I had the excact same probleme. After my first attempt to VILD, my heart started to beat extremely fast (probably due to a state my body has never felt - at least not when councious).
I tried VILDing again, and my heart and body were way calmer about the state, though the attempt failed against, since I had to breath more. If you try again, then don't supress the need for air. It's almost impossible to supress the need for air.

My best hint is to practice is more. Eventually, your body will get used to it, and you will succeed . I am still practicing VILD. I believe it's the best technique for me.

Just keep trying