blocked carotid arteries

I have an 85 year old uncle who had a stroke many years ago. He has now been monitoring his carotid arteries and he tells me they are blocked and is asking me for help. Any advice will be greatly appreciated.

I also have a 91 year old father who is pretty healthy. He has never been on any medication, even though in the last year he has developed high blood pressure. Also, when he stands from a sitting position he gets a bit dizzy and also has a problem with equilibrium/balance. This problem becomes resolved after a few seconds of standing but he is very worried about these symptoms. Is there anything I can tell him to do in order to resolve this problem?

Thank you very much,

Margo