How do work golden hearts?

[Lücky]

I unlocked the Golden Heart achievement yesterday and only got a couple of drops in Womb/Utero, so I don't know if it protects you from the next damage you receive (whatever it's 1/2 or 1 heart damage) or if it gives you like an extra heart that protects you from the next one heart damage or two half heart damage.

[HoneyDrake]

it doesnt negate any dmg

if you lose the heart, then you get money dropped

doesnt work if you lost health because of any active items effect