The concept of "heart" can be expressed a couple of different ways in ASL.
A good general way is to poke your chest twice with the tip of the middle finger of a modified "five" hand that has the middle finger bent at the large knuckle.
If you just poke once using a somewhat larger movement it means "touched" as in "I was touched by his generosity."
Version two: Draw a heart shape on your chest with the tips of both index fingers. Start at the top center of the heart.
Version three: Instead of using the tips of the index fingers to draw a heart on your chest, use the tips of the middle fingers of modified "five" hands that have the middle fingers bent at the large knuckle.
Notes: