I personally dont care for it, but one of my buddies pickles the heart of every deer he gets. Here's the recipe he uses:
Boil heart until tender. Trim & slice, discard water.
Then gently boil all the following until sugar & salt are fully dissolved, then allow to cool:
2 cups water
3 cups vinegar (cider or white)
1 cup sugar
5 tsp salt
Pour over heart in a jar. Cover. Ready to eat in 2-3 days, keeps for weeks in the fridge.
Optionally add sliced onion, a garlic clove, red pepper flakes, whatever suits your fancy.