Passing out heart condition

Fainting: Is It Your Head or Your Heart?

Fainting, also called passing out, can be frightening. But it’s actually a common occurrence. An estimated one in three people will faint at some point in their lives.

The person usually regains consciousness within a few minutes, recovers quickly, and returns to normal. But sometimes fainting can signal a serious medical condition, even heart disease, so getting to the reason behind the incident is important.

The Signs and Causes of Fainting

Fainting occurs when one’s blood pressure suddenly drops, resulting in a decrease of blood flow to the brain.

A number of things can affect blood pressure, from abrupt changes in posture (like going from lying down to standing), dehydration, and certain medications. Feeling faint can include dizziness, lightheadedness, and nausea. One’s field of vision may even “black out.” This loss of consciousness triggers a loss in muscle control. That’s what causes the person to fall to the ground.

One of the most common types of fainting is caused by a sort of crossed signal between the brain and the vagus nerve, a large nerve that runs from the brain to the stomach. When this nerve is overstimulated, a person may faint. In such cases, you can usually figure out the reason — maybe you were standing for a long time, fainted at the sight of blood, or due to some kind of emotional distress, trauma, or pain.

Some people faint because they’ve suddenly constricted their carotid artery (the artery in the neck) by turning their head abruptly or wearing a too-tight collar. Straining to make a bowel movement or even urinating can sometimes cause fainting, too.

Fainting can also occur in people who have hypoglycemia, or low blood sugar, most common among diabetics because of fluctuating insulin levels. Dehydration can also cause fainting, particularly in the elderly. Certain types of medications, including

diuretics, heart medications, psychiatric drugs, antihistamines, and narcotics, can also trigger a fainting episode, as can alcohol.

The following can cause fainting, too:

  • Diseases of the autonomic nervous system. Your autonomic nervous system is the part of the nervous system that controls involuntary vital functions, such as the beating of your heart, the degree to which your blood vessels are constricted, and breathing. Autonomic nervous system problems include acute or subacute dysautonomia, chronic post-ganglionic autonomic insufficiency, and chronic pre-ganglionic autonomic insufficiency. If you have one of these disorders, you are likely to have other symptoms, such as erectile dysfunction (inability to have or maintain an erection), loss of bladder and bowel control, loss of the normal reflexes of your pupils, or decreased sweating, tearing, and salivation.
  • Conditions that interfere with the parts of the nervous system that regulate blood pressure and heart rate. These conditions include diabetes, alcoholism, malnutrition, and amyloidosis (in which waxy protein builds up in the tissues and organs). If you take certain high blood pressure drugs, which act on your blood vessels, you may be more likely to suffer from fainting. If you are dehydrated, which may affect the amount of blood in your body and, thus, your blood pressure, you may be more likely to faint.
  • Heart or blood vessel problems that interfere with blood flow to the brain. These may include heart block (a problem with the electrical impulses that control your heart muscle), problems with the sinus node (a specialized area of your heart that helps it beat), heart arrhythmia (irregular heart rhythm), a blood clot in the lungs, an abnormally narrowed aortic heart valve, or certain other problems with the structure of your heart.
  • Conditions that may cause unusual patterns of stimulation to particular nerves. These include micturition syncope (fainting during or after urination), glossopharyngeal neuralgia (fainting due to inflammation and pain in a particular nerve to the mouth); cough syncope (fainting after intense coughing), and stretch syncope (fainting that occurs when stretching the neck and arms).
  • Hyperventilation. If you become intensely anxious or panicked and breathe too quickly, you may feel faint from hyperventilation (taking in too much oxygen and getting rid of too much carbon dioxide too quickly).

Syncope (Fainting)

The sudden, transient, loss of consciousness in an individual is known as syncope or fainting. Syncope typically lasts for seconds or minutes and is usually followed by a complete recovery. Although the act of syncope can be terrifying, it is usually harmless and most likely does not signify a serious disease or a life threatening problem.

