Clinical Practice Guideline
for
SYNCOPE
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 |
|
|
780.2 |
Syncope and collapse |
|
992.1 |
Heat collapse |
|
337.01 |
Carotid sinus syndrome |
=============================================================================
References:
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: http://europace.oxfordjournals.org/cgi/reprint/3/4/253.
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: http://www.utdol.com/utd/index.do.
Rayman RB,
Hastings JD, Kruyer WB, Levy RA, Pickard JS. Clinical Aviation Medicine. 4th ed.
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