Only a doctor will be able to give a reliable answer.

Another aspect you should consider:

Many airlines have a clause in their T&C that pax who have had a stroke/heart attack etc. will need to contact the airline in advance and seek permission to fly. IŽd definitely recommend getting an official medical certificate from the hospital that the pax is fit to fly, as he may otherwise be liable for any costs resulting from a medical emergency, diversion etc.