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Fainting

What is fainting?

Fainting is a brief, sudden loss of consciousness. You become unresponsive, lose muscle tone, and may fall. Usually, you will recover completely in a few seconds or minutes.

Usually fainting is not caused by a serious or life-threatening medical problem. However, if you are known to have heart disease, or you faint during even mild exercise, the cause may be serious and you may need prompt medical attention.

Fainting is fairly common. The medical term for fainting is syncope.

How does it occur?

There are many possible reasons for fainting.

  • One of the most common and least worrisome reasons for fainting is anxiety or other emotional upset.
  • You may faint if you have not had enough liquids, especially if you stand up too quickly. This happens more often after being sick or working in the hot sun.
  • As you get older, it can be harder for your body to control your blood pressure. Standing up after sitting or lying down, or standing for a long time, may cause low blood pressure. This condition, called orthostatic hypotension, can cause fainting. It happens because not enough blood is pumped to the brain. It may be worse right after you eat.
  • The most common cause of fainting in healthy young adults is vasovagal syncope. It can happen when you take a deep breath and push down but don't allow yourself to breathe out. You may do this, for example, when you urinate or have a bowel movement or when you cough hard or long. Vasovagal syncope can also happen if you stand in one place for too long. Before you faint, you may feel giddy, lightheaded, or flushed. The fainting is caused by nerve impulses that slow the heart rate. As a result, the heart temporarily pumps less blood to the brain.
  • Low blood sugar can also cause fainting. For example, if you have diabetes, your medicines might make your blood sugar too low.
  • Some medicines, such as diuretics (water pills) and blood pressure-lowering medicines, may cause fainting.
  • Temporary pressure on a sensitive spot in the neck causes fainting in some people.
  • Sometimes heart problems cause fainting.
    • Irregular heart rhythms are the most common heart-related cause of fainting. The heart may beat so rapidly that too little blood gets to the brain. Or a very slow heart rate caused by heart block or pacemaker failure may cause fainting.
    • Some heart attacks immediately damage the pumping muscle and cause fainting.
    • Abnormal heart valves can cause drops in blood pressure that lead to fainting.

What are the symptoms?

You may faint suddenly without any other symptoms. Or at first you may feel nauseous or sweaty. If your fainting is caused by a heart problem, you may have a fast or irregular pulse. Sometimes people say they felt like their heart was jumping around in their chest. You may feel short of breath, or you may feel pressure in your chest. If you have a heart valve problem, you may have some chest pain, especially with exertion, before you faint.

How is it diagnosed?

Your healthcare provider will ask about your medical history, particularly about the times you have fainted. How you felt before and after you fainted are important facts that can help your provider diagnose the problem.

Your provider will ask about the medicines you take and will examine you.

Depending on your age and health history, you may have some tests.

  • If your healthcare provider thinks a heart problem may be the cause of the fainting, you may have an electrocardiogram (ECG or EKG). The ECG measures and records the electrical activity of your heart. If the first ECG is normal, your provider may want to monitor your heart for a longer period of time. You may wear a small, portable ECG recorder called a Holter monitor to record your heart rhythm for 1 to 3 days. Or another type of monitor called an event recorder may be used for several weeks at a time.
  • You may have an ultrasound test of the heart called an echocardiogram to check for problems with the heart muscle or the heart valves.
  • You may have a stress test, which will give information about the heart rhythm and blood flow to the heart.
  • You may have a chest X-ray.
  • A tilt table test may be done to measure your blood pressure while you lie on a table that is gradually tilted toward the head-up position.
  • You may have a test of the electrical system of the heart called an electrophysiology study.

Even if you have all of these tests, the exact cause for fainting may not be found.

How is it treated?

The treatment of fainting is based on the cause.

  • If vasovagal syncope is the problem, pay attention to what happens right before you faint. When you have these symptoms, take precautions to avoid fainting, or to stop from getting hurt if you do faint. For example, try to lie down before you faint.
  • A careful review by your healthcare provider of the medicines and dosages you take can eliminate drugs as a cause for fainting.
  • Orthostatic hypotension can be helped by wearing support hose. It also helps to get up slowly after you have been sitting or lying down.
  • Heart problems can often be treated. Heart valves causing blockage can be replaced. Pacemakers can be inserted to correct very slow heart rates.

How do I prevent fainting?

  • Follow your healthcare provider's instructions carefully.
  • Drink plenty of liquids, especially in hot weather.
  • Eat a healthy diet and eat at regular times throughout the day.
  • Let your healthcare provider know if your symptoms are getting worse or happening more often. Also let your provider know if you have had a recent change in medicines.
Developed by RelayHealth.
Published by RelayHealth.
Last modified: 2010-12-10
Last reviewed: 2010-12-10
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2011 RelayHealth and/or its affiliates. All rights reserved.
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