Fainting, otherwise called syncope in medical parlance, results from a temporary and often sudden drop in the amount of blood that flows to the brain. While this may be from many non-serious causes, fainting may sometimes indicate a serious underlying medical issue requiring prompt attention.

Every episode of fainting must therefore be treated as a medical emergency until the cause is identified and proper treatment initiated. Most patients can prevent problems with syncope once they get an accurate diagnosis and proper treatment. In this article, we look at why fainting occurs and when to seek medical treatment.

How common is fainting (syncope)?

Fainting or syncope is a common condition. It affects three to five per cent of the population at some point in life and is a frequent cause of visits to A&Es, accounting for about five per cent of emergency room visits. Fainting appears to be more common in older individuals and may affect up to six to 10 per cent of people older than 75 years of age. The condition can occur at any age and happens in people with and without other medical problems.

Fainting is a survival mechanism and usually results from a lack of adequate oxygen delivery to the brain. Fainting occurs when there is a sudden drop in blood pressure, a drop in heart rate, or changes in the amount of blood in areas of the body. These aberrations occur when the body fails to properly regulate or respond to changes in posture, blood pressure, heart rate or blood volume. These regulatory activities are performed by the autonomic nervous system.

A normally functioning autonomic nervous system is therefore essential to prevent fainting episodes. Many times, patients feel an episode of an impending syncope. They may have what are called “premonitory symptoms,” such as feeling nauseous, light-headed, and heart palpitations. 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.

The Autonomic Nervous System (ANS)

The ANS automatically regulates and controls many essential bodily functions such as breathing, blood pressure, heart rate and postural responses to blood pressure and heart rate. The ANS functions without our input and so these activities occur seamlessly without our notice or active participation.

Types of Fainting

There are several different types of syncope or fainting disorders. We will address only the most common types. The type you have depends on what causes the problem.

Vasovagal syncope (also called neurocardiogenic syncope)

Vasovagal syncope is the most common type of syncope and is responsible for most fainting disorders especially in young persons. This is caused by a sudden drop in blood pressure, which causes a drop in cardiac output and ultimately, a decrease in blood flow to the brain leading to temporary loss of consciousness.

When you stand up, gravity causes blood to settle in the lower part of your body, below your diaphragm. With increased amount of blood pooling in your lower extremities, there is less blood returned to the heart. The decreased blood return to the heart results in the reduced amount of blood pumped out by the heart with each beat (stroke volume). This will result in a reduction in cardiac output which is the sum of the blood pumped out by the heart with each heartbeat. When that happens, the heart and ANS work to keep your blood pressure stable.

In a normal functioning autonomic nervous system, various activities are triggered between the heart and the brain to appropriately adjust blood pressure and heart rate to maintain equilibrium. In individuals with neurocardiogenic syncope, the ANS fails to function properly and mixed messaging occurs between the heart and the brain leading to a brief loss of consciousness and fainting occurs. Individuals tend to recover consciousness quickly after the fainting episode. There are many types of vasovagal syncope, but three main types are classified under neurocardiogenic syncope (NCS). One type manifests mainly with severe drop in blood pressure, another with profound fall in heart rate and the third type is a mixture of abnormal blood pressure and abnormal heart rate response to posture.

Situational Syncope

Situational syncope is also a type of vasovagal syncope and, as the name implies, happens only during certain situations. In these situations, the autonomic nervous system is affected and fails to respond appropriately or adequately leading to fainting. Some of these situations include:

• pain

• dehydration

• urinating (micturition syncope)

• hunger

• fear

• intense emotional stress

• anxiety

• use of alcohol or drugs

• coughing forcefully, turning the neck, or wearing a tight collar (carotid sinus hypersensitivity)

Postural Orthostatic Hypotension Syndrome (POHS)

Some patients with vasovagal syncope have a condition called postural orthostatic hypotension syndrome (POHS). 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.

Postural syncope is caused by a sudden drop in blood pressure due to a quick change in position, such as rising from lying down to a standing position. Postural hypotension and fainting may result from certain medications that cause drop blood pressure or cause intense vasodilation of the blood vessels in the lower extremities.

Dehydration can also lead to this condition. Patients with this type of fainting usually have changes in their blood pressure that cause it to drop by 20 mmHg (systolic/top number) and at least 10 mmHg (diastolic/bottom number) when they stand.

Postural Orthostatic Tachycardia Syndrome (POTS)

Yet another group of individuals may have a condition called postural orthostatic tachycardia syndrome (POTS). POTS affects blood flow and usually manifests with uncomfortable rapid increase in heart rate associated with lightheadedness and fainting. This often occurs when rising from a reclining position and relieved by lying down or sitting.

POTS is a condition that is most seen in women but may also occur in men. POTS is thought to be caused by a rapid acceleration of heart rate (tachycardia) that occurs when a susceptible individual rises from a sitting or lying down position. In this condition, the heart rate may accelerate by more than 30 beats per minute within 10 minutes of rising from a sitting or lying position.

Cardiac Causes of Fainting

Fainting may occur when there are issues with the heart or blood vessel that affects blood flow to the brain. These conditions include structural heart disease (the way the heart is formed), blockage in the blood vessels to the heart (myocardial ischemia), valve disease, blood clot to the blood vessels in the lungs, heart failure or an abnormal heart rhythm (arrhythmia).

