What game came up with the Heart metaphor for health?

Solution 1:

What game came up with the Heart metaphor for health?

From various sources, it is implied that the first game to utilize the Heart symbol to represent health is the first Legend of Zelda games, released in 1986.

Heart symbols were used to symbolize "health" or "lives" in video games; influentially so in The Legend of Zelda (1986)
_{Heart Symbol}

and

The original Zelda is the very first game to incorporate the trope and the franchise has been using it sinnce.
_{HeartsAreHearts¹}

How did this come to be?

Two years prior of Zelda's release, a game title Dragon Buster was the known as the first game to implement a health bar to indicate the players remaining health. It's possible Nintendo copied the idea and changed it to use hearts instead of a bar. But without a statement from the director, this is speculation

¹ Credits to snoozingnewt

Solution 2:

Chubby Cherub uses hearts to represent how many lives you have left. Released in Japan in 1985, it's older than Legend of Zelda. Not a health bar though. Heart metaphor is used in this game because the main character is based on Cupid.