So, I was wondering about this 'heart' feature and am convinced it doesn't work. It's essentially a secondary form arrow that doesn't move or do anything. I tried a couple of friendly matches tonight and noted the heart of the players before, during and towards the end of the match, and their heart didn't move for any of them. The feature simply doesn't change, unless it doesn't show on the game plan, in which case you'd think why bother with it if you can't see which players are playing badly, and if it does, then I can't notice any difference.
Also, I took another look at the PES2014 video from E3, the one where Kei Masuda is being interviewed through an interpreter while playing the game. The interview claims the players have a direct relationship with the crowd, so doing poor passes causes the crowd to get on their back, and that in turn makes their heart get worse, and the opposite goes for doing good things. They claim the crowd respond to good things, and their performance will be felt in player control and accuracy.
I actually bought the game looking for this as a major new feature and to my knowledge it doesn't seem to exist. Fom my experience with the game, the crowd doesn't respond to anything beyond what it did in previous games, and player performance certainly doesn't fluctuate during the match.
Not only does the feature not seem to work, I can't find any evidence that it's even there.