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Did you recently pass out? – Syncope

Syncope is the medical term to describe passing out. This article explains all there is to know about fainting.

Syncope is a medical term that encompasses expressions like fainting, passing out, blacking out, or whiting out. In syncope, full recovery usually takes around 5 minutes or less. There are no permanent sequels (unless the fall results in significant injury). After a few minutes, the complete recovery separates syncope from other conditions like seizures, coma, or shock.

Importantly, syncope is quite common and can happen at any age, although the frequency increases with age.

Syncope accounts for 5% of all emergency room visits in the United States. Approximately 45% of the general population experiences a syncopal episode at some point in their lifetimes. There is no significant difference between men and women when it comes to syncope frequency.

Young syncope patients tend to have noncardiac causes, while in older patients, cardiovascular syncope is more frequent. In pediatric populations, syncope is relatively uncommon. I am a medical doctor, and in this article, o will describe everything there is to know about syncope. 

What is passing out?

Most of the time, when people say they passed out or fainted, they mean that they had a syncope.

Syncope, like many other medical terms, has a more strict definition than colloquial terms like passing out or blacking out.

The strict medical definition of syncope is a transient, self-limited loss of consciousness with an inability to maintain postural tone, that recovers spontaneously. This definition might be sound a bit complicated, but it is straightforward, let us break it down. 

The first, and probably more important thing, is that syncope is transient. This means it is a permanent condition like the coma. Most episodes of syncope last only a few minutes, usually less than five.

Moreover, it says self-limited, which means the patient regains consciousness by himself without needing any kind of medical assistance. When someone is brought into the emergency room for having a syncope, he or she has already regained consciousness by the time they get to the hospital (unless they live very close by).

The phrase “inability to maintain postural tone,” simply means that having a syncope involves falling down. Spontaneous recovery means that patients quickly return to their usual selves. In some cases, there might be some confusion during the first minutes of regained consciousness.

Presyncope is a sensation that you are about to faint. Presyncope symptoms might include feeling lightheaded and weak but without actually fainting or falling. Just like syncope, presyncope usually lasts for a few seconds or a few minutes at most.

Syncope ad presyncope causes are the same, including low blood pressure, heart disease, and cardiac arrhythmias.

Any episode of loss of consciousness that does not meet the syncope parameters may have other more serious causes.

What causes a person to pass out?

Fainting can be a terrifying experience for most people. In most cases, syncope is due to benign causes and tends to be a once in a lifetime kind of thing. However, in a minority of cases, syncope has a serious underlying cause and can precede a life-threatening event.

Contrary to what you might think, transitory loss of consciousness is more of a heart issue that a brain issue. Fainting happens when, for any reason, brain flood flow decreases for a few seconds or a few minutes.

Importantly, unlike most tissues in the body, the brain cannot store energy and save it up for a rainy day (like the muscles do, for example). Therefore it relies 100% on the oxygen and glucose brought by the blood to produce enough energy to function.

A cessation of cerebral blood flow of only 3 to 5 seconds is enough to produce a syncope.

Blood flow to the brain depends on three main factors:

  • Cardiac output: The amount of blood your heart pumps per minute. When there are a physical output obstruction or a significant arrhythmia that causes the heart to stop for a few seconds, cardiac output decreases, and brain blood flow decreases, in conditions like congestive heart failure, a weakened heart muscle may become momentarily unable to pump blood to the brain. 
  • Mean arterial pressure: When blood pressure suddenly decreases and the rises up again, brain blood flow can be compromised for a few seconds in between. Orthostatic hypotension probably is the best example.
  • Decreased blood volume: For example, dehydration due to diarrhea, combined with a sudden drop in blood pressure.

Conditions like brain hemorrhage, electrolyte imbalances (decreased or increased sodium and potassium, for example), or low blood glucose can mimic syncope. 

What heart conditions cause syncope?

Cardiac syncope is responsible for approximately 15% of all syncopes. The risk of having cardiac syncope increases with age, male sex, and history of heart disease.

