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
12 Sep 09