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Bundle branch block
Electrical impulses that cause your heart to beat (contract) originate in the upper right chamber (right atrium) of the heart and travel to the lower chambers (ventricles). In bundle branch block, the pathway that these impulses travel on is delayed or blocked. The pathway includes a bundle with two branches — the left and right bundles. If one of these is damaged, it can make it harder for your heart to beat normally, as your ventricles don’t beat in coordination with each other.