Cardiac causes of syncope usually fall into one of the following categories:

  • Structural heart disease: Diseases like ischemic cardiomyopathy, in which past infarcts have left the heart muscle weak enough to produce heart failure. Heart valve disorders like aortic insufficiency cause blood to regurgitate into the heart, causing it to dilate. All of these conditions can result in hypotension and can transiently decrease or stop brain blood flow. These patients often take medications like enalapril, losartan, and bisoprolol that can further decrease blood pressure.
  • Cardiac arrhythmia: Arrhythmias are electrical problems of the heart that cause an abnormal heart rhythm. Sometimes an arrhythmia can cause the heart to transitory (or permanently) stop. Depending on their location, arrhythmias are divided into supraventricular arrhythmias, ventricular arrhythmias. When the arrhythmia causes the heart to beat to slow, it is a tachyarrhythmia (i.e., ventricular tachycardia). When the arrhythmia causes the heart to beat to slow, it is a bradyarrhythmia (i.e., sinus bradycardia). Some arrhythmias are permanent, and some are transitory, some are dangerous, some are not. Any arrhythmia capable of producing a syncope is probably hazardous and require treatment. 
  • Cardiac outflow obstruction: The heart is a pump that expels blood through the aortic valve into the aorta. Conditions like hypertrophic cardiomyopathy and aortic stenosis can block the outflow tract of the heart and produce sudden fainting and sudden cardiac death.
  • Other heart conditions: Several other heart conditions can also produce syncope but don’t fall into the previous two categories. These conditions include acute heart attack and pulmonary embolism.

What are the noncardiac causes of syncope?

Noncardiac causes account for the majority of syncopal episodes. In the majority of cases, noncardiac causes are benign and do not represent life-threatening conditions. We can divide them into two main groups:

Orthostatic syncope

In normal conditions, when you switch from a sitting position to a standing position, your autonomic nervous system automatically causes blood vessels to constrict to maintain stable blood pressure. Orthostatic hypotension occurs when this automatic system fails, causing transitory hypotension (lasting only a few seconds or minutes), leading to a presyncope or syncope. Some causes of orthostatic syncope include: 

  • Dehydration: by diarrhea, vomiting or fluid deprivation, and excessive exercise
  • Blood loss ( during menstruation, or intestinal bleeding)
  • Medication: antihypertensive medication, diabetes medication, and antidepressants
  • Alcohol abuse
  • Neurologic conditions: Including Parkinson, diabetic neuropathy, and multiple sclerosis

Reflex syncope

Reflex syncope or neurally mediated syncope is the most common type of syncope. It happens when certain autonomic reflexes do not work correctly, resulting in a slowed heart rate or a drop in blood pressure. There are three kinds of reflex syncope:

  • Vasovagal syndrome: Vasovagal syndrome is the most common cause of fainting; it is usually triggered by a specific factor like pain, stress, standing to long, sudden scare. Excess activation of the vagus nerve activates the parasympathetic system, causing a slow heart rate and low blood pressure. It is particularly frequent in young adults. 
  • Situational syncope: It is a form of recurrent syncope that always happens when the patient performs a specific action like laughing, sneezing, or drinking. 
  • Carotid sinus syncope: In this case, fainting occurs as a result of pressure over the carotid sinus, just beneath the jawline. Patients faint while shaving, wearing ties, tight shirts, or necklaces.  

Is syncope a sign of a stroke?

Syncope can be a sign of stroke. However, this is extremely rare. Strokes rarely cause loss of consciousness; common symptoms of stroke include one-sided weakness or paralysis, facial paralysis, incoherent words, trouble speaking or understanding language, difficulty walking, loss of coordination, and vertigo.

Most cases of stroke do not have any of these symptoms. Loss of consciousness due to a stroke is rarely transitory. Patients do not make a quick and complete recovery as syncope patients do.

A particular type of stroke that affects the cerebellum and the posterior part of the brain causes a sudden loss of balance that can result in a fall. This type of stroke (posterior stroke) can be mistaken for syncope. However, it rarely causes a loss of consciousness.

Other neurologic causes of syncope include migraines, transient ischemic attack, and normal pressure hydrocephalus. But syncope due to any of these causes is extremely rare.

Although stroke is rarely the cause of syncope, certain syncope causes are considered risk factors for having a stroke. Cardiac disease, certain arrhythmias, and orthostatic vertigo increase the risk of stroke at some point.

What drugs can cause syncope?

