Here "walking" is an idiom for the way a person lives. The word "heart" is a metonym for a person's desires and emotions. Alternate translation: "Each person has refused to change and has been living by his own wicked desires" or "Each person has refused to change and continues to do the evil things that they want to do" (See: [[rc://en/ta/man/jit/figs-idiom]] and [[rc://en/ta/man/jit/figs-metonymy]])