Fainting (Syncope)

What is fainting?

Fainting is a brief, sudden loss of consciousness. You become unresponsive, lose muscle tone, and may fall. Usually, there is complete recovery in a matter of seconds to a few minutes.

Fainting is fairly common and happens more often as people get older. The medical term for fainting is syncope.

How does it occur?

There are different reasons for fainting. 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 when you are physically exerting yourself, the cause may be serious and you may need prompt medical attention.

One of the most common and least worrisome reasons for fainting is anxiety or other emotional upset. The anxiety causes fast breathing (hyperventilation), which alters your body chemistry enough to cause you to faint.

You may faint if you have not had enough liquids, especially if you stand up too quickly. This happens more often after illness or working in the hot sun. But, it seems that some people, especially older adults, are just generally more likely to faint than others from a lack of liquids.

If you are an older adult, you may faint after meals, especially when you stand up after a meal. This is because a lot of blood pools in the abdomen as it absorbs nutrients from the meal and less blood gets to your brain.

As people age, the ability of the nervous system to control blood pressure becomes less sensitive. Rising from a lying to a standing position, or standing for a long time, may cause low blood pressure. This condition, called orthostatic hypotension, can cause fainting. This happens because not enough blood is pumped from the heart to the brain.

Low blood sugar from diabetic treatment or other causes can also cause fainting.

Some medicines such as diuretics (water pills), blood pressure-lowering medicines, antidepressants, and anti-psychotics may cause fainting.

A type of fainting called vasovagal syncope can happen when you take a deep breath and push down but don’t allow yourself to breath out. You may do this, for example, when you urinate or have a bowel movement. It can happen when you cough hard or 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.

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.

Faints also occur because not enough oxygen is getting to the brain. A rare condition called subclavian steal may cause unconsciousness when you move your arms vigorously.

What are the symptoms?

You may faint suddenly without any 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 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 health care provider will ask about your medical history, particularly about the times you have fainted. He or she will ask about the medicines you take and will examine you.

Depending on your age and health history, your health care provider may want to do some tests.

If your health care provider thinks a heart problem may be the cause of the fainting, you may have an electrocardiogram (ECG or EKG). The ECG records the electrical impulses from your heart. If the first ECG is normal, your provider may want to monitor your heart for a longer period of time. A special type of ECG called a Holter monitor can be worn for 1 to 3 days to make a recording of your heart rhythm, or another type of monitor called an event recorder can be used for several weeks at a time.
You may have a chest x-ray.
A tilt table test helps to diagnose reflex syncope. In this test, your blood pressure is measured while the table on which you are lying is progressively tilted toward the head-up position.
Sometimes your health care provider may order a test of the electrical system of the heart called an electrophysiology study.

Even with all these tests, the exact cause for fainting may not be discovered.

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 health care provider of the medicines and dosages you take can eliminate drugs as a cause for fainting.
Orthostatic hypotension, or a marked fall in blood pressure when you are standing up, can be helped by wearing support hose. Getting up slowly from lying or sitting also helps.
Heart-related problems can often be repaired. Heart valves causing blockage can be replaced. Pacemakers can be inserted to correct very slow heart rates.

How do I prevent fainting?

Follow your health care 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 health care provider know if your symptoms are getting worse or happening more often, and if you have had a recent change in medicines.

Information obtained from GE Medical Systems; authorization given to reproduce on HCNW web site 9/02.
Developed by McKesson Clinical Reference Systems.
Published by McKesson Clinical Reference Systems.
Copyright © 1997-2002 McKesson Health Solutions LLC. All rights reserved.

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.