First, I am not an expert on acclimatization in general. I have trained many athletes to be ready for it, but I am still learning a lot along the way. Carolyn may have more knowledge on this topic!
I am editing this message from yesterday as I chatted with one of our altitude experts this morning about this very topic. They said it is expected that your zones and AeT is going to be 10-15bpm lower at altitude. This is if you are coming from sea level and going to 6,000-8,000ft. If you are doing more than 8,000ft change you may see even more suppression in your HR. It is smart to train by feel and don’t push to your normal AeT because that will likely result in exhaustion!
I hope that helps, and maybe CP will chime in a little more on this topic 🙂