Myocardial infarction: causes, symptoms, diagnosis and treatment
When people commonly speak of an infarction, they are referring to the necrosis of cardiac muscle tissue, thus, medically speaking, we speak of a myocardial infarction
What happens is an insufficient supply of oxygen to the cells that make up a more or less extensive region of the heart, for a wide variety of causes.
Also known as a ‘heart attack’, myocardial infarction is one of the most serious cardiovascular events in Western countries.
Regardless of the cause, during a heart attack, the blood flow to the heart muscle is blocked because one or more arteries (the coronary arteries) are obstructed.
If the blood flow is not restored quickly, the affected part of the heart is damaged due to lack of oxygen, so necrosis (beginning to die) occurs.
Myocardial infarction affects the muscle tissue of the heart or myocardium, whereas when the problem affects the brain tissue, an ischaemic stroke occurs.
How to detect an ongoing myocardial infarction?
It is usually preceded by certain warning signs that we might call symptoms, namely
- chest pain: arises when the subject has exerted himself, or is experiencing a sudden strong emotion. The pain varies in intensity, is localised in the centre of the chest, behind the sternum and causes a sensation of constriction. It may also cause a pain/burning that may spread to the jaw, shoulders, arms, hands and back. Its duration is variable, it may be felt for only a few minutes or last longer and be accompanied by a feeling of severe fatigue, nausea and cold sweats;
- more localised pain: burning sensation or sensation similar to what one feels with a wound;
- light-headedness and dizziness.
In women, the symptoms may be less pronounced than in men.
These symptoms may occur even at rest, or when exertion is already over, within a few minutes or in a blur in the hours, or even days, immediately preceding the infarction.
Many people confuse myocardial infarction with cardiac arrest.
They are not the same thing: myocardial infarction may cause cardiac arrest, but it is not the only cause and a myocardial infarction does not necessarily lead to cardiac arrest.
Myocardial infarction is caused by atherosclerosis, a disease that arises as a result of the accumulation of fat along the walls of the coronary arteries, which over time comes to form a true atherosclerotic plaque.
During a heart attack, these plaques rupture and a blood clot forms, the size of which can block the flow of blood through the artery.
There is thus a partial or total occlusion of a coronary artery.
In rare cases, the infarction is the result of a malformation of the coronary arteries or the disconnection between the coronary wall leaflets.
There is also a more common form of myocardial infarction among women, namely Takotsubo syndrome, an apex myocardial infarction caused by intense emotional stress.
The heart muscle does not contract, the coronary arteries are free from narrowing or occlusion, but the heart tends to take on an appearance reminiscent of the typical basket used by Japanese fishermen, hence the name of this infarct.
If a myocardial infarction is preceded by several days of mild but nevertheless worrying symptoms, a visit to your doctor should be requested.
During the anamnesis, the doctor investigates the patient’s symptoms and may prescribe urgent tests to investigate the likelihood of a myocardial infarction occurring in the near future.
In addition to taking into account symptoms, personal and family medical history, the diagnosis then considers the results of diagnostic tests, which include
- electrocardiogram (ECG), with which certain changes in the appearance of electrical waves in the ECG or abnormal heartbeats (arrhythmias) can be detected;
- blood tests investigating the level of certain particular proteins released by the heart, the cardiac enzymes (troponins, CK or CK-MB);
- coronary angiography, a special X-ray test of the heart and blood vessels, which detects blockages in the coronary arteries.
Risk factors and complications of myocardial infarction
Risk factors for atherosclerosis have been identified, some modifiable, others not.
Among the non-modifiable factors, i.e. those on which we can do nothing to prevent a heart attack, are:
- age: the risk of a heart attack, as with almost all cardiovascular diseases, increases with age;
- gender: atherosclerosis and heart attack are more common in men, at least until the female menopause, after which the risk of atherosclerosis and heart attack is similar to that of men;
- familiarity: individuals who have relatives in their family who have suffered a heart attack, especially at a young age, are at greater risk of a heart attack themselves.
Modifiable factors, i.e. aspects of our lives on which we can intervene to lower the probability of a heart attack, are
- lifestyle: sedentary life and/or work and tobacco smoking are among the most important cardiovascular risk factors;
- diet: a diet that includes too many calories and fats contributes to increasing the level of cholesterol and other fats in the blood;
- high blood pressure: ‘high blood pressure’ affects a large percentage of the population over the age of 50;
- diabetes: excess glucose in the blood damages the arteries and promotes myocardial infarction;
- drugs: they can greatly increase the chance of myocardial infarction and are the most common cause among younger people.
Since myocardial infarction has a very high mortality rate, if action is not taken in time, it is necessary, if the classic symptoms are felt, to seek immediate help and to take the patient to a hospital equipped with competent personnel and appropriate instruments to intervene, as quickly as possible.
Complications of myocardial infarction in the acute phase can in fact be
- shock, low blood pressure and tachycardia
- acute pulmonary oedema
- arrhythmias, some of them potentially fatal
- ischaemia of other organs, due to the heart’s poor ability to pump blood
Today, infarction remains a fatal disease the later the patient with an acute myocardial infarction is admitted to hospital.
In fact, the first few hours are decisive in order to be able to treat fatal complications such as severe arrhythmias at an early stage and to start administering the first drugs effective on the coronary clot or thrombus.
Once in hospital, the first goal of treating myocardial infarction is to attempt to reopen the occluded coronary artery in the hope that the heart muscle has not been irreversibly damaged.
A catheter with an inflatable balloon is then introduced at the apex, which passes through the clot at the point of maximum narrowing of the coronary artery itself and squeezes its components on the walls (coronary angioplasty).
A mesh prosthesis is then placed inside the vessel (stent) which helps to keep it open after unblocking.
If angioplasty or a stent are not viable solutions for a patient, there are drugs that are able to dissolve the thrombus after being administered intravenously (thrombolytics), but they are not suitable for everyone as they have important side effects, such as the onset of bleeding, even serious bleeding.
Other drugs, including anticoagulants, antiplatelets, beta-blockers, ACE inhibitors and statins, are almost always prescribed to patients suffering a myocardial infarction, but clearly their use and dosage must be assessed according to the patient’s level of haemorrhagic risk, individual tolerance and contraindications that vary from person to person.
Finally, in all cases where severe or extensive coronary artery disease is detected and where coronary angioplasty and stents are not possible, coronary bypass surgery can be used, which consists of surgically creating a communication channel between the aorta and the obstructed coronary artery using other arteries or veins.
Preventing a myocardial infarction
The only way to prevent a heart attack is to intervene on modifiable risk factors, although there is never absolute certainty that a correct lifestyle can 100% prevent this eventuality.
However, quitting smoking and leading an active life, regularly doing at least 20 to 30 minutes of physical activity per day, is certainly advice to follow in order to prevent cardiovascular problems and to protect one’s health.
Just as a healthy, balanced diet is of great value in terms of preventing cardiovascular disease: avoid seasoned or fried foods, do not overdo alcohol (limit yourself to one glass of wine per meal per day) and sweets.
It is better to prefer vegetable fats and meals based on vegetables, fibre, lean meat and fish
Linked to diet, weight control is also important: a value that is within the normal range for a person’s age and sex must be achieved.
However, it is not only a question of body weight in absolute terms, but also of controlling the body mass index or BMI, a unit of volume whose values are considered normal by the international scientific community.
Finally, it is necessary to keep high blood pressure at bay.