Had a pulmonary Embolism back in the mid 90's. This occurred days after a long period sat at the front (flight Deck) at touching 38 at the time the only answer the Medics came up with was the long periods sitting down, there was never any mention from any of the medical experts of affects of altitude! Having initially done the intensive care bit and then three months on the Rat Poison I was cleared to fly again, and yes, I do get out of my seat now and have a walk around when working long haul
Regards
Pikey
PS: I have since learned of several Pilots who have had a PE albeit they were in their mid to late fifties.