I have the same history you do, of valve surgery and post-surgical HIT. You can take
warfarin with a history of HIT. If you happen to have a mechanical valve, I'm sure you already are taking warfarin. If you're on warfarin, and you're wondering what to use for bridging, that would be Arixtra (fondaparinux). Fondaparinux is dispensed in syringes for subcutaneous injection, to be self-administered once a day. I've used it, and it's easy.