Relates to narrowing and leaking through the aortic and mitral heart valves
The function of the heart is to move blood through the lungs where it picks up oxygen, and then through the rest of the body where it gives off the oxygen to fuel the many types of cell which make a human being. The passage of the blood through the heart is maintained by the pumping action of the heart muscle and the presence of non-return valves to direct the flow. The most important of these valves are in the left side of the heart. The mitral valve lies between the upper and lower chambers of the heart and the aortic valve is at the outlet of the lower chamber. These are the valves most likely to become diseased and are therefore the ones most likely to cause medical certification problems for pilots and air traffic controllers.
Narrowing of the mitral valve (mitral stenosis) is usually caused by rheumatic heart disease as a child, and is normally not acceptable for medical certification.
Reflux backwards through the mitral valve (mitral regurgitation) can be caused by a congenital abnormality of the valve. The thin leaflets that open and shut to cause only forward flow of the blood, become disorganised and allow blood to flow backwards as well. If this is progressive, the heart muscle has to work harder to maintain the flow and eventually will fail, causing breathlessness, initially on exercise and then at rest. Other complications can include rapid irregular heart beats which may cause incapacitation and also the passage of small clots into the brain where they can cause small strokes.
Mitral regurgitation is often first found at a routine medical examination by the presence of a heart murmur. The standard investigation of such a murmur is an ultrasound scan of the heart (echocardiogram) which measures the heart size and function, and the amount of regurgitant flow back through the valve. Once these measurements show a significant backwards flow and/or a significant enlargement of the heart muscle, then medical certification to fly/control is not possible.
It is possible to have a regurgitant mitral valve repaired without requiring an artificial heart valve. Ideally the repair should be done before irreversible damage is done to the heart muscle. Medical certification to fly following a mitral valve repair is possible if there is demonstrated recovery of heart function.
The commonest aortic valve problem in aviators is narrowing of the valve (stenosis). This is usually due to the valve leaflets becoming stiff and calcified (with chalky deposits). The function of the heart will gradually deteriorate as it has to push blood through an ever narrowing orifice. This will eventually lead to heart failure. Aortic valve disease is often discovered at a routine medical examination by the presence of a murmur and it will need to be investigated with an ultrasound scan (echocardiogram). This can measure the pressure gradient across the valve, which is a measure of the amount of extra work imposed on the heart muscle. This extra work may also be shown by the heart muscle increasing in size.
If the stenosis becomes severe, surgery may be recommended. If the valve can be replaced with a substitute made of treated human or animal tissue then certification following surgery, assuming the heart muscle recovers, is possible.
The protocols for certification are given below.