The heart has two specialized ventricular conduction bundles: the right and left. In cardiology, branch blocks of these two bundles are the obstacle of our hearts’ lower ventricles, making the heartbeat signal late and out of sync.
They are two electrical pathways that allow the cardiac electrical impulses to spread evenly through the ventricles.
Key Takeaways
- The Right Bundle Branch Block (RBBB) affects the right ventricle’s electrical conduction, while Left Bundle Branch Block (LBBB) impacts the left ventricle.
- RBBB can be a normal finding in healthy individuals, but LBBB signifies an underlying heart condition.
- RBBB and LBBB can cause irregular heartbeats; doctors diagnose them using electrocardiograms (ECGs).
Right vs Left Bundle Branch Block
Right Bundle Branch Block is a medical condition that is caused by heart diseases and blood clots in the lungs, and it is located at the right ventricle of a person’s heart. Left Bundle Branch Block is a condition caused by heart infections, and its located at the left ventricle in the heart.
The right bundle branch block, or RBBB, is the blockage of the heart’s electrical pathways to the right ventricle. If you have RBBB and there are no serious symptoms, then there is no need to worry.
But continuous treatment is necessary if you have a heart attack. The blockage makes the signal of the heartbeat irregular. It can be diagnosed by an ECG.
The stimulation of the left-sided lower ventricle of our hearts is delayed in LBBB. LBBB can carry more risk of death. It happens when the normal direction of the septal depolarisation is reversed.
However, there is no known cause of LBBB, but sometimes a heart attack or high blood pressure can cause a left bundle branch block.
Comparison Table
| Parameters of Comparison | Right Bundle Branch Block | Left Bundle Branch Block |
|---|---|---|
| Location | The right ventricle of the heart. | The left-sided ventricle of the heart. |
| Symptoms | Chest pain, dizziness, syncope, fatigue, slower heart rate, shortness of breath, etc. | Slower heart rate, fainting, chest pain, etc. |
| Causes | Clots in the lungs, heart disease, high blood pressure, right-sided heart failure. | Higher blood pressure, coronary artery, heart attack, heart infection, aortic valve disease, etc. |
| Diagnosis | Using an ECG test. | Electrocardiogram ( ECG) |
| ECG criteria | QRS complex shape is W in the V1 lead and M shape in the V8 lead. | QRS complex shape is M in the V1 and W shape in the V6 lead. |
| Treatment | Most people do not need any treatment. Some need pacemakers or cardiac resynchronization therapy. | Pacemakers, sinus node suppression, or cardiac resynchronization therapy. |
| Life risk | The death rate is low. After a heart attack, it can be life-threatening. | Grater risk of death for people with serious complications. |
What is the Right Bundle Branch Block?
The blockage of the right bundle branch or RBBB creates a problem in heart electrical signals. The heart has 4 chambers, atria ( two upper chambers) and ventricles ( lower chambers). Generally, our heartbeat begins in the area of the sinoatrial node.
It is very rare in healthy people. Older people are affected by it. Most people with RBBB do not have any symptoms and don’t need any treatment, but it can create a greater risk in people after a heart attack.
With the help of an ECG or electrocardiogram test, the RBBB is diagnosed. ECG determines the heart’s condition and how our heart’s electrical system works.
Several conditions can cause RBBB. People with high blood pressure and heart disease are at risk of RBBB. A minor heart attack can also cause RBBB.
Blood clots in the lungs, right-side heart failure, and heart muscle infection by bacteria can cause RBBB.
According to some studies, RBBB can occur in 0.2 % to 1.3 % of people. It increases with age.
There are some ECG criteria for RBBB, such as QRS duration should be more or equal to 120 milliseconds, RSR in leads V1 and V2, R wave peak time in V1 is greater than 50 milliseconds, etc. In RBBB, sometimes patients need pacemakers.
What is Left Bundle Branch Block?
In cardiology, LBBB is an abnormal condition of the cardiac where the electrical conduction system of our heart is interrupted, and it is very common. This problem is not reversible if you have any serious heart disease.
If you don’t have serious symptoms and no heart disease, it is not life-threatening. It is rare in young and healthy people.
Nonischemic pathologies cause the left bundle branch block. Dilated cardiomyopathy is considered the primary cause of LBBB.
Research shows that about 6% of 80-year-olds and less than 1% of people under 50 have LBBB. It occurs as a result of underlying heart complications.
There are some criteria to diagnose LBBB on the electrocardiogram, such as the QRS duration should be less than 120 milliseconds.
In lead V1, the rs and QS complex are a must. ECG represents the electrical impulse travelling across the ventricles of our heart.
In LBBB, there is W shape QRS complex in V1 lead. The left bundle branch block is a completely complex disease that can cause serious complications.
Infection of the heart muscle or weekend heart muscle, heart attack, high blood pressure, etc., can cause LBBB. Symptoms may include fainting, slow heart rate, and chest pain.
Main Differences Between Right and Left Bundle Branch Block
- RBBB is located in the heart’s right ventricle. On the other hand, LBBB is located in the heart’s left ventricle ( lower chambers).
- In the case of RBBB, the V1 lead has a W shape QRS complex and an M shape in the V8 lead. On the other hand, in LBBB, the QRS complex in the V1 lead looks like M, and in the V6 lead, it looks like W.
- Two R waves characterize RBBB, and a large S wave in V5 or V6 leads. On the other hand, in LBBB, there is a deep and broad S wave in V1 or V2 lead and broad R waves in V5 or V6.
- LBBB is worse than RBBB and carries a greater risk of death.
- The scar size in RBBB is slightly larger than the scar size of LBBB in the ventricles.
References
- https://www.ahajournals.org/doi/pdf/10.1161/01.CIR.31.4.551
- https://journals.physiology.org/doi/abs/10.1152/ajpheart.00051.2002
Last Updated : 11 June, 2023
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.
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