What is syncope?
Syncope (pronounced “sin-ko-pea”) is the medical term for fainting or passing out. It happens when you have a sudden, temporary drop in the amount of blood that flows to your brain. Most of the time, a harmless, short-term cause makes you faint.
Syncope can happen if you have:
- A sudden drop in blood pressure.
- A drop in your heart rate.
- Changes in the amount of blood in areas of your body.
If you pass out, you’ll likely become conscious and alert after a few seconds or minutes. However, you may feel confused or tired for a bit. You can recover fully in minutes or hours.
Syncope can be a sign of a more serious condition. It’s important to get treatment right away after you have an episode of syncope. Most people can prevent problems with syncope once they get an accurate diagnosis and proper treatment.
Types of Syncope
There are several different types of syncope. They are:
- Vasovagal syncope (also called neurocardiogenic syncope). This is the most common type of syncope. Nearly half of syncope cases are the vasovagal type.
- Situational syncope (a type of vasovagal syncope).
- Postural or orthostatic syncope (also called postural hypotension).
- Cardiac syncope.
- Neurologic syncope.
- Postural Orthostatic Tachycardia Syndrome (POTS).
- Syncope with an unknown cause.
How common is syncope?
Syncope is a common condition. It affects 3% of men or people assigned male at birth (AMAB) and 3.5% of women or people assigned female at birth (AFAB) at some point in life. Syncope is more common as you get older and affects up to 6% of people over age 75. The condition can occur at any age and happens in people with and without other medical issues.
Symptoms and Causes
What are the symptoms of syncope?
The most common syncope symptoms include:
- Blacking out.
- Feeling lightheaded.
- Falling for no reason.
- Feeling dizzy.
- Feeling drowsy or groggy.
- Fainting, especially after eating or exercising.
- Feeling unsteady or weak when standing.
- Changes in vision, such as seeing spots or having tunnel vision.
What causes syncope?
Syncope, or passing out, happens when you don’t have enough blood flowing to your brain. There are many causes for this, depending on the type of syncope. Many people have a medical condition they may or may not know about that affects their nervous system or heart. You may also have a condition that affects blood flow through your body and causes your blood pressure to drop when you change positions (for example, going from lying down to standing).
Vasovagal syncope causes
Vasovagal syncope happens when you have a sudden drop in blood pressure, which causes a drop in blood flow to your brain. It often occurs after standing for a while or under emotional distress. Normally, when you stand up, gravity makes blood settle in the lower part of your body, below your diaphragm. When that happens, your heart and autonomic nervous system work to keep your blood pressure stable.
In vasovagal syncope, your heart rate and blood pressure inappropriately decrease severely. This causes decreased blood flow to your brain and leads to passing out. Typically, vasovagal syncope is benign.
Situational syncope causes
Situational syncope happens only during certain situations that affect your nervous system and lead to syncope. Some of these situations are:
- Intense emotional stress.
- Use of alcohol or drugs.
- Hyperventilation (breathing in too much oxygen and getting rid of too much carbon dioxide too quickly).
- Coughing forcefully, turning your neck or wearing a tight collar (carotid sinus hypersensitivity).
- Urinating (micturition syncope).
Postural syncope causes
Postural syncope (also called postural hypotension or orthostatic hypotension) happens when your blood pressure drops suddenly due to a quick change in position, such as standing up after lying down. Certain medications and dehydration can lead to this condition. People with this type of syncope usually have changes in their blood pressure that cause it to drop by at least 20 millimeters of mercury (systolic/top number) and at least 10 millimeters of mercury (diastolic/bottom number) when they stand.
Cardiac syncope causes
Cardiac syncope can occur if you have a heart or blood vessel condition that affects blood flow to your brain. These conditions can include:
- Abnormal heart rhythm (arrhythmia).
- Obstructed blood flow in your heart because of your heart’s structure (hypertrophic cardiomyopathy).
- Blockage in your heart’s blood vessels (myocardial ischemia).
- Valve disease.
- Aortic stenosis (narrowing).
- Blood clot.
- Heart failure.
If you have cardiac syncope, it’s important to see a cardiologist for proper treatment.
Neurologic syncope causes
Neurologic syncope can happen when you have a neurological condition such as a seizure, stroke or transient ischemic attack (TIA). Other less common conditions that lead to neurologic syncope include migraines and normal pressure hydrocephalus.
Postural orthostatic tachycardia syndrome (POTS)
If you have postural orthostatic tachycardia syndrome, you may have a very fast heart rate (tachycardia) that happens when you stand after sitting or lying down. Your heart rate can speed up by 30 beats per minute or more. The increase usually happens within 10 minutes of standing. The condition is most common in women and people AFAB, but it can also occur in men and people AMAB.
Unknown causes of syncope
The cause of syncope is unknown in about 33% of people who have it. However, an increased risk of syncope is a side effect of some medications. Be sure to follow up with a provider if you don’t know what caused your syncope.
Diagnosis and Tests
How is syncope diagnosed?
If you have syncope, you should see a provider who can refer you to a syncope specialist for a complete evaluation.
A syncope specialist will do a physical exam and a careful review of your medical history. They’ll ask you detailed questions about your symptoms and syncope episodes, including whether you have any symptoms before you faint and when and where you faint.
They may measure and record your heart rate and blood pressure while you’re in different positions, including lying down, sitting and standing.
You may then have one or more tests to help determine the cause of your syncope. These tests check things like:
- The condition of your heart.
