By MS are you referring to mitral valve stenosis? Multiple sclerosis?
Right bundle branch block RBBB indcates a blockage of electricla impulse. The wall that separates the left and right side of the heart has a group of pathways for electrical impulses to pass from the upper right chamber down to the left and right ventricles to contract the ventricles to pump blood into circulation.
Sometimes one of the pathways is blocked, and according to your report there may be some blockage to the right ventricle. It may not be serious if the RBB it is partially blocked, but completely blocked can have some significance.
Thanks for your question, and if you have any further questions or comments you are welcome to respond. Take care,
Ken