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Bundle Branch Block

by Hratch L Karamanoukian, MD and Pierre Aoukar, MD
Posted: February 17

The left and right bundle branches of the heart are part of the conduction system of the heart beyond the atrioventricular node. The right bundle branch supplies electrical current to the right ventricle and left bundle branch to the left ventricle.

BUNDLE BRANCH BLOCK, left – new onset

The development of a new left bundle branch block in the setting of a heart attack is concerning. This scenario is associated with high likelihood of dying if angioplasty or thrombolytic (“clot buster”) therapy is not instituted.

Angioplasty or thrombolytic therapy improve function of the left ventricle and reduce the risk of dying from the heart attack.


If left bundle branch block is known to exist (on old electrocardiograms; ECG) before a new heart attack, the diagnosis of heart attack is made more difficult for the physician unless cardiac enzyme levels suggest otherwise.


Complete right bundle branch block indicates that both ventricles (pumping chambers) of the heart receive electrical activation from the left bundle branch. Unless acutely associated with a heart attack, meaning that this is a “new” right bundle branch block, it is a condition that requires no further treatment.

Excerpt from the book: Everything Is Bad For Your Heart: The A to Z Guide, Hratch L Karamanoukian, MD and Pierre Aoukar, MD. Magalhaes Scientific Press

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in press

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