Many different and conventional medications can cause syncope in certain patients. Therefore a medication history should be provided in the emergency room after having a stroke. Some of the agents that can cause syncope to include:

  • Drugs that lower the blood pressure: Antihypertensive medications like ACE inhibitors (enalapril), diuretics (furosemide), drugs that dilate vessels ( nitroglycerine)
  • The ones that decrease cardiac output: Beta-blockers (bisoprolol), antiarrhythmic drugs (lidocaine)
  • Drugs that alter electrolyte levels: Mostly diuretics
  • Drugs that cause rhythm abnormalities in the heart: Tricyclic antidepressants (amitriptyline), amiodarone, quinidine, phenothiazine, amiodarone, hydroxychloroquine, ciprofloxacin, azithromycin

In the case of antihypertensive drugs, there is usually another factor that, combined with the drug, leads to syncope. For example, neither dehydration nor taking enalapril causes syncope by themselves, but combined can produce syncope in a susceptible person.

If you are currently taking any of these drugs and have suffered from syncope or presyncope, consult with your attending physician.

How often are the causes of syncope established? 

Because a syncope is a short, transitory event, and most patients are asymptomatic by the moment they reach the emergency room, finding the syncope’s cause may be challenging. Many syncopal episodes are the consequence of a transitory alteration. There is a sudden drop in blood pressure or a transient arrhythmia that disappears by the time of the examination.

A recent study shows that up to 47% of syncope episodes fall into unexplained syncope categories after initial interrogatory, physical exam, and electrocardiogram. Noncardiac syncope rarely reoccurs, and many times the exact cause is never discovered.

Cardiac syncope, on the other hand, is more dangerous and has a 1-year mortality of 30%. Patients with initially unexplained syncope with risk factors for a cardiac cause should undergo extensive testing to determine the syncope’s exact cause.  

What are the signs and symptoms of syncope?

Syncopal episodes are often preceded by warning signs and symptoms before the fainting happens. However, this is not always the case. Some warning signs include:

  • Nausea
  • Slurred speech
  • Pale skin
  • Sudden, cold sweat 
  • Numbness or dizziness
  • Rapid heartbeat
  • Headache 
  • Shakiness
  • Body weakness


If the loss of consciousness lasts for over 5 minutes, and there are not complete recovery minutes after the episode, it is not a syncope.

Is there any difference between the symptoms of cardiac syncope and the symptoms of noncardiac syncope?

Although there might not be any meaningful differences between them at first glance, there are some subtle key differences that may point towards one specific cause:

  • On average, neurocardiogenic syncopes like vasovagal syncope last 2.5 minutes. Cardiac syncope, on the other hand, lasts only 30 seconds on average.
  • Cardiogenic syncope tends to be more sudden, reflex syncope tends to have a triggering factor and has warning signs like dizziness, stomach pain, or pallor.
  • Syncope, when sitting on lying down, is highly suggestive of a cardiac cause.
  • Syncope when exercising in also suggestive of a heart origin, classically aortic stenosis, and hypertrophic cardiomyopathy produces syncope or sudden death with exertion.
  • Nausea and vomiting after the event are suggestive of vasovagal syncope.
  • Palpitations (awareness of one’s heartbeat) or having a slowed down, or speedy pulse are all signs of arrhythmic syncope.

What information is important for the doctor in the emergency room?

The first thing your doctor is going to do is assessing if the episode was actually a syncope. He might ask any of the following questions:

  • Was the loss of consciousness complete?
  • Is the episode abrupt and of a short duration?
  • Was recovery spontaneous, complete, and without any other symptoms?
  • Was there a loss of balance?

If the answer to most of these questions is yes, it is very likely the fainting was a syncopal episode. If one or more of these questions has a negative answer, your doctor might prefer to explore other diagnostics. 

A careful interrogation and a thorough physical exam are two of the essential tools doctors use to determine the cause of syncope and give appropriate treatment. Probably, the most critical question is what were you doing before fainting and if there were any precipitating factors.

 Precipitating factors include sleep deprivation, food deprivation, alcohol consumption, strong emotions, pain, or loud noises.

Vasovagal syncope always has a triggering factor like pain, seeing blood, prolonged standing, severe pain, or overheating.

On the other hand, situational syncope is triggered by activities such as urinating, swallowing, or coughing.

