Plastic heart?

What I kept thinking after Mare Winningham gets the plastic heart is that it somehow was affecting her in a negative way. I thought that's what they were going to go to when she was acting strange about it all. If your emotions are mostly felt in the heart--every little feeling you have is felt there, what happens when the heart is plastic? Can you still feel there in that way? I think if they remade this movie, that's what they would have done with the story.

GG's-Sophia: ". . .my dear husband Sal, may he rest in peace until I get there. . ."