Is it safe to live at high altitude with heart problems?

I live at high altitude (house at 6,300 and ski at 10,000) for 6 months of the year. I have a watchman to prevent blood clots so no longer on Xarelto. All seems to be fine. Good luck. Kathe

We live in Denver and my sister had an incident where her blood pressure went terribly high. She went to the hospital and is waiting for her doctor to make a decision on changing her blood pressure medicine. She wants to know if she should take a trip into the mountains where the altitude is 8 or 9 thousand feet.