Before the episode and the posture, the activity is also essential; for example, in carotid sinus syndrome, there is usually a history of shaving or putting on a tie, perhaps a strong kiss in the neck.

In orthostatic syncope, there is a history of switching from sitting to standing position within 2 minutes before the episode. Syncope, when lying or sitting, is more likely to be of cardiac origin

Other factors, like a history of heart disease or diabetes, are also important. Let your doctor know what medications are you currently taking since medication syncope is a significant cause of syncope.

When should I seek immediate care?

Red flag symptoms are symptoms that should raise the alarm and prompt you to visit the emergency room immediately. Also, red flag symptoms may represent a serious underlying disease. They should be assessed by a healthcare professional as soon as possible.

Red flag symptoms in syncope include:

  • Exertional onset: It points towards hypertrophic cardiomyopathy and aortic stenosis. It usually reoccurs if not treated and can lead to sudden cardiac death. 
  • Chest pain: Points towards a coronary artery problem like a heart attack or unstable angina, both life-threatening conditions.
  • Severe headache: points towards a neurological problem, like brain hemorrhage.
  • Focal neurological deficits: This means things like one-sided paralysis, slurred speech, vertigo and loss of balance, one-sided loss of sensitivity, facial paralysis, and eye paralysis.
  • Loss of consciousness lasting for more than 5 minutes: It can be due to seizures, metabolic abnormalities, or stroke.
  • Tongue biting, usually caused by a seizure.
  • The confusion that lasts more than 30 seconds after the episode: It is seen in a post-ictal state of a seizure
  • Irregular heartbeat

What are the physical exam findings significant in syncope?

In many cases, a good physical exam provides valuable information about the probable cause of the syncope. However, unfortunately, this isn’t always the case. Some useful findings your doctor might use to make a diagnosis include the following:

  • Tachycardia (accelerated pulse): Might be a symptom of arrhythmia, low blood volume due to dehydration, heart attack, pulmonary embolism.
  • Bradycardia (slow pulse): Might be a sign of arrhythmia, cardiac conduction defect, and a heart attack.
  • Blood pressure sitting and standing: Postural changes in blood pressure point towards syncope caused by coronary hypotension. 
  • Fever: Might point towards a triggering factor such as urinary infection or pneumonia.
  • Rapid fingerstick test for blood glucose: Low blood glucose can mimic the syncope symptoms, and patients usually improve after IV glucose administration. Hypoglycemia is a widespread side effect of diabetes treatment. It should always be considered in a diabetic patient with a loss of consciousness.
  • Auscultation of heart sounds: Your doctor will likely want to hear your heartbeats with the help of his stethoscope. Irregular heartbeats can point towards an arrhythmia, and murmurs are a sign of Valvular defects like aortic stenosis. 
  • Neurological examination: Patients with true syncope should have a completely normal mental status and an unremarkable neurologic exam.
  • Look for trauma: Syncope involves falling; the doctor should rule out any fractures. In some cases determining if the fainting resulted in the fall or the fall was resulted in the fainting, the fewer the witnesses, the easier to get confused. Patients with true syncope to recall falling, some patients with loss of consciousness due to trauma can have some recollection of the fall. 

What lab tests and other studies are required in syncope?

So far, no specific testing has an absolute indication in the diagnosis of syncope; the choice of tests will mainly depend on the history and the findings in the physical exam. Some tests are more frequent than others; here is a list of the most common tests in syncope assessment:

  • Complete blood cell count: It is done because of the protocol in most cases. However, the diagnostic yield in syncope is quite low. Anemia appears to suggest poorer outcomes, according to some studies.  
  • Electrolyte levels: Abnormalities in potassium can cause dangerous heart arrhythmias, other than that electrolyte levels are not particularly useful in syncope, only when suspecting seizures or prolonged loss of consciousness.
  • Cardiac enzymes: In patients with chest pain or a history of heart disease.
  • Uranalysis: In the elderly, a urinary tract infection is common and can precipitate syncope. Besides, in the elderly urinary tract infections can present with syncope as the only symptom.
  • Electrocardiogram: Electrocardiography is the study with the highest diagnostic yield in syncope. It is the only exam recommended in every medical guideline for syncope since the year 2007. It is an essential tool for risk stratification in syncope patients; normal EKG findings are a good prognostic sign and decrease the risk of having a serious or life-threatening condition. Abnormal findings in the EKG of syncope patients include heart attack or coronary disease, arrhythmias, cardiac blocks, and Brugada syndrome. However, it is worth noting that some arrhythmias are transitory and may not appear in a routine EKG (more on this later). 
  • Echocardiography: Although it is not a routine test in syncope, it is the gold standard in diagnosing mechanical cardiac causes of syncope in patients with a suggestive history and physical exam.
  • Radiography: In elderly patients that present pneumonia without typical symptoms.

