I'm certainly not a health professional, but sometimes the vegal nerve is compromised when a pacemaker is inplanted, and it can lead to physical discomfort. In my case, when they check my pacer and put a magnet on it, I burp uncontrollably and I'm told it has to do with the pacer leads and proximity to the vegal nerve. Also, my daughter had a problem with internal bleeding when in high school and blood dripping on her vegal nerve caused discomfort like you describe. I'd start by getting a copy of the procedure report, and then go to a neurologist for a followup.
Does your husband has any previous back problems?
It is not the fist time that I heard that, particularly with people with previous back (spine) issues. During the implant they are forced to stay still on the hard operation table and for some people that can produce back strain which can translate into nerve damage and pain.
I suggest go to a neurologist for that.
Jesus.