- How fast your heart beats (heart rate).
- The amount of blood in your body (blood volume).
- Blood flow when your body is in different positions.
What tests will be done to diagnose syncope?
Tests to determine causes of syncope include:
- Laboratory testing: Blood work to check for anemia or metabolic changes.
- Electrocardiogram (EKG): A test that records your heart’s electrical activity.
- Exercise stress test: There are many types of stress tests that involve you exercising or using a medication to stress your heart. Some types of stress tests will look at EKG changes or do an ultrasound of your heart. A stress test can also be done with nuclear imaging.
- Ambulatory monitor: A monitor you wear that uses electrodes to record information about your heart’s rate and rhythm.
- Echocardiogram: A test that uses sound waves to create an image of your heart’s structures.
- Tilt table (head-up tilt test): A test that records your blood pressure and heart rate on a minute-by-minute or beat-by-beat basis while a provider tilts the table to different levels as you stay head-up. The test can show abnormal cardiovascular reflexes that cause syncope.
- Autonomic reflex testing: A series of different tests monitors your blood pressure, blood flow, heart rate, skin temperature and sweating in response to certain stimuli. These measurements can help your provider determine if your autonomic nervous system is working normally or if you have nerve damage.
You may need other tests, including electrophysiology studies, autonomic nervous system testing, neurological evaluation and computed tomography (CT) scan. You may need vestibular function testing to rule out issues in the inner ear. If you need any additional testing, your provider will explain what they are and why you need them.
Management and Treatment
What is the proper treatment for syncope?
If someone faints, follow these steps:
- Check to make sure they’re breathing.
- Make sure they lie down or sit with their head between their knees for at least 10 to 15 minutes.
- Offer the person cold water to drink.
Treatment options will depend on what’s causing your syncope and the results of your evaluation and testing. The goal of treatment is to keep you from having episodes of syncope.
Syncope treatment options include:
- Taking medications or making changes to medications you already take.
- Wearing support garments or compression stockings to improve blood circulation.
- Making changes to your diet. Your provider may suggest that you eat small, frequent meals, eat more salt (sodium), drink more fluids, increase the amount of potassium in your diet and avoid caffeine and alcohol.
- Being extra cautious when you stand up.
- Elevating the head of your bed while you sleep. To do this, you can use extra pillows or place risers under the legs of the head of the bed.
- Avoiding or changing the situations or “triggers” that cause a syncope episode (avoiding standing for long periods of time, heat or emotional stressors).
- Biofeedback training to control a fast heartbeat.
- Getting treatment for structural heart disease.
- Getting a pacemaker to keep your heart rate regular (only for certain medical conditions).
- Getting an implantable cardioverter defibrillator (ICD). This device constantly monitors your heart rate and rhythm and corrects a fast, abnormal rhythm (only for certain medical conditions).
Your healthcare team will develop a treatment plan that’s right for you and talk to you about your treatment options.
What medications/treatments are used?
Medicines for syncope include:
- Fludrocortisone (Astonin® or Florinef®).
Side effects of the treatment
Side effects of the medicines may include:
- Urinary issues.
- Stomach issues.
How can I reduce my risk?
To reduce your risk of syncope, you need to know what caused it. Reducing your risk may be as easy as staying hydrated if that was the issue. If you have a heart condition that caused it, you may need medicine or a device to treat abnormal heart rhythms.
How can I prevent syncope?
Many times, people feel an episode of syncope coming on. They feel lightheaded, nauseous and have heart palpitations (irregular heartbeats that feel like “fluttering” in the chest). You’ll likely be able to keep from fainting if you:
- Sit or lie down and put your legs up.
- Make a fist with your hands.
- Make your arms tense or tight.
- Cross your legs or squeeze your thighs against each other.
Outlook / Prognosis
What can I expect if I have syncope?
With the proper diagnosis and treatment, you can manage and control syncope. If you’ve had an episode of syncope, there’s about a 30% chance you will have another episode. Your risk of another episode and how the condition affects you depends on several factors, including the cause and your age, sex and other medical issues you have. If you have questions about your risks, talk to your provider.
If you have a syncope diagnosis, check your state laws. Some states require drivers with syncope to contact the license bureau. A provider may recommend you find out the cause and get treatment before driving.
Is syncope life-threatening?
Although most episodes of syncope aren’t dangerous, they can be life-threatening if you have abnormal heart rhythms or a neurologic cause. People with a heart or neurologic issue need to follow up with a provider who can help.
When should I see my healthcare provider?
Depending on the cause of your syncope, you should have a follow-up appointment with a provider two to four weeks after you get hospital or outpatient treatment for it. If a provider discovers an issue with your heart’s structure or rhythm, you’ll need more follow-up appointments for that.
When should I go to the ER?
Anyone who collapses and is in cardiac arrest needs CPR and an ambulance. People often go to the ER for syncope as well.
What questions should I ask my doctor?
Questions to ask your provider include:
- Do you know what caused my syncope?
- How can I prevent the type of syncope I had?
- Do I need additional tests or follow-up appointments?
A note from Cleveland Clinic
The unexpected and attention-getting nature of syncope can make it seem more dangerous than it is. For most people, it’s a temporary condition that doesn’t point to any serious health issues. Seeing a provider after you faint can give you peace of mind knowing that you don’t have a serious condition. Be sure to get treatment for your heart condition if that caused your syncope.
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