What Causes Hearing Of Heart Beat In Ears?

When I traveled to Angel Fire, New Mexico, I started hearing my pulse beating in my ears which continued for the 3 days we were there. I attributed this to altitude change (about 8,000 ft.) It stopped when we descended to lower levels. I was wondering if this was an indication of heart trauma. I want to go to the top of Pike's Peak (14,000ft.)but am afraid.

Appreciate feedback,
Thanks,
Martha