Pain On Using The Arm Muscles, Using Medtronic Defibrillator. Cause Of Concern?

I had my Medtronic defibrillator put in around 4 years ago this year and now when I use my arm muscle that goes into the chest where it is, it is painful, whether it is when I just lean on my arm holding my head or try to get up. It is just when I use my muscle though and does not hurt just sitting still. I have never had this before but now it bothers me. Is this something to be concerned about?