Are these compatible with crampons? for high altitude trekking?

This boot is not at all designed for high altitude trekking. You could use strap-on crampons with it, but the boot is way to flexible to do any sort of technical climbing or mountaineering. You should look at the technical mountaineering boot section of this website instead. There are a great deal of awesome winter mountaineering boots from La Sportiva, Scarpa, Ice 9, Mammut...the list goes on and on. But be advised that fit is a huge issue with those kind of boots. It would be good to have a professional fit you to the boot you want so you know what size to order off backcountry.com.

Some of the cheaper, strap-on crampons will work on this boot, but for serious crampons with a heel throw, you'll need something geared towards mountaineering. This boot is just supposed to be an everyday boot for really cold weather.