The most common type of heart attack is caused by a coronary thrombosis, which occurs when a clot (thrombus) blocks one or more of the blood vessels that nourish the heart muscle. As a result of the lack of blood, part of the muscle may be damaged, and its ability to contract may be lost. This is known as a myocardial infarction. If the infarct is small and the electrical impulses that control the heart’s contractions (beats) are not disturbed, chances for recovery are excellent.
Coronary Artery Disease
Coronary thrombosis is one of the manifestations of coronary artery disease. As we grow older, our blood vessels tend to lose their elasticity, a process known as arteriosclerosis. The arteries may also become narrowed or clogged with deposits of fatty material called atheromas, a condition called atherosclerosis. Atherosclerosis is progressive and usually does not produce symptoms until there is significant blockage in the blood flow. Sometimes, in fact, the first symptom of this heart disease is a heart attack.
Although the specific cause of atherosclerosis is not known, it has been found that certain risk factors help in identifying population groups that are more likely to develop it. Three major risk factors are high levels of cholesterol and other blood fats, high blood pressure (hypertension) and cigarette smoking. Others include diabetes, obesity, a sedentary life style, aging, being male and heredity.
Atherosclerosis begins forming as a fatty streak on the inner wall of an artery, usually at its branching-out point, and disturbs the smooth flow of blood. As patches of fatty tissue build up, the inner wall becomes narrower, which inhibits blood flow in a more significant way. An artery continues to narrow as the tissue buildup progresses, and in time, the fatty deposit becomes a hard mass of fatty tissue with a tough outer lining of cells – a plaque. As plaques spread and thicken, they erode the wall of the artery, which interferes with blood flow and makes it increasingly turbulent. This turbulence may trigger the blood to form a clot (thrombus), partially or completely blocking the artery. Further, a fragment of the clot (embolus) may be carried by the bloodstream and block an artery at some distant, narrower point.
Heart attacks sometimes occur in people with little or no coronary artery disease. Some experts believe that a spasm or sudden constriction of the coronary artery may be the cause of these heart attacks. It appears that a spasm may occur in a coronary artery that is totally free of atherosclerosis (as well as in one that is heavily affected by that condition), and this would explain why many people suffer angina and other cardiac problems without any evidence of underlying blockage in the arteries.
Symptoms of a Heart Attack
A heart attack can come on gradually, preceded by several attacks of angina over days, weeks, months or even years. (Angina is the name given to the chest pain that arises when the muscular wall of the heart is temporarily deprived of sufficient oxygen.) But a heart attack may also occur without any apparent warning, and in people who have never previously experienced any chest pain.
Typically, the pain of a heart attack is a sensation of constriction in the central chest area; it may vary in intensity from a feeling of tightness to one of agonizing crushing or bursting. The pain may be continuous, or it may last a few minutes, fade and then recur. It commonly spreads to the back, jaw and left arm. Although a heart attack may be precipitated by physical or emotional stress, the pain, unlike that of angina, does not subside when the stress ceases.
Pain is commonly accompanied by shortness of breath, sweating, nausea, dizziness and pallor. (Some people experience a heart attack without any of these symptoms. This is known as a “silent” infarct, which may be confirmed by changes in an electrocardiogram or certain other hospital tests.)
A Medical Emergency
Most deaths from heart attack occur within minutes to hours after the onset of symptoms. Therefore, when sudden and severe chest pain occurs, an ambulance should be called immediately and the individual taken to a hospital. Denying that these symptoms represent a life-threatening illness may cause a delay that could be fatal.
One of the major cause of death from coronary thrombosis is the development of abnormal heart rhythms in the hours immediately following the attack. Emergency treatment, therefore, concentrates on stabilizing the heart rhythm, as well as on relieving pain and preventing shock.
In the hospital’s intensive-care or cardiac-care unit, the rate and rhythm of the heart will be continuously monitored by an electrocardiograph machine. Blood tests to detect enzymes released from the heart aid in assessing the infarct further and various medications may be given. Mood changes and feelings of apprehension are very common following a heart attack, and a mild tranquilizer is often given to the patient.
Depending on the severity of the attack, the patient may be allowed out of bed within three or four days and be discharged after two weeks. Bed rest for more than a short time should be avoided, where possible, because it results in a rapid loss of the body’s muscle tone and in increased heart rate on exertion. Physical activity is gradually increased and most patients are able to return to their full range of normal activity within a few months.
Long-Term Treatment
Depending on such factors as the patient’s age and general physical condition, and the extent of the heart damage, a variety of different approaches may be taken to deal with the underlying coronary artery disease and to reduce the possibility of another heart attack.
Changes in life style. A number of steps can be taken to prevent or slow down the progression of heart disease. These include stopping smoking, exercising regularly and adopting a low-cholesterol diet.
Drug treatment. The use of drugs depends upon the nature of the heart attack and underlying coronary disease. Antihypertensive drugs may be prescribed to lower the blood pressure. Other drugs may be given to improve heart function, prevent chest pain or lower the level of blood cholesterol.
Other treatments A number of other treatments, including coronary bypass surgery, are available. Obviously, their use depends upon individual needs.