For most people, syncope occurs once or twice in a lifetime; for others, various medical conditions may lead to numerous fainting spells throughout their life. Anyone who experiences syncope should always notify a doctor immediately. If physical injury occurs as a result of fainting, then one should call 911 and head to the closest emergency room.

Syncope Causes

There are numerous causes of syncope that fall into two broad categories:

  • Cardiogenic syncope: This type of syncope is heart-related, caused by either an abnormal heart rhythm or structural damage to the heart. This is a dangerous form of syncope.
  • Non-cardiogenic syncope: This type was not caused by a heart problem, but rather a transient drop in blood pressure, heart rate, or change in vagal tone, most of which is controlled by the autonomic nervous system. In some people, despite numerous tests, no obvious cause is ever found.

Syncope Diagnosis

It is always important to see a doctor if you have fainted. The doctor will need to know the history surrounding the event, which is very important when trying to determine the cause of the syncope. For example, symptoms such as dizziness, sweating, nausea, diarrhea, vomiting, headache, visual changes, abnormal body movements, loss of control of bowel or bladder, and chest pain are important clues. In addition, it is also helpful to convey what you were doing when the event occurred. Many benign fainting spells are triggered by a vasovagal reaction (a sudden, transient drop in blood pressure resulting in a temporary loss of consciousness), which typically occurs during activities such as eating, urinating , defecating, or standing for long periods.

Medical history (including medications) and age are also important when trying to determine the cause of syncope. Older people are at higher risk for serious conditions and diseases that may lead to syncope. People with known heart conditions, alcohol or drug problems, known seizure disorders, diabetes, or neurological disorders are more likely to have fainting spells.

A variety of tests, mostly cardiovascular, are used when trying to determine the cause of syncope. Treatment for the syncope will depend on the cause. These tests include:

  • electrocardiogram (ECG or EKG)
  • event/holter monitor
  • echocardiogram
  • neurologic testing
  • tilt table testing
  • electrophysiology study.
  • implantable loop recorder (sometimes)

Syncope (Fainting)

What is syncope?

Syncope (SINK-a-pee) is another word for fainting or passing out. Someone is considered to have syncope if they become unconscious and go limp, then soon recover. For most people, syncope occurs once in a great while, if ever, and is not a sign of serious illness. However in others, syncope can be the first and only warning sign prior to an episode of sudden cardiac death. Syncope can also lead to serious injury. Talk to your physician if syncope happens more often.

Pre-syncope is the feeling that you are about to faint. Someone with pre-syncope may be lightheaded (dizzy) or nauseated, have a visual “gray out” or trouble hearing, have palpitations, or feel weak or suddenly sweaty. When discussing syncope with your doctor, you should note episodes of pre-syncope as well.

Becoming unconscious due to a seizure, heart attack, head injury, stroke, intoxication, blow to the head, diabetic hypoglycemia or other emergency condition is not considered syncope.

Someone who faints should be moved so they are lying down to allow blood to flow to the brain. If they do not regain consciousness promptly, start CPR.

What causes syncope?

Syncope occurs when there is not enough blood flow to the brain. There are many potential causes, but the most common ones include:

Serious Cardiovascular Conditions (Cardiac Syncope)

If fainting occurs frequently and is not because of dehydration or sudden postural change, you may need to be tested for a serious heart or vascular condition. Cardiac syncope often occurs suddenly, without dizziness or other pre-syncope symptoms.
Common causes of cardiac syncope:

  • Arrhythmia and abnormal heart rhythm: During episodes of heart arrhythmia, the heart works inefficiently and not enough oxygenated blood can circulate to the brain. There are many types of cardiac arrhythmias that may cause syncope. These include bradyarrhythmias (the heart beats too slowly) and tachyarrhythmias (the heart beats too fast).

  • Aortic dissection, a tear in the large artery that carries blood from the heart to the rest of the body. This is a very rare but life-threatening condition.

  • Aortic valve stenosis, a narrowing of the valve between the heart and the aorta. Aortic valve stenosis can be congenital (present from birth) or can develop in old age.

