Skipped heart beat cause? mitral valve prolapse?

Possibly: Some people with mitral valve prolapse are more prone to get palpitations when under stress or with stimulants ( alcohol or caffeine or pseudoephedrine).

Many causes: A skipped heartbeat can be caused by many things. Mitral valve disease is often seen with abnormal cardiac rhythms, but it is not exclusive nor would it be first in my differential diagnosis. If the abnormal rhythm is concerning (and it probably should) i suggest you go visit your personal physician. The internet is not the best place to get answers - always remember to talk to your doctor.