That is an excellent question.
Leg cramps are often caused by what is called intermittant claudication, which is related to blood circulation. A pacemaker may limit blood circulation under certain circumstances. Unlikely, but not impossible. Speak to your cardiologist about this. They question is not that silly. He need a color dopplar of his legs to evaluate circulatory status, to keep well-hydrated, and excercise regularly, walking as much as possible.