Reflex Syncope (Neurally Mediated Syncope, Vasovagal Syncope, Vasodepressor Syncope, the Common Faint)

Reflex syncope is the result of a reflex response to some trigger, in which the heart slows or blood vessels dilate (widen). This causes blood pressure to drop, so less blood flows to the brain and fainting (syncope) or near-fainting (pre-syncope) occurs. Reflex syncope is the most frequent cause of fainting.

Vasovagal syncope — the common faint — occurs in one third of the population. It is by far the most common form of reflex syncope. Vasovagal syncope is often triggered by a combination of dehydration and upright posture. But it can also have an emotional trigger such as seeing blood (“fainting at the sight of blood”).

Some Vasovagal Syncope Triggers

  • Seeing blood (not considered a serious symptom)

  • Getting an injection or having blood drawn (not considered serious)

  • Standing up quickly (a “head rush” is considered pre-syncope)

  • Standing upright for a long time

  • Sudden and unexpected trauma, stress or pain, such as being hit

  • Blood donation

Other types of reflex syncope include:

Situational syncope, a sudden reflex response to a trigger other than those listed above. Triggers include:

  • Coughing, sneezing, laughing, swallowing

  • Pressure on the chest after exertion or exercise

  • Defecating

  • Urinating (post-micturition syncope: occurs in men while standing to urinate)

  • Eating a meal

  • Sudden abdominal pain

  • Blowing a brass instrument or lifting weights

Carotid Sinus Syncope, a response in older adults that occurs when pressure is applied to the carotid artery in the neck. A hard twist of the neck, wearing a tight collar and pressing on the artery are triggers for carotid sinus syncope.

Orthostatic Hypotension

Orthostatic (upright) hypotension (low blood pressure when standing) can also cause fainting because blood has trouble going against gravity to reach the brain. Orthostatic hypotension is defined as a fall in systolic blood pressure of 20 mmg Hg or more on standing, resulting in syncope or pre-syncope. Orthostatic hypotension is common in elderly individuals and is often exacerbated by dehydration or medications that lower blood pressure, such as diuretics. Less commonly, orthostatic hypotension can be caused by a neurologic condition such as Parkinson’s disease or multisystem atrophy, formerly known as Shy-Drager syndrome.

Postural Orthostatic Tachycardia Syndrome (POTS)

Postural orthostatic tachycardia syndrome (increased heart rate when standing), or POTS, is a rare clinical syndrome characterized by an increase in heart rate of at least 30 beats per minute on standing and orthostatic intolerance — when standing brings on symptoms such as palpitations, lightheadedness and fatigue. POTS generally appears in young women. After excluding other causes, the diagnosis is made on physical examination, medical history and tilt-table test. Treatment usually consists of increased salt and fluid intake, recumbent exercise (not standing upright) and education in avoiding triggers. POTS does not usually get worse with age.

How is syncope diagnosed?

It’s important to identify the cause of syncope, if possible, to rule out a dangerous heart condition. Depending on your symptoms and circumstances, the following tests may be used to find the cause:

On-site Diagnostic Tests

  • Electrocardiogram (ECG or EKG): wires taped to various parts of your body to create a graph of your heart’s electrical rhythm

  • Exercise stress test: ECG recorded while strenuously exercising

  • Echocardiogramor transesophageal echocardiogram: ultrasound of the heart

  • Physical examination, including orthostatic vital signs and carotid sinus massage

  • Tilt table test: measurement of heart rate and blood pressure in response to upright tilt, which simulates prolonged standing

  • Electrophysiology study (EP): test that examines the heart’s electrical activity from the inside; used to diagnose many heart rhythm disorders

In-home Diagnostic Monitors

  • Holter monitor: a portable ECG you wear continuously for one to seven days to record your heart rhythms over time

  • Event monitor: a portable ECG you wear for one or two months, which records only when triggered by an abnormal heart rhythm or when you manually activate it

How is syncope treated?

