Myocardial infarction: causes, symptoms and risk factors

By Cristiano Antonino On Nov 7, 2022

Myocardial infarction consists of cell death (necrosis) of a part of the heart muscle, caused by a prolonged absence of blood flow (usually more than 30 minutes), due, in turn, to the sudden occlusion of the coronary artery that normally supplies the region

The greater the area of cardiac muscle affected by the infarction, the greater the severity of the infarction itself, as less cardiac muscle will remain viable to perform its contraction function.

Myocardial infarction is a frequent event in today’s population and alone accounts for more than 20% of the mortality rate in Western countries.

Causes and risk factors of myocardial infarction

Very often one hears the question “doctor, why did I have a heart attack?” In reality, it is not possible to give a precise answer to this question.

Infarction is, in fact, a pathology of multifactorial origin, i.e. a pathology for which several factors are responsible, to varying degrees, and which, moreover, are not the same in all patients.

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The main risk factors for myocardial infarction, as numerous studies have shown, are smoking, hypertension, diabetes, stress, abdominal obesity, physical inactivity, hypercholesterolaemia, and a diet low in fruit and vegetables.

Having one or more of these risk factors does not represent a ‘condemnation’ to having a heart attack, but an increase in the risk of having one, just as the absence of risk factors is not an insurance against having a heart attack, but simply entails a considerable reduction in risk.

However, it is essential to bear in mind that for myocardial infarction, as for many diseases, the best therapy is prevention, which involves reducing, or rather eliminating, risk factors.

As mentioned, the acute event responsible for myocardial infarction is the occlusion of a coronary artery, and this, in the vast majority of cases, is caused by the formation of a thrombus (i.e. a blood clot) within the coronary artery.

In turn, thrombus formation is triggered by a rupture or ulceration of an atherosclerotic plaque

The atherosclerotic plaque, on which much cardiovascular research has focused in the last ten years, is a protuberance within a vessel (in this case a coronary artery) that causes its narrowing and is due to accumulation of fat and inflammatory cells.

It is precisely the latter, when activated, that are said to be responsible, in many cases, for the rupture of the plaque.

Once ruptured or ulcerated, the plaque stimulates clotting of the blood that comes into contact with it, resulting in the formation of a clot (thrombus).

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As mentioned above, the thrombus occludes the coronary artery at the level of the complicated plaque, causing occlusion of the vessel and interruption of blood flow in the affected artery, resulting in the death of the myocardial region habitually supplied by the vessel.

The extent of the damage is the major determinant of the patient’s future prognosis, in terms of both duration and quality of life.

Therefore, the greatest efforts of clinical research have focused on the most effective methods of reopening an occluded coronary vessel as soon as possible, in order to restore flow and try to save as much myocardium as possible.

Typical symptoms of myocardial infarction

The typical symptoms of myocardial infarction consist, first of all, of an oppressive pain, often described as a vice or a boulder, in the centre of the chest. The pain may radiate to the neck, jaw, arms, and back.

It may sometimes be localised to only one of these areas and may often be present only in the stomach, sometimes accompanied by nausea and vomiting, to the extent that it may be confused with gastritis.

Although the symptoms may vary, it is important to know that when symptoms typical or suggestive of a heart attack occur, one should immediately seek medical attention and arrive at the emergency room as soon as possible.

Many patients, in fact, die before arriving at the hospital due to arrhythmic complications that cause cardiac arrest, and many arrive when the damage to the heart muscle is already extensive and irreversible.

In the last twenty years, enormous progress has been made in the treatment of myocardial infarction, in particular with thrombolysis first, i.e. the use of drugs that, given into a vein, dissolve the thrombus present in the coronary artery, and then with primary angioplasty, an invasive treatment that allows the affected artery to be quickly and permanently reopened with the use of a catheter.

Thanks to these advances, in-hospital mortality from heart attack has fallen from over 20% to less than 5% in patients treated on time with these therapies.

Of patients with myocardial infarction, adequately treated, many will have an essentially normal subsequent life

Some patients, however, will need, due to the extent of the infarction, intensive pharmacological treatment for decompensation, as well as the use of certain implantable devices, such as resynchronising pacemakers and defibrillators (See Pacemakers and defibrillators).

These are the patients who could benefit from stem cell therapies in the future.

All heart attack patients, however, are at risk of relapses in the following months and years, and this is because the pathological process underlying the heart attack, i.e. the formation of coronary atherosclerotic plaques, is a chronic process, which tends to persist or worsen with time, facilitating new episodes.

To try to prevent recurrences, in addition to careful correction of risk factors, certain drugs, such as aspirin and statins in particular, are indispensable.