Cardiac patients should be careful while taking three-hour-plus flights, sitting cramped may cause the blood to clot putting them at the risk of deep-vein thrombosis (DVT). But on an aircraft, the air pressure may cause linear clots in any part of the body. Even healthy passengers who sit with their legs pressed to the edge of the seat may develop oedema or swelling.

I never knew this before, because I have never experienced traveling thru airplane, LOL! Thank you for posting this information. At least now I have an idea in case we would go to Disneyland. My wife has a weak heart.

I would be careful then - get her checked out before flying