Everyone is familiar with fainting — it’s something that happens to female heroines in movies, when their corsets are tied too tightly, or if they see something that looks totally gross.

In truth, fainting (“passing out” or “blacking out”) is a common symptom that affects about half of all people at some point. Many people will faint multiple times in their lives, and although it is usually triggered by some stressful circumstance, it may occur due to a variety of health problems, especially heart conditions.

If you’ve found yourself confused about what causes fainting spells and need a better understanding of what they mean for your health, this article is a smart place to start.

What Is Fainting?

Also called syncope (SIN-co-pee), fainting is medically defined as a sudden, temporary loss of consciousness due to a reduction of blood flow to the brain. This usually occurs because of a sudden drop in blood pressure (which normally pushes the blood uphill from the heart to the head) but it can occur if the heart isn’t pumping enough oxygenated blood. Often preceded by a sense of “lightheadedness,” the loss of consciousness can last for a few seconds to several minutes before a person comes around again.

Single spells of fainting in otherwise healthy people are relatively common and not considered dangerous, especially when triggered by factors like pain, stress, grief, dehydration or exhaustion. Often the stress of having a medical procedure (like getting your blood drawn) is enough to trigger a faint. In some cases, a severe fluid loss from vomiting or diarrhea can also cause fainting, because of the resulting drop in blood pressure.

However, some forms of fainting can be deadly, especially if it occurs during exercise or if fainting is associated with heart damage or arrhythmias (heart rhythm disturbances). The most dangerous types of fainting are directly related to heart health, and arrhythmias and fainting are often tied together.  In fact, “cardiac syncope” carries a poor prognosis if left untreated.

Common Causes of Fainting

There are several different conditions that can cause loss of consciousness, and fainting is only one of them. Others include seizures, low blood sugar, shock, and general issues with the nervous system.  Fainting is very specific and it can occur due to a number of different mechanisms including an abnormal brain reflex (“vasovagal” syncope) or heart conditions (such as an irregular heartbeat or heart valve problems).

Some forms of fainting have a genetic component and run in families. When the fainting is due to an inherited tendency towards heart arrhythmias (such as the Congenital Long QT Syndrome) there could be an increased risk of sudden death.

Vasovagal syncope is the most common cause of fainting and is responsible for about 2/3 of all fainting spells in children and adults. Generally, these spells are caused by a sudden drop in blood pressure and sometimes a dramatic slowing of the heart rate, which markedly reduces oxygen delivery to the brain. These are often triggered by stress and are associated with nausea, feelings of warmth, lightheadedness, sweating, palpitations, and eventual loss of consciousness. In about 15% of patients who faint, slight shaking and rolling back of the eyes can mimic a seizure, though it is very different from a true seizure that someone with epilepsy might experience.

Some people are prone to fainting because they have a condition that affects their body’s ability to regulate the blood pressure. Called postural hypotension or “orthostatic hypotension,” this condition can cause the blood pressure to drop if the person moves too quickly from a lying or sitting to a standing position, resulting in a fainting spell. This condition is more common in older adults who have underlying problems with their nervous system (like Parkinson’s Disease) or poor muscle tone.

Sometimes fainting spells are triggered by mental stresses rather than just physical ones. Anxiety, pain, fear, hunger, and intense emotional stress can lead to fainting, even if you have never experienced this before.

Though fainting is a very common symptom, fainting is never “normal.”  Although it may be a reflection of a benign imbalance in the blood pressure reflexes of otherwise healthy individuals, it could be the first symptom of serious heart disease and could be a warning sign of potentially fatal complications.  Even a “benign” faint can be dangerous, as a fall that occurs from sudden loss of consciousness can occasionally cause severe physical injury, especially in frail or elderly patients. Today, fainting accounts for about 3 percent of emergency room visits and 6 percent of general hospital admissions.

Connections Between Arrhythmia and Fainting

Arrhythmia (an abnormal heart rhythm) is directly responsible for about 10-20% of all fainting spells. This form of fainting is often called cardiac syncope, and can be considerably more dangerous than the benign vasovagal faint.  It may occur in the setting of structural damage to the heart itself or it may occur in people with no prior cardiac history. Signs of cardiac syncope include sudden loss of consciousness with no warning, prolonged (over 2 minutes) period of unconsciousness, convulsions, or fainting that occurs during exercise. Any person who faints with a prior history of heart disease (such as a heart attack, coronary artery blockages, congestive heart failure, or abnormalities in the heart muscle) should be evaluated by a heart specialist immediately.

If you frequently feel lightheaded or experience symptoms consistent with an irregular heartbeat, it’s important to meet with your doctor to rule out more serious problems.

Common Treatment Options for Fainting Spells

The treatment of syncope depends on the cause of the faint and the frequency of the episodes, as well as how much warning a person has. In people who faint on rare occasions, triggered by predicable stresses, with recognizable symptoms preceding the faint, treatment may not be necessary. You can discuss lifestyle changes that may help prevent future episodes with a fainting specialist.

If you regularly experience fainting spells, it’s important to schedule an appointment with your physician and meet with a specialist experienced in the diagnosis and management of this condition. The doctor will try to get as much detail about your symptoms as possible by asking questions like:

  • What are you doing right before you faint?
  • Do fainting episodes comes quickly or gradually?
  • How long do the episodes last, and how long does it take you to return to normal?
  • What kinds of symptoms do you feel just before you faint?

Along with a detailed history of your past medical problems and your family history, these questions will help your doctor narrow down the likely cause of your fainting episodes. From there, he will take your pulse and blood pressure in different positions (lying, sitting, and standing) to see if your normal reflexes are working correctly.  Sometimes a formal blood pressure test known as a Tilt Table Test may be indicated. In this test, you will be placed in an upright position using a tilting table, and then your blood pressure and heart rate will be monitored while you are standing for up to 30 minutes to see if a fainting episode can be reproduced.

If a heart arrhythmia is considered responsible, your doctor might order further testing like an ECG, echocardiogram, Holter Monitor, Event Recorder, or exercise stress test. In some unexplained cases of fainting, an implantable loop recorder (“ILR”) may be very helpful to diagnose heart arrhythmias.

As long as you meet with a professional and are candid about your symptoms, your doctor should be able to get to the root of your fainting condition without too much difficulty, ensuring that you will be back to full health soon. If your doctor is not certain of the cause or if you have any other concerns, then definitely ask to be referred to a fainting specialist.

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