Interesting question. I've only ever cooked veal/beef heart. I marinate the slices in a red wine with pepper, garlic, thyme or rosemary, a bit of lemon juice for about an hour. I pan fry in olive oil and serve with a red wine reduction. Or you could grill it, I suppose. Please, post your results.
Pork heart can be lovely stuff. I don't know if you do any Chinese cooking, but a great way to prepare it is by the technique called "red cooking" ("hongshao" in Mandarin). I won't go into the details here--you'll have to look that up yourself, and I'm sure there's a lot online--but it involves a long, slow cook in a rich soy-sauce-based liquid flavored with things like star anise and orange peel. Not difficult to do. Let it cool and slice it thin. Great texture. It's traditional, by the way, to offer it on a platter with other red-cooked items, also often organ meats.