Can hiking at a higher elevation (8000ft) lead to elevated heart rate i.e. around 170bpm? at sea level, i am a frequent runner so i'm used to higher heart rates, but not such abrupt rises while only hiking. thanks?

At 8000 feet the effective oxygen concentration is 15-16% , significantly less than the 20% at sea level. This factor alone would be expected to trigger in increase in heart & respiratory weight at rest and with any exertion.

Agree with Dr. Ferguson. You should take time to acclimatize to the higher altitude before engaging in physical activity, especially strenuous activity.