Item is never built at all in high elo, because of how it lacks active effects or base hp. it is pretty useless when it is compared to other items like randuins, which gives a nice aoe slow every 60 seconds and very nice tank stats, or thornmail, which applies grievous wounds and does more dmg to adcs if you build more armor and gives a bit of hp. I would suggest giving frozen heart an item active that temporarily slows the attack speed of its surrounding enemies by 40%, and make that aoe like the randuin's active effect, and nerf the base armor on frozen heart by a bit if that is too strong to directly give to frozen heart. There is no reason any top laner would care about the 20% cdr on frozen heart, because they could just go ice born gauntlet and randuin/thornmail. and that would be a much better option because ibg gives them 20% cdr and waveclear and armor/mana, and then they get to choose a much better 2nd armor item.