directly damage the hearts cells in the right bundle branch.
In situations where the pressure inside the right side of the heart increases suddenly or over time, such as in a lung blood clot or chronic lung heart disease, the right bundle branch could stretch and cause a block. Medical procedures such as right heart catheterizations and ethanol ablation, a treatment for a type of heart muscle disease, could also cause right bundle branch block.
A less common cause of right bundle branch block is Lenegre’s disease or Lev’s disease, conditions that involve scarring and calcification, hardening due to deposit of calcium, of the heart’s conduction system. This usually happens in older adults. People with underlying heart problems causing deterioration of the electrical pathway can experience bundle branch block when the heart rate rises and decouples from the refractory period. This essentially means that the heart’s rate gets too fast for the right bundle branch’s ability to carry the electrical signals, thus blocking them from moving forward.
Risk Factors and Frequency for Right Bundle Branch Block
Right bundle branch block is a slow-developing ailment that affects the heart muscle. Its occurrence usually goes up as people age, affecting as many as 11.3% of people by the time they hit 80. Despite it being a heart-related condition, it has no significant connection with other heart diseases, diseases caused by reduced blood supply to the heart, or factors that put the heart at risk.
Signs and Symptoms of Right Bundle Branch Block
Right bundle branch block usually doesn’t cause any symptoms and is often discovered by chance during an electrocardiogram (ECG) – a test that measures your heart’s electrical activity. The findings of this test don’t result in any noticeable symptoms. However, during a physical examination, doctors might observe a split second heart sound.
Testing for Right Bundle Branch Block
When your doctor is diagnosing a right bundle branch block, which is a type of heart block, they will use an electrocardiogram (ECG). The ECG shows the electrical activity of your heart and can help your doctor identify any abnormalities. If you have a right bundle branch block, your ECG might show:
- a heartbeat that lasts longer than usual (120 milliseconds or more),
- a specific pattern observed in lead sections V1 and V2 of your ECG, known as ‘RSR’ pattern,
- specific patterns in the wave measurements in leads 1 and V6. For example: the S wave (one of the waves on the ECG tracing) lasting longer than the R wave, or the S wave lasting more than 40 milliseconds,
- a regular R wave (another wave on the ECG tracing) peak time in leads V5 and V6,
- an R wave peak time that lasts more than 50 milliseconds in lead V1.
In addition, the T waves, which is the part of the ECG that relates to the recovery or “repolarisation” phase of a heartbeat, might also appear to be inconsistent. This inconsistency could result in upside-down T waves in certain lead sections on the right side and upright T waves on the left side.
Treatment Options for Right Bundle Branch Block
In simple terms, if you only have a condition known as right bundle branch block, you generally won’t have any symptoms and won’t need any further check-ups or treatment. However, if you have heart failure along with a low heart pumping rate (a condition known as low ventricular ejection fraction) as well as right bundle branch block, your doctor might recommend a treatment called cardiac resynchronization therapy.
What else can Right Bundle Branch Block be?
When a patient’s heart test shows a condition called ‘right bundle branch block’, doctors need to rule out a few other similar conditions. These include:
- Incomplete left bundle branch block: This resembles ‘right bundle branch block’ but with a specific heart beat duration.
- Ventricular tachycardia or an accelerated idioventricular rhythm: These conditions might look like ‘right bundle branch block’ if the heart’s natural pacemaker originates from the lower chambers (ventricles).
- Brugada syndrome: This condition’s heart tests look very similar to those of ‘right bundle branch block’.
Pacemaker patients who show signs of ‘right bundle branch block’ need to be checked for potential issues related to their device. This could be a perforation in the right ventricle lead, or wrongly placed left ventricle lead.
What to expect with Right Bundle Branch Block
For people who don’t have severe heart disease, having a right bundle branch block—a condition where the electrical impulses that control the heartbeat are delayed—doesn’t usually pose any extra risk. However, for those with heart disease, it can increase the risk of overall mortality, or death.
The existence of a right bundle branch block around the time of a heart attack—including before, during and after—can be linked with higher death rates. Similarly, for people with heart failure, having a right bundle branch block has been associated with increased mortality.
