Syncope is another word for passing out or fainting. While the event can happen at any age, it is more common in older adults and affects up to six percent of people over 75. Most episodes of fainting are benign, though it can be a symptom of an underlying medical condition.

Cerebral Blood Flow

The brain needs a constant supply of oxygen and glucose to function, and it gets this from an adequate blood supply. If anything interrupts the brain's blood flow, even for a few seconds, it stops working as it should, and the person passes out. Multiple things can disrupt blood flow. Syncope should not last more than a few minutes. If it does, the episode is more likely due to another condition, most commonly seizures.

blood flow brain fstop123 / Getty Images


Reflex Syncope

Reflex syncope is the result of a trigger, something that causes a slow heart rate or dilated blood vessels. This causes lower blood pressure, which leads to inadequate cerebral perfusion. Reflex syncope is the most common type and can be caused by carotid sinus syncope. This even happens in older adults when pressure is applied to the carotid artery in the neck.

reflex syncope perfusion RealPeopleGroup / Getty Images


Vasovagal Syncope

Vasovagal syncope or the common faint is the most common type of reflex syncope, making up half of all cases. Many things can trigger vasovagal syncope, including dehydration, blood donation, getting an injection, seeing blood, standing up too quickly, or sudden or unexpected stress, pain, or trauma.

vasovagal common faint dturphoto / Getty Images


Situational Syncope

Situational syncope is another form of vasovagal and reflex syncope. It happens when situations such as dehydration, pain, fear, hunger, hyperventilation, or coughing forcefully affect the nervous system. Other possible triggers are sneezing, laughing, drug and alcohol use, bowel movements, blowing brass instruments, and lifting weights.

situational sneezing reflex Nikola Stojadinovic / Getty Images


Postural Syncope

Postural syncope is also known as orthostatic hypotension. This occurs when the blood pressure drops significantly within 15 seconds of standing. Some researchers believe this is due to vascular resistance changes occurring when the leg muscles are engaged, which affects cardiac output. The person usually recovers within one minute.

orthostatic hypotension postural RealPeopleGroup / Getty Images


Postural Orthostatic Tachycardia Syndrome

Postural orthostatic tachycardia syndrome (POTS) is a rare condition that increases the heart rate by at least 30 beats per minute when the person stands from a lying or sitting position. Symptoms include fatigue, lightheadedness, and palpitations. Because it is so rare, doctors must usually rule out all other causes before they can make this diagnosis. POTS typically affects young women and does not worsen with age.

Postural Orthostatic Tachycardia Syndrome courtneyk / Getty Images


Cardiac Syncope

Cardiac syncope can be caused by a variety of heart conditions. People at higher risk for cardiac syncope include men, people older than 60, and those with brief palpitations, a diagnosis of known heart disease, and having an abnormal cardiac exam. Older adults have a sharp increase in cardiac syncope after age 70.

cardiac symptoms heart KatarzynaBialasiewicz / Getty Images


Premonitory Symptoms

People who experience syncope may be able to feel an episode coming on. These premonitory symptoms include nausea, lightheadedness, and heart palpitations. Other signs are feeling dizzy or drowsy, headaches, and vision changes like tunnel vision or seeing spots. When these symptoms appear, sitting or lying down can prevent a fainting episode.

Premonitory Symptoms Stop Kanawa_Studio / Getty Images



Since most syncope is vasovagal and, therefore, benign, testing rarely results in a diagnosis. Diagnostic tests are based on physical exams and patient history. In the emergency room, common blood tests for a patient with syncope include electrolyte, glucose, and hemoglobin along with an ECG. A thorough cardiac workup can identify cardiac etiology, and a CT, MRI, or carotid ultrasound can find perfusion problems in the head or neck.

ECG test monitor Thierry Dosogne / Getty Images



Treatment of syncope episodes depends on the cause. Cardiovascular syncope often resolves with treatment of the underlying cardiac condition. Orthostatic hypotension can be controlled by sitting and standing slowly and avoiding certain heart medications. It is also important to drink enough fluids. For common vasovagal syncope, people can prevent future episodes by avoiding stimuli and situations that have caused problems in the past.

treatment cause doctor Thomas Barwick / Getty Images


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