heart-trouble and air-travel?

There are two separate issues here

1) Will air travel, in itself, have a negative effect on the existing medical condition ? This really needs to be discussed with a doctor who is familiar with the patient and their specific medical history, however relevant factors may include :

• effects of being in a pressurised cabin
• effects of sitting in a confined space for a long period
• effects of stress and general anxiety associated with air travel

2) If the patient does have a sudden complications it may be some time before they can get proper medical attention eg if you have a heart attack halfway across the Atlantic you will only have access to whatever medical facilities are on-board the plane for several hours.

This also raises the question of liability and insurance. A medical emergency on a flight can end up being very expensive for an airline plus they won't want to expose themselves to any legal liability. Similarly a pre-existing medical condition may complicate obtaining travel insurance and you need to consider the cost and availability of medication and potential treatment/repatriation at your destination.

On this subject, the preferred guidance should come from those within the medical community, such as this shared by the American Heart Association (and updated September 30, 2016):

Travel and Heart Disease

Travel precautions help people with heart disease.

Traveling to a faraway place doesn’t need to be off limits because you have heart disease or are a caretaker of someone who has had a cardiac event like heart attack or stroke. In fact, a few simple precautions can help make your trip a smooth one.

An obvious step is to be as equipped for your vacation or business trip as you would be at home.

“Make sure when you travel that you have your medicine,” said Winston H. Gandy Jr., M.D., a cardiologist at Northside Hospital in Atlanta.

Some people feel more comfortable bringing a copy of their original prescriptions in case they lose their medication. That’s fine, Gandy said, but it’s sufficient to have a list of your medications and your cardiologist’s phone number. Download this medication chart to help keep track. It’s also a good idea to let your cardiologist or internist know where you’ll be. Your doctor might know physicians or reputable heart institutes in the area if help is needed.

“Chances are your cardiologist is going to know someone there, either personally or by reputation,” said Gandy.

Do a little research. Be aware of a medical facility at your destination and understand what your health insurance covers. For instance, some insurance policies pay part of the cost of an emergency flight home from abroad. That can help you make quick decisions if a problem arises. Some healthcare providers recommend taking a copy of your pertinent medical records with you while traveling.

High Altitudes, Exotic Spots
Traveling to higher altitudes shouldn’t necessarily worry you, especially if your medical condition is well controlled, Gandy said.

But be mindful of your fluid consumption and sodium (salt) intake if you have cardiomyopathy or a history of heart failure, he said. A balanced fluid intake is important with these conditions.

High altitudes can make you more symptomatic if you have coronary artery disease because of the thin air and how oxygen is carried in your blood, Gandy said. He compared it to a train that’s transporting smaller loads and making more trips. The engine — or in this case, your heart — has to work harder, especially if you already have blockage.

Watch out for shortness of breath or other symptoms that could indicate you’re tipping from a stable to an unstable state, he said.

If you’re traveling to a developing country where certain vaccines are needed to guard against disease, it’s not likely the immunization will affect your heart. The bigger concern, Gandy said, is that an exotic place may have less access to good medical care.

“That’s a personal choice,” he said. “One has to understand the risk they’re taking.”

Consider making some adjustments, such as selecting an alternative destination in the same part of the world. Instead of a rural safari in Africa, choose a more populated part of the continent. “You might elect to go to Johannesburg and go to a game park for the day,” Gandy said.

Plane Precautions
Sitting immobile on long plane flights can slightly increase a normal person’s risk of blood clots in the legs, but associated medical issues usually contribute to it. If someone has peripheral artery disease (PAD) also called vascular disease or a history of heart failure, the clot risk increases. Getting up and walking around when possible is recommended for long flights, just be sure the seatbelt light is not on when you do so.

Tell your doctor about your travel plans to get the best advice on what precautions, if any, you may need to take. For example, some people might need compression stockings or additional oxygen. Others might need to watch fluids closely or avoid alcohol. And some may not be able to fly.