What causes heart palpitations and the simultaneous opening of my sinus passages?

Palpitations. If you have catecholamines being secreted they could cause both at the same time. This happens during/after sex so you might notice this at those times...
Not sure. Those 2 things don't usually go together. I could certainly a guess, but the bottom line is that heart palpitations are never a good thing and you should get them checked out soon. If you experience shortness of breath, chest pain, or any serious issues with the palpitations head to the er or call 911. If the "opening of the sinuses" is a problem, see your ENT afterwards. Best wishes.