Basic Facts

  • Syncope (fainting) is a sudden temporary loss of consciousness, which results when the blood pressure falls sufficiently to reduce the amount of oxygenated blood reaching the brain.
  • Syncope is characterized by rapid onset, short duration and spontaneous complete recovery. 
  • Since syncope can occur without warning, some people who have syncope also have injuries related to falling or other accidents.
  • Heart disease, including blocked coronary arteries, arrhythmias, and congestive heart failure, can cause syncope.

Treatment for syncope focuses on identifying and treating the underlying cause. 

Syncope often recurs, and it can be harmless or life threatening. Therefore, people who experience an episode of syncope should seek medical attention.

Physicians group syncope into three categories: 

  • Noncardiac syncope,
  • Cardiac syncope, and
  • Syncope whose cause is unknown. 

Most commonly, syncope does not occur because of a heart condition (noncardiac syncope). 

Cardiac syncope results from abnormal heart rhythms or a disorder that reduces the heart's ability to pump enough blood to meet the body's needs. 

Syncope often occurs without any symptoms. Symptoms can include:

  • Lightheadedness
  • Sweating, 
  • Dizziness,
  • Weakness,
  • Visual disturbances,
  • Nausea, and
  • Pallor.


Causes of non-cardiac syncope include:

  • Malfunction of the body’s blood pressure regulation system (neurocardiogenic syncope, or vasovagal syncope),
  • Syncope can be precipitated by:
    • Being in a crowded area,
    • Being in a warm area,
    • Emotional stress,
    • Pain,
    • Dehydration,
    • Rising suddenly from a prone position,
    • Vigorously coughing, swallowing, or straining to defecate,
    • Narrowed carotid arteries,
    • A stroke or transient ischemic attack,
    • Diabetes,
    • Autonomic nervous system disorders such as a spinal cord injury, and
    • Medications such as antihypertensives, antidepressants, or Parkinson's drugs.

Cardiac syncope is caused by rhythm abnormalities or other conditions that can reduce
the amount of blood that reaches he brain, including:

  • Sick sinus syndrome (abnormal heart rhythm),
  • Heart block (abnormal heart rhythm),
  • Ventricular arrhythmias (abnormal heart rhythm),
  • Valve disorders (abnormal, leaky or narrowed heart valves),
  • Hypertrophic cardiomyopathy (weakened heart muscle),
  • Pulmonary embolism (blood clot in lungs),
  • Certain congenital heart disorders (heart defects present from birth),
  • Myocardial ischemia (reduced blood flow to heart),
  • Pulmonary hypertension (high blood pressure in lung’s arteries), and
  • Congestive heart failure (inadequate blood flow to body).

Syncope can also be a symptom of a malfunctioning man-made replacement heart valve or a malfunctioning pacemaker.

Factors that increase a person's risk for syncope include female gender and age.


The physician will perform a detailed medical history and a physical examination. 

The physician may also order the following tests:

  • Electrocardiogram (ECG), Resting – This noninvasive test records the electrical activity of the heart.
  • Electrocardiogram (ECG) Stress Test – If a patient has symptoms most often during exercise, the physician may ask that he/she walk on a treadmill or ride a stationary bike during an ECG. This is known as an exercise stress test. A resting ECG may be done first because it may show a heart problem that would make an ECG stress test unsafe. 
  • Electroencephalogram – This test records the electrical signals of the brain.
  • Electrolyte Level Test – This test measures substances in the blood that help regulate the proper balance of body fluids.
  • Electrophysiology Testing – Used to diagnoses abnormal heart rhythms, this test examines the electrical function of the heart from inside the heart itself, using small catheters (long, thin tubes). 
  • Echocardiogram – This test uses sound waves to create a moving picture of the heart, showing its size and shape, as well as how the heart chambers and valves are working.
  • Cardiac Catheterization and Angiography - Cardiac catheterization involves the insertion of a thin tube called a catheter into an artery. During angiography, physicians inject dye through the catheter that allows them to study blood flow through the heart and blood vessels and look at the pumping function of the heart.



Treatment of syncope depends on its cause.

Patients with syncope should consult with their physicians regarding potentially dangerous activities, such as driving, certain professional activities, or recreational activities.

Immediate treatment for most forms of noncardiac syncope includes having the person lie horizontally and raise his/her legs slightly to restore consciousness. Treatment to prevent recurrent noncardiac syncope includes:

  • Education and  maintaining adequate hydration,
  • Adjusting or prescribing medications, and
  • Implanting a pacemaker to help maintain normal heart rhythm.

Treatment of cardiac syncope is based on addressing the underlying cardiac condition and includes:

  • Medications
  • Pacemaker Implantation - A small device is implanted under the skin in the upper chest to help maintain a normal heart rhythm.  
  • Cardiac Defibrillator Implantation (ICD) – Similar to a pacemaker, an ICD also prevents the heart from beating too rapidly. 
  • Radiofrequency Catheter Ablation – This minimally invasive treatment for abnormal heart rhythms destroys heart tissue that is causing the arrhythmia.
  • Valvular Surgery – This is a surgery to repair one of the heart’s four valves.
  • Bypass Surgery - A physician replaces, or bypasses, the blocked artery with a healthy blood vessel harvested from the person or made from synthetic fabric.
  • Angioplasty and Stenting - During this non-surgical procedure, a balloon attached to a small catheter is inflated within an artery to flatten the plaque against the artery wall, increasing the artery's diameter. In most cases, a stent, a metal-mesh tube, is expanded and left inside the artery to support the expansion and maintain blood flow.
  • Congenital Heart Surgery – This is a surgery to correct heart defects present from birth.
  • Vena Cava Filter – This is the implantation of a filter to stop blood clot from travelling to heart or lungs.