The treatment for syncope will depend upon the underlying condition but may include:

  • Catheter ablation: procedure to cauterize the specific heart cells that cause abnormal heart rhythms

  • Pacemakers: device inserted under the skin below the collarbone to deliver regular electrical pulses through thin, highly durable wires attached to the heart; used to treat bradycardia, heart block and some types of heart failure

  • Implantable cardioverter-defibrillators (ICDs): a small implanted device that delivers an electrical pulse to the heart to reset a dangerously irregular heartbeat; often used to treat ventricular tachycardia or heart failure

  • Avoiding known triggers





The goal of treatment is to prevent another fainting episode. Sometimes, this can be accomplished with simple lifestyle changes. Other times, medication is needed.

Lifestyle Changes

  • Avoiding potential triggers like hot environments, prolonged standing, dehydration, certain medications
  • Consuming adequate fluid and salt
  • Wearing support stockings
  • Standing up more slowly


If you continue to have fainting spells after making some lifestyle changes, your doctor may prescribe a medication. It is helpful to determine the cause of the fainting in order to recommend the most appropriate medicine for your condition.

Pacemaker or Implantable Cardioverter Defibrillator (ICD)

If your healthcare team determines that your syncope is related to an abnormal heart rhythm, a medical device like a pacemaker or an implantable cardioverter defibrillator (ICD) may be implanted to control or reset the heart rhythm so it doesn’t beat too quickly or too slowly.

Catheter Ablation

During catheter ablation, radiofrequency energy is directed through a catheter inserted in an artery toward abnormal electrical pathways in the heart tissue that are causing an arrhythmia. This scars the tissue, normalizes the erratic electrical signals and corrects the arrhythmia.

What is fainting, and what causes it?

Different underlying causes can cause a person to faint. We discuss some of them in detail below:

Neurocardiogenic syncope

Neurocardiogenic syncope develops due to a short term malfunction of the autonomous nervous system (ANS). Some people call it neurally mediated syncope (NMS).

The ANS controls automatic body functions, including heart rate, digestion, and respiration rate.

In NMS, a drop in blood pressure slows the heartbeat and pulse rate. This temporarily interrupts the brain’s blood and oxygen supply.

Possible triggers of neurocardiogenic syncope include:

  • an unpleasant or shocking image, such as seeing blood
  • sudden exposure to an unpleasant sight or experience
  • abrupt emotional upset, such as after receiving tragic news
  • extreme embarrassment
  • standing still for a long time
  • being in a hot and stuffy environment for a long time

Occupational syncope

Occupation, or situational, syncope is a type of neurocardiogenic syncope with physical rather than emotional, mental, or abstract triggers. Triggers include:

  • laughing or swallowing
  • passing stools or urine
  • coughing or sneezing
  • strenuous physical activities, such as lifting a heavy weight

Orthostatic hypotension

Share on PinterestExcessive alcohol consumption may increase the risk of fainting.

Orthostatic hypotension refers to fainting after standing up too quickly from a seated or horizontal position.

Gravity pulls blood into the legs, bringing down blood pressure elsewhere in the body. The nervous system usually reacts to this by increasing the heartbeat and narrowing the blood vessels. This stabilizes blood pressure.

However, if something undermines this stabilization process, there may be poor blood and oxygen supply to the brain, leading to fainting.

Triggers include:

Dehydration: If body fluid levels drop, so will blood pressure. This can make it harder for the blood pressure to stabilize. Therefore, less blood and oxygen reaches the brain.

Uncontrolled diabetes: A person with diabetes may need to urinate frequently, leading to dehydration. High blood sugar levels can damage certain nerves, especially those that regulate blood pressure.

Some medications: Taking diuretics, beta-blockers, and antihypertensive drugs may cause orthostatic hypotension in some people.

Alcohol: Some people faint if they consume too much alcohol in a short amount of time.

Some neurological conditions: Parkinson’s disease and other neurological conditions affect the nervous system. This may lead to orthostatic hypotension.

Carotid sinus syndrome: The carotid artery is the main artery that supplies blood to the brain. When there is pressure on the pressure sensors, or carotid sinus, in the carotid artery, it can cause fainting.

