Bundle branch block is a condition in which there's a delay or blockage along the pathway that electrical impulses travel to make the heart beat. It sometimes makes it harder for the heart to pump blood to the rest of the body.The delay or blockage can occur on the pathway that sends electrical impulses either to the left or the right side of the bottom chambers (ventricles) of the heart.Bundle branch block might not need treatment. When it does, treatment involves managing the underlying health condition, such as heart disease, that caused bundle branch block.