I know at this point Tinkers Construct support is in place, but Heart Canisters should not go in the grave as they are not supposed to be dropped on death (you are supposed to respawn with them still equipped).

References:
Item drop code https://github.com/SlimeKnights/TinkersConstruct/blob/master/src/main/java/tconstruct/armor/player/ArmorExtended.java#L241-L253
Heart canister slot enumeration https://github.com/SlimeKnights/TinkersConstruct/blob/master/src/main/java/tconstruct/armor/items/HeartCanister.java#L105

As you can see in the code, only slots 0-3 are dropped on death and heart canisters are in slots 4-6