Causes of Heart Attacks

 

Unfortunately, there is no simple test which can be used to detect coronary disease in the way that the chest X-Ray can be used to detect lung cancer. To be effective, such a test would have to be simple, quick cheap, safe and very reliable.

A lot of effort is going into ways of devising a suitable method, but at the moment the only methods we have are the electrocardiogram, the exercise test, isotope techniques and arteriogram. The electrocardiogram measures the heart’s electricity but although it invariably becomes abnormal after a heart attack, it is often normal in patients who have angina, let alone those with no angina whose arteries may be narrowed. An improvement is stressed by physical activity, when some of the heart’s reserve is being used. This test it still a poor indicator of those with incipient trouble, however, and can even be misleading because in those with no symptoms the test is falsely positive more often than truly positive; in other words, it may suggest an abnormality where none exists, more often than suggesting an abnormality where there actually is one. This is because the flow of blood through the arteries may not be significantly reduced until the artery is narrowed to about 60 or 70% of its cross-sectional area, and because abnormal electrocardiograms can be caused by other types of abnormality.

Isotope techniques are more reliable but they are expensive and need complex equipment. Minute amounts of radio-active materials which localize in the heart are injected into the blood stream during exercise and the heart is then “imaged” with a gamma camera. Because of its expense and complexity it cannot be applied to routine screening for people without symptoms, and although better than the exercise electrocardiogram this is also not foolproof.

The final method is the coronary arteriogram in which the coronary arteries are visualized by injection of X-Ray opaque fluid during cine X-Ray filming. It is very reliable but it is an “invasive” test requiring the passage of a fine tube (catheter) from a blood vessel in the arm or leg into the heart.

It is an uncomfortable rather than a painful test and may carry a very small element of risk. In certain circumstances it is essential, but it can hardly be used as a screening method where the suspicion of coronary disease is not very high, not only because of the risk but also because it is time consuming and expensive. It is likely that in the future ways will be found of imaging the coronary arteries in similar fashion non-invasively without the passage of a catheter.

Heart Attack and Family History

 

There is some tendency for arterial narrowing, involving especially the coronary arteries and the cerebral arteries (which feed blood to the brain and whose narrowing causes strokes), to run in families. There is obviously not a great deal that can be done about this. If you have it in the family you may be stuck with it! A family trait however is not especially strong so there is no need for undue worry, but it does mean that attention to other risk factors is even more important.

On the other hand, if the family trend is very bad, for example several members of the family having or dying from heart attacks at a young age, and especially if it involves several generations and women in the family (in which it is unusual before the menopause) it may be due to a profound abnormality of blood cholesterol or related body fats, which can be diagnosed easily in a blood sample taken after fasting. Such people may have a very high blood level of cholesterol or the related substance triglyceride, and it is now known that treatment with a diet, drugs, or both, can have a favorable effect on the risk of coronary attacks. It should be emphasized however that this type of abnormality is very rare.

Raised cholesterol as a risk factor, except in those very profoundly abnormal patients, is of doubtful importance. Quite a lot of publicity has been given to it over the years, but it is still controversial whether the small rises of cholesterol and triglycerides which are found in many people are of any significance. Many doctors nowadays feel that its importance has been overestimated and that attempts to decrease the intake in the diet are not all that helpful. It seems surprising that although many years of research has been carried out the answer it still not clear cut Many feel that in this current state of uncertainty it is wise to adopt a so-called “prudent” diet where the in-take of certain dietary fats – particularly saturated fatty acids is reduced.

The diet involves the reduction of animal fats and dairy products. Fat on meat is reduced and vegetable oils used for cooking. Special margarines which are rich is so-called polyunsaturated fatty acids are used, and a reduction is made in the amount of milk, cheese, cream and eggs. The evidence that taking this diet to extremes is helpful is really lacking, but for the time being diets of this type is considered “prudent”.