Coronary Artery Disease

The heart is a pump with four chambers.  The two on the right pump blood through the lungs, and the two on the left through the rest of the body.  The heart works by contracting and relaxing the muscular walls of the chambers causing blood to be pumped through non-return valves into the main arteries of the body.  Like any muscle, the energy for this work comes from oxygen in the blood.  This oxygen is supplied by special arteries to the heart muscle - the coronary arteries and the supply of oxygen has to be continuous.  Once the blood supply to an area of heart muscle is cut off, that muscle dies and never recovers.  This is described as a heart attack or myocardial (heart muscle) infarction.

Coronary artery disease starts with a narrowing of the artery due to a build up of fatty deposits on the inside of the artery wall.  Why this occurs in some people, but not in others, is unknown.  It is linked to lifestyle factors which include smoking, a high fat diet, lack of exercise, obesity and a family tendency to heart disease.  There are however other, currently unknown, factors involved.  Initially this narrowing cause no symptoms, but as they become more severe they cause a lack of blood to the heart muscle during exercise, leading to chest pain known as angina.  If the artery suddenly blocks with a blood clot (a thrombosis), a heart attack occurs and leads to an area of dead muscle.

Recovery following a heart attack depends on the amount of muscle that has died, and the presence of narrowing in other coronary arteries.  The greatest risk of further problems is soon after the attack.  For this reason a pilot is grounded and an ATCO must not control, for six months.  If the risk factors noted above have been reduced or eliminated, and if the pilot/ATCO is on no drugs (except aspirin, lipid lowering agents or blood pressure tablets) then certification can be considered if certain tests are satisfactory.  An angiogram done before or during surgery, or just after a heart attack, will need to be seen.  Routinely the test undertaken to prove recovery following a heart attack is an exercise ECG.  It gives some indication of how well the heart muscle is working, and changes on the ECG during exercise can indicate narrowing in other heart arteries. 

Treatment for coronary artery disease can be medical in the form of aspirin to thin the blood and ‘statin’ drugs to lower the blood lipid levels.  Surgical treatment is aimed at narrowing that might subsequently block and cause a heart attack (once an artery has blocked, nothing can be done for the already dead muscle).  Coronary artery bypass surgery takes veins or arteries from elsewhere in the body and bypasses the narrowing.  Coronary angioplasty dilates the narrowing with a balloon threaded into the heart from a leg artery.  Nowadays a small tube called a stent is often inserted subsequently, and left in place to keep the artery open.  As after a heart attack, six months must pass before medical certification is possible.  The requirements for certification at six months following bypass surgery are the same as after a heart attack (see above).  After angioplasty/stenting, because of the slightly increased tendency for early re-narrowing, an extra test called a myocardial perfusion scan is required.  This gives a measurement of the amount of blood getting to the heart muscle by using a radioactive tracer technique.  This test is also required five years (and sometimes earlier) after bypass surgery.

The protocols for certification following a heart attack (Myocardial Infarction), coronary artery disease, and angioplasty/stenting procedure are given below. 

AIrcrew

Coronary Artery Disease

ATCOs

Coronary Artery Disease

September 2009