Bundle Branch Block


Bundle branch block is a condition where there is a delay or obstruction along the pathway that carries electrical impulses for the heartbeat. This delay can make it more challenging for the heart to effectively pump blood to the rest of the body. It can also result in an irregular heart rhythm. The blockage can occur on either the left or right side of the heart’s lower chambers (ventricles).

Normally, electrical impulses travel through bundle branches, causing both ventricles to contract simultaneously. However, in the presence of bundle branch block, the electrical signal is delayed, causing one ventricle to contract later than the other.

Treatment for bundle branch block may not always be necessary. When treatment is required, it primarily involves managing the underlying health condition, such as heart disease, that led to the development of bundle branch block.


Bundle branch block can be asymptomatic, but when symptoms do occur, they can manifest as follows:

  • Dizziness
  • Fainting (syncope)
  • Sensation of impending fainting (presyncope)

If bundle branch blockage affects both sides, additional symptoms may arise:

  • Irregular heartbeat (arrhythmia)
  • Difficulty breathing (dyspnea)
  • Slow heart rate (bradycardia)

If you experience fainting, it is important to seek medical attention to exclude any underlying serious conditions. For individuals with pre-existing heart disease or a known diagnosis of bundle branch block, it is advisable to consult with a healthcare provider regarding the recommended frequency of follow-up visits. Regular check-ups can help monitor the condition and ensure appropriate management.


When the electrical impulses in the heart muscle are disrupted, such as due to a heart attack, the heart’s contraction pattern can become irregular. This disruption often occurs in the pathway of the electrical signals, which includes two branches known as the right and left bundles. If one or both of these bundles are damaged, the impulses can be blocked, leading to an irregular heartbeat. The specific causes of bundle branch blocks can vary depending on whether the left or right bundle branch is affected, although in some cases, the cause may remain unknown.

Common causes of a bundle branch block may include:

  • Left bundle branch block
    • Myocardial infarction
    • Myocarditis
    • Cardiomyopathy
    • Hypertension
  • Right bundle branch block
    • Pulmonary embolism
    • Myocardial infarction
    • Congenital heart disease, such as atrial septal defect
    • Pulmonary hypertension
    • Myocarditis
    • Chronic obstructive pulmonary disease (COPD)

Risk factors

Anyone can have a bundle branch block. However, certain risk factors may increase one’s risk, such as:

  • Aging: As the person grows older, the higher is the risk of developing bundle branch block. It may affect about 0.8% of people at age 50 and up to 11.3% of people by age 80.
  • Underlying health issues: People with other health issues such as heart disease and high blood pressure are more susceptible of bundle branch block.