How do the hearts work?

[Old Git]

I've been on my second playthrough (hard) recently, when it suddenly struck me: I STILL don't really know what the hearts do. I thought it was supposed to kill all the enemies within a certain radius around me, but whenever I use them demons just die randomly regardless of type, and it has something to do with if I'm aiming at them...
Has someone less blatantly stupid than me figured this out?

[FireStar]

Go really near to an enemy and press LMB, Lo will squeez the heart. Minor Enemy will die, major enemy will take a lot of damage.

[Pubmaster Drax]

When you use it, minor enemies around you will have a heart attack and die. Bigger enemies take damage.

[Elenoe]

but yes, it's random. 2-3 enemies dies. Maybe their combined HP are used to determine. Never saw two shamans die. But weak opponents are not limited to one but not all around or before you either. It was "unpredictable". Good for shamans eventually or just for fun.

[Sweetz]

The radius is pretty small, and there's a big question of when the action actually takes effect. E.g. it takes a second or two for the animation to play out, and enemies can certainly move away from your during that time - so the question is does it kill enemies within the radius when you press the button, or enemies with the radius when the heart is actually crushed?

[Batou]

you have to look at them