There are other brands of wireless monitors so I wouldn't limit your search to Zio. I'd be really surprised if the average EP at Mass. General doesn't use some type of wireless monitors, so you could just call a few of their offices and ask.
Another option would be to call Zio or some of the other companies and ask them for doctors in the area who use their product. I did that back in 2014 when I was looking for an EP who did FIRM ablations (seemed like a good idea in 2014). I called the Topera company who makes the FIRM mapping system and asked for a list of EPs in the area who used it. I got a prompt reply with a list of a half dozen doctors.
