Syncope (medicine)
Syncope, commonly known as fainting or passing out, is a loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery.[1] It is caused by a decrease in blood flow to the brain, typically from low blood pressure.[1] There are sometimes symptoms before the loss of consciousness such as lightheadedness, sweating, pale skin, blurred vision, nausea, vomiting, or feeling warm.[3][1] Syncope may also be associated with a short episode of muscle twitching.[1][3] Psychiatric causes can also be determined when a patient experiences fear, anxiety, or panic; particularly before a stressful event, usually medical in nature.[4][5] When consciousness and muscle strength are not completely lost, it is called presyncope.[1] It is recommended that presyncope be treated the same as syncope.[1]
"Passing out", "Syncopy", and "Fainting" redirect here. For the completion of a military course, see passing out (military). For the film production company, see Syncopy Inc. For other uses, see Faint (disambiguation).Syncope
Fainting, blacking out, passing out, swooning
Loss of consciousness and muscle strength[1]
Injury[1]
Fast onset[1]
Short duration[1]
Cardiac, reflex, orthostatic hypotension[1]
Medical history, physical examination, electrocardiogram[1]
Based on underlying cause[2]
Depends on underlying cause[2]
~5 per 1,000 per year[1]
Causes range from non-serious to potentially fatal.[1] There are three broad categories of causes: heart or blood vessel related; reflex, also known as neurally mediated; and orthostatic hypotension.[1][3] 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.[1] 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.[1] Neurally mediated syncope occurs when blood vessels expand and heart rate decreases inappropriately.[1] This may occur from either a triggering event such as exposure to blood, pain, strong feelings or a specific activity such as urination, vomiting, or coughing.[1] Neurally mediated syncope may also occur when an area in the neck known as the carotid sinus is pressed.[1] The third type of syncope is due to a drop in blood pressure when changing position such as when standing up.[1] This is often due to medications that a person is taking but may also be related to dehydration, significant bleeding or infection.[1] There also seems to be a genetic component to syncope.[6]
A medical history, physical examination, and electrocardiogram (ECG) are the most effective ways to determine the underlying cause.[1] The ECG is useful to detect an abnormal heart rhythm, poor blood flow to the heart muscle and other electrical issues, such as long QT syndrome and Brugada syndrome.[1] Heart related causes also often have little history of a prodrome.[1] Low blood pressure and a fast heart rate after the event may indicate blood loss or dehydration, while low blood oxygen levels may be seen following the event in those with pulmonary embolism.[1] More specific tests such as implantable loop recorders, tilt table testing or carotid sinus massage may be useful in uncertain cases.[1] Computed tomography (CT) is generally not required unless specific concerns are present.[1] Other causes of similar symptoms that should be considered include seizure, stroke, concussion, low blood oxygen, low blood sugar, drug intoxication and some psychiatric disorders among others.[1] Treatment depends on the underlying cause.[1][3] Those who are considered at high risk following investigation may be admitted to hospital for further monitoring of the heart.[1]
Syncope affects about three to six out of every thousand people each year.[1] It is more common in older people and females.[7] It is the reason for one to three percent of visits to emergency departments and admissions to hospital.[7] Up to half of women over the age of 80 and a third of medical students describe at least one event at some point in their lives.[7] Of those presenting with syncope to an emergency department, about 4% died in the next 30 days.[1] The risk of a poor outcome, however, depends very much on the underlying cause.[2]
ECG showing HOCM
Long QT syndrome
A short PR in Wolff–Parkinson–White syndrome
Type 2 Brugada ECG pattern
Epidemiology[edit]
There are 18.1–39.7 syncope episodes per 1000 people in the general population. Rates are highest between the ages of 10–30 years old. This is likely because of the high rates of vasovagal syncope in the young adult population. Older adults are more likely to have orthostatic or cardiac syncope.
Syncope affects about three to six out of every thousand people each year.[1] It is more common in older people and females.[7] It is the reason for 2–5% of visits to emergency departments and admissions to hospital.[7] Up to half of women over the age of 80 and a third of medical students describe at least one event at some point in their lives.[7]
Prognosis[edit]
Of those presenting with syncope to an emergency department, about 4% died in the next 30 days.[1] The risk of a poor outcome, however, depends very much on the underlying cause.[2] Situational syncope is not at increased risk of death or adverse outcomes.[37] Cardiac syncope is associated with worse prognosis compared to noncardiac syncope.[46] Factors associated with poor outcomes include history of heart failure, history of myocardial infarction, ECG abnormalities, palpitations, signs of hemorrhage, syncope during exertion, and advanced age.[37]