I Had Surgery For A 90% Blockage On Right Side

I had surgery for a 90% blockage on right side carotoid artery....they also found some blood clots and they were removed. Ever since the operation I have has pain in the upper part of my right shoulder....especially when I raise my arm. Why is this happening?? I am 69 yr old female ..with heart problems .1 stent 50% heart damage. I am active and mainly just get tired more quickly than I used to,