What causes organ malfunctions in the circulatory system?

Many things. Generally speaking, many things. If the organ was previously functioning normally, usually malfunction is caused by some sort of injury on the gross level (like mechanical trauma) or on the cellular or sub-cellular level (i.e. some sort of disease process). Causes can also generally be grouped into "acquired" or "congenital" (meaning you were born with it). Hope this helps.