Good idea to check with your cardiologist.  Having said that, I've had
patients with pacemakers whom I was told needed no special precautions.
    This was for a simple arrhythmia (bradycardia).  You may of course have
other cardiac issues that may require premedication, so you should check.

Steve

Having a pacemaker alone is considered to be in the "Negligible Risk
Category" and no antibiotic prophylaxis is required:

www.ada.org/prof/resources/pubs/jada/reports/report_endocarditis01.pdf

However, as Dr. Steve said, if you have other coexisting cardiac issues,
this may change.

J Suljak DDS

basically if you have a heart defect or heart prosthesis such as a
valve that can cause turbulence of blood within the heart itself you
need to have antibiotics.
heart bypass are generally on vessels outside the heart feeding it,
inside the heart means all the valves chambers etc.. that can pick up
stray bacteria and allow it to grow on these defects. Since you are not
sure the reason for the  pacemaker you need to check with your
cardiologist. If he is unavailable then better safe than sorry and get
the pre-med or change your appointment.