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Check out these newly released Special Health Reports from Harvard Medical School
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You can't buy good health but you can buy good health information. Check out these newly released Special Health Reports from Harvard Medical School:

Why fainting happens and how to nip it in the bud, from the Harvard Heart Letter

Faint, black out, swoon, pass out. They're all names for the same thing—a temporary loss of consciousness followed by a fairly rapid and complete recovery. Fainting occurs when something interrupts blood flow to the brain. Although usually harmless, fainting can cause injuries and sometimes signals a problem with the heart or circulatory system, reports the August 2009 issue of the Harvard Heart Letter.

The most common reason for fainting stems from crossed wires between the brain and the vagus nerve, the part of the nervous system that regulates blood pressure and heart rate. In response to some trigger, the blood vessels in your legs relax and the heart rate slows, making it difficult for blood to return to the heart. Blood pressure drops, and so do you. Triggers can range from fear and pain to standing for too long or even sneezing or going to the bathroom. Some people faint when they get out of bed or stand up from a chair.

Sometimes fainting is caused by trouble in the heart. This is more worrisome than fainting due to noncardiac causes. Heart rhythm problems are the most common culprit here. Anything that obstructs blood flow through the heart can also lead to fainting, such as a blocked or narrowed heart valve or a blood clot.

The Harvard Heart Letter notes that most people get a few seconds of warning that a faint is on its way. They turn pale, become dizzy, and may feel clammy and nauseated. Sitting or lying down often works to stop a faint. Tensing the muscles in your hands, arms, and legs can also help.

Read the full-length article: “When the lights suddenly go out”

Also in this issue of the Harvard Heart Letter

  • Trials test closing a PFO
  • August 2009 references and further reading
  • Stomach-protecting drug could block Plavix
  • Hole in the heart opens questions
  • 13 ways to add fruits and vegetables to your diet
  • When the lights suddenly go out
  • Heart Beat: New name for TIA?
  • Heart Beat: Preventable threats to survival
  • Heart Beat: Extending the time for stroke treatment
  • In Brief
  • Ask the doctor: Are isometric exercises safe for the heart?
  • Ask the doctor: What are silent heart attacks?
  • Ask the doctor: Why do I get chest pain when I don't warm up before exercising?
  • Ask the doctor: How can you tell when a leaky mitral valve needs to be fixed?

More Harvard Health News »


About Harvard Health Publications

Harvard Health Publications publishes four monthly newsletters--Harvard Health Letter, Harvard Women's Health Watch, Harvard Men's Health Watch, and Harvard Heart Letter--as well as more than 50 special health reports and books drawing on the expertise of the 8,000 faculty physicians at Harvard Medical School and its world-famous affiliated hospitals.