What if there is no specific diagnosis after a day in the emergency room?

Often, doctors do not reach a final diagnosis in the first visit to the emergency room, in those cases, the patient remains under observation for a few hours and then is discharged for further evaluation in an outpatient setting.

When leaving the emergency room, your doctor might provide you with a Holter monitor for 24-hour monitoring. A Holter monitor is a small, battery-powered device that measures your heart rhythm and rate for 24 hours or more.

The idea is to detect any off on and on arrhythmia that did not appear on the initial EKG in the emergency room. The device has electrodes that read your heart rhythm the same way as a typical EKG does, with the added advantage that you can wear it during your everyday activities and for long periods. It is essential to keep the monitor close to your body during the testing period to get accurate readings.

Your doctor should teach you how to reattach the electrodes if any of the breaks lose. You should engage in your normal activities while wearing the monitor. That way, it makes more accurate reading of how your heart typically works on a typical day. It also helps your doctor determine how your heart responds to certain activities. However, it is vital to avoid showering, bathing, and swimming while wearing the monitor. Wearing a Holter monitor is painless, and there are no risks involved.

Your doctor might also suggest a treadmill or effort test in an outpatient setting. During this test, you will be asked to exercise on a treadmill while hooked up on an EKG machine; this allows your doctor to see how your heart responds to exercise. It helps to discard a coronary artery problem

How is the vasovagal syncope diagnosed?

The diagnosis of vasovagal is mostly a clinical and exclusion diagnosis. Your doctor will suspect it if your syncope occurred after a trigger like standing up for too long, being scared, hearing a loud noise, or being exposed to too much heat.

The absence of cardiovascular risk factors, palpitations, and orthostatic hypotension also points towards a vasovagal cause. Normal blood work and EKG in a young patient without any other abnormalities is the diagnostic hallmark of vasovagal syncope.

The tilt-table test can help confirm the diagnosis in many cases, but not always. The tilt-table test as it sounds, it allows a medical professional to adjust the angle of the flat top you are lying in. It changes a person’s position quickly to see how the blood pressure and the heart respond.

The test lasts for about an hour and a half if you don’t experience any significant changes in your vital signs during the test. On the other hand, if your vital signs change substantially during the test or you feel extremely unwell, the doctor will suspend the test immediately. Besides, it probably has all the information it needs by this point. 

Doctors usually ask patients not to eat two to eight hours before the test; this will minimize the risk of vomiting.

Most of the time, you can drive yourself home after the test. However, suppose you fainted or fell during or after the test. In that case, your doctor may refer you to stay overnight for observation. If you feel extremely nauseous after the test, the nurse might provide some anti-vomit medication.

Is a head CT mandatory?

Many people think fainting represents a neurological issue rather than a heart problem, so logically they might expect a head CT right after the episode. However, a CT of the head is not a routine test in syncope.

Head CT can help patients with other neurological symptoms like paralysis or slurred speech and those with significant head trauma due to the fall. 

What should I do if I pass out?

If you experience any warning signs like lightheadedness, cold sweat, or blurred vision, stop whatever you are doing and try to lie down for a while.

Try lowering your body and elevating your legs higher than your head; this helps improve blood flow to the brain and, in some cases, might prevent the syncope from happening.

This technique also prevents falls that can cause fractures or a severe head injury. After the episode subsides call your doctor or go to the emergency room, try not to drive yourself there ask a family member or friend to take or call an ambulance.

What should I do if I see someone faint?

If a person faints around you and doesn’t regain consciousness in the next minute, call an ambulance or any other emergency services in your community.

