Using a single heart that's square in dimensions loaded to the tiled background object, and scaled to 4 times its original width.
For example if the heart was 32x 32 scaled to 128x 32
On damage received
heart set width to heart.width- 32
Or you set health variable for the player. Private variable health=4
And on events:
Always
TiledBackround: Set width to Player.Value('health')*32