What is "heartline"

Usage examples of "heartline".

He kissed her palms softly, bit gently at the fleshy mound of her thumb, traced her heartline with the tip of his tongue, and tasted the skin between her fingers.

Small, pale blue turquoise eyes, and a turquoise heartline running across his left side.

The wound there had now healed completely, leaving only a short white scar - it also zigzagged, crossing lifeand heartlines like a lightning bolt.