While waiting for help to arrive, gently roll the person to his side, make sure they have a pulse, and breathe. Also, lose any tight clothes or garments that might obstruct breathing, such as ties, necklaces, or scarfs. Remember, never, for any reason, leave them alone.

What is the proper treatment for syncope?

Although syncope can be due to a serious condition in some cases, it is not generally an emergency. Propper treatment depends on the cause.

Carotid sinus syncope treatment, for example, consists of educating the patient about their condition and instructing them to avoid tight collars and being careful when shaving are essential starting points. In some cases, these patients might require the installation of a permanent pacemaker at some point

Orthostatic syncope treatment also consists of educating the patient. Important instructions include advising patients to elevate their beds’ heads to prevent rapid fluctuations when arising to bed, avoiding standing up suddenly.

The medications these patients take should be carefully reviewed to eliminate any hypotensive drugs. Keeping hydrated and drinking great amounts of water can also help to prevent episodes of orthostatic hypotension. Medications like mineralocorticoids and midodrine can help patients in which prevention by itself is not enough.

Vasovagal syncope does not require any specific treatment most of the time. In most cases recognizing and avoiding triggers is more than enough. In cases where repeated fainting is affecting daily life, pharmacologic treatment can be beneficial. 

Antidepressants like fluoxetine can regulate the nervous system response that leads to vasovagal syncope, corticosteroids like prednisone help raise fluid levels and avoid hypotension and adrenergic drugs also help to elevate blood pressure. Severe cases require a permanent pacemaker.

Many cardiac arrhythmias do not require any treatment. However, when they become symptomatic in the form of syncope, treatment with anti-arrhythmic drugs is almost always needed.

Some examples of antiarrhythmic medicines include quinidine, beta-blockers, lidocaine, verapamil, and diltiazem. Some cases do not respond to medical treatment and require a permanent pacemaker

Cardiac mechanical obstruction can be treated with beta-blockers, but most valvular diseases require the valve’s surgical replacement.

How can I prevent syncopal episodes?

The best way to prevent a syncopal episode is to detect what triggers the events and avoiding those triggers.

Some triggers can even be compensated with training. For example, people who faint from standing up for too long benefit from flexing and exercising their feet to avoid blood from pooling in them. Using compression socks is also very helpful.

Drinking plenty of fluids, and keeping yourself hydrated most of the time can also prevent syncope due to low blood pressure. 

What are the most critical points to take from this article?

  • Syncope is a ubiquitous symptom. Most of the time, it doesn’t represent anything serious and is not a medical emergency.
  • Ruling out cardiovascular causes is the most critical part of the medical assessment for syncope.
  • Let your doctor know about any medications you are taking, previous medical records, and what you were doing at the time of the attack.
  • If you feel you are about to faint, try switching to a resting position in which your feet are placed above your head.
  • If someone does not regain consciousness within 5 minutes, has other neurological symptoms, and doesn’t make a full recovery seconds after the episodes. Probably, it is not a syncope.

Are you having episodes of syncope?

This tool is a syncope symptoms checker. It gathers the most important signs, symptoms, and risk factors of the conditions underlying this symptom.

It will aid anybody who uses it to know if it has probabilities of developing the conditions that prompt this symptom besides if you have been suffering from syncopes; this tool would also help to determine that, indeed, it is syncope and not another disease.

The most important feature about the syncope symptoms checker is that it is free and would only take you a few minutes.

What do you think?

Written by Dr. Esteban Kosak

Doctor of Medicine - MD Recently Graduated from Medical School and inspired to aid the global population during this situation. I think that we shall no longer be waiting to see a doctor when we feel sick. Several times we feel disease searches in Google drive us to a rabbit hole and come out thinking that we may die of cancer or something very serious, given that symptoms may seem to fit a wide variety of illnesses. Since I recently graduated from medical school. I have all the medical information fresh in my mind. My thorough experience as an expert researcher allows me to very-well known the different diseases and conditions that affect human bodies. Empowered by the United Nations 17 Sustainable Development Goals (SGDs). I think that we all can provide a grain of sand to help humanity. That's why we created Symptoms.Care a place where you can come and screen your symptoms and find what different illnesses can be related to them. Armed with the right information you can instantly, discretely, secure and from the comfort of your home talk with a Doctor that can Evaluate your Symptoms and help you seek the right treatment.


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