Following my heart attack in December I was given Bisprololl as part of my cocktail of drugs. These had the effect of reducing my resting heart rate to low 50's. Two weeks ago I went skiing and probably due to altitude it increased about 10-15 beats per min. I expected it to reduce once I returned to the UK however it is still in the high 60's. Can anyone give me a reason for this and should I be worried?