https://southdenver.com/what-is-the-relationship-between-high-altitude-and-heart-conditions/
I have seen two different altitudes above which it is 'high altitude' , or rather 'not low altitude'. One site says anything above 8250' ASL, this one I site says just over 6300' ASL and under 9000'ish is 'moderate altitude'. Whatever the case may be, the sited reference makes it clear that altitude, with its drop in oxygen availability compared to at sea level, is going to cause the heart to work a little harder. For your condition, it might feel to the heart's valves like 'a lot harder.' It isn't necessarily the higher rate. It's the higher pressure that goes along with the heart's internal programming to 'do more' at altitude.
If I were deciding for myself, and if I had some sort of idea of how bad my valve(s) is/are on a Likert scale (1-7), and if my valves were less than 3.0, I don't think I would pass up a trip to 'moderate altitude', but I might tone back the demands I place on my heart with very low levels of activity. Walking, bowling, swimming slowly, skiing downhill....but I would do no hiking, very little stair climbing, aerobics at a gym...that kind of thing.
The other thing is that this is not going to be forever. It's for a limited time, short, and then you'll return to a much lower level. So, yes, it might strain things a bit, but I don't see that a short visit up there is going to compromise your health. Living up near 7000' and up is not something I would do.....and it's just me. Not until I was given a thumb up by whichever doctor I trusted the most.