Syncope, also known as fainting or passing out, is defined as a short loss of consciousness and muscle strength, characterized by a fast onset, short duration, and spontaneous recovery. It is due to a decrease in blood flow to the entire brain usually from low blood pressure.
Causes range from non-serious to potentially fatal. There are three broad categories of causes: heart or blood vessel related, reflex also known as neurally mediated, and orthostatic hypotension. Issues with the heart and blood vessels are the cause in about 10% and typically the most serious while neurally mediated is the most common. Heart related causes may include an abnormal heart rhythm, problems with the heart valves or heart muscle and blockages of blood vessels from a pulmonary embolism or aortic dissection among others. Neurally mediated syncope occurs when blood vessels expand and heart rate decreases inappropriately. This may occur from either a triggering event such as exposure to blood, pain or strong feelings or a specific activity such as urination, vomiting, or coughing. This type of syncope may also occur when an area in the neck known as the carotid sinus is pressed. The final type of syncope is due to a drop in blood pressure from standing up. This is often due to medications that a person is taking but may also be related to dehydration, significant bleeding or infection.
What are the symptoms of syncope?
The most common symptoms of syncope include:
Syncope is often preceded by other symptoms (called premonitory symptoms), such as light-headedness, nausea and palpitations (irregular heartbeats that feel like “fluttering” in the chest).
Many people with syncope learn, on their own, to avoid a syncopal event or “passing out.” They recognize the premonitory symptoms and sit or lie down quickly and elevate their legs.
Because syncope could be the sign of a more serious condition, it is important to seek treatment right away after a syncope episode occurs. With accurate diagnosis and appropriate treatment, syncope can be resolved in most patients.