Clinical Practice Guideline



Developed for the

Aerospace Medical Association

by their constituent organization

American Society of Aerospace Medicine Specialists


Overview: Syncope is a temporary loss of consciousness and postural tone due to global cerebral hypoperfusion.  “Near syncope” occurs when an individual has symptoms of hypoperfusion, such as feeling faint or experiencing tunnel vision, but does not lose consciousness.  An underlying condition that predisposes a flyer to syncope or near syncope could have significant aeromedical significance due to the potential for incapacitation or loss of aircraft control.


Syncope is a common clinical problem, and has been estimated to account for 3-5 percent of emergency room visits and 1 percent of hospital admissions.  The etiology is diverse: syncope can be caused by disturbances in homeostasis or neurally-mediated reflexes, cardiovascular disease or arrhythmias, neurologic or psychiatric conditions, medications and a variety of metabolic disorders.  Careful evaluation is required to determine the etiology and risk for recurrence or long-term complications.  Even after evaluation, the cause of syncope remains unknown in many cases.


The most common causes of syncope in people without underlying disease are vasodepressor and vasovagal syncope.  These terms are often used synonymously; however, vasodepressor syncope refers to the collapse of peripheral resistance and hypotension without bradycardia, while vasovagal syncope involves both collapse of peripheral resistance and vagus-mediated bradycardia.  These result from disturbances in the homeostatic mechanisms that normally interact to maintain normal cerebral perfusion.  These homeostatic mechanisms are affected by a variety of neural influences including visual and emotional stimuli.  Patients with vasodepressor or vasovagal syncope do not appear to be at increased risk for all-cause or cardiovascular mortality, but may be subject to recurrent symptoms.  The overall recurrence rate for vasovagal syncope has been estimated at 30 percent.  Risk factors for recurrence have not been well-characterized, but a history of previous syncopal episodes and the number of episodes indicate a greater risk of recurrence.


In contrast, syncope due to underlying cardiac disease or arrhythmia is associated with significantly higher all-cause and cardiovascular mortality, and risk of recurrence.  Thus it is important to evaluate patients with a history of syncope for potential cardiac causes.


In addition, it is very important to distinguish syncope from epileptic seizures, since the latter have a high risk of recurrence and cause severe incapacitation.


The clinical history is the most important factor in establishing a diagnosis in syncope patients.  When evaluating patients, the flight surgeon should consider the postural setting, pre-syncopal (premonitory) symptoms, the syncopal episode, and the syncopal setting.


Posture: Syncope almost always occurs in the upright position, while seizures may occur in any position.  Significant cardiac dysrhythmias can cause loss of consciousness in any position.


Pre-syncopal symptoms: Vasodepressor or vasovagal syncope is often preceded by a prodrome which may last for several minutes.  Symptoms may include nausea, repetitive yawning, deep breathing, visual symptoms (tunnel vision or abnormal perception of color), sweating and dry mouth.  The individual may appear pale, and the skin may be cool and clammy.  This prodrome should be distinguished from the “aura” of seizures.  Arrhythmias may cause sudden loss of consciousness without a prodrome.


Syncopal episode: In syncope, collapse is sudden, with complete loss of muscle tone.  Duration of vasodepressor or vasovagal syncope is usually brief, usually 5-20 seconds, unless restoration of cerebral perfusion is prevented due to a non-supine position.  Breathing is usually shallow; pulse may be weak and/or bradycardic.  Recovery following vasodepressor/vasovagal syncope is rapid, with little or no amnesia or confusion.  Convulsive accompaniments, manifested by asynchronous myoclonic jerks, twitching of the face and hands and tonic posturing, are common in syncope, especially if duration is prolonged due to upright posture.  This is due to global hypoxia as opposed to the excessive neuronal discharges seen in epilepsy.  In contrast, seizures are associated with prolonged post-ictal confusion; generalized and prolonged tonic-clonic movements are more likely; and tongue-biting is common.  Urinary incontinence may occur in up to 10 percent of patients with syncope, so it is not useful in distinguishing seizure from syncope.


Syncopal Setting: It is very important to determine the sequence of events or environmental factors that might have contributed to the suspected syncopal episode.  Vasodepressor or vasovagal episodes are frequently induced by prolonged standing, venipuncture, heat exposure, painful or noxious stimuli, fear of bodily injury, or exertion.  Dehydration, salt loss, fluid loss, concurrent illness, alcohol consumption or medications may alter homeostatic mechanisms.  Sudden standing from a recumbent or squatting position may precipitate orthostatic hypotension.  Other physiologic activities or maneuvers, such as voiding, defecation, cough, swallowing or inadvertent carotid massage may induce reflex hypotension.


Aeromedical Concerns: Any underlying condition that predisposes an aviator to suffer syncopal attacks could lead to incapacitation and loss of aircraft control.  For this reason, loss or disturbances of consciousness, orthostatic or symptomatic hypotension, or recurrent vasodepressor syncope are disqualifying.


Medical Work-up: Medical evaluation for these aviators should include the following: A detailed history; if possible, the flight surgeon should interview witnesses personally and the record should indicate which elements of the history were provided by witnesses.  Past medical history, medications, allergies, and family history (especially of sudden death, arrhythmia or epilepsy) should be well documented.  The cardiovascular exam should assess pulses for rate, rhythm and differences between extremities; resting and orthostatic blood pressure, auscultation for murmurs or abnormal heart sound, and an ECG.  Orthostatic hypotension is diagnosed when one or more of the following is present within two to five minutes of quiet standing:

·         ³20 mmHg fall in systolic pressure

·         ³10 mmHg fall in diastolic pressure

·         Symptoms of cerebral hypoperfusion

Neurologic exam should assess mental status, cranial nerves, motor and sensory function, deep tendon and plantar reflexes, coordination, gait and Rhomberg test.  Any neurological deficit(s) or cardiovascular abnormalities require further evaluation and waiver submission.  A cardiology consultation is required if cardiac etiology is suspected or etiology is unknown.  If clinically indicated, tertiary testing such as echocardiogram, Holter or event monitor, tilt-table testing, stress-test, electrophysiology studies, etc may be necessary.  Neurology consultation should be sought if the LOC cannot be attributed to syncope and/or neurologic deficits are identified or suspected.  Psychology or psychiatry consultation should be considered if psychogenic factors are suspected.


