My bad news for you is that I never had this problem PRE-op, but I experienced it POST-op! Now (3 weeks post-op) it seems to have faded a lot, but for a while I think the main thing interrupting my sleep was my "heart beating out of my chest"! While awake, I'd notice it in my gut or in my throat. But it was the big loud beats in the throat that seemed to wake me up.
I think the take-home message is that "It's not easy being a heart," and it's especially hard being one with defective parts or that's been through traumatic surgery recently.
BAV, extended ARoot, some MV damage.
68 y.o. (65 @OHS), keen active athlete until shortly pre-op, only symptomatic 1-2 months pre-op.
AVR (Medtronics Hancock II) Dec. 1 2010 w/ Dr. C.M. Feindel at UHN aka Toronto General. Also a "tuck" on the Aortic root, and a (Dacron) Medtronics Simplici-T ring on my MV. I did ACT for 3 months for the ring, and Metoprolol (BB) for 3 months for A-fib.