What Are the Causes of Right Bundle Branch Block?

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  • Written By: Susan Abe
  • Edited By: Jessica Seminara
  • Last Modified Date: 14 October 2019
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A right bundle branch block is a problem with the heart's electrical conduction system. Every heartbeat is orchestrated by an electrical impulse or charge that travels from the sinoatrial (SA) node controlling contraction of the left and right atria, to a substation — the bundle of His — located between the atria and the ventricles. The conduction pathways divide at this electrical node into a left and right branch to serve the respective ventricles and coordinate a synchronized contraction of the heart as a single muscle. A block in either of these two systems can be a complete failure — a "short" so to speak — or a delayed impulse. Possible causes of right bundle branch block may include a previous heart attack, a congenital deformity, or the result of developing cardiovascular disease, among other etiologies.

Bundle branch blocks are diagnosed by a 12-lead electrocardiogram (EKG) and specifically identified as right or left-sided depending on the specific shape and length of the QRS complex, the pictorial representation of the ventricles' contraction traced on the EKG paper. There are three kinds of right bundle branch blocks identifiable by electrocardiogram, named for the area along the electrical pathway that is problematic. A more helpful classification system for patients and their families may be considering these blocks as temporary or permanent in nature.


Temporary causes of right bundle branch block may include ongoing heart attacks, also known as acute myocardial infarctions (MI). As the heart receives insufficient oxygen and heart cells begin to die, the electrical system of the heart may be disrupted at any level. A block may result until supplemental oxygen and drugs are administered to help limit the infarction. Unfortunately, if enough of the electrical system is within an area of dead tissue, the resulting block may be permanent.

An acute pulmonary embolism, or blood clot to the lungs, is another of the temporary causes of right bundle branch block as increasing pulmonary pressures affect the heart's electrical activity. A heart infection, myocarditis, is another cause of temporary blocks due to the muscle's tissue inflammation. High blood pressure or hypertension can also result in a right bundle branch block that is potentially reversible if the condition is successfully and quickly treated.

Permanent causes of right bundle branch block include uncorrected congenital malformations and post-operative cardiac surgery scar formation. Ironically, correction of congenital heart malformations is the most common cause of this condition in children in the US. A similar permanent block can affect adults undergoing late repair of congenital malformations or repair to valves that have been damaged by infection, cardiac disease or respiratory disease.


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