Cardiovascular problems account for the majority of serious illnesses that occur on airplanes, and half of all deaths among American travelers abroad are due to heart attacks.

The Harvard Heart Letter offers readers 12 tips for traveling safely with heart disease:

1. Check with your doctor to make sure it is safe to fly with your current heart condition.

2. Flu and pneumonia vaccinations should be up to date. Get all appropriate region-specific immunizations.

3. Get the name of a doctor or hospital at your destination.

4. Check with your insurance to see if you're covered outside of your home area.

5. Pack a copy of your ECG (electrocardiogram).

6. Do you have an implanted heart device? Carry a card or letter from your doctor saying you have an implanted device.

7. Carry all medications with you and bring enough to last the trip.

8. If you use oxygen, find out the airline's policies and prices.

9. Get to the airport early, so you don't have to run to the terminal.

10. Long flight? Drink plenty of water, stay away from caffeine, and move your legs as much as possible to prevent blood clots.

11. Know the warning signs of a heart attack.

12. Jet lag should fade within a few days of your return. If it doesn't, see your doctor.

Harvard Heart Letter is available from Harvard Health Publications, the publishing division of the Harvard Medical School. You can subscribe at www.health.harvard.edu or by calling 1-877-649-9457 toll-free.