Does your current valve situation cause an elevated heart rate, presumably because your heart is is compensating for not pumping as efficiently as it should?

I had a different issue and I'm extremely unqualified to have an opinion here, but based on my personal experience I'd be willing to put down a pretty decent sum of money on a bet that lowering your heart rate will reduce your anxiety directly.

(And then you'll of course have lower stress in general I should think, because you won't be worrying about the upcoming valve replacement and all the uncertainly surrounding a major operation. But that part is pretty clear, I would think)

Good luck!