Difference Between Right and Left Bundle Branch Block (With Table)

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The heart has two specialized ventricular conduction bundles that are the right and the left bundle. In cardiology, branch blocks of these two bundles are the obstacle of the lower ventricle of our hearts that makes 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.

Right vs Left Bundle Branch Block

The difference between the right and left bundle branch blocks is that the right bundle branch block is located in the right ventricle of the heart and is known as RBBB. On the other hand, the left bundle branch is located at the left ventricle (lower chambers) of the heart and is also known as LBBB. The left bundle branch block carries more risk of death than the blockage of right bundle.

The right bundle branch block or RBBB is the blockage of the electrical pathways of the heart to the right ventricle. If you have RBBB and there are no serious symptoms, then there is no need to worry. But a 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 Between Right and Left Bundle Branch Block

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 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 generally 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 the electrical system of our heart is working.

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, infection of the heart muscle by bacteria can cause RBBB.

According to some studies, RBBB can occur in 0.2 % to 1.3 % of people. It typically 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, then it is not life-threatening for you. It is rare in young and healthy people.

Left bundle branch block is generally caused by nonischemic pathologies. Dilated cardiomyopathy is considered the primary cause of LBBB. Research shows that about 6% of 80-year-olds and less than 1% of the 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 traveling across the ventricles of our heart.

In LBBB, there is W shape QRS complex in V1 lead. Left bundle branch block is a completely complex disease, and it 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

  1. RBBB is located in the heart’s right ventricle. On the other hand, LBBB is located in the heart’s left ventricle ( lower chambers).
  2. 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.
  3. RBBB is characterized by two R waves, and a large S wave in V5 or V6 leads. On the other hand, in LBBB, there is deep and broad S wave in V1 or V2 lead and broad R waves in V5 or V6.
  4. LBBB is worse than RBBB and carries a greater risk of death.
  5. The scar size in RBBB is slightly larger than the scar size of LBBB in the ventricles.

Conclusion

Our heart has two ventricular conduction bundles that are the right bundle and the left bundle, which originated at the AV node and spread to the right and left ventricle. The AV node is the electrical pathway, and every impulse passes through it.

Some people are born with these complications like RBBB and LBBB. These complications can be diagnosed by the QRS complex on the electrocardiogram. In this condition, the person must visit a healthcare provider.

References

  1. https://www.ahajournals.org/doi/pdf/10.1161/01.CIR.31.4.551
  2. https://journals.physiology.org/doi/abs/10.1152/ajpheart.00051.2002
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