HRV & Pacemakers

Can HRV be measured while an individual is using a pacemaker?

This is a great question to which there is unfortunately no singular answer.

If the pacemaker is actively pacing, then it will skew the HRV reading and likely not be useful. 

However, if the pacemaker is  not actively pacing when you take your HRV readings, and you take many readings over time, then the relative changes in HRV over time could still be useful to see.