Yes they did sometime in the 60's. I was actually involved with research in the early eighties where one option for an artificial heart (not a pace-maker) was to use a tiny Stirling Engine powered by an isotope heat source.
The general public has a revulsion for anything 'radioactive', however radio-active material if handled properly is quite safe. For many years people did not realized it, but all Smoke detectors had radioactive americium 241. If you ever renovate an old home just don't put them in your pockets :)
Nuclear power sources have already been safely powering a variety of devices, such as pacemakers...
It seems sort of strange that the article writer talks about how up until now nuclear batteries have had to be very large to work effectively. Yet then the statement is made that such batteries have been used in pacemakers, which I assume must be much smaller.
Does anyone know anything more about pacemakers and this claim that nuclear batteries have already been used to power them?