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  • A sudden, brief loss of consciousness also known as "fainting"
  • Two types of syncope: vasovagal syncope and cardiac syncope
  • Treatments include medications, lifestyle changes, and in some cases addressing a heart issue
  • Involves internal medicine, cardiology, cardiovascular medicine



Some people faint from the sight of blood. Others may faint because they’re dehydrated. In other cases, serious heart conditions may cause an abnormal rhythm, preventing the heart from sending sufficient blood and oxygen to the brain and leading to a loss of consciousness. 

While some fainting is not a cause for concern, it’s critical to identify the cause and to treat any serious underlying conditions. In some cases, fainting can be caused by problems with the heart’s valves or arteries.

 At Yale Medicine, our doctors use the latest technology to diagnose and treat this condition.

What causes syncope?

There are two types of syncope: vasovagal syncope and cardiac syncope.  

Vasovagal syncope accounts for more than half of fainting incidents. When a person experiences extreme pain or fear, sees something that disgusts them (such as blood) or stands for a long period, it can cause an abnormal reflex in the part of the nervous system that regulates heart rate and blood pressure. This causes the heart rate to slow and decreases the amount of blood flowing to the brain, which causes a person to faint. Sometimes, if a person has prolonged vasovagal syncope, it can trigger a seizure.

Cardiac syncope occurs when the heart is not pumping enough blood to the brain. This can occur because of an abnormal heart rhythm that is either too slow or too fast. This can also occur if there is a problem with heart structure or function that causes the pumping function to become ineffective.

What should others do if a person near them faints?

First check to if they are breathing. If not, check their pulse and call for help. If the person has a pulse and is breathing, help them to regain consciousness by raising their legs to restore blood flow to the head and ensuring they have fresh air. Once the person has awakened, they should remain lying down for at least 10-15 minutes, preferably in a cool and quiet space.  If this isn’t possible, such as on an airplane, have the person sit forward and lower their head below their shoulders and between their knees. The person who has fainted should consult with their physician as soon as possible.

When should you see a doctor for fainting?

Fainting is very common. Most of the time, there’s nothing to worry about. However, if you faint during exercise, experience syncope together with heart palpitations or chest pain, or have a personal or family history of recurrent syncope, you should go see a doctor.

How is syncope diagnosed?

If a person is examined by a Yale Medicine physician for fainting, the first thing doctors do is figure out whether the fainting is caused by heart problems, blood pressure abnormalities, or neurological abnormalities—or it’s vasovagal, a more benign cause.

“We’ll evaluate the heart’s structure, conduct tests using an echocardiogram or treadmill to see what their blood flow is like, and we’ll look for electrical abnormalities,” says Yale Medicine cardiologist Rachel Lampert, MD.

How is syncope treated?

The treatment for syncope depends on what is found to be the underlying problem. If an abnormal heart rhythm is found, doctors determine which treatments to administer for each patient. If the problem is an underlying heart abnormality, such as a blocked artery or heart-valve problem, our cardiologists may recommend a stent or a valve-replacement procedure. For vasovagal syncope, the first step is understanding lifestyle factors that cause fainting, such as excess caffeine or alcohol.  Physical maneuvers, like pressing the palms together at chest level, can sometimes be helpful. Occasionally, the patient will require medication.

Why Yale Medicine?

At Yale, we use state-of-the-art technology to diagnose and treat syncope. For instance, we use tiny implantable monitors to check if the fainting is caused by abnormal heart rhythm, as well as a variety of external monitors, such as a patch that can be applied to the skin. These devices allow user-friendly monitoring for as long as it takes to determine the root cause of the condition.