Has anyone here flown an 11 hr flight and has blood pressure issues and has had blood clots?

I'm wanting to know if anyone here has flown an 11 hour flight and has blood pressure issues and possibly blood clots or, DVT? Since my father who has blood pressure issues and has had bypass surgery 5yrs ago will be with us to fly an 11 hour flight. He is currently taking blood pressure medications, as well as cholesterol, and aspirin.