I've used that source as well. I've always just asked the cardiologist for clearance and "can we put a magnet on their device during the procedure?" All but one time they've said yes. The only exception was when they said, "Yes, but I want my pacer/defib rep there to check the device before and after the procedure. I've never fried a pacer/defib, to my knowledge and (knock on wood) no cardiac events during any RFs.