Neurologic Causes of Fainting

Certain neurologic conditions may lead to fainting or fainting-like disorders. Such neurologic conditions that may lead to fainting or fainting-like disorders include seizure, stroke, or transient ischemic attack (TIA). Other less common conditions that lead to neurologic syncope include migraines and normal pressure hydrocephalus.

COVID-19 and Fainting

Many studies have described several cardiovascular manifestations of COVID-19, including myocardial ischemia, myocarditis, thromboembolism, and malignant arrhythmias. However, syncope (fainting) appears to be an infrequent presenting complaint with COVID-19. What we have recently observed at HIC is that several individuals who have recovered from COVID-19 appear to be experiencing fainting and other symptoms suggestive of impairment in the function of the autonomic nervous system. A few reports have emerged in the medical literature suggesting that this may be a phenomenon to monitor.

Diagnosis of Fainting

If you have had a fainting episode or suffer from recurrent fainting episodes, it is important that you see a doctor, preferably a cardiologist with specialised training in diagnosing or managing syncope for a complete evaluation.

The evaluation begins with a careful review of your medical history and a physical exam.

You would most likely have several tests performed to help your doctor determine the cause of your syncope (fainting). 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.

Do I need CT scan of the head to diagnose the cause of fainting?

The answer for the most part is an emphatic ‘No’. A CT scan may be necessary only if other causes have been excluded and there are other neurologic signs to suggest a neurologic cause of fainting.

Often, patients present to the A&E after a fainting episode and are referred to do a CT scan of the brain. Unfortunately, there is no data to support such an approach unless there are associated neurologic findings or the patient has suffered a head injury following the fainting episode. Otherwise, CT scan of the brain for routine evaluation of fainting disorder has a very low yield and is of very limited value in identifying the cause of fainting.

What is a Tilt Table Test?

A tilt table test is a test done to evaluate symptoms of syncope (fainting). This test is done routinely at the Heart Institute of the Caribbean locations in Kingston and Mandeville and will soon be offered at our Montego Bay location

Tilt table test is the most important diagnostic tool for fainting. When properly done, a properly interpreted tilt table testing will yield important diagnostic clues for most fainting disorders, especially those secondary to neurocardiogenic syncope.

The purpose of a tilt table test is to determine the cause of fainting by simulating changes in posture from lying down to standing. During the test, the patient will be required to lie flat on a special table with special safety belts and a footrest while connected to electrocardiogram (ECG), pulse oximeter and blood pressure monitors. The tilt table is then elevated to a 60° to 80° vertical angle to simulate standing up from a lying position. The blood pressure and ECG are measured every minute during the test to evaluate blood pressure and heart rate changes in response to postural changes. If fainting occurs during the test, the table is quickly returned to a flat position to help restore consciousness. The information collected will be used to make a diagnosis of the cause of fainting and determine the best treatment options for the patient.

In addition to evaluation of patients with fainting disorders, tilt table testing is also used as a diagnostic for patients with the following conditions:

• Unexplained low blood pressure (hypotension)

• Fast heart rate or tachycardia when standing.

• Orthostatic palpitations.

• Unexplained dizziness (unexplained)

• Lightheadedness.

• Unexplained frequent or recurrent falls.

Other tests that may be done to make a proper diagnosis of fainting may include blood work to exclude anaemia or metabolic changes, electrocardiogram to check the heart’s electrical activity, 24-hour Holter monitoring to evaluate the heart’s electrical activity over an extended period, echocardiogram to exclude valve or structural heart problems. If no diagnosis is made and fainting continues to occur, vestibular function testing and more comprehensive testing of the autonomic nervous system may be required.

Treatment

In most cases of vasovagal syncope, identifying and avoiding the fainting triggers provide significant benefit to patients. Non-drug therapies like finding ways to decrease the pooling of blood in the legs are often effective. These may include foot exercises, wearing compression stockings or tensing the leg muscles when standing.

We frequently would recommend liberalisation of salt in the diet for individuals without pre-existing high blood pressure. Avoiding prolonged standing especially in hot, crowded places and drink plenty of fluids is a very effective solution.

For individuals with recurrent fainting episodes and positive tilt table testing unresponsive to nondrug therapies above, several medications like fludrocortisone acetate and midodrine have been shown to be helpful. Another class of drugs called selective serotonin inhibitors may also provide relief.

On rare occasions, it may be appropriate and necessary to insert an electrical pacemaker to regulate the heartbeat in some individuals with vasovagal syncope who have been refractory to other treatment options.

Dr Ernest Madu, MD, FACC, and Paul Edwards, MD, FACC are consultant cardiologists at Heart Institute of the Caribbean (HIC) and HIC Heart Hospital.

Dr Madu is a main TED Speaker whose TED talk has been translated into 19 languages, seen, and shared by more than 500,000 viewers. He has received the Distinguished Cardiologist Award, the highest award from the American College of Cardiology, and has been named among the 100 most influential people in health care and among the 30 most influential in public health. Dr Madu is also a recipient of the Global Health Champion Award from the University of Pennsylvania. He is also past CEO of HIC and is currently the chairman of IHS Holdings Ltd, an asset management company with interests in the USA, Africa, and the Caribbean.

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