Aeromedical Disposition:


Air Force: Consideration for waiver is limited to cases in which the risk of recurrence is low and/or the underlying condition or triggering factor can be adequately controlled.  Benign syncope limited to predictable settings may be waived if there is negligible risk of recurrence in the aviation environment.  If a treatable etiology for syncope is found, then correction of the underlying condition may allow a return to flying status.  However, certain conditions (e.g., arrhythmia) and/or medications may pose unacceptable risks of recurrence or side effects.  If the etiology of syncope remains unknown despite extensive diagnostic evaluation, then a clinical judgment based on careful consideration of all available information must be made before allowing a flyer to return to the cockpit.


Army: Syncope is a symptom resulting from a plethora of pathologies, primarily cardiac and neurologic. Waiver is granted based on the underlying disorder discovered in the work-up.  The Army does not require a waiver for simple episodes of vasovagal syncope.  A waiver is necessary only for unexplained syncope, recurrent syncope, syncope associated with pathology, or when associated with incontinence or convulsions lasting over 6 seconds.


Navy: Syncope in the Navy is approached as it is in the Air Force and Army.


Civilian: As it was mentioned above the history of the event is highly important.  If an Aviation Medical Examiner obtains a history that is compatible with a vasodepressor or vasovagal event then they are taught to grant medical certification.  An Authorization for Special Issuance will not be required.  If an airman experiences another similar event then it would require a decision by the Aerospace Medical Certification Division.  If the airman experiences a similar third event then medical certification may not be likely.


The required workup will depend entirely on the medical history.  There are no minimum tests other than a good history and physical examination.  Make sure that you obtain the ambulance and emergency room records should the airman end up going this route.  If the history is vague or the workup does not aid one in making a diagnosis then the airman is grounded and will not be reconsidered for 2 years.  The airman will then need to demonstrate that he/she had no further events. 


It is not uncommon in the civil sector for an airman to undergo a tilt table test (TTT).  This test is not required by the FAA to demonstrate Neurocardiogenic syncope (another name for vasovagal syncope).  The history is still most important If one has a TTT and the airman demonstrates what is called “malignant Neurocardiogenic syncope” the airman will be denied medical certification even if the airman is being successfully treated.  Malignant Neurocardiogenic syncope occurs when the airman has an arrhythmia along with the syncope.  Usually this is asystole.  Even if the airman is treated with a permanent pacemaker the FAA will not allow the airman to fly for a two year period.  Note, the human body will “learn” how to positively respond to TTT and result in a negative test even without treatment.  So, treating someone who has a positive TTT and then repeating the test after some time demonstrating no syncope, will not result in the granting of an authorization.  Recurrent (more than three events) may result in permanent disqualification.


Waiver Experience:


Air Force: A query of the AIMWTS database revealed the following experience: Initial pilot/navigator training (FC I/IA): 10 waiver submissions with 5 approved for waiver and 5 disqualified.  Most approved waivers had single syncopal episodes with well-defined precipitating factors and minimal aeromedical risk, or remote history of syncopal episode and the disqualified applicants tended to have multiple syncopal episodes, low threshold for syncope, or atypical syncopal features.  FC II: 40 submissions with 26 approved for waivers, 13 disqualified.  FC III: 36 submissions with 19 approved for waiver and 17 disqualified.  Approved and disapproved cases for FC II and FC III were similar to FC I/IA.


Army: The Army’s Aeromedical Epidemiological Data Registry was queried for the period of 1960 to 2009.  This case series contains 160,000 individuals.  This is a long span of time during which aeromedical policy has evolved.  There were 637 cases of syncope.  Of those, 503 were retained in aviation.   Of these 165 were rated aviators.  Note that flight applicants were included in the data set, but not included as rated aviators.


Navy: No numbers to report at this time.


Civilian: As of August 2009 the number of airmen who have been granted medical certification with a history of syncope were 2,240 first-, 1,314 second-, and 3,643 third-class. 


ICD 9 Codes for Syncope


Syncope and collapse


Heat collapse


Carotid sinus syndrome





Air Force Instruction 48-123, medical examinations and standards volume 3 - flying and special operational duty.  2006 June.


Barón-Esquivias G, Errázquin F, Pedrote A, et al.  Long-term outcome of patients with vasovagal syncope.  American Heart Journal.  2004 May; 147(5):  884-9.


Brignole M, Alboni P, Benditt L, et al.  Part 1. The initial evaluation of patients with syncope.  Europace.  2001; 3:  253-60.  Retrieved February 3, 2007, from the World Wide Web:


Olshansky B.  Pathogenesis and etiology of syncope.  UpToDate.  On Line Version 14.3.  March 3, 2006.  Retrieved February 3, 2007, from the World Wide Web:


Rayman RB, Hastings JD, Kruyer WB, Levy RA, Pickard JS.  Clinical Aviation Medicine. 4th ed.  New York: Professional Publishing Group, 2006.


Soteriades ES, Evans JC, Larson MG, Chen MH, et al.  Incidence and prognosis of syncope.  NEJM.  2002; 347(12):  878-85




Prepared by Dr. Jon Casbon

Date: September 12, 2009