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for cerebral anoxia to provoke epileptic seizure. Twitching movements during the period of
unconsciousness are common and should not be confused with epileptic seizure.
1 Adams-Stokes attack: an episode of syncope in Adams-Stokes syndrome, i.e. episodic cardiac arrest due to
transient complete atrioventricular block, caused by failure of normal and escape pacemakers. After Robert Adams,
Irish physician (1791-1875) and William Stokes, Irish physician (1804-1878).
ICAO Preliminary Unedited Version — October 2008 III-1-46
Maintenance of the systemic blood pressure requires adequate circulating blood volume, sufficient
peripheral arteriolar tone in the “resistance” vessels, regulation of the “capacitance” vessels (which
contain 70 per cent of the circulating blood volume), and also regulation of the inotropic and chronotropic
state of the heart. All patients experiencing an episode of vasovagal syncope suffer a fall in the blood
pressure with ensuing impairment of consciousness; in some there is a profound bradycardia but in others
there is a tachycardia. This paradox involves loss of regulation of venous tone (and return of circulating
blood to the heart), inadequate arteriolar tone, and ventricular myocardial mechanisms.
The symptoms of vasovagal syncope include a prodromal syndrome of variable duration with lightheadedness,
weakness, a sensation of air hunger or hyperventilation, detachment from surroundings,
palpitations, blurring of vision, and field disturbance, nausea, dizziness and eventually syncope.
“Malignant” syncope is characterized by little or no warning and injury may result. Another definition of
the malignant form relates to the period of asystole during tilt testing. Depending on the circumstances,
recovery may be prolonged by repeated episodes of hypotension followed by partial recovery of
consciousness. Recovery invariably takes place but the symptoms can persist for hours. Patients with the
condition have a normal life expectancy unless the incident causes hazard.
Provocative factors in vasovagal syncope are several although some of the features may form part of the
syndrome. Specifically, nausea, vomiting, a sensation of abdominal churning, diarrhoea, an awareness of
warmth, heat or coldness, and sweatiness are common. Other input may come from fatigue, emotional
disturbance or anxiety, circadian stress, dehydration, pain or visual stimuli, such as the sight of a needle.
Sometimes cause and effect can be blurred. A glass of wine on an empty stomach in a susceptible
individual may have the same effect. As up to one-third of aircrew may experience incapacitation at some
time in their career, in 60 per cent of cases due to gastroenteritis, the likelihood of such an event in a
susceptible individual is significant.
Sufficient investigation of suspected vasovagal syncope is needed to exclude other causes and establish
the diagnosis. An exercise and 24-hour (Holter) ECG and echocardiography, should be undertaken and be
within acceptable limits. An electroencephalogram (EEG) and brain CT/MRI scan are not indicated,
unless there is doubt as to the cause. The head-up tilt test, in which the subject is raised from the supine
position to an angle of 60-70 degrees for 45 minutes, is the procedure of choice if tilt table testing
information is thought necessary to improve the certificatory decision. In the most severely affected
individuals, the test is almost 100 per cent sensitive; in others, it is about 70 per cent sensitive with
provocation with nitroglycerine. The false-positive rate is about 13 per cent, rising to 20 per cent with
nitroglycerine. The reproducibility of the test is in the range of 70 to 80 per cent, but a negative test
cannot be taken as an assumption that the diagnosis in incorrect or that the condition has improved.
The treatment of vasovagal syncope is unsatisfactory due partly to its sporadic appearance, often with
long intervals between attacks. Drug therapy e.g. with beta-blocking agents, has to be taken continuously,
and the results are disappointing. Few convincing trials have been carried out. Endocardial pacemaking is
helpful in a few cases. Subjects with the syndrome have a normal life expectancy unless syncope causes
some accident, such as falling under a vehicle, or occurs while driving a vehicle or flying as single pilot in
a light aircraft. This has been recorded by at least one Contracting State. Intervention is for symptoms
alone, as it has no effect on prognosis.
The certification of subjects with vasovagal syncope in the aviation environment is problematic, as it is a
potential cause of sudden, incomplete or total incapacitation, yet no underlying physical pathology will be
demonstrated. Whereas a single syncopal episode, when the diagnosis is secure, need not preclude
　
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