@elizadolittle
I see you had your implanted 4 years ago. I have had one since 2006 and on my 3rd one. Mine was put in below my chest muscle on left side because I did not have enough skin thickness.

I was told would take a year to get used to it and they were right. However you have a foreign object in your body. Your body will automatically encapsulate the pacemaker. Thus using muscles, movement in that area will cause the pacemaker to interact more.

I found that raising my left arm above my head really affected my pacemaker and movement. I do water aerobics and a lot of movement was above your head. I quit doing arm movements above my head on left side and it really helped. Try doing things that reduce the irritation in that area. I also found doing slow movements and not quick jerks can also help when using the muscles and arm movements on upper left side.

I am not sure if you have a PACE CLINIC like Mayo Jacksonville has. They can work with you to reduce the discomfort you are feeling. Just remember that the device is not that small that it is not going to move or be affected by arm and muscle movements in that area. Just find ways to redue it and talk to your EP and Pace Clinic if you have one.