38. CORONARY HEART DISEASE

by Michael Oliver

The chief functions of the heart are to send blood to the lungs, so that they can receive oxygen from the inhaled air, and then to pump this oxygenated blood all over the body. The activity of every tissue in the body depends upon its receiving a constant supply of oxygenated blood. This is particularly true for the heart itself which contracts 10,000 times a day, and requires a very large amount of oxygen for conversion into the energy necessary to produce regular and efficient contractions. The heart muscle, or myocardium, receives its oxygenated blood from the main artery, or aorta, which leads out of the heart. The first arteries that are fed by the aorta are the two coronary arteries, so called because they circle like a crown the upper part of the heart.

It is obvious that any decrease in this blood supply might impair the functions of the heart. Inadequate blood supply to the myocardium results either from a decrease in the blood flow through the coronary arteries, or from an increase in the demands of the heart muscle without any corresponding increase in coronary blood flow. Of these, decreased flow is the more common, and it is due to structural changes in the walls of the coronary arteries. Loss of elasticity, increased rigidity, fatty, fibrous, and even bony changes occur patchily along the inner coats of the coronary arteries, and are known as atherosclerosis.

Serious disease of the coronary arteries can lead to their obstruction either gradually or suddenly. When the obstruction is gradual it will cause some isolated muscle fibres to die and deprive others of their source of energy. The change may be so gradual that it never leads to any symptoms, or on the other hand, it may result in the pain of angina pectoris. Sudden obstruction of one of the coronary arteries cuts off all the flow of blood to the area of the heart muscle beyond the obstruction and usually results in the severe, prolonged, and intense pain of a heart attack, and when it occurs at a critical site the result may be disastrous.

Coronary atherosclerosis' is not a new disease. It has been found in the mummified bodies of men who lived 5,000 years ago. Moreover, there is evidence to suggest that it may not be increasing. Yet there has, in contrast, been an alarming increase in angina and in coronary heart attacks during the last forty years. There is no doubt that to find an explanation of this big increase is one of the most pressing problems for medical research today.

One of the earliest changes in the development of atherosclerosis is the appearance in the inner coats of the artery of a fat, called cholesterol; and as the artery is progressively destroyed, a large amount of cholesterol accumulates. Fifty years ago Russian research workers showed that cholesterol fed to rabbits produced changes very similar to human coronary atherosclerosis. There is sufficient evidence to suggest that the richness of our Western diet may be one of the contributory causes of coronary heart attacks, but it is far from clear whether this is due to an excess of calories, the high protein content, the high fat content, or even to certain deficiencies in our diet. At present, it is not possible to confirm or to refute the suggestion that there is a causal relationship between the amount of fat or the type of fat we eat and the incidence of heart attacks.

One thing that is reasonably certain is that there is no single cause for coronary atherosclerosis or for the increased ten dency to coronary thrombosis. Physical activity, for example, is less in privileged communities than in others. Scars in the heart muscle result when the blood supply is grossly in adequate, and the numbers of these scars are less in those who are physically active than in those who are not, although the degree of coronary artery damage is the same. The sex of the individual is also of importance. At the age of forty, coronary thrombosis is seven times more common in men than in women. Heredity is also important, particularly in families with a high degree of cholesterol in the blood. Coronary heart attacks occur more commonly in those with high blood pressure, in the over fat, in cigarette smokers, and in those subjected to prolonged emotional and mental strain.

(from The Listener, 16th March, 1961)