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the average pilot spends some eight to ten per cent of his/her year on duty, the possibility of some
manifestation at work is to be expected. Although in safety terms, incapacitation (obvious or subtle) will
be at greatest risk of occurrence at the time of the index event, the risk of fatal event is still increased
substantially in the days and weeks that follow. With the exponential increase in cardiovascular events
that occurs with increasing age, older pilots will be at greatest risk of an event, particularly if other risk
factors such as hypertension, hyperlipidaemia, smoking, insulin resistance and/or a family history are
present.
Most of the coronary syndromes are attributable to obstruction of the vessels with atheroma. This lipidrich
material, which accumulates at sites of vascular injury, may be present in early adulthood and it may
progress very slowly. These atheromatous foci are known as plaques and contain “foamy macrophages”
— cells of monocytic origin, smooth muscle cells and lipids in the form of cholesterol, fatty acids and
lipoproteins. There is significant variation in the composition of the plaques, their state of development
and their behaviour in individuals. Their behaviour may also be modified by medication. Thrombosis
occurs in association with plaque rupture, tripping the clotting cycle via several different mechanisms.
The subsequent sequence of events depends on the morphology of the plaque, its site in the coronary
artery, the extent of the related thrombus and the presence or absence of a collateral circulation. Flow
varies as the fourth power of the radius and symptoms may not be present until one or more major
epicardial arteries are occluded by 50 to 70 per cent of the luminal diameter. Myocardial infarction due
plaque rupture can occur on a minimally obstructing plaque, however.
If the thrombotic event is minimal and the plaque not large, there may be no symptoms. Or, with
disruption in the plaque, symptoms such as angina pectoris may occur. If the vessel is occluded, infarction
of the myocardium subtended by the vessel will occur unless an adequate collateral circulation is present.
ICAO Preliminary Unedited Version — October 2008 III-1-15
As collateral formation is most common when near-obstruction has been long-standing, such an outcome
is less likely to apply to aviators who must not only be asymptomatic but also pass routine medical
surveillance. By way of these patho-physiological processes, the coronary syndromes of stable/ unstable
angina pectoris and myocardial infarction occur.
Angina pectoris
The pain or discomfort that is angina pectoris is one of the more familiar symptoms in medicine. Yet the
diagnosis is sometimes made casually with little thought of the consequences for the patient. Its
characteristics — crushing central pain or discomfort, commonly but not exclusively radiating to the left
arm and brought on by exertion, should make its identification possible. But it may also be present on the
right, in the back or in the throat. Unless presenting as an unstable syndrome or during myocardial
infarction, angina is of brief duration (<2 to 3 minutes) and likely to be associated with exercise,
especially first thing in the morning, in the cold or after a meal. It may also be provoked by emotion.
The severity of angina pectoris correlates poorly with the extent of coronary artery disease present. An
inactive subject may have no symptoms in spite of significant three-vessel obstruction; a branch vessel
obstruction may give rise to symptoms in an active individual. Crude mortality in angina pectoris is of the
order of four per cent per annum. “Chest pain ? cause” is a familiar cardiological default diagnosis which
underscores the difficulty sometimes experienced in the diagnosis of chest pain (see below). Angina
pectoris may also occur in the presence of normal coronary arteries as Prinzmetal1 or variant angina.
There is a diurnal pattern, pain often occurring in the early morning. Other, non-coronary explanations for
angina include hypertrophic or dilated cardiomyopathy, aortic stenosis, severe hypertension and anaemia.
Such diagnoses should not have passed unnoticed in an otherwise healthy aviator.
The presence of angina pectoris from whatever cause, even when symptoms are suppressed by
medication, disbars from all classes of medical certification. .
Chest pain ? cause
“Chest pain ? cause” is a common cardiological diagnosis in outpatient clinics implying that, although
there may be symptoms, full evaluation does not lead to a cardiovascular explanation. Such a diagnosis is
rare in aircrew but the presence of obstructive coronary artery disease needs to be excluded, often with
the help of an exercise ECG. Any recurrent symptoms should be pursued in view of their potential to
　
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本文鏈接地址：Manual of Civil Aviation Medicine 1(79)