Causes of myocardial infarction: causes and predisposing factors

Myocardial infarction (MI) is included in coronary heart disease, since its main cause is insufficient blood circulation with the development of a local ischemic zone. The presence of a heart attack does not become clear immediately, but when specific changes are recorded on the electrocardiogram and signs of its breakdown are detected in the blood - necrosis of the heart muscle. Clinical symptoms with insufficient diagnostic information are designated as acute coronary syndrome (ACS), that is, there is already an understanding that trouble has happened to the coronary arteries supplying the myocardium, but whether it is an angina attack or a developing heart attack is still unclear.

Our expert in this field:

Tafintseva Ekaterina Anatolevna

Head of hospital, general practitioner

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What kind of disease is this and what are its causes?

The main etiological cause of the development of acute myocardial infarction is atherosclerotic damage to the intima (inner lining) of the coronary arteries.
As a result of the formation of deposits, the lumen of the vessel narrows, and blood begins to flow in limited quantities. This is how IHD begins with angina attacks. When exposed to provoking factors (physical or emotional stress), the artery is completely blocked and permanent ischemia develops with the formation of an area of ​​necrosis. Other (very rare) causes of heart attack are conditions in which blood flow is disrupted:

• rheumatism;
• vasculitis;
• tumors;
• allergy;

During my practice, I often encountered the fact that many patients do not eliminate bad habits and poor nutrition from their lifestyle. But these risk factors for myocardial infarction often lead to fatal consequences.

Deterioration of the blood supply to the heart occurs more often in the elderly: men after 45 years of age and women after 55 years of age should beware of the disease. Psycho-emotional shocks can provoke an attack - many patients come to our department after the death of loved ones, dismissal from work, divorce.

Risk group

One of the main causes of heart attack is vascular atherosclerosis, which occurs due to the large amount of trans fats, chemical fillers, and salts in the body.

Also, some circumstances in life play an important role in being at risk:

• Men are most often affected.
• The highest risk age is for women after 50 years.
• Heredity is important. There is a high risk of getting sick if close relatives have had at least one case of heart attack or stroke.
• Presence of high cholesterol (200 mg/dl)
• Diabetes. The amount of glucose makes the process of deposit formation on the heart vessels faster.
• People with obesity and a sedentary lifestyle are at risk of getting sick.
• Hypertension or arterial hypertension. As a result of constant hard work, the myocardium quickly wears out.
• Those who eat a lot of fatty foods are at risk.
• Smoking, which is one of the primary risk factors.
• Complex operations and injuries, for example during cardiac stenosis, during operations on the blood vessels of the legs, death can occur on the operating table.
• Those who have character traits such as aggression and impatience, as well as those who are easily stressed. There are a lot of cases of heart attack among those who had a responsible job.

The presence of each of these signs increases the risk of a heart attack; the more of them, the correspondingly higher the risk, and it increases exponentially.

Classification

Classification of myocardial infarction is carried out according to several principles.

Based on the time of occurrence, they are distinguished:

• first appeared (primary);
• recurrent (repeated within 1.5 months after the first);
• repeated (occurring later than 6 weeks after the primary).

The following types of myocardial infarction are determined by location:

• left ventricle (anterior, posterior, lateral and septal walls);
• extensive, affecting several departments at once;
• right ventricle (occurs extremely rarely, often accompanied by damage to other areas of the heart muscle).

According to the degree of prevalence of ischemia and necrosis, there are the following types of acute myocardial infarction:

• intramural (located deep in the wall of the organ);
• subendocardial (develops in the inner layer);
• transmural (passes through all three layers of the heart);
• subepicardial (disorder in the outer part of the organ).

Diagnostics

The main method for diagnosing a heart attack is ECG, electrocardiography. In addition to it, an ultrasound of the heart (echocardiography) and a biochemical blood test are performed. One of the methods specific for infarction to confirm the diagnosis is the troponin test, which can detect even minor myocardial damage. An increase in troponin in the blood is observed for several weeks after the attack.

The main method for diagnosing a heart attack is an ECG.

How many heart attacks can a person have?

Almost all patients who have had a heart attack once ask me about the risk of another at their appointment. Understanding their concerns very well, I will still say that no specialist will give a definite answer in this case. It is necessary to take into account the location of the scar, the depth and width of the lesion, and the presence of complications. The degree of restoration of cardiac function depends on the development of collateral circulation (additional vascular pathways). I have seen cases where the patient remained alive after the fifth episode, although death can also occur as a result of a primary heart attack.

