I see lots of questions on here like..... "If I take iodine, will it do ________"
People have such varied histories, metabolisms, other conditions, etc. that it is not possible to provide a meaningful answer, although there are always internet self-professed geniuses willing to throw in blurbs about what to do. I see it as being impossible to answer whether if your father takes Iodine it will damage his heart.
Depends on his current condition (many aspects there), and also the definition of "damage" and also which part of the heart one is talking about. Prof. Don Miller could be another good potential source, he's a heart surgeon.
But my guess is that for ethical reasons, practical reasons of lack of knowledge of your dad's condition, liability reasons, no MD can render an opinion from a letter or internet message.
I don't intend to be a bad guy, just the cold hard facts.