Hourglass Heart

Info
Hourglass Heart has a whopping 60 HP (3x that of Lesser Heart), but it comes at a cost: this heart cannot regenerate health in any means throughout the entire game.

Strategies
This heart is not very good. Put it in the left-most slot as its only purpose is to potentially give you a few rooms of additional boost to take you to dream 99 from dream 95 if you lose all your other hearts. Overall don't buy this at the shop unless you're backtracking to dream shop. You're much better off with a Jumbo or even a Lesser Heart.

Trivia

 * This heart has the highest HP in the game and ironically is the weakest one (flip side of Undying Heart which is one of the strongest with the least HP)
 * This heart took a lot of demos to work properly: it could be healed previously by:
 * Life Drain Aura
 * Heart Swapping
 * Room Reloading+Heart Swapping in a later demo
 * This heart is the only heart whose sprite is not a heart
 * This heart is the only heart whose sprite changed shapes completely through the demos
 * Recollection does not allude clearly to the fact that this heart cannot be healed, instead calling it "expiration" and slowly losing health over time (tldr, recollection is wrong)
 * According to ramaf, beast heart can heal this heart