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Causes
By Mayo Clinic staff
Normally, electrical impulses within your heart's muscle signal it to beat (contract). These impulses travel along a pathway, including a slender cluster of cardiac fibers called the bundle of His. This bundle divides into two branches — the right and the left bundles — one for each of your heart's two lower chambers (ventricles).
If one or both of these branch bundles become damaged — due to a heart attack, for example — this change can prevent your heart from beating normally. The heart's electrical impulses that make your heart beat may be slowed down or blocked. When this occurs, your heart's ventricles no longer contract in perfect coordination with one another.
The underlying cause for bundle branch blocks may differ depending on whether the right or left bundle branch is affected. Causes may include:
Left bundle branch block
- Heart disease
- Congestive heart failure
- Thickened, stiffened or weakened heart muscle (cardiomyopathy)
- High blood pressure (hypertension)
Right bundle branch block
- A heart abnormality that's present at birth (congenital) — such as atrial septal defect, a hole in the wall separating the upper chambers of the heart
- A heart attack (myocardial infarction)
- A viral or bacterial infection of the heart muscle (myocarditis)
- High blood pressure (hypertension)
- Scar tissue that develops after heart surgery
- A blood clot in the lungs (pulmonary embolism)
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- Francia P, et al. Left bundle-branch block — Pathophysiology, prognosis and clinical management. Clinical Cardiology. 2007;30:110.
- ACC/AHA 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices) developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. Journal of the American College of Cardiology. 2008;51:e1.
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- Horton CL, et al. Right bundle-branch block in acute coronary syndrome: Diagnostic and therapeutic implications for the emergency physician. The American Journal of Emergency Medicine. 2009;27:1130.
- Wong CK, et al. Prognostic differences between different types of bundle branch block during the early phase of acute myocardial infarction: Insights from the Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial. European Heart Journal. 2006;27:21.
- ABC's of preventing heart disease, stroke and heart attack. American Heart Association. http://www.americanheart.org/print_presenter.jhtml?identifier=3035374. Accessed Jan. 12, 2010.
- Grogan M (expert opinion). Mayo Clinic, Rochester, Minn. Jan. 25, 2010.
- Arnsdorf MF. Overview of left bundle branch block. http://www.uptodate.com/home/index.html. Accessed Jan. 13, 2010.
- Arnsdorf MF. Overview of right bundle branch block. http://www.uptodate.com/home/index.html. Accessed Jan. 13, 2010.
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