Coronary Heart Disease (Part 1) |
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Coronary heart disease is one of the greatest scourges of modern times. The gradual narrowing of many arteries of the body is an 'age-related' process and especially affects the arteries to the brain, the major cause of strokes, and the arteries of the heart (the coronary arteries), the major cause of heart attacks. The basic process which causes this narrowing remains unknown, although there are many known factors which make it worse including smoking, physical inactivity, diabetes, hypertension (high blood pressure), obesity and hereditary factors Including abnormalities of the way that the body - handles fats. This narrowing is a slow, progressive process known start early in life, but it does not interfere with the heart's function until, sometimes many years later, it becomes severe. Many affected people may be unaware of any abnormality until a narrowing blocks an artery completely, leading to irreversible damage of a segment of heart muscle to which blood was supplied by that artery. This event is termed a 'myocardial infarction' by the medical profession and a 'heart attack' by the public; this latter term is not very precise as it may mean different things to different people. The event is often unheralded by previous warning symptoms, and takes the person by surprise. Although he finds it difficult to believe that there has been an underlying abnormality continuing for years, it is inevitably the case. This presents modern diagnostic cardiology the study (the diagnosis of heart disease) with one of it greatest headaches. How do you determine the presence of this underlying narrowing of arteries before any major problems have occurred if the patient remains symptom-free? Routine examination may show no abnormalities, a chest X-ray, w probably be normal, and even an electrocardiogram can also be normal. The basic problem is that the supply of blood through the coronary arteries to the myocardium (heart muscle) can remain normal especially when the body is at rest, in spite of the narrowing of an artery by 50 or even 60 per cent of its diameter. Only when this reaches about 70 per cent does the blood flow become sufficiently impaired to make the myocardium deprived of fuel—that is oxygen—and it is only at this stage that the suffered may begin to notice symptoms and the electrocardiogram to start to become abnormal. Tests which attempt to uncover the effects of these arterial narrowings rely on making the heart work harder to the point where it requires more fuel. The most obvious and easiest way is by physical exercise and this is usually carried out by using a stationary, bicycle or a treadmill. The most convenient monitor of heart function is the electrocardiogram, and one that is normal at the peak of exercise is a fair indication of a normally functioning heart and arteries. Additional and more sophisticated tests during exercise may also be made, the most valuable being the use of the aforementioned radio-isotopes which may be injected into the blood during exercise —these will go to the heart and an image can then be seen by a gamma camera designed to pick up the emissions from radio-isotopes. Unfortunately this latter test, although more sensitive than an electrocardiogram, requires expensive equipment and radio-isotopes and is therefore not practical as a routine screening test. Furthermore its value as a routine screening tool for the vast majority of symptom-free people has yet to established. Even the value of the simple exercise electrocardiogram for this purpose is not clearly established, and there is still a great need for a simple Info method of establishing the presence and severity of coronary heart disease before it becomes a problem. Pain is the classical symptom produced by a deficiency of oxygen-carrying blood to the myocardium. This deficiency is usually referred to as ischaemia. The pain has a characteristic distribution: it is usually-in the chest and tends to be central or equally distributed on both sides; it may spread to either or both shoulders or arms or into the neck or jaws. It Is usually described as having a tight or gripping quality, and is usually initiated by physical or emotional stress. Both oxygen deficiency and subsequent pain tend to appear in these conditions of stress, as they cause the heart to beat faster and stronger due to stimulation by the sympathetic nervous system or by adrenaline being secreted into the bloodstream. When oxygen deficiency is shortlived—perhaps during stress—then the pain is equally short-lived. The term angina is used for this pain when it is limited in duration. If the deficiency in oxygen supply to the myocardium is prolonged or even permanent (as occurs when a total blockage of a previously narrowed artery leads to the death --infarction — of a segment of the myocardium), the same type of pain occurs, but is more severe and more persistant. It often occurs at, or is unrelieved by, rest. Any patient who experiences such a symptom which persists for more than 10-15 minutes should seek medical help as quickly as possible. |
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