It is difficult to answer your question when I don't have a lot information about your grandfather. First of all, the Cardiologist needs to be consulted in his case to find out why his heart rate
is slow. Some of the other answers here have talked about beta blockers.
Beta blockers are medications that are the first line drugs that are used for people with heart problems. A side effect of these medications is slowing of the heart rate.
Is your grandfather symptomatic with the low heart rate? Symptoms dizziness
. If so he should go to the doctor and maybe see if the medications can be lowered.
Medicare does pay for pacemakers if they are needed. If he is not old enough for that there is always Medical assistance he can apply for through your local aging department of the county that you live in.