If a person’s carotid sinus is very sensitive, blood pressure may drop when they turn the head to one side, wear a tight collar or tie, or move over the carotid sinus while shaving. This may result in fainting.

This is more common among older males.

Cardiac syncope

An underlying heart problem may reduce blood and oxygen supply to the brain.

Possible heart conditions include:

  • arrhythmias, or an abnormal heartbeat
  • stenosis, or a blockage of the heart valves
  • hypertension, or high blood pressure
  • a heart attack, in which the heart muscle dies due to lack of blood and oxygen

This cause of fainting usually requires immediate medical treatment and extensive monitoring.


It may be explained by factors such as stress, grief, overheating, dehydration, painful stimuli, exhaustion, or illness. Profound blood loss or fluid loss (severe diarrhea or vomiting) may also cause syncope. Many causes of syncope, however, are not easy to explain and are not serious. However, some are life threatening, especially fainting during exertion. The most serious causes of syncope are related to heart damage or abnormal electrical system disorders that affect the heart’s ability to pump blood efficiently. In some cases, fainting is the only warning sign of an abnormal heart rhythm (arrhythmia) that could lead to sudden cardiac arrest and death.

Types of Syncope

  • Cardiovascular syncope – The most dangerous but rare type of fainting is caused by an abnormal heart rhythm (arrhythmia) or by structural damage to the heart.
  • Non-cardiovascular syncope – The most common type (also called vasovagal type). There are a variety of causes not necessarily related to the heart. This type of syncopy is often related to problems with the autonomic nervous system (ANS), which controls functions such as heart rate and blood pressure. They may occur even in young, otherwise healthy people with normal heart function.

People with underlying heart disease are at higher risk for cardiovascular syncope, although this may be the initial symptom suggesting such a problem.

Cardiovascular Diseases


Cardiovascular syncope is a brief loss of consciousness (from a few seconds to a few minutes), that is characterized by rapid onset and spontaneous recovery. It is caused by decreased blood flow to the brain.

This type of syncope is different from other causes of fainting that occur without a decrease in cerebral blood circulation. These causes include hypoglycemia, epilepsy and stroke.

Causes and/or risk factors

The most common cause is vasovagal syncope, which is a drop in pressure with a sudden slowing of the heart. This type of syncope is often triggered by pain or emotional shock, particularly if the individual is dehydrated or has been standing for a long period. Over 20% of people in the general population experience vasovagal syncope at least once in their lifetimes. Syncope is a harmless event that does not lead to lasting effects in the majority of cases.

The other causes of syncope include heart valve disease, cardiomyopathy and pericarditis, high blood pressure medication and cardiac arrhythmia.

Vasovagal syncope is more common in young people and women. The other causes are more frequent in older people and especially in people with heart disease.


In general, your family doctor is the best person to make an initial exam, eliminate any non-heart-related causes of the fainting, and determine whether you need a more comprehensive cardiac assessment.

A cardiologist will then fill out a comprehensive questionnaire, perform a physical exam, and prescribe certain tests to confirm the diagnosis, establish the severity of the problem and determine the best treatment if he or she suspects a cardiovascular cause of the syncope.

  • Electrocardiogram
  • Holter monitor
  • Echocardiogram
  • Cardiac magnetic resonance imaging
  • Tilt table test
  • Electrophysiology study
  • Implantable heart monitor


In the case of vasovagal syncope, the doctor will recommend that you avoid becoming dehydrated. Unless otherwise contraindicated, an increase in salt intake may be recommended for some patients to promote fluid retention and an increase in blood pressure, which in this case is beneficial. Patients who experience a vasovagal reaction must try to avoid situations that have triggered syncope in the past and avoid medications that can cause a drop in blood pressure. In rare cases of severe vasovagal syncope, medication or even a pacemaker may be recommended.


The treatment of other causes of syncope depends on the specific cause. The possible treatments include an adjustment in medication, surgery to treat a valve disease, catheter ablation for fast arrhythmias, a pacemaker for a slow heart beat, or an implantable cardioverter defibrillator for patients at risk of sudden death.

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