Syncope

Basic Facts

  • Syncope is the medical term for fainting or passing out. It is defined by a brief and transient loss of adequate blood flow to the brain, usually due to a sudden drop in blood pressure. 
  • Syncope is characterized by a rapid onset, short duration and spontaneous and complete recovery. 
  • Treatment for syncope focuses on identifying and treating the underlying cause, but the cause is not always known. 
  • Syncope often recurs, and though sometimes harmless, it can be life threatening. Therefore, people who experience an episode of syncope should seek immediate medical attention.

Though syncope can happen without much warning, most patients have a brief period of symptoms beforehand, known as “presyncope.” These symptoms could include: 

  • Lightheadedness

  • Sweating 

  • Feeling warm or cold 

  • Nausea 

  • Pallor (looking pale to others) 

  • Visual disturbances (“tunnel vision,” “white out,” “black out”) 

  • Decreased hearing or hearing unusual (often "whooshing") sounds 

  • Neurologic changes or confusion during the recovery period may suggest a stroke or seizure, not true syncope.  

By far the most common cause is vasovagal syncope, a type of reflex syncope, which is due to naturally occurring reflex responses in the body that result in dilation of blood vessels, bradycardia, or both.  This can occur after:

  • Prolonged standing, especially in a warm environment 

  • Coughing, sneezing, swallowing, urinating, or defecating--  especially if straining

  • A sudden and/or unexpected unpleasant sight, sound, smell, pain, or fear 

  • Pressure put on the carotid sinus (tumors, shaving, tight collars, certain turning of the neck, etc)--  called carotid sinus syndrome 

Reflex syncope often comes with presyncope symptoms, and it is more likely to have nausea, pallor, diaphoresis, and fatigue that persist for minutes to hours afterwards. 

Next most common cause is orthostatic (postural) hypotension, which is defined as a drop in blood pressure of at least 20 / 10 mmHg upon sitting up or standing. This can be caused by: 

  • Dehydration 

  • Alcohol 

  • Aging 

  • Arrhythmia causing the heart to beat too fast or too slow (examples include AV block, bradycardia, SVT, VTach). 

  • Medications that lower blood pressure and/or heart rate, especially if taken together (including meds for blood pressure, Parkinson’s, and depression).  

  • Something blocking blood from leaving the heart (heart attack, hypertrophic obstructive cardiomyopathy, certain congenital heart disease, or valve disease such as severe aortic stenosis). 

  • Disorders that affect the “autonomic nervous system,” which is the branch of the nervous system that helps maintain blood pressure. Examples include Parkinson’s disease, diabetes mellitus, multisystem atrophy, primary autonomic failure, amyloidosis, spinal cord injuries, or other neuropathies 

Blockages in arteries are almost never the cause of true syncope, as the brain has a very redundant blood supply.  

Rarely, blood flow to the brain is decreased during arm exercise in patients with subclavian steal syndrome. 

 Research shows that 20-30% of syncope is unexplained.  

Nearly all syncope patients are referred to cardiology in order to screen for a heart problem that could have caused it, as potential cardiac causes could be life-threatening, though are often correctable.  

If syncope was observed, a witness should try to provide as much information as possible, including the position of the patient, how long it lasted, and if it recurred. A mobile phone video can be very helpful if possible. 

It can be difficult to determine the cause, because syncope may be unpredictable and brief. In addition to taking a person's medical history, listening to the patient describe symptoms, and conducting a physical examination, the provider may also recommend: 

  • ECG – noninvasive test, stickers attached to wires placed on the chest, provides a 6 second “snapshot” of heart’s electrical activity. Can be done at a visit. Can show any arrhythmia if it is occurring at that time. 

  • Holter/Cardiac ambulatory monitoring – wearable ECG sticker that can record the heart's activity constantly for days to weeks, think of it as a “movie” rather than a “snapshot”. Monitor can be applied at home or at a visit. It is paired with a provided smartphone that stores/sends data. Worn 24/7. Returned via UPS. 

  • Implantable Loop Recorder ILR – small monitor implanted under the skin on the upper left chest by an EP doctor. It stores events automatically or can be triggered by the patient. It “talks” to a bedside device that stores/sends the data. ILR is used if the syncope is infrequent, an arrhythmia is suspected, but it hasn’t been seen on the above forms of testing. 

  • Echocardiogram – painless, noninvasive study that uses ultrasound waves to evaluate heart structure and function in real time. 

  • Electrophysiologic study – hospital-based non-surgical procedure performed by an EP doctor to see where inside the heart a potential arrhythmia is coming from, and possibly ablate it. 

  • Stress Testing – to evaluate blood flow to the heart at rest and under stress, especially if syncope during exercise.

 

Syncope usually recovers quickly without treatment. However, injuries due to falls can result, especially in older patients.  

Immediate treatment is aimed at ensuring safety of the patient and determining whether it is due to a benign or life-threatening condition. Therefore, people who experience an episode of syncope should seek immediate medical attention! 

 If a person feels they are going to pass out, they should immediately lie down and elevate the legs. Doing this and/or tensing the leg, abdomen, and arm muscles helps push blood upstream to the brain, thus hopefully preventing syncope, but also reducing risk of injury. 

 Prevention measures: 

  • Staying well hydrated is one of the basics of treatment to prevent syncope. 

  • Wearing elastic compression stockings on the feet and lower legs 

  • Tensing the leg and abdomen muscles before standing up from a seated or lying-down position. 

  • Rising to stand slowly and in stages  

Medicines such as fludrocortisone (Florinef) or midodrine may be used to help increase blood pressure.  

If syncope due to abnormal heart rhythm, medicines may be used to control the rhythm, or a Pacemaker or Implantable cardioverter-defibrillator may be implanted by an EP doctor. 

Virginia state law is 6 months no driving unless an obvious cause for the syncope is found and corrected.