Stages of disease development

The clinical course of a heart attack goes through five main periods:

1. Subromal or pre-infarction. It can be short (up to several hours or days) or quite long (1-2 weeks or a month). At this time, pain attacks become more frequent and prolonged. The same option includes a heart attack, which manifests itself against the background of sudden and rapidly progressing angina.
2. The sharpest. Consists of persistent ischemia followed by the development of necrosis. Lasts from 20-30 minutes to 2 hours (but no more). Anginal pain by this time becomes weaker or completely disappears. Blood pressure drops, signs of heart failure appear or increase.
3. Spicy. Necrosis smoothly progresses into melting of the heart tissue (can last from two days to two weeks).
4. Subacute (from 1 to 45 days from the onset of the episode). At this stage, the formation of connective tissue in the affected area begins, and the remaining myocardiocytes adapt to continue further work.
5. Post-infarction. The scar is completely organized, granulations appear at the site of necrosis. It takes from the beginning of the acute stage from 1.5 months to six months.

I would like to draw your attention to the fact that the provision of qualified assistance during the deterioration of angina pectoris or during the acute period of myocardial infarction helps prevent the development of necrosis. In this case, the process is reversible and the prognosis is favorable.

Read more about what happens and how to act correctly at each of the above stages of a heart attack here.

Early signs of a heart attack

Most of the patients (approximately 60 to 80%) who were observed by me with this diagnosis indicate that the disease did not begin suddenly in them. It was preceded by precursors of a heart attack, or a prodromal period. The most favorable outcome was observed in those patients who sought help or were brought by the team in the first hours of the attack.

I would like to make a small disclaimer - early signs of myocardial infarction do not always occur, it all depends on the pain threshold and the state of the patient’s nervous system.

But in most cases I have seen the following symptoms:

1. Pain along the anterior surface of the chest radiating to the left arm, part of the lower jaw, and scapula.
2. The unpleasant sensation is not relieved by taking nitro-containing drugs and goes away only after the administration of narcotic analgesics.
3. It has a constant, increasing or wave-like character with periods of subsidence and resumption.
4. Lasts more than 20-30 minutes.
5. The patient begins to sweat and tries to sit down or lie down as high as possible. This position makes the attack a little easier.
6. Shortness of breath develops, the skin becomes pale, and the nasolabial triangle turns blue.
7. When it comes to the first signs of myocardial infarction, rhythm disturbances cannot be ignored. According to my observations, they are observed in 90% of cases at the stage of ischemia development and before scar formation.

Any suspicion of a heart attack requires an immediate ECG, which will reveal all signs of ischemia, and at a later stage, necrosis and scar formation. Read more about what changes will be visible on film here.

Expert advice

When the first signs of a heart attack appear, measures should be taken immediately.
I advise you to immediately call an ambulance, and while the doctor is on the way, provide the patient with complete rest, sit him down or put him in a position that will alleviate the condition as much as possible. Give Corvalol, Nitroglycerin, Aspirin, ventilate the room. The most dangerous period is the most acute period, which is usually manifested by very severe pain, shortness of breath, and rhythm disturbances. The patient’s life depends on the speed and correctness of the actions of the person nearby. When calling a doctor, it is best to describe the symptoms so that a specialized team can arrive to take an ECG, give oxygen, and administer medications to limit the area of ​​necrosis.

Consequences and complications

In any period from the onset of an acute infarction to its resolution in the form of the formation of a connective tissue scar, the following complications may be observed:

• cardiogenic shock;
• heart failure;
• ventricular fibrillation;
• wall rupture due to myomalacia;
• formation of a parietal thrombus and thromboembolism;
• pericarditis.

The lethal outcome of this disease is recorded in the early stages in approximately 35% of cases. Its cause is rhythm disturbance, cardiogenic shock and acute heart failure. Later death may occur as a result of the formation of an aneurysm with rupture, thromboembolic complications, or acute pericardial tamponade.

After the acute period, the heart muscle adapts to new working conditions, but there remains a high risk of repeated episodes.

Division by anatomy of the lesion

Assessing how deeply the heart tissue is affected and where the focus is located, we can list what other types of heart attacks there are.

1. Transmural. Penetrating type, characterized by damage to the entire thickness of the cardiac tissue. This is an acute variety, most often large-focal.
2. Intramural. Necrosis occurs in the thickness of the myocardium. Pathological changes do not directly affect the epicardium or endocardium. The pathological Q wave on the ECG is most often absent in this situation.
3. Subendocardial. With this type of MI, the layers of the heart muscle adjacent to the endocardium are affected.
4. Subepicardial. This type of heart attack is different in that the layers of the heart muscle adjacent to the epicardium are affected.

And also read on our website: Pressure during a heart attack

Treatment

Treatment of myocardial infarction should be carried out in an intensive care unit with qualified personnel and special equipment. But assistance should begin at the prehospital stage.

