Like any muscle, the heart needs oxygen in order to function. If the blood supplying the heart has very little oxygen in it because, for example, the person has choked or been asphyxiated as a result of being gassed or nearly drowning, this will probably result in the heart stopping altogether (cardiac arrest). Alternatively, the blood supply to a large area of the heart may be interrupted by a clot in one of the coronary arteries, so that the muscle supplied by that blood vessel runs out of oxygen, dies and ceases to contract when it should. This is called a myocardial infarction; the clotting is known as a coronary thrombosis. The whole process is also known by the less precise term of ‘heart attack’. If a large part of the heart muscle dies as a result of myocardial infarction, this may be enough to cause cardiac arrest. At the other end of the spectrum of heart failure, a person may suffer a – for the time being – less serious heart disorder. In ischaemic heart disease, for example, the patient suffers from angina. This causes a severe chest pain similar to that experienced by someone having a myocardial infarction, the difference being that it is usually brought on by exercise and ceases when the person rests. This kind of heart disorder is, in contrast to a myocardial infarction, reversible. Angina develops when insufficient blood for the needs of the moment reaches the heart muscle, usually because of atherosclerosis of the blood vessels. This is a build-up of fatty deposits that narrows and hardens the vessel. People who suffer from angina are therefore predisposed to myocardial infarction.
When myocardial infarction occurs, death of part of the heart muscle may affect the ability of the whole heart to contract efficiently: instead of beating regularly, as usual, it trembles or quivers. This is called fibrillation and results in an irregular heart beat and pulse. Without immediate first aid or medical attention, fibrillation may be fatal. Both cardiac arrest and fibrillation may also result if someone has received an electric shock, because the electric current interferes with the normal, mild electric impulses that control the regular movements of the heart muscle. On the other hand, an electric current is also sometimes used to restore the normal heartbeat following cardiac arrest or fibrillation, using a machine called a defibrillator.
How to recognize a heart attack
The major symptom of a heart attack is pain in the centre of the chest. This may be extremely severe – it is often described as ‘crushing’ or ‘vice-like’ – or so mild as to be confused by the sufferer with indigestion. People who have had angina will recognize it as the same kind of pain, with the difference that it does not stop when they cease physical activity. The pain often spreads to other parts of the body: up to the throat and jaw and down the left arm. The casualty may be pale, sweating heavily and, if he or she has not passed out, feeling weak and dizzy. Breathlessness is another common symptom.
First aid treatment
Summon medical help as soon as possible. If the casualty is still conscious, settle him or her in a comfortable position, loosen tight clothing and try to keep him or her as quiet as possible. The aim is to reduce the heart’s need for oxygen by rest; getting the casualty to breathe deeply will also help. Any kind of anxiety or exertion is bad for someone who has just had a heart attack, so give the casualty plenty of reassurance and prevent him or her from moving. Shock is the body’s reaction to injury or illness, resulting in the blood supply being diverted to the major organs. It is common following a heart attack, in which case the casualty will look pale and will be sweating heavily. You should assist the flow of blood to the heart and brain by getting the casualty to lie down and raise his or her legs, on a chair, for example, if he or she is lying on the floor. If the person’s condition becomes worse, he or she may become unconscious. Provided he or she is breathing normally, you should put the casualty in the recovery position, keeping a constant check on the pulse. The best place to feel for the pulse is in the neck, just to the side of the windpipe, and not in the wrist. Always do this on only one side. If the pulse stops, the casualty will also stop breathing, and his or her face and lips will turn blue. In this event, artificial respiration and external chest compression need to be started. The same procedure applies if you arrive on the scene of an accident to find someone who has stopped breathing and whose heart has stopped beating, whether from a heart attack or for other reasons.
External chest compression
Never give someone external chest compression unless you are certain that his or her heart has stopped beating. If there is even the faintest pulse or heartbeat, the procedure may be very harmful. The aim of external chest compression is to pump the oxygenated blood in the lungs, which has been introduced by artificial respiration, around the body and particularly to the brain, which is easily damaged if it is deprived of oxygen for even a short while. In the case of an unconscious casualty who has no heartbeat and who has stopped breathing, begin by rapidly inflating his or her lungs four times, as this may be enough to revive him or her. An initial blow, delivered very firmly with the fist to the centre of the chest, may also start the heart. If you are still unable to feel a pulse after this, you should give chest compressions at the normal pulse rate – 80 per minute for adults and slightly faster for children – alternating with lung inflations. Press down with the ‘heels’ (flats) of your hands over the lower breastbone, keeping arms straight, to compress the heart and so force some blood around the circulation. (The practical details of this technique should preferably be learned from a qualified instructor.) Stop external chest compression as soon as you can detect the pulse again; colour will also return to the casualty’s face.
Remember, never practise external chest compression on anyone, healthy or otherwise, whose heart is beating.
Preventing a heart attack
Cardiac arrest is the single most important cause of premature death in most Western countries. Apart from cases in which the heart malfunctions because of a congenital or hereditary defect, it would appear that the vast majority of heart attacks that occur in middle-age are preventable. Research shows that four main factors contribute to the likelihood of heart failure, all of which are directly linked to modern styles of living. Stress from the pressures of earning a living in an increasingly complex and competitive society (or, indeed, the stress of unemployment) may cause high blood pressure, which in turn puts an extra burden on the heart. Relaxation techniques practised regularly can do a great deal to reduce blood pressure and ward off the possibility of heart failure. Cigarette-smoking increases the amount of carbon monoxide and reduces the amount of oxygen in the bloodstream, depriving the heart of vital fuel. The obvious remedy is simply to break the habit. An unbalanced diet high in cholesterol (obtained from animal fats) and lack of sufficient exercise also contribute to the likelihood of heart failure. A build up of cholesterol in the lining of the arteries constricts the flow of blood to the heart, overstraining it; lack of exercise makes the heart less efficient. Again, it is up to the individual to make the necessary adjustments to his or her life-style.