Abnormal Heart Rhythm

Syncope

Signs and Symptoms
Diagnosis
Treatment

Signs and Symptoms

Syncope, also known as fainting, or a sudden and brief loss of consciousness, occurs when the brain does not get enough blood flow and oxygen.

There are many causes of syncope. A common type of syncope -- vasovagal syncope or neurocardiogenic syncope -- is caused by a malfunction of the nerves that control the action of the heart and blood vessels, called the autonomic nervous system. This type of syncope may be triggered by fear, severe pain, emotional distress or standing for a long time. Dehydration and low salt intake may also contribute to the condition.

Syncope may also be caused by very fast heart rhythms or arrhythmias called tachycardias, as in supraventricular tachycardia (SVT) (link to SVT) or ventricular tachycardia (VT) (link to VT). In some cases, syncope is caused by very slow heart rhythms, called bradycardias, as in sinus node dysfunction (SND) (link) or heart block (link).

The hallmark symptom of syncope is fainting, or near fainting. The condition may also cause the following symptoms:

• Palpitations, which can be skipping, fluttering or pounding in the chest
• Fatigue
• Chest pressure or pain
• Shortness of breath
• Vision changes
• Nausea
• Lightheadedness or dizziness

Reviewed by health care specialists at UCSF Children's Hospital.
Last updated May 8, 2007