Do you agree with the statement that they "replace" the human heart?

Not necessarily. I have no background on this kind of thing. I would say that they do not only for the facts of 1, where would they get a new heart? 2, I was born with three holes in my heart (I swear to God) and merely got patches. 3, Replacing the heart would be hard so as though when your heart stops beating you die. There would be only a very small space of time that would have to do so.  

The light is great source of energy