Syncope (Fainting)

Woman with hand on her forehead on the ground after faintingFainting (syncope) is a sudden transient loss of consciousness. It most often happens when the blood pressure is too low (hypotension) and the heart does not pump enough oxygen to the brain. Typically, a fainting spell lasts only a few seconds or minutes, and then the person regains consciousness. Fainting is common and a single spell usually is not serious. 

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.

The risk of cardiovascular syncope increases with age. Cardiovascular syncope usually is sudden. There may be no warning signs that an individual is about to faint. 

Signs of Cardiovascular Syncope

Cardiovascular syncope is usually sudden. There may be no warning signs that an individual is about to faint. Some people do feel the following:

  • Shortness of breath
  • Heart palpitations (feeling like your heart is racing, pounding, or fluttering)
  • Pain, pressure, tightness, or discomfort in the chest
  • Loss of consciousness

Cardiovascular Syncope and Long QT Syndrome

Fainting is the primary symptom - and may be the only warning sign - of Long QT Syndrome (LQTS), an inherited electrical disorder of the heart. LQTS is believed to be a common cause of sudden and unexplained death in children and young adults. It may occur in as many as 1 in 2,000 individuals and causes up to 4,000 deaths in children and young adults each year in the United States.

There are two types of syncope (fainting) to watch out for:

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.

Risk Factors for Cardiovascular Syncope

The risk of cardiovascular syncope increases with age. Those at greatest risk are people who have any of the following conditions:

  • Coronary artery disease (clogged blood vessels to the heart)
  • Chest pain caused by angina (lower blood supply to the heart)
  • Prior heart attack (myocardial infarction)
  • Ventricular dysfunction (weakness in the heart's pumping chambers)
  • Cardiomyopathy (structural problems with the heart's muscles)
  • An abnormal electrocardiogram (a common test to check for abnormal heart rhythms)
  • Recurrent episodes of fainting that come on suddenly and without warning
  • Fainting during exertional activity or exercise
  • Some congenital heart defects or syndromes (like William's syndrome)
  • Channellopathies (defects of the electrical system of the heart) like Long QT syndrome and Brugada Syndrome

Syncope is a symptom that can be caused by many different factors. When it comes to treatment, there is no "one size fits all" approach, making an accurate diagnosis very important.

Treatment should address the underlying cause of syncope.

Depending on the diagnosis, cardiovascular syncope may be stopped or controlled with one or more of the following therapies:

  • Simple reassurance, proper hydration, anticipatory guidance, safety precautions, and increased salt intake are helpful for common type fainting (vasovagal syncope) especially in children and young adults.
  • Insertion of a pacemaker is the standard treatment for syncope caused by a slow heartbeat (bradycardia). The pacemaker continuously monitors the heart's natural rhythm. It delivers an electrical impulse to stimulate (pace) the heart's muscle contractions if the heart rate drops below a certain number of beats per minute.
  • Treatment for a rapid heartbeat (tachycardia) depends on whether it occurs in the upper chambers (atria) or lower chambers (ventricles) of the heart. These treatments may include:
    • Medications to control irregular heart rhythms or underlying disease.
    • Catheter ablation, which is a procedure in which one or more flexible, thin wires (catheters) are inserted using x-ray or three dimensional computerized navigation system guidance into the blood vessels and directed to the heart muscle. Most commonly, a burst of energy heats and destroys very small areas of tissue that cause abnormal electrical signals.
    • Cardioversion is a controlled, electric shock that is delivered to restore the heart's normal rhythm. It is most often used to treat abnormal rhythms that come from the heart's upper chambers or atria.
    • An implantable cardioverter defibrillator (ICD) is a pacemaker-like device that continually monitors the heart, and delivers a life-saving shock if a dangerous heart rhythm is detected. The device significantly improves survival in certain groups of patients who are at high risk for a deadly heart rhythm disorder called ventricular fibrillation (VF). VF is the primary cause of sudden cardiac arrest, also known as sudden cardiac death.