This is usually done by the ambulance crew.

After taking an ECG and establishing a presumptive diagnosis, you should:

• put a Nitroglycerin tablet under your tongue;
• give 300 mg of Aspirin to drink;
• administer narcotic analgesics to eliminate pain;
• if necessary, use intravenous antiarrhythmic drugs;
• carry out resuscitation measures in case of cardiac arrest and clinical death.

Read more about how to properly provide emergency care to a patient with a heart attack here.

Drug therapy

After the patient is admitted, my colleagues and I provide care according to the established protocol. All measures are aimed at relieving pain, limiting the area of ​​necrosis, preventing the development of complications, and restoring blood flow through the coronary arteries.

Treatment of myocardial infarction begins with the elimination of pain. Since conventional drugs are ineffective in this case, doctors use intravenous administration of the narcotic analgesics Promedol or Morphine. This helps normalize a person’s emotional state, lower the heart rate and equalize blood pressure. When discomfort is relieved, the likelihood of reflex cardiogenic shock decreases.

Acute myocardial infarction is a coronary thrombosis. Therefore, the patient is administered a direct anticoagulant, thereby performing the procedure of thrombolysis - dissolving the blood clot.

The modern and most effective approach is considered to be a stenting procedure, which allows you to instantly restore blood flow in the affected heart vessel. After this, Clopidogrel with Acetylsalicylic acid is prescribed for 2 years to prevent platelet aggregation and the development of a recurrent attack.

The use of beta blockers can reduce the load on the heart and also prevent the development of arrhythmia. Treatment of myocardial infarction necessarily includes prolonged nitrates (“Kardiket”). They allow, by dilating the coronary vessels, to improve blood flow to the heart and limit the area of ​​necrosis.

An important point is the prescription of high doses of statins (“Rosuvastatin” up to 40 mg, “Atorvastatin” up to 80 mg) - drugs. Their use can reduce the degree of inflammatory reaction.

Symptoms of myocardial infarction and their characteristics are also taken into account during treatment. In case of severe anxiety, the patient is given sedatives; if the pressure remains high, antihypertensive drugs are used.

I would like to note that treatment after a heart attack does not end. The patient will need to take blood thinners and cholesterol-lowering drugs (statins) throughout his life. Read about how to properly undergo rehabilitation after an attack here.

Surgical methods

In the absence of treatment effectiveness and in order to prevent the recurrence of a heart attack in the same area, the following operations are used:

1. Coronary artery bypass grafting. It consists of restoring the passage of blood through the heart arteries by creating an artificial anastomosis.
2. Balloon angioplasty. A tube with a ball at the end is inserted into the lumen of the vessel. Having reached the point of application, it is inflated and the atherosclerotic plaque is pressed against the wall, restoring normal blood flow.

Kinds

This syndrome can occur with varying degrees of intensity, symptoms and localization.

Myocardial infarctions differ according to the size of the affected area:

1. Finely focal.
2. Large-focal.

Small-focal infarction, as the name suggests, has a small area of ​​the affected area of ​​the heart and a small number of foci of necrosis. They occur in a fairly mild form and have more favorable prognoses. There are no ruptures in the muscles or the appearance of a cardiac aneurysm. Very rarely, heart failure and ventricular fibrillation may occur after a heart attack.

Large-focal infarctions are characterized by correspondingly large affected areas. A huge number of myocardial cells die. Treatment and rehabilitation after this is very long, and subsequently complications may arise, including a second heart attack or death. The most dangerous is an infarction of the anterior wall of the myocardium.

During large focal heart attacks there is always a risk of death in the first 6-12 weeks.

Clinical case

A patient was admitted to the hospital with severe chest pain and other typical symptoms of myocardial infarction.
He was sent from the clinic, where a cardiogram was taken, which revealed large-focal necrosis in the acute stage of development along the anterior wall of the left ventricle. He notes that lately there have been warning signs of a heart attack - angina attacks became stronger and were poorly controlled with Nitroglycerin. The patient was referred for percutaneous coronary intervention—stenting. On the second day after the procedure, the patient felt much better, and therefore he was transferred to the general cardiology department. Recommendations were issued: follow a diet with limited fluid and salt, as well as the exclusion of fatty foods and foods high in cholesterol, lifelong use of Aspirin and statins, adequate physical rehabilitation.

Localization

Depending on the location, myocardial infarction occurs in the following clinical variants:

• left and right ventricles - blood flow to the left ventricle often stops, and several walls may be affected at once.
• septal , when the interventricular septum suffers;
• apical - necrosis occurs at the apex of the heart;
• basal - damage to the high parts of the posterior wall.