What does it mean to have a leaky heart valve that causes palpitations?

Not causative : Leaky heart valves do not cause palpitations. However, patients with mitral valve prolapse have a higher incidence of palpitations and arrhythmias (eg premature beats) for unknown reasons.

These are actually: Separate issues...One electrical and the other structural. Mitral valve prolapse is frequently cited as contributing to both. Echocardiogram and ECG could further characterize nature and severity of both.