What is syncope?
Syncope (pronounced “sin ko pea”) is the medical term for fainting or passing out. It is caused by a temporary drop in the amount of blood that flows to the brain.
Syncope can happen if you have a sudden drop in blood pressure, a drop in heart rate, or changes in the amount of blood in areas of your body. If you pass out, you will likely become conscious and alert right away, but you may be feel confused for a bit.
Autonomic Nervous System (ANS)
The ANS automatically controls many functions of the body, such as breathing, blood pressure, heart rate and bladder control. Most times, these things happen without us noticing.
How common is syncope?
Syncope is a common condition. It affects 3% of men and 3.5% of women 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 problems.
Types of Syncope
There are several different types of syncope. The type you have depends on what causes the problem.
Vasovagal syncope (also called cardio-neurogenic syncope)
Vasovagal syncope is the most common type of syncope. It is caused by a sudden drop in blood pressure, which causes a drop in blood flow to the brain. When you stand up, gravity causes blood to settle in the lower part of your body, below your diaphragm. When that happens, the heart and autonomic nervous system (ANS) work to keep your blood pressure stable.
Some patients with vasovagal syncope have a condition called orthostatic hypotension. This condition keeps the blood vessels from getting smaller (as they should) when the patient stands. This causes blood to collect in the legs and leads to a quick drop in blood pressure.
Situational syncope is a type of vasovagal syncope. It happens only during certain situations that affect the 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 the neck, or wearing a tight collar (carotid sinus hypersensitivity)
- Urinating (micturition syncope)
Postural syncope (also called postural hypotension)
Postural syncope is caused by a sudden drop in blood pressure due to a quick change in position, such as from lying down to standing. Certain medications and dehydration can lead to this condition. Patients with this type of syncope usually have changes in their blood pressure that cause it to drop by at least 20 mmHg (systolic/top number) and at least 10 mmHg (diastolic/bottom number) when they stand.
Cardiac syncope is caused by a heart or blood vessel condition that affects blood flow to the brain. These conditions can include an abnormal heart rhythm (arrhythmia), obstructed blood flow in the heart due to structural heart disease (the way the heart is formed), blockage in the cardiac blood vessels (myocardial ischemia), valve disease, aortic stenosis, blood clot, or heart failure. If you have cardiac syncope, it is important to see a cardiologist for proper treatment.
Neurologic syncope is caused by a neurological condition such as 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)
Postural-Orthostatic Tachycardia Syndrome is caused by a very fast heart rate (tachycardia) that happens when a person stands after sitting or lying down. The 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, but it can also occur in men.
Unknown Causes of Syncope
The cause of syncope is unknown In about one-third of patients. However, an increased risk of syncope is a side effect for some medications.
What are the symptoms of syncope?
The most common symptoms of syncope 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
Many times, patients feel an episode of syncope coming on. They have what are called “premonitory symptoms,” such as feeling lightheaded, nauseous, and heart palpitations (irregular heartbeats that feel like “fluttering” in the chest). If you have syncope, you will likely be able to keep from fainting if you sit or lie down and put your legs up if you feel these symptoms.
Syncope can be a sign of a more serious condition. So, it is important to get treatment right away after you have an episode of syncope. Most patients can prevent problems with syncope once they get an accurate diagnosis and proper treatment.
What causes syncope?
Syncope can be caused by many things. Many patients have a medical condition they may or may not know about that affects the 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).
How is syncope diagnosed?
If you have syncope, you should see your doctor, who can refer you to a syncope specialist for a complete evaluation.
The evaluation begins with a careful review of your medical history and a physical exam. Your doctor will ask you detailed questions about your symptoms and syncope episodes, including whether you have any symptoms before you faint and when and where the episodes happen.
You may then have one or more tests to help your doctor determine the cause of your syncope. These tests check things like the condition of your heart, how fast your heart is beating (heart rate), the amount of blood in your body (blood volume), and blood flow in different positions.
Your heart rate and blood pressure will be measured and recorded while you are in different positions including lying down, sitting and standing.
Tests to determine causes of syncope include:
- Laboratory testing: Blood work to check for anemia or metabolic changes.
- Electrocardiogram (EKG or ECG): A test that records the electrical activity of your heart. Electrodes (small sticky patches) are applied to your skin to collect this information.
- Exercise stress test: A test that uses an ECG to record your heart’s electrical activity while you are active. This is done on a treadmill or stationary bike, which helps you reach a target heart rate.
- Ambulatory monitor: You will wear a monitor that uses electrodes to record information about your heart’s rate and rhythm.
- Echocardiogram: A test that uses high-frequency sound waves to create an image of the heart 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 the table is tilted to different levels as you stay head-up. The test can show abnormal cardiovascular reflexes that cause syncope.
- Blood volume determination: A test to see if you have the right amount of blood in your body, based on your gender, height and weight. A small amount of a radioactive substance (tracer) is injected through an intravenous (IV) line placed in a vein in your arm. Blood samples are then taken and analyzed. The blood volume analyzer system used at Cleveland Clinic can provide accurate test results within 35 minutes.
- Hemodynamic testing: A test to check the blood flow and pressure inside your blood vessels when your heart muscle contracts and pumps blood throughout the body. A small amount of a radioactive substance (tracer) is injected through an intravenous (IV) line placed in a vein in your arm and three sets of images are taken.
- Autonomic reflex testing: A series of different tests are done to monitor blood pressure, blood flow, heart rate, skin temperature and sweating in response to certain stimuli. These measurements can help your doctor determine if your autonomic nervous system is working normally or if there is nerve damage.
The test results will help your doctor determine what is causing you to have syncope. You may need other tests, including electrophysiology studies, autonomic nervous system testing, neurological evaluation, and computed tomography (CT) scan. Vestibular function testing may be done to rule-out problems in the inner ear. If you need any additional testing, your doctor will explain them and why they are needed.
What are my treatment options?
Your treatment options will depend on what is causing your syncope and the results of your evaluation and testing. The goal of treatment is to keep you from having episodes of 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 doctor 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 sleeping. You can do this by using extra pillows or by placing risers under the legs of the head of the bed.
- Avoiding or changing the situations or “triggers” that cause a syncope episode.
- Biofeedback training to control a fast heartbeat.
- Treatment for structural heart disease.
- Implanting a pacemaker to keep your heart rate regular (only needed for patients with certain medical conditions).
- An implantable cardiac defibrillator (ICD). This device constantly monitors your heart rate and rhythm and corrects a fast, abnormal rhythm (only needed for patients with certain medical conditions).
Your doctor and other members of your healthcare team will develop a treatment plan that is right for you and talk to you about your treatment options.
How will syncope affect my life?
With the proper diagnosis and treatment, syncope can be managed and controlled. If you have had an episode of syncope, there is 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, gender and other medical problems you have. If you have questions about your risks, please talk to your doctor.