Caffeine tends to cause the heart to speed up slightly, how much depends on how much caffeine in the system and how sensitive you are to the effects. As a rule, people with MVP don't have a lot of trouble with the occasional drink of a caffeinated drink, unless the prolapse is severe. You reallly ought to discuss this with the cardiologist, though, as they would be most familiar with your particular case and the severity of it. If you had symptoms that caused you alarm, it may be you are one of the more sensitive folks and would benefit from a caffeine free diet. But that's